\input texinfo @c -*-texinfo-*- @c %**start of header @setfilename slib.info @settitle SLIB @setchapternewpage on @c Choices for setchapternewpage are {on,off,odd}. @paragraphindent 2 @defcodeindex ft @syncodeindex ft cp @syncodeindex tp cp @c %**end of header @iftex @finalout @c DL: lose the egregious vertical whitespace, esp. around examples @c but paras in @defun-like things don't have parindent @parskip 4pt plus 1pt @end iftex @ifinfo This file documents SLIB, the portable Scheme library. Copyright (C) 1993 Todd R. Eigenschink@* Copyright (C) 1993, 1994, 1995, 1996, 1997 Aubrey Jaffer Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. @ignore Permission is granted to process this file through TeX and print the results, provided the printed document carries copying permission notice identical to this one except for the removal of this paragraph (this paragraph not being relevant to the printed manual). @end ignore Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the author. @end ifinfo @titlepage @title SLIB @subtitle The Portable Scheme Library @subtitle Version 2c0 @author by Aubrey Jaffer @page @vskip 0pt plus 1filll Copyright @copyright{} 1993 Todd R. Eigenschink@* Copyright @copyright{} 1993, 1994, 1995, 1996, 1997 Aubrey Jaffer Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the author. @end titlepage @node Top, The Library System, (dir), (dir) @ifinfo @cindex SLIB @dfn{SLIB} is a portable library for the programming language @cindex Scheme @dfn{Scheme}. It provides a platform independent framework for using @dfn{packages} of Scheme procedures and syntax. @cindex packages @cindex package As distributed, SLIB contains useful packages for all implementations. Its catalog can be transparently extended to accomodate packages specific to a site, implementation, user, or directory. @quotation Aubrey Jaffer @* @i{Hyperactive Software} -- The Maniac Inside!@* http://www-swiss.ai.mit.edu/~jaffer/SLIB.html @end quotation @end ifinfo @menu * The Library System:: How to use and customize. * Scheme Syntax Extension Packages:: * Textual Conversion Packages:: * Mathematical Packages:: * Database Packages:: * Other Packages:: * About SLIB:: Install, etc. * Index:: @end menu @node The Library System, Scheme Syntax Extension Packages, Top, Top @chapter The Library System @iftex @section Introduction @noindent @cindex SLIB @dfn{SLIB} is a portable library for the programming language @cindex Scheme @dfn{Scheme}. It provides a platform independent framework for using @dfn{packages} of Scheme procedures and syntax. @cindex packages @cindex package As distributed, SLIB contains useful packages for all implementations. Its catalog can be transparently extended to accomodate packages specific to a site, implementation, user, or directory. @quotation Aubrey Jaffer @* @i{Hyperactive Software} -- The Maniac Inside!@* @ifset html @end ifset http://www-swiss.ai.mit.edu/~jaffer/SLIB.html @ifset html @end ifset @end quotation @end iftex @menu * Feature:: SLIB names. * Requesting Features:: * Library Catalogs:: * Catalog Compilation:: * Built-in Support:: * About this manual:: @end menu @node Feature, Requesting Features, The Library System, The Library System @section Feature @noindent @cindex feature SLIB denotes @dfn{features} by symbols. SLIB maintains a list of features supported by the Scheme @dfn{session}. The set of features @cindex session provided by a session may change over time. Some features are properties of the Scheme implementation being used. The following features detail what sort of numbers are available from an implementation. @itemize @bullet @item 'inexact @item 'rational @item 'real @item 'complex @item 'bignum @end itemize @noindent Other features correspond to the presence of sets of Scheme procedures or syntax (macros). @defun provided? feature Returns @code{#t} if @var{feature} is supported by the current Scheme session. @end defun @deffn Procedure provide feature Informs SLIB that @var{feature} is supported. Henceforth @code{(provided? @var{feature})} will return @code{#t}. @end deffn @example (provided? 'foo) @result{} #f (provide 'foo) (provided? 'foo) @result{} #t @end example @node Requesting Features, Library Catalogs, Feature, The Library System @section Requesting Features @noindent @cindex catalog SLIB creates and maintains a @dfn{catalog} mapping features to locations of files introducing procedures and syntax denoted by those features. @noindent At the beginning of each section of this manual, there is a line like @code{(require '@var{feature})}. @ftindex feature The Scheme files comprising SLIB are cataloged so that these feature names map to the corresponding files. @noindent SLIB provides a form, @code{require}, which loads the files providing the requested feature. @deffn Procedure require feature @itemize @bullet @item If @code{(provided? @var{feature})} is true, then @code{require} just returns an unspecified value. @item Otherwise, if @var{feature} is found in the catalog, then the corresponding files will be loaded and an unspecified value returned. Subsequently @code{(provided? @var{feature})} will return @code{#t}. @item Otherwise (@var{feature} not found in the catalog), an error is signaled. @end itemize @end deffn @noindent The catalog can also be queried using @code{require:feature->path}. @defun require:feature->path feature @itemize @bullet @item If @var{feature} is already provided, then returns @code{#t}. @item Otherwise, if @var{feature} is in the catalog, the path or list of paths associated with @var{feature} is returned. @item Otherwise, returns @code{#f}. @end itemize @end defun @node Library Catalogs, Catalog Compilation, Requesting Features, The Library System @section Library Catalogs @noindent At the start of a session no catalog is present, but is created with the first catalog inquiry (such as @code{(require 'random)}). Several sources of catalog information are combined to produce the catalog: @itemize @bullet @item standard SLIB packages. @item additional packages of interest to this site. @item packages specifically for the variety of Scheme which this session is running. @item packages this user wants to always have available. This catalog is the file @file{homecat} in the user's @dfn{HOME} directory. @cindex HOME @item packages germane to working in this (current working) directory. This catalog is the file @file{usercat} in the directory to which it applies. One would typically @code{cd} to this directory before starting the Scheme session. @end itemize @noindent Catalog files consist of one or more @dfn{association list}s. @cindex Catalog File In the circumstance where a feature symbol appears in more than one list, the latter list's association is retrieved. Here are the supported formats for elements of catalog lists: @table @code @item (@var{feature} . @i{}) Redirects to the feature named @i{}. @item (@var{feature} . "@i{}") Loads file @i{}. @item (@var{feature} source "@i{"}) @code{slib:load}s the Scheme source file @i{}. @item (@var{feature} compiled "@i{"} @dots{}) @code{slib:load-compiled}s the files @i{} @dots{}. @end table @noindent The various macro styles first @code{require} the named macro package, then just load @i{} or load-and-macro-expand @i{} as appropriate for the implementation. @table @code @item (@var{feature} defmacro "@i{"}) @code{defmacro:load}s the Scheme source file @i{}. @item (@var{feature} macro-by-example "@i{"}) @code{defmacro:load}s the Scheme source file @i{}. @end table @table @code @item (@var{feature} macro "@i{"}) @code{macro:load}s the Scheme source file @i{}. @item (@var{feature} macros-that-work "@i{"}) @code{macro:load}s the Scheme source file @i{}. @item (@var{feature} syntax-case "@i{"}) @code{macro:load}s the Scheme source file @i{}. @item (@var{feature} syntactic-closures "@i{"}) @code{macro:load}s the Scheme source file @i{}. @end table @noindent Here is an example of a @file{usercat} catalog. A Program in this directory can invoke the @samp{run} feature with @code{(require 'run)}. @example ;;; "usercat": SLIB catalog additions for SIMSYNCH. -*-scheme-*- ( (simsynch . "../synch/simsynch.scm") (run . "../synch/run.scm") (schlep . "schlep.scm") ) @end example @node Catalog Compilation, Built-in Support, Library Catalogs, The Library System @section Catalog Compilation @noindent SLIB combines the catalog information which doesn't vary per user into the file @file{slibcat} in the implementation-vicinity. Therefore @file{slibcat} needs change only when new software is installed or compiled. Because the actual pathnames of files can differ from installation to installation, SLIB builds a separate catalog for each implementation it is used with. @noindent The definition of @code{*SLIB-VERSION*} in SLIB file @file{require.scm} is checked against the catalog association of @code{*SLIB-VERSION*} to ascertain when versions have changed. I recommend that the definition of @code{*SLIB-VERSION*} be changed whenever the library is changed. If multiple implementations of Scheme use SLIB, remember that recompiling one @file{slibcat} will fix only that implementation's catalog. @noindent The compilation scripts of Scheme implementations which work with SLIB can automatically trigger catalog compilation by deleting @file{slibcat} or by invoking a special form of @code{require}: @deffn Procedure require @r{'new-catalog} This will load @file{mklibcat}, which compiles and writes a new @file{slibcat}. @end deffn @noindent Another special form of @code{require} erases SLIB's catalog, forcing it to be reloaded the next time the catalog is queried. @deffn Procedure require @r{#f} Removes SLIB's catalog information. This should be done before saving an executable image so that, when restored, its catalog will be loaded afresh. @end deffn @noindent Each file in the table below is descibed in terms of its file-system independent @dfn{vicinity} (@pxref{Vicinity}). The entries of a catalog in the table override those of catalogs above it in the table. @table @asis @item @code{implementation-vicinity} @file{slibcat} @cindex slibcat This file contains the associations for the packages comprising SLIB, the @file{implcat} and the @file{sitecat}s. The associations in the other catalogs override those of the standard catalog. @item @code{library-vicinity} @file{mklibcat.scm} @cindex mklibcat.scm creates @file{slibcat}. @item @code{library-vicinity} @file{sitecat} @cindex sitecat This file contains the associations specific to an SLIB installation. @item @code{implementation-vicinity} @file{implcat} @cindex implcat This file contains the associations specific to an implementation of Scheme. Different implementations of Scheme should have different @code{implementation-vicinity}. @item @code{implementation-vicinity} @file{mkimpcat.scm} @cindex mkimpcat.scm if present, creates @file{implcat}. @item @code{implementation-vicinity} @file{sitecat} @cindex sitecat This file contains the associations specific to a Scheme implementation installation. @item @code{home-vicinity} @file{homecat} @cindex homecat This file contains the associations specific to an SLIB user. @item @code{user-vicinity} @file{usercat} @cindex usercat This file contains associations effecting only those sessions whose @dfn{working directory} is @code{user-vicinity}. @end table @node Built-in Support, About this manual, Catalog Compilation, The Library System @section Built-in Support @noindent The procedures described in these sections are supported by all implementations as part of the @samp{*.init} files or by @file{require.scm}. @menu * Require:: Module Management * Vicinity:: Pathname Management * Configuration:: Characteristics of Scheme Implementation * Input/Output:: Things not provided by the Scheme specs. * Legacy:: * System:: LOADing, EVALing, ERRORing, and EXITing @end menu @node Require, Vicinity, Built-in Support, Built-in Support @subsection Require @defvar *features* Is a list of symbols denoting features supported in this implementation. @var{*features*} can grow as modules are @code{require}d. @var{*features*} must be defined by all implementations (@pxref{Porting}). Here are features which SLIB (@file{require.scm}) adds to @var{*features*} when appropriate. @itemize @bullet @item 'inexact @item 'rational @item 'real @item 'complex @item 'bignum @end itemize For each item, @code{(provided? '@var{feature})} will return @code{#t} if that feature is available, and @code{#f} if not. @end defvar @defvar *modules* Is a list of pathnames denoting files which have been loaded. @end defvar @defvar *catalog* Is an association list of features (symbols) and pathnames which will supply those features. The pathname can be either a string or a pair. If pathname is a pair then the first element should be a macro feature symbol, @code{source}, or @code{compiled}. The cdr of the pathname should be either a string or a list. @end defvar @noindent In the following functions if the argument @var{feature} is not a symbol it is assumed to be a pathname.@refill @defun provided? feature Returns @code{#t} if @var{feature} is a member of @code{*features*} or @code{*modules*} or if @var{feature} is supported by a file already loaded and @code{#f} otherwise.@refill @end defun @deffn Procedure require feature @var{feature} is a symbol. If @code{(provided? @var{feature})} is true @code{require} returns. Otherwise, if @code{(assq @var{feature} *catalog*)} is not @code{#f}, the associated files will be loaded and @code{(provided? @var{feature})} will henceforth return @code{#t}. An unspecified value is returned. If @var{feature} is not found in @code{*catalog*}, then an error is signaled. @deffnx Procedure require pathname @var{pathname} is a string. If @var{pathname} has not already been given as an argument to @code{require}, @var{pathname} is loaded. An unspecified value is returned. @end deffn @deffn Procedure provide feature Assures that @var{feature} is contained in @code{*features*} if @var{feature} is a symbol and @code{*modules*} otherwise.@refill @end deffn @defun require:feature->path feature Returns @code{#t} if @var{feature} is a member of @code{*features*} or @code{*modules*} or if @var{feature} is supported by a file already loaded. Returns a path if one was found in @code{*catalog*} under the feature name, and @code{#f} otherwise. The path can either be a string suitable as an argument to load or a pair as described above for *catalog*. @end defun @node Vicinity, Configuration, Require, Built-in Support @subsection Vicinity @noindent A vicinity is a descriptor for a place in the file system. Vicinities hide from the programmer the concepts of host, volume, directory, and version. Vicinities express only the concept of a file environment where a file name can be resolved to a file in a system independent manner. Vicinities can even be used on @dfn{flat} file systems (which have no directory structure) by having the vicinity express constraints on the file name. On most systems a vicinity would be a string. All of these procedures are file system dependent. @noindent These procedures are provided by all implementations. @defun make-vicinity filename Returns the vicinity of @var{filename} for use by @code{in-vicinity}. @end defun @defun program-vicinity Returns the vicinity of the currently loading Scheme code. For an interpreter this would be the directory containing source code. For a compiled system (with multiple files) this would be the directory where the object or executable files are. If no file is currently loading it the result is undefined. @strong{Warning:} @code{program-vicinity} can return incorrect values if your program escapes back into a @code{load}.@refill @end defun @defun library-vicinity Returns the vicinity of the shared Scheme library. @end defun @defun implementation-vicinity Returns the vicinity of the underlying Scheme implementation. This vicinity will likely contain startup code and messages and a compiler. @end defun @defun user-vicinity Returns the vicinity of the current directory of the user. On most systems this is @file{""} (the empty string). @end defun @defun home-vicinity Returns the vicinity of the user's @dfn{HOME} directory, the directory @cindex HOME which typically contains files which customize a computer environment for a user. If scheme is running without a user (eg. a daemon) or if this concept is meaningless for the platform, then @code{home-vicinity} returns @code{#f}. @end defun @c @defun scheme-file-suffix @c Returns the default filename suffix for scheme source files. On most @c systems this is @samp{.scm}.@refill @c @end defun @defun in-vicinity vicinity filename Returns a filename suitable for use by @code{slib:load}, @code{slib:load-source}, @code{slib:load-compiled}, @code{open-input-file}, @code{open-output-file}, etc. The returned filename is @var{filename} in @var{vicinity}. @code{in-vicinity} should allow @var{filename} to override @var{vicinity} when @var{filename} is an absolute pathname and @var{vicinity} is equal to the value of @code{(user-vicinity)}. The behavior of @code{in-vicinity} when @var{filename} is absolute and @var{vicinity} is not equal to the value of @code{(user-vicinity)} is unspecified. For most systems @code{in-vicinity} can be @code{string-append}.@refill @end defun @defun sub-vicinity vicinity name Returns the vicinity of @var{vicinity} restricted to @var{name}. This is used for large systems where names of files in subsystems could conflict. On systems with directory structure @code{sub-vicinity} will return a pathname of the subdirectory @var{name} of @var{vicinity}.@refill @end defun @node Configuration, Input/Output, Vicinity, Built-in Support @subsection Configuration @noindent These constants and procedures describe characteristics of the Scheme and underlying operating system. They are provided by all implementations. @defvr Constant char-code-limit An integer 1 larger that the largest value which can be returned by @code{char->integer}.@refill @end defvr @defvr Constant most-positive-fixnum The immediate integer closest to positive infinity. @end defvr @defvr Constant slib:tab The tab character. @end defvr @defvr Constant slib:form-feed The form-feed character. @end defvr @defun software-type Returns a symbol denoting the generic operating system type. For instance, @code{unix}, @code{vms}, @code{macos}, @code{amiga}, or @code{ms-dos}. @end defun @defun slib:report-version Displays the versions of SLIB and the underlying Scheme implementation and the name of the operating system. An unspecified value is returned. @example (slib:report-version) @result{} slib "2c0" on scm "5b1" on unix @end example @end defun @defun slib:report Displays the information of @code{(slib:report-version)} followed by almost all the information neccessary for submitting a problem report. An unspecified value is returned. @defunx slib:report #t provides a more verbose listing. @defunx slib:report filename Writes the report to file @file{filename}. @example (slib:report) @result{} slib "2c0" on scm "5b1" on unix (implementation-vicinity) is "/home/jaffer/scm/" (library-vicinity) is "/home/jaffer/slib/" (scheme-file-suffix) is ".scm" loaded *features* : trace alist qp sort common-list-functions macro values getopt compiled implementation *features* : bignum complex real rational inexact vicinity ed getenv tmpnam abort transcript with-file ieee-p1178 rev4-report rev4-optional-procedures hash object-hash delay eval dynamic-wind multiarg-apply multiarg/and- logical defmacro string-port source current-time record rev3-procedures rev2-procedures sun-dl string-case array dump char-ready? full-continuation system implementation *catalog* : (i/o-extensions compiled "/home/jaffer/scm/ioext.so") ... @end example @end defun @node Input/Output, Legacy, Configuration, Built-in Support @subsection Input/Output @noindent These procedures are provided by all implementations. @deffn Procedure file-exists? filename Returns @code{#t} if the specified file exists. Otherwise, returns @code{#f}. If the underlying implementation does not support this feature then @code{#f} is always returned. @end deffn @deffn Procedure delete-file filename Deletes the file specified by @var{filename}. If @var{filename} can not be deleted, @code{#f} is returned. Otherwise, @code{#t} is returned.@refill @end deffn @deffn Procedure tmpnam Returns a pathname for a file which will likely not be used by any other process. Successive calls to @code{(tmpnam)} will return different pathnames.@refill @end deffn @deffn Procedure current-error-port Returns the current port to which diagnostic and error output is directed. @end deffn @deffn Procedure force-output @deffnx Procedure force-output port Forces any pending output on @var{port} to be delivered to the output device and returns an unspecified value. The @var{port} argument may be omitted, in which case it defaults to the value returned by @code{(current-output-port)}.@refill @end deffn @deffn Procedure output-port-width @deffnx Procedure output-port-width port Returns the width of @var{port}, which defaults to @code{(current-output-port)} if absent. If the width cannot be determined 79 is returned.@refill @end deffn @deffn Procedure output-port-height @deffnx Procedure output-port-height port Returns the height of @var{port}, which defaults to @code{(current-output-port)} if absent. If the height cannot be determined 24 is returned.@refill @end deffn @node Legacy, System, Input/Output, Built-in Support @subsection Legacy These procedures are provided by all implementations. @defun identity x @var{identity} returns its argument. Example: @lisp (identity 3) @result{} 3 (identity '(foo bar)) @result{} (foo bar) (map identity @var{lst}) @equiv{} (copy-list @var{lst}) @end lisp @end defun @noindent The following procedures were present in Scheme until R4RS (@pxref{Notes, , Language changes ,r4rs, Revised(4) Scheme}). They are provided by all SLIB implementations. @defvr Constant t Derfined as @code{#t}. @end defvr @defvr Constant nil Defined as @code{#f}. @end defvr @defun last-pair l Returns the last pair in the list @var{l}. Example: @lisp (last-pair (cons 1 2)) @result{} (1 . 2) (last-pair '(1 2)) @result{} (2) @equiv{} (cons 2 '()) @end lisp @end defun @node System, , Legacy, Built-in Support @subsection System @noindent These procedures are provided by all implementations. @deffn Procedure slib:load-source name Loads a file of Scheme source code from @var{name} with the default filename extension used in SLIB. For instance if the filename extension used in SLIB is @file{.scm} then @code{(slib:load-source "foo")} will load from file @file{foo.scm}. @end deffn @deffn Procedure slib:load-compiled name On implementations which support separtely loadable compiled modules, loads a file of compiled code from @var{name} with the implementation's filename extension for compiled code appended. @end deffn @deffn Procedure slib:load name Loads a file of Scheme source or compiled code from @var{name} with the appropriate suffixes appended. If both source and compiled code are present with the appropriate names then the implementation will load just one. It is up to the implementation to choose which one will be loaded. If an implementation does not support compiled code then @code{slib:load} will be identical to @code{slib:load-source}. @end deffn @deffn Procedure slib:eval obj @code{eval} returns the value of @var{obj} evaluated in the current top level environment.@refill @end deffn @deffn Procedure slib:eval-load filename eval @var{filename} should be a string. If filename names an existing file, the Scheme source code expressions and definitions are read from the file and @var{eval} called with them sequentially. The @code{slib:eval-load} procedure does not affect the values returned by @code{current-input-port} and @code{current-output-port}.@refill @end deffn @deffn Procedure slib:warn arg1 arg2 @dots{} Outputs a warning message containing the arguments. @end deffn @deffn Procedure slib:error arg1 arg2 @dots{} Outputs an error message containing the arguments, aborts evaluation of the current form and responds in a system dependent way to the error. Typical responses are to abort the program or to enter a read-eval-print loop.@refill @end deffn @deffn Procedure slib:exit n @deffnx Procedure slib:exit Exits from the Scheme session returning status @var{n} to the system. If @var{n} is omitted or @code{#t}, a success status is returned to the system (if possible). If @var{n} is @code{#f} a failure is returned to the system (if possible). If @var{n} is an integer, then @var{n} is returned to the system (if possible). If the Scheme session cannot exit an unspecified value is returned from @code{slib:exit}. @end deffn @node About this manual, , Built-in Support, The Library System @section About this manual @itemize @bullet @item Entries that are labeled as Functions are called for their return values. Entries that are labeled as Procedures are called primarily for their side effects. @item Examples in this text were produced using the @code{scm} Scheme implementation. @item At the beginning of each section, there is a line that looks like @ftindex feature @code{(require 'feature)}. Include this line in your code prior to using the package. @end itemize @node Scheme Syntax Extension Packages, Textual Conversion Packages, The Library System, Top @chapter Scheme Syntax Extension Packages @menu * Defmacro:: Supported by all implementations * R4RS Macros:: 'macro * Macro by Example:: 'macro-by-example * Macros That Work:: 'macros-that-work * Syntactic Closures:: 'syntactic-closures * Syntax-Case Macros:: 'syntax-case Syntax extensions (macros) included with SLIB. Also @xref{Structures}. * Fluid-Let:: 'fluid-let * Yasos:: 'yasos, 'oop, 'collect @end menu @node Defmacro, R4RS Macros, Scheme Syntax Extension Packages, Scheme Syntax Extension Packages @section Defmacro Defmacros are supported by all implementations. @c See also @code{gentemp}, in @ref{Macros}. @defun gentemp Returns a new (interned) symbol each time it is called. The symbol names are implementation-dependent @lisp (gentemp) @result{} scm:G0 (gentemp) @result{} scm:G1 @end lisp @end defun @defun defmacro:eval e Returns the @code{slib:eval} of expanding all defmacros in scheme expression @var{e}. @end defun @defun defmacro:load filename @var{filename} should be a string. If filename names an existing file, the @code{defmacro:load} procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain defmacro definitions. The @code{macro:load} procedure does not affect the values returned by @code{current-input-port} and @code{current-output-port}.@refill @end defun @defun defmacro? sym Returns @code{#t} if @var{sym} has been defined by @code{defmacro}, @code{#f} otherwise. @end defun @defun macroexpand-1 form @defunx macroexpand form If @var{form} is a macro call, @code{macroexpand-1} will expand the macro call once and return it. A @var{form} is considered to be a macro call only if it is a cons whose @code{car} is a symbol for which a @code{defmacr} has been defined. @code{macroexpand} is similar to @code{macroexpand-1}, but repeatedly expands @var{form} until it is no longer a macro call. @end defun @defmac defmacro name lambda-list form @dots{} When encountered by @code{defmacro:eval}, @code{defmacro:macroexpand*}, or @code{defmacro:load} defines a new macro which will henceforth be expanded when encountered by @code{defmacro:eval}, @code{defmacro:macroexpand*}, or @code{defmacro:load}. @end defmac @subsection Defmacroexpand @code{(require 'defmacroexpand)} @ftindex defmacroexpand @defun defmacro:expand* e Returns the result of expanding all defmacros in scheme expression @var{e}. @end defun @node R4RS Macros, Macro by Example, Defmacro, Scheme Syntax Extension Packages @section R4RS Macros @code{(require 'macro)} is the appropriate call if you want R4RS @ftindex macro high-level macros but don't care about the low level implementation. If an SLIB R4RS macro implementation is already loaded it will be used. Otherwise, one of the R4RS macros implemetations is loaded. The SLIB R4RS macro implementations support the following uniform interface: @defun macro:expand sexpression Takes an R4RS expression, macro-expands it, and returns the result of the macro expansion. @end defun @defun macro:eval sexpression Takes an R4RS expression, macro-expands it, evals the result of the macro expansion, and returns the result of the evaluation. @end defun @deffn Procedure macro:load filename @var{filename} should be a string. If filename names an existing file, the @code{macro:load} procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The @code{macro:load} procedure does not affect the values returned by @code{current-input-port} and @code{current-output-port}.@refill @end deffn @node Macro by Example, Macros That Work, R4RS Macros, Scheme Syntax Extension Packages @section Macro by Example @code{(require 'macro-by-example)} @ftindex macro-by-example A vanilla implementation of @cite{Macro by Example} (Eugene Kohlbecker, R4RS) by Dorai Sitaram, (dorai@@cs.rice.edu) using @code{defmacro}. @itemize @bullet @item generating hygienic global @code{define-syntax} Macro-by-Example macros @strong{cheaply}. @item can define macros which use @code{...}. @item needn't worry about a lexical variable in a macro definition clashing with a variable from the macro use context @item don't suffer the overhead of redefining the repl if @code{defmacro} natively supported (most implementations) @end itemize @subsection Caveat These macros are not referentially transparent (@pxref{Macros, , ,r4rs, Revised(4) Scheme}). Lexically scoped macros (i.e., @code{let-syntax} and @code{letrec-syntax}) are not supported. In any case, the problem of referential transparency gains poignancy only when @code{let-syntax} and @code{letrec-syntax} are used. So you will not be courting large-scale disaster unless you're using system-function names as local variables with unintuitive bindings that the macro can't use. However, if you must have the full @cite{r4rs} macro functionality, look to the more featureful (but also more expensive) versions of syntax-rules available in slib @ref{Macros That Work}, @ref{Syntactic Closures}, and @ref{Syntax-Case Macros}. @defmac define-syntax keyword transformer-spec The @var{keyword} is an identifier, and the @var{transformer-spec} should be an instance of @code{syntax-rules}. The top-level syntactic environment is extended by binding the @var{keyword} to the specified transformer. @example (define-syntax let* (syntax-rules () ((let* () body1 body2 ...) (let () body1 body2 ...)) ((let* ((name1 val1) (name2 val2) ...) body1 body2 ...) (let ((name1 val1)) (let* (( name2 val2) ...) body1 body2 ...))))) @end example @end defmac @defmac syntax-rules literals syntax-rule @dots{} @var{literals} is a list of identifiers, and each @var{syntax-rule} should be of the form @code{(@var{pattern} @var{template})} where the @var{pattern} and @var{template} are as in the grammar above. An instance of @code{syntax-rules} produces a new macro transformer by specifying a sequence of hygienic rewrite rules. A use of a macro whose keyword is associated with a transformer specified by @code{syntax-rules} is matched against the patterns contained in the @var{syntax-rule}s, beginning with the leftmost @var{syntax-rule}. When a match is found, the macro use is trancribed hygienically according to the template. Each pattern begins with the keyword for the macro. This keyword is not involved in the matching and is not considered a pattern variable or literal identifier. @end defmac @node Macros That Work, Syntactic Closures, Macro by Example, Scheme Syntax Extension Packages @section Macros That Work @code{(require 'macros-that-work)} @ftindex macros-that-work @cite{Macros That Work} differs from the other R4RS macro implementations in that it does not expand derived expression types to primitive expression types. @defun macro:expand expression @defunx macwork:expand expression Takes an R4RS expression, macro-expands it, and returns the result of the macro expansion. @end defun @defun macro:eval expression @defunx macwork:eval expression @code{macro:eval} returns the value of @var{expression} in the current top level environment. @var{expression} can contain macro definitions. Side effects of @var{expression} will affect the top level environment.@refill @end defun @deffn Procedure macro:load filename @deffnx Procedure macwork:load filename @var{filename} should be a string. If filename names an existing file, the @code{macro:load} procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The @code{macro:load} procedure does not affect the values returned by @code{current-input-port} and @code{current-output-port}.@refill @end deffn References: The @cite{Revised^4 Report on the Algorithmic Language Scheme} Clinger and Rees [editors]. To appear in LISP Pointers. Also available as a technical report from the University of Oregon, MIT AI Lab, and Cornell.@refill @center Macros That Work. Clinger and Rees. POPL '91. The supported syntax differs from the R4RS in that vectors are allowed as patterns and as templates and are not allowed as pattern or template data. @example transformer spec @expansion{} (syntax-rules literals rules) rules @expansion{} () | (rule . rules) rule @expansion{} (pattern template) pattern @expansion{} pattern_var ; a symbol not in literals | symbol ; a symbol in literals | () | (pattern . pattern) | (ellipsis_pattern) | #(pattern*) ; extends R4RS | #(pattern* ellipsis_pattern) ; extends R4RS | pattern_datum template @expansion{} pattern_var | symbol | () | (template2 . template2) | #(template*) ; extends R4RS | pattern_datum template2 @expansion{} template | ellipsis_template pattern_datum @expansion{} string ; no vector | character | boolean | number ellipsis_pattern @expansion{} pattern ... ellipsis_template @expansion{} template ... pattern_var @expansion{} symbol ; not in literals literals @expansion{} () | (symbol . literals) @end example @subsection Definitions @table @asis @item Scope of an ellipsis Within a pattern or template, the scope of an ellipsis (@code{...}) is the pattern or template that appears to its left. @item Rank of a pattern variable The rank of a pattern variable is the number of ellipses within whose scope it appears in the pattern. @item Rank of a subtemplate The rank of a subtemplate is the number of ellipses within whose scope it appears in the template. @item Template rank of an occurrence of a pattern variable The template rank of an occurrence of a pattern variable within a template is the rank of that occurrence, viewed as a subtemplate. @item Variables bound by a pattern The variables bound by a pattern are the pattern variables that appear within it. @item Referenced variables of a subtemplate The referenced variables of a subtemplate are the pattern variables that appear within it. @item Variables opened by an ellipsis template The variables opened by an ellipsis template are the referenced pattern variables whose rank is greater than the rank of the ellipsis template. @end table @subsection Restrictions No pattern variable appears more than once within a pattern. For every occurrence of a pattern variable within a template, the template rank of the occurrence must be greater than or equal to the pattern variable's rank. Every ellipsis template must open at least one variable. For every ellipsis template, the variables opened by an ellipsis template must all be bound to sequences of the same length. The compiled form of a @var{rule} is @example rule @expansion{} (pattern template inserted) pattern @expansion{} pattern_var | symbol | () | (pattern . pattern) | ellipsis_pattern | #(pattern) | pattern_datum template @expansion{} pattern_var | symbol | () | (template2 . template2) | #(pattern) | pattern_datum template2 @expansion{} template | ellipsis_template pattern_datum @expansion{} string | character | boolean | number pattern_var @expansion{} #(V symbol rank) ellipsis_pattern @expansion{} #(E pattern pattern_vars) ellipsis_template @expansion{} #(E template pattern_vars) inserted @expansion{} () | (symbol . inserted) pattern_vars @expansion{} () | (pattern_var . pattern_vars) rank @expansion{} exact non-negative integer @end example where V and E are unforgeable values. The pattern variables associated with an ellipsis pattern are the variables bound by the pattern, and the pattern variables associated with an ellipsis template are the variables opened by the ellipsis template. If the template contains a big chunk that contains no pattern variables or inserted identifiers, then the big chunk will be copied unnecessarily. That shouldn't matter very often. @node Syntactic Closures, Syntax-Case Macros, Macros That Work, Scheme Syntax Extension Packages @section Syntactic Closures @code{(require 'syntactic-closures)} @ftindex syntactic-closures @defun macro:expand expression @defunx synclo:expand expression Returns scheme code with the macros and derived expression types of @var{expression} expanded to primitive expression types.@refill @end defun @defun macro:eval expression @defunx synclo:eval expression @code{macro:eval} returns the value of @var{expression} in the current top level environment. @var{expression} can contain macro definitions. Side effects of @var{expression} will affect the top level environment.@refill @end defun @deffn Procedure macro:load filename @deffnx Procedure synclo:load filename @var{filename} should be a string. If filename names an existing file, the @code{macro:load} procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The @code{macro:load} procedure does not affect the values returned by @code{current-input-port} and @code{current-output-port}.@refill @end deffn @subsection Syntactic Closure Macro Facility @center A Syntactic Closures Macro Facility @center by Chris Hanson @center 9 November 1991 This document describes @dfn{syntactic closures}, a low-level macro facility for the Scheme programming language. The facility is an alternative to the low-level macro facility described in the @cite{Revised^4 Report on Scheme.} This document is an addendum to that report. The syntactic closures facility extends the BNF rule for @var{transformer spec} to allow a new keyword that introduces a low-level macro transformer:@refill @example @var{transformer spec} := (transformer @var{expression}) @end example Additionally, the following procedures are added: @lisp make-syntactic-closure capture-syntactic-environment identifier? identifier=? @end lisp The description of the facility is divided into three parts. The first part defines basic terminology. The second part describes how macro transformers are defined. The third part describes the use of @dfn{identifiers}, which extend the syntactic closure mechanism to be compatible with @code{syntax-rules}.@refill @subsubsection Terminology This section defines the concepts and data types used by the syntactic closures facility. @itemize @bullet @item @dfn{Forms} are the syntactic entities out of which programs are recursively constructed. A form is any expression, any definition, any syntactic keyword, or any syntactic closure. The variable name that appears in a @code{set!} special form is also a form. Examples of forms:@refill @lisp 17 #t car (+ x 4) (lambda (x) x) (define pi 3.14159) if define @end lisp @item An @dfn{alias} is an alternate name for a given symbol. It can appear anywhere in a form that the symbol could be used, and when quoted it is replaced by the symbol; however, it does not satisfy the predicate @code{symbol?}. Macro transformers rarely distinguish symbols from aliases, referring to both as identifiers.@refill @item A @dfn{syntactic} environment maps identifiers to their meanings. More precisely, it determines whether an identifier is a syntactic keyword or a variable. If it is a keyword, the meaning is an interpretation for the form in which that keyword appears. If it is a variable, the meaning identifies which binding of that variable is referenced. In short, syntactic environments contain all of the contextual information necessary for interpreting the meaning of a particular form.@refill @item A @dfn{syntactic closure} consists of a form, a syntactic environment, and a list of identifiers. All identifiers in the form take their meaning from the syntactic environment, except those in the given list. The identifiers in the list are to have their meanings determined later. A syntactic closure may be used in any context in which its form could have been used. Since a syntactic closure is also a form, it may not be used in contexts where a form would be illegal. For example, a form may not appear as a clause in the cond special form. A syntactic closure appearing in a quoted structure is replaced by its form.@refill @end itemize @subsubsection Transformer Definition This section describes the @code{transformer} special form and the procedures @code{make-syntactic-closure} and @code{capture-syntactic-environment}.@refill @deffn Syntax transformer expression Syntax: It is an error if this syntax occurs except as a @var{transformer spec}.@refill Semantics: The @var{expression} is evaluated in the standard transformer environment to yield a macro transformer as described below. This macro transformer is bound to a macro keyword by the special form in which the @code{transformer} expression appears (for example, @code{let-syntax}).@refill A @dfn{macro transformer} is a procedure that takes two arguments, a form and a syntactic environment, and returns a new form. The first argument, the @dfn{input form}, is the form in which the macro keyword occurred. The second argument, the @dfn{usage environment}, is the syntactic environment in which the input form occurred. The result of the transformer, the @dfn{output form}, is automatically closed in the @dfn{transformer environment}, which is the syntactic environment in which the @code{transformer} expression occurred.@refill For example, here is a definition of a push macro using @code{syntax-rules}:@refill @lisp (define-syntax push (syntax-rules () ((push item list) (set! list (cons item list))))) @end lisp Here is an equivalent definition using @code{transformer}: @lisp (define-syntax push (transformer (lambda (exp env) (let ((item (make-syntactic-closure env '() (cadr exp))) (list (make-syntactic-closure env '() (caddr exp)))) `(set! ,list (cons ,item ,list)))))) @end lisp In this example, the identifiers @code{set!} and @code{cons} are closed in the transformer environment, and thus will not be affected by the meanings of those identifiers in the usage environment @code{env}.@refill Some macros may be non-hygienic by design. For example, the following defines a loop macro that implicitly binds @code{exit} to an escape procedure. The binding of @code{exit} is intended to capture free references to @code{exit} in the body of the loop, so @code{exit} must be left free when the body is closed:@refill @lisp (define-syntax loop (transformer (lambda (exp env) (let ((body (cdr exp))) `(call-with-current-continuation (lambda (exit) (let f () ,@@(map (lambda (exp) (make-syntactic-closure env '(exit) exp)) body) (f)))))))) @end lisp To assign meanings to the identifiers in a form, use @code{make-syntactic-closure} to close the form in a syntactic environment.@refill @end deffn @defun make-syntactic-closure environment free-names form @var{environment} must be a syntactic environment, @var{free-names} must be a list of identifiers, and @var{form} must be a form. @code{make-syntactic-closure} constructs and returns a syntactic closure of @var{form} in @var{environment}, which can be used anywhere that @var{form} could have been used. All the identifiers used in @var{form}, except those explicitly excepted by @var{free-names}, obtain their meanings from @var{environment}.@refill Here is an example where @var{free-names} is something other than the empty list. It is instructive to compare the use of @var{free-names} in this example with its use in the @code{loop} example above: the examples are similar except for the source of the identifier being left free.@refill @lisp (define-syntax let1 (transformer (lambda (exp env) (let ((id (cadr exp)) (init (caddr exp)) (exp (cadddr exp))) `((lambda (,id) ,(make-syntactic-closure env (list id) exp)) ,(make-syntactic-closure env '() init)))))) @end lisp @code{let1} is a simplified version of @code{let} that only binds a single identifier, and whose body consists of a single expression. When the body expression is syntactically closed in its original syntactic environment, the identifier that is to be bound by @code{let1} must be left free, so that it can be properly captured by the @code{lambda} in the output form.@refill To obtain a syntactic environment other than the usage environment, use @code{capture-syntactic-environment}.@refill @end defun @defun capture-syntactic-environment procedure @code{capture-syntactic-environment} returns a form that will, when transformed, call @var{procedure} on the current syntactic environment. @var{procedure} should compute and return a new form to be transformed, in that same syntactic environment, in place of the form.@refill An example will make this clear. Suppose we wanted to define a simple @code{loop-until} keyword equivalent to@refill @lisp (define-syntax loop-until (syntax-rules () ((loop-until id init test return step) (letrec ((loop (lambda (id) (if test return (loop step))))) (loop init))))) @end lisp The following attempt at defining @code{loop-until} has a subtle bug: @lisp (define-syntax loop-until (transformer (lambda (exp env) (let ((id (cadr exp)) (init (caddr exp)) (test (cadddr exp)) (return (cadddr (cdr exp))) (step (cadddr (cddr exp))) (close (lambda (exp free) (make-syntactic-closure env free exp)))) `(letrec ((loop (lambda (,id) (if ,(close test (list id)) ,(close return (list id)) (loop ,(close step (list id))))))) (loop ,(close init '()))))))) @end lisp This definition appears to take all of the proper precautions to prevent unintended captures. It carefully closes the subexpressions in their original syntactic environment and it leaves the @code{id} identifier free in the @code{test}, @code{return}, and @code{step} expressions, so that it will be captured by the binding introduced by the @code{lambda} expression. Unfortunately it uses the identifiers @code{if} and @code{loop} within that @code{lambda} expression, so if the user of @code{loop-until} just happens to use, say, @code{if} for the identifier, it will be inadvertently captured.@refill The syntactic environment that @code{if} and @code{loop} want to be exposed to is the one just outside the @code{lambda} expression: before the user's identifier is added to the syntactic environment, but after the identifier loop has been added. @code{capture-syntactic-environment} captures exactly that environment as follows:@refill @lisp (define-syntax loop-until (transformer (lambda (exp env) (let ((id (cadr exp)) (init (caddr exp)) (test (cadddr exp)) (return (cadddr (cdr exp))) (step (cadddr (cddr exp))) (close (lambda (exp free) (make-syntactic-closure env free exp)))) `(letrec ((loop ,(capture-syntactic-environment (lambda (env) `(lambda (,id) (,(make-syntactic-closure env '() `if) ,(close test (list id)) ,(close return (list id)) (,(make-syntactic-closure env '() `loop) ,(close step (list id))))))))) (loop ,(close init '()))))))) @end lisp In this case, having captured the desired syntactic environment, it is convenient to construct syntactic closures of the identifiers @code{if} and the @code{loop} and use them in the body of the @code{lambda}.@refill A common use of @code{capture-syntactic-environment} is to get the transformer environment of a macro transformer:@refill @lisp (transformer (lambda (exp env) (capture-syntactic-environment (lambda (transformer-env) ...)))) @end lisp @end defun @subsubsection Identifiers This section describes the procedures that create and manipulate identifiers. Previous syntactic closure proposals did not have an identifier data type -- they just used symbols. The identifier data type extends the syntactic closures facility to be compatible with the high-level @code{syntax-rules} facility.@refill As discussed earlier, an identifier is either a symbol or an @dfn{alias}. An alias is implemented as a syntactic closure whose @dfn{form} is an identifier:@refill @lisp (make-syntactic-closure env '() 'a) @result{} an @dfn{alias} @end lisp Aliases are implemented as syntactic closures because they behave just like syntactic closures most of the time. The difference is that an alias may be bound to a new value (for example by @code{lambda} or @code{let-syntax}); other syntactic closures may not be used this way. If an alias is bound, then within the scope of that binding it is looked up in the syntactic environment just like any other identifier.@refill Aliases are used in the implementation of the high-level facility @code{syntax-rules}. A macro transformer created by @code{syntax-rules} uses a template to generate its output form, substituting subforms of the input form into the template. In a syntactic closures implementation, all of the symbols in the template are replaced by aliases closed in the transformer environment, while the output form itself is closed in the usage environment. This guarantees that the macro transformation is hygienic, without requiring the transformer to know the syntactic roles of the substituted input subforms. @defun identifier? object Returns @code{#t} if @var{object} is an identifier, otherwise returns @code{#f}. Examples:@refill @lisp (identifier? 'a) @result{} #t (identifier? (make-syntactic-closure env '() 'a)) @result{} #t (identifier? "a") @result{} #f (identifier? #\a) @result{} #f (identifier? 97) @result{} #f (identifier? #f) @result{} #f (identifier? '(a)) @result{} #f (identifier? '#(a)) @result{} #f @end lisp The predicate @code{eq?} is used to determine if two identifers are ``the same''. Thus @code{eq?} can be used to compare identifiers exactly as it would be used to compare symbols. Often, though, it is useful to know whether two identifiers ``mean the same thing''. For example, the @code{cond} macro uses the symbol @code{else} to identify the final clause in the conditional. A macro transformer for @code{cond} cannot just look for the symbol @code{else}, because the @code{cond} form might be the output of another macro transformer that replaced the symbol @code{else} with an alias. Instead the transformer must look for an identifier that ``means the same thing'' in the usage environment as the symbol @code{else} means in the transformer environment.@refill @end defun @defun identifier=? environment1 identifier1 environment2 identifier2 @var{environment1} and @var{environment2} must be syntactic environments, and @var{identifier1} and @var{identifier2} must be identifiers. @code{identifier=?} returns @code{#t} if the meaning of @var{identifier1} in @var{environment1} is the same as that of @var{identifier2} in @var{environment2}, otherwise it returns @code{#f}. Examples:@refill @lisp (let-syntax ((foo (transformer (lambda (form env) (capture-syntactic-environment (lambda (transformer-env) (identifier=? transformer-env 'x env 'x))))))) (list (foo) (let ((x 3)) (foo)))) @result{} (#t #f) @end lisp @lisp (let-syntax ((bar foo)) (let-syntax ((foo (transformer (lambda (form env) (capture-syntactic-environment (lambda (transformer-env) (identifier=? transformer-env 'foo env (cadr form)))))))) (list (foo foo) (foobar)))) @result{} (#f #t) @end lisp @end defun @subsubsection Acknowledgements The syntactic closures facility was invented by Alan Bawden and Jonathan Rees. The use of aliases to implement @code{syntax-rules} was invented by Alan Bawden (who prefers to call them @dfn{synthetic names}). Much of this proposal is derived from an earlier proposal by Alan Bawden.@refill @node Syntax-Case Macros, Fluid-Let, Syntactic Closures, Scheme Syntax Extension Packages @section Syntax-Case Macros @code{(require 'syntax-case)} @ftindex syntax-case @defun macro:expand expression @defunx syncase:expand expression Returns scheme code with the macros and derived expression types of @var{expression} expanded to primitive expression types.@refill @end defun @defun macro:eval expression @defunx syncase:eval expression @code{macro:eval} returns the value of @var{expression} in the current top level environment. @var{expression} can contain macro definitions. Side effects of @var{expression} will affect the top level environment.@refill @end defun @deffn Procedure macro:load filename @deffnx Procedure syncase:load filename @var{filename} should be a string. If filename names an existing file, the @code{macro:load} procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The @code{macro:load} procedure does not affect the values returned by @code{current-input-port} and @code{current-output-port}.@refill @end deffn This is version 2.1 of @code{syntax-case}, the low-level macro facility proposed and implemented by Robert Hieb and R. Kent Dybvig. This version is further adapted by Harald Hanche-Olsen to make it compatible with, and easily usable with, SLIB. Mainly, these adaptations consisted of: @itemize @bullet @item Removing white space from @file{expand.pp} to save space in the distribution. This file is not meant for human readers anyway@dots{} @item Removed a couple of Chez scheme dependencies. @item Renamed global variables used to minimize the possibility of name conflicts. @item Adding an SLIB-specific initialization file. @item Removing a couple extra files, most notably the documentation (but see below). @end itemize If you wish, you can see exactly what changes were done by reading the shell script in the file @file{syncase.sh}. The two PostScript files were omitted in order to not burden the SLIB distribution with them. If you do intend to use @code{syntax-case}, however, you should get these files and print them out on a PostScript printer. They are available with the original @code{syntax-case} distribution by anonymous FTP in @file{cs.indiana.edu:/pub/scheme/syntax-case}.@refill In order to use syntax-case from an interactive top level, execute: @lisp (require 'syntax-case) @ftindex syntax-case (require 'repl) @ftindex repl (repl:top-level macro:eval) @end lisp See the section Repl (@xref{Repl}) for more information. To check operation of syntax-case get @file{cs.indiana.edu:/pub/scheme/syntax-case}, and type @lisp (require 'syntax-case) @ftindex syntax-case (syncase:sanity-check) @end lisp Beware that @code{syntax-case} takes a long time to load -- about 20s on a SPARCstation SLC (with SCM) and about 90s on a Macintosh SE/30 (with Gambit). @subsection Notes All R4RS syntactic forms are defined, including @code{delay}. Along with @code{delay} are simple definitions for @code{make-promise} (into which @code{delay} expressions expand) and @code{force}.@refill @code{syntax-rules} and @code{with-syntax} (described in @cite{TR356}) are defined.@refill @code{syntax-case} is actually defined as a macro that expands into calls to the procedure @code{syntax-dispatch} and the core form @code{syntax-lambda}; do not redefine these names.@refill Several other top-level bindings not documented in TR356 are created: @itemize @bullet @item the ``hooks'' in @file{hooks.ss} @item the @code{build-} procedures in @file{output.ss} @item @code{expand-syntax} (the expander) @end itemize The syntax of define has been extended to allow @code{(define @var{id})}, which assigns @var{id} to some unspecified value.@refill We have attempted to maintain R4RS compatibility where possible. The incompatibilities should be confined to @file{hooks.ss}. Please let us know if there is some incompatibility that is not flagged as such.@refill Send bug reports, comments, suggestions, and questions to Kent Dybvig (dyb@@iuvax.cs.indiana.edu). @subsection Note from maintainer Included with the @code{syntax-case} files was @file{structure.scm} which defines a macro @code{define-structure}. There is no documentation for this macro and it is not used by any code in SLIB. @node Fluid-Let, Yasos, Syntax-Case Macros, Scheme Syntax Extension Packages @section Fluid-Let @code{(require 'fluid-let)} @ftindex fluid-let @deffn Syntax fluid-let @code{(@var{bindings} @dots{})} @var{forms}@dots{} @end deffn @lisp (fluid-let ((@var{variable} @var{init}) @dots{}) @var{expression} @var{expression} @dots{}) @end lisp The @var{init}s are evaluated in the current environment (in some unspecified order), the current values of the @var{variable}s are saved, the results are assigned to the @var{variable}s, the @var{expression}s are evaluated sequentially in the current environment, the @var{variable}s are restored to their original values, and the value of the last @var{expression} is returned.@refill The syntax of this special form is similar to that of @code{let}, but @code{fluid-let} temporarily rebinds existing @var{variable}s. Unlike @code{let}, @code{fluid-let} creates no new bindings; instead it @emph{assigns} the values of each @var{init} to the binding (determined by the rules of lexical scoping) of its corresponding @var{variable}.@refill @node Yasos, , Fluid-Let, Scheme Syntax Extension Packages @section Yasos @c Much of the documentation in this section was written by Dave Love @c (d.love@dl.ac.uk) -- don't blame Ken Dickey for its faults. @c but we can blame him for not writing it! @code{(require 'oop)} or @code{(require 'yasos)} @ftindex oop @ftindex yasos `Yet Another Scheme Object System' is a simple object system for Scheme based on the paper by Norman Adams and Jonathan Rees: @cite{Object Oriented Programming in Scheme}, Proceedings of the 1988 ACM Conference on LISP and Functional Programming, July 1988 [ACM #552880].@refill Another reference is: Ken Dickey. @ifset html @end ifset Scheming with Objects @ifset html @end ifset @cite{AI Expert} Volume 7, Number 10 (October 1992), pp. 24-33. @menu * Yasos terms:: Definitions and disclaimer. * Yasos interface:: The Yasos macros and procedures. * Setters:: Dylan-like setters in Yasos. * Yasos examples:: Usage of Yasos and setters. @end menu @node Yasos terms, Yasos interface, Yasos, Yasos @subsection Terms @table @asis @item @dfn{Object} Any Scheme data object. @item @dfn{Instance} An instance of the OO system; an @dfn{object}. @item @dfn{Operation} A @var{method}. @end table @table @emph @item Notes: The object system supports multiple inheritance. An instance can inherit from 0 or more ancestors. In the case of multiple inherited operations with the same identity, the operation used is that from the first ancestor which contains it (in the ancestor @code{let}). An operation may be applied to any Scheme data object---not just instances. As code which creates instances is just code, there are no @dfn{classes} and no meta-@var{anything}. Method dispatch is by a procedure call a la CLOS rather than by @code{send} syntax a la Smalltalk.@refill @item Disclaimer: There are a number of optimizations which can be made. This implementation is expository (although performance should be quite reasonable). See the L&FP paper for some suggestions.@refill @end table @node Yasos interface, Setters, Yasos terms, Yasos @subsection Interface @deffn Syntax define-operation @code{(}opname self arg @dots{}@code{)} @var{default-body} Defines a default behavior for data objects which don't handle the operation @var{opname}. The default default behavior (for an empty @var{default-body}) is to generate an error.@refill @end deffn @deffn Syntax define-predicate opname? Defines a predicate @var{opname?}, usually used for determining the @dfn{type} of an object, such that @code{(@var{opname?} @var{object})} returns @code{#t} if @var{object} has an operation @var{opname?} and @code{#f} otherwise.@refill @end deffn @deffn Syntax object @code{((@var{name} @var{self} @var{arg} @dots{}) @var{body})} @dots{} Returns an object (an instance of the object system) with operations. Invoking @code{(@var{name} @var{object} @var{arg} @dots{}} executes the @var{body} of the @var{object} with @var{self} bound to @var{object} and with argument(s) @var{arg}@dots{}.@refill @end deffn @deffn Syntax object-with-ancestors @code{((}ancestor1 init1@code{)} @dots{}@code{)} operation @dots{} A @code{let}-like form of @code{object} for multiple inheritance. It returns an object inheriting the behaviour of @var{ancestor1} etc. An operation will be invoked in an ancestor if the object itself does not provide such a method. In the case of multiple inherited operations with the same identity, the operation used is the one found in the first ancestor in the ancestor list. @end deffn @deffn Syntax operate-as component operation self arg @dots{} Used in an operation definition (of @var{self}) to invoke the @var{operation} in an ancestor @var{component} but maintain the object's identity. Also known as ``send-to-super''.@refill @end deffn @deffn Procedure print obj port A default @code{print} operation is provided which is just @code{(format @var{port} @var{obj})} (@xref{Format}) for non-instances and prints @var{obj} preceded by @samp{#} for instances. @end deffn @defun size obj The default method returns the number of elements in @var{obj} if it is a vector, string or list, @code{2} for a pair, @code{1} for a character and by default id an error otherwise. Objects such as collections (@xref{Collections}) may override the default in an obvious way.@refill @end defun @node Setters, Yasos examples, Yasos interface, Yasos @subsection Setters @dfn{Setters} implement @dfn{generalized locations} for objects associated with some sort of mutable state. A @dfn{getter} operation retrieves a value from a generalized location and the corresponding setter operation stores a value into the location. Only the getter is named -- the setter is specified by a procedure call as below. (Dylan uses special syntax.) Typically, but not necessarily, getters are access operations to extract values from Yasos objects (@xref{Yasos}). Several setters are predefined, corresponding to getters @code{car}, @code{cdr}, @code{string-ref} and @code{vector-ref} e.g., @code{(setter car)} is equivalent to @code{set-car!}. This implementation of setters is similar to that in Dylan(TM) (@cite{Dylan: An object-oriented dynamic language}, Apple Computer Eastern Research and Technology). Common LISP provides similar facilities through @code{setf}. @defun setter getter Returns the setter for the procedure @var{getter}. E.g., since @code{string-ref} is the getter corresponding to a setter which is actually @code{string-set!}: @example (define foo "foo") ((setter string-ref) foo 0 #\F) ; set element 0 of foo foo @result{} "Foo" @end example @end defun @deffn Syntax set place new-value If @var{place} is a variable name, @code{set} is equivalent to @code{set!}. Otherwise, @var{place} must have the form of a procedure call, where the procedure name refers to a getter and the call indicates an accessible generalized location, i.e., the call would return a value. The return value of @code{set} is usually unspecified unless used with a setter whose definition guarantees to return a useful value. @example (set (string-ref foo 2) #\O) ; generalized location with getter foo @result{} "FoO" (set foo "foo") ; like set! foo @result{} "foo" @end example @end deffn @deffn Procedure add-setter getter setter Add procedures @var{getter} and @var{setter} to the (inaccessible) list of valid setter/getter pairs. @var{setter} implements the store operation corresponding to the @var{getter} access operation for the relevant state. The return value is unspecified. @end deffn @deffn Procedure remove-setter-for getter Removes the setter corresponding to the specified @var{getter} from the list of valid setters. The return value is unspecified. @end deffn @deffn Syntax define-access-operation getter-name Shorthand for a Yasos @code{define-operation} defining an operation @var{getter-name} that objects may support to return the value of some mutable state. The default operation is to signal an error. The return value is unspecified. @end deffn @node Yasos examples, , Setters, Yasos @subsection Examples @lisp ;;; These definitions for PRINT and SIZE are already supplied by (require 'yasos) (define-operation (print obj port) (format port (if (instance? obj) "#" "~s") obj)) (define-operation (size obj) (cond ((vector? obj) (vector-length obj)) ((list? obj) (length obj)) ((pair? obj) 2) ((string? obj) (string-length obj)) ((char? obj) 1) (else (error "Operation not supported: size" obj)))) (define-predicate cell?) (define-operation (fetch obj)) (define-operation (store! obj newValue)) (define (make-cell value) (object ((cell? self) #t) ((fetch self) value) ((store! self newValue) (set! value newValue) newValue) ((size self) 1) ((print self port) (format port "#" (fetch self))))) (define-operation (discard obj value) (format #t "Discarding ~s~%" value)) (define (make-filtered-cell value filter) (object-with-ancestors ((cell (make-cell value))) ((store! self newValue) (if (filter newValue) (store! cell newValue) (discard self newValue))))) (define-predicate array?) (define-operation (array-ref array index)) (define-operation (array-set! array index value)) (define (make-array num-slots) (let ((anArray (make-vector num-slots))) (object ((array? self) #t) ((size self) num-slots) ((array-ref self index) (vector-ref anArray index)) ((array-set! self index newValue) (vector-set! anArray index newValue)) ((print self port) (format port "#" (size self)))))) (define-operation (position obj)) (define-operation (discarded-value obj)) (define (make-cell-with-history value filter size) (let ((pos 0) (most-recent-discard #f)) (object-with-ancestors ((cell (make-filtered-call value filter)) (sequence (make-array size))) ((array? self) #f) ((position self) pos) ((store! self newValue) (operate-as cell store! self newValue) (array-set! self pos newValue) (set! pos (+ pos 1))) ((discard self value) (set! most-recent-discard value)) ((discarded-value self) most-recent-discard) ((print self port) (format port "#" (fetch self)))))) (define-access-operation fetch) (add-setter fetch store!) (define foo (make-cell 1)) (print foo #f) @result{} "#" (set (fetch foo) 2) @result{} (print foo #f) @result{} "#" (fetch foo) @result{} 2 @end lisp @node Textual Conversion Packages, Mathematical Packages, Scheme Syntax Extension Packages, Top @chapter Textual Conversion Packages @menu * Precedence Parsing:: * Format:: Common-Lisp Format * Standard Formatted I/O:: Posix printf and scanf * Program Arguments:: Commands and Options. * Printing Scheme:: Nicely * Time and Date:: * Vector Graphics:: @end menu @node Precedence Parsing, Format, Textual Conversion Packages, Textual Conversion Packages @section Precedence Parsing @code{(require 'precedence-parse)} or @code{(require 'parse)} @ftindex parse @ftindex precedence @noindent This package implements: @itemize @bullet @item a Pratt style precedence parser; @item a @dfn{tokenizer} which congeals tokens according to assigned classes of constituent characters; @item procedures giving direct control of parser rulesets; @item procedures for higher level specification of rulesets. @end itemize @menu * Precedence Parsing Overview:: * Ruleset Definition and Use:: * Token definition:: * Nud and Led Definition:: * Grammar Rule Definition:: @end menu @node Precedence Parsing Overview, Ruleset Definition and Use, Precedence Parsing, Precedence Parsing @subsection Precedence Parsing Overview @noindent This package offers improvements over previous parsers. @itemize @bullet @item Common computer language constructs are concisely specified. @item Grammars can be changed dynamically. Operators can be assigned different meanings within a lexical context. @item Rulesets don't need compilation. Grammars can be changed incrementally. @item Operator precedence is specified by integers. @item All possibilities of bad input are handled @footnote{How do I know this? I parsed 250kbyte of random input (an e-mail file) with a non-trivial grammar utilizing all constructs.} and return as much structure as was parsed when the error occured; The symbol @code{?} is substituted for missing input. @end itemize @noindent Here are the higher-level syntax types and an example of each. Precedence considerations are omitted for clarity. @xref{Grammar Rule Definition} for full details. @deftp Grammar nofix bye exit @example bye @end example calls the function @code{exit} with no arguments. @end deftp @deftp Grammar prefix - negate @example - 42 @end example Calls the function @code{negate} with the argument @code{42}. @end deftp @deftp Grammar infix - difference @example x - y @end example Calls the function @code{difference} with arguments @code{x} and @code{y}. @end deftp @deftp Grammar nary + sum @example x + y + z @end example Calls the function @code{sum} with arguments @code{x}, @code{y}, and @code{y}. @end deftp @deftp Grammar postfix ! factorial @example 5 ! @end example Calls the function @code{factorial} with the argument @code{5}. @end deftp @deftp Grammar prestfix set set! @example set foo bar @end example Calls the function @code{set!} with the arguments @code{foo} and @code{bar}. @end deftp @deftp Grammar commentfix /* */ @example /* almost any text here */ @end example Ignores the comment delimited by @code{/*} and @code{*/}. @end deftp @deftp Grammar matchfix @{ list @} @example @{0, 1, 2@} @end example Calls the function @code{list} with the arguments @code{0}, @code{1}, and @code{2}. @end deftp @deftp Grammar inmatchfix ( funcall ) @example f(x, y) @end example Calls the function @code{funcall} with the arguments @code{f}, @code{x}, and @code{y}. @end deftp @deftp Grammar delim ; @example set foo bar; @end example delimits the extent of the restfix operator @code{set}. @end deftp @node Ruleset Definition and Use, Token definition, Precedence Parsing Overview, Precedence Parsing @subsection Ruleset Definition and Use @defvar *syn-defs* A grammar is built by one or more calls to @code{prec:define-grammar}. The rules are appended to @var{*syn-defs*}. The value of @var{*syn-defs*} is the grammar suitable for passing as an argument to @code{prec:parse}. @end defvar @defvr Constant *syn-ignore-whitespace* Is a nearly empty grammar with whitespace characters set to group 0, which means they will not be made into tokens. Most rulesets will want to start with @code{*syn-ignore-whitespace*} @end defvr @noindent In order to start defining a grammar, either @example (set! *syn-defs* '()) @end example @noindent or @example (set! *syn-defs* *syn-ignore-whitespace*) @end example @defun prec:define-grammar rule1 @dots{} Appends @var{rule1} @dots{} to @var{*syn-defs*}. @code{prec:define-grammar} is used to define both the character classes and rules for tokens. @end defun @noindent Once your grammar is defined, save the value of @code{*syn-defs*} in a variable (for use when calling @code{prec:parse}). @example (define my-ruleset *syn-defs*) @end example @defun prec:parse ruleset delim @defunx prec:parse ruleset delim port The @var{ruleset} argument must be a list of rules as constructed by @code{prec:define-grammar} and extracted from @var{*syn-defs*}. The token @var{delim} may be a character, symbol, or string. A character @var{delim} argument will match only a character token; i.e. a character for which no token-group is assigned. A symbols or string will match only a token string; i.e. a token resulting from a token group. @code{prec:parse} reads a @var{ruleset} grammar expression delimited by @var{delim} from the given input @var{port}. @code{prec:parse} returns the next object parsable from the given input @var{port}, updating @var{port} to point to the first character past the end of the external representation of the object. If an end of file is encountered in the input before any characters are found that can begin an object, then an end of file object is returned. If a delimiter (such as @var{delim}) is found before any characters are found that can begin an object, then @code{#f} is returned. The @var{port} argument may be omitted, in which case it defaults to the value returned by @code{current-input-port}. It is an error to parse from a closed port. @findex current-input-port @end defun @node Token definition, Nud and Led Definition, Ruleset Definition and Use, Precedence Parsing @subsection Token definition @defun tok:char-group group chars chars-proc The argument @var{chars} may be a single character, a list of characters, or a string. Each character in @var{chars} is treated as though @code{tok:char-group} was called with that character alone. The argument @var{chars-proc} must be a procedure of one argument, a list of characters. After @code{tokenize} has finished accumulating the characters for a token, it calls @var{chars-proc} with the list of characters. The value returned is the token which @code{tokenize} returns. The argument @var{group} may be an exact integer or a procedure of one character argument. The following discussion concerns the treatment which the tokenizing routine, @code{tokenize}, will accord to characters on the basis of their groups. When @var{group} is a non-zero integer, characters whose group number is equal to or exactly one less than @var{group} will continue to accumulate. Any other character causes the accumulation to stop (until a new token is to be read). The @var{group} of zero is special. These characters are ignored when parsed pending a token, and stop the accumulation of token characters when the accumulation has already begun. Whitespace characters are usually put in group 0. If @var{group} is a procedure, then, when triggerd by the occurence of an initial (no accumulation) @var{chars} character, this procedure will be repeatedly called with each successive character from the input stream until the @var{group} procedure returns a non-false value. @end defun @noindent The following convenient constants are provided for use with @code{tok:char-group}. @defvr Constant tok:decimal-digits Is the string @code{"0123456789"}. @end defvr @defvr Constant tok:upper-case Is the string consisting of all upper-case letters ("ABCDEFGHIJKLMNOPQRSTUVWXYZ"). @end defvr @defvr Constant tok:lower-case Is the string consisting of all lower-case letters ("abcdefghijklmnopqrstuvwxyz"). @end defvr @defvr Constant tok:whitespaces Is the string consisting of all characters between 0 and 255 for which @code{char-whitespace?} returns true. @end defvr @node Nud and Led Definition, Grammar Rule Definition, Token definition, Precedence Parsing @subsection Nud and Led Definition This section describes advanced features. You can skip this section on first reading. @noindent The @dfn{Null Denotation} (or @dfn{nud}) @cindex Null Denotation, nud of a token is the procedure and arguments applying for that token when @dfn{Left}, an unclaimed parsed expression is not extant. @noindent The @dfn{Left Denotation} (or @dfn{led}) @cindex Left Denotation, led of a token is the procedure, arguments, and lbp applying for that token when there is a @dfn{Left}, an unclaimed parsed expression. @noindent In his paper, @quotation Pratt, V. R. Top Down Operator Precendence. @cite{SIGACT/SIGPLAN Symposium on Principles of Programming Languages}, Boston, 1973, pages 41-51 @end quotation the @dfn{left binding power} (or @dfn{lbp}) was an independent property of tokens. I think this was done in order to allow tokens with NUDs but not LEDs to also be used as delimiters, which was a problem for statically defined syntaxes. It turns out that @emph{dynamically binding} NUDs and LEDs allows them independence. @noindent For the rule-defining procedures that follow, the variable @var{tk} may be a character, string, or symbol, or a list composed of characters, strings, and symbols. Each element of @var{tk} is treated as though the procedure were called for each element. @noindent Character @var{tk} arguments will match only character tokens; i.e. characters for which no token-group is assigned. Symbols and strings will both match token strings; i.e. tokens resulting from token groups. @defun prec:make-nud tk sop arg1 @dots{} Returns a rule specifying that @var{sop} be called when @var{tk} is parsed. If @var{sop} is a procedure, it is called with @var{tk} and @var{arg1} @dots{} as its arguments; the resulting value is incorporated into the expression being built. Otherwise, @code{(list @var{sop} @var{arg1} @dots{})} is incorporated. @end defun @noindent If no NUD has been defined for a token; then if that token is a string, it is converted to a symbol and returned; if not a string, the token is returned. @defun prec:make-led tk sop arg1 @dots{} Returns a rule specifying that @var{sop} be called when @var{tk} is parsed and @var{left} has an unclaimed parsed expression. If @var{sop} is a procedure, it is called with @var{left}, @var{tk}, and @var{arg1} @dots{} as its arguments; the resulting value is incorporated into the expression being built. Otherwise, @var{left} is incorporated. @end defun @noindent If no LED has been defined for a token, and @var{left} is set, the parser issues a warning. @node Grammar Rule Definition, , Nud and Led Definition, Precedence Parsing @subsection Grammar Rule Definition @noindent Here are procedures for defining rules for the syntax types introduced in @ref{Precedence Parsing Overview}. @noindent For the rule-defining procedures that follow, the variable @var{tk} may be a character, string, or symbol, or a list composed of characters, strings, and symbols. Each element of @var{tk} is treated as though the procedure were called for each element. @noindent For procedures prec:delim, @dots{}, prec:prestfix, if the @var{sop} argument is @code{#f}, then the token which triggered this rule is converted to a symbol and returned. A false @var{sop} argument to the procedures prec:commentfix, prec:matchfix, or prec:inmatchfix has a different meaning. @noindent Character @var{tk} arguments will match only character tokens; i.e. characters for which no token-group is assigned. Symbols and strings will both match token strings; i.e. tokens resulting from token groups. @defun prec:delim tk Returns a rule specifying that @var{tk} should not be returned from parsing; i.e. @var{tk}'s function is purely syntactic. The end-of-file is always treated as a delimiter. @end defun @defun prec:nofix tk sop Returns a rule specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item If @var{sop} is a procedure, it is called with no arguments; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop} is incorporated. @end itemize @end defun @defun prec:prefix tk sop bp rule1 @dots{} Returns a rule specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item The rules @var{rule1} @dots{} augment and, in case of conflict, override rules currently in effect. @item @code{prec:parse1} is called with binding-power @var{bp}. @item If @var{sop} is a procedure, it is called with the expression returned from @code{prec:parse1}; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop} and the expression returned from @code{prec:parse1} is incorporated. @item The ruleset in effect before @var{tk} was parsed is restored; @var{rule1} @dots{} are forgotten. @end itemize @end defun @defun prec:infix tk sop lbp bp rule1 @dots{} Returns a rule declaring the left-binding-precedence of the token @var{tk} is @var{lbp} and specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item The rules @var{rule1} @dots{} augment and, in case of conflict, override rules currently in effect. @item One expression is parsed with binding-power @var{lbp}. If instead a delimiter is encountered, a warning is issued. @item If @var{sop} is a procedure, it is applied to the list of @var{left} and the parsed expression; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop}, the @var{left} expression, and the parsed expression is incorporated. @item The ruleset in effect before @var{tk} was parsed is restored; @var{rule1} @dots{} are forgotten. @end itemize @end defun @defun prec:nary tk sop bp Returns a rule declaring the left-binding-precedence of the token @var{tk} is @var{bp} and specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item Expressions are parsed with binding-power @var{bp} as far as they are interleaved with the token @var{tk}. @item If @var{sop} is a procedure, it is applied to the list of @var{left} and the parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop}, the @var{left} expression, and the parsed expressions is incorporated. @end itemize @end defun @defun prec:postfix tk sop lbp Returns a rule declaring the left-binding-precedence of the token @var{tk} is @var{lbp} and specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item If @var{sop} is a procedure, it is called with the @var{left} expression; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop} and the @var{left} expression is incorporated. @end itemize @end defun @defun prec:prestfix tk sop bp rule1 @dots{} Returns a rule specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item The rules @var{rule1} @dots{} augment and, in case of conflict, override rules currently in effect. @item Expressions are parsed with binding-power @var{bp} until a delimiter is reached. @item If @var{sop} is a procedure, it is applied to the list of parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop} and the parsed expressions is incorporated. @item The ruleset in effect before @var{tk} was parsed is restored; @var{rule1} @dots{} are forgotten. @end itemize @end defun @defun prec:commentfix tk stp match rule1 @dots{} Returns rules specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item The rules @var{rule1} @dots{} augment and, in case of conflict, override rules currently in effect. @item Characters are read untile and end-of-file or a sequence of characters is read which matches the @emph{string} @var{match}. @item If @var{stp} is a procedure, it is called with the string of all that was read between the @var{tk} and @var{match} (exclusive). @item The ruleset in effect before @var{tk} was parsed is restored; @var{rule1} @dots{} are forgotten. @end itemize Parsing of commentfix syntax differs from the others in several ways. It reads directly from input without tokenizing; It calls @var{stp} but does not return its value; nay any value. I added the @var{stp} argument so that comment text could be echoed. @end defun @defun prec:matchfix tk sop sep match rule1 @dots{} Returns a rule specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item The rules @var{rule1} @dots{} augment and, in case of conflict, override rules currently in effect. @item A rule declaring the token @var{match} a delimiter takes effect. @item Expressions are parsed with binding-power @code{0} until the token @var{match} is reached. If the token @var{sep} does not appear between each pair of expressions parsed, a warning is issued. @item If @var{sop} is a procedure, it is applied to the list of parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop} and the parsed expressions is incorporated. @item The ruleset in effect before @var{tk} was parsed is restored; @var{rule1} @dots{} are forgotten. @end itemize @end defun @defun prec:inmatchfix tk sop sep match lbp rule1 @dots{} Returns a rule declaring the left-binding-precedence of the token @var{tk} is @var{lbp} and specifying the following actions take place when @var{tk} is parsed: @itemize @bullet @item The rules @var{rule1} @dots{} augment and, in case of conflict, override rules currently in effect. @item A rule declaring the token @var{match} a delimiter takes effect. @item Expressions are parsed with binding-power @code{0} until the token @var{match} is reached. If the token @var{sep} does not appear between each pair of expressions parsed, a warning is issued. @item If @var{sop} is a procedure, it is applied to the list of @var{left} and the parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of @var{sop}, the @var{left} expression, and the parsed expressions is incorporated. @item The ruleset in effect before @var{tk} was parsed is restored; @var{rule1} @dots{} are forgotten. @end itemize @end defun @node Format, Standard Formatted I/O, Precedence Parsing, Textual Conversion Packages @section Format (version 3.0) @code{(require 'format)} @ftindex format @menu * Format Interface:: * Format Specification:: @end menu @node Format Interface, Format Specification, Format, Format @subsection Format Interface @defun format destination format-string . arguments An almost complete implementation of Common LISP format description according to the CL reference book @cite{Common LISP} from Guy L. Steele, Digital Press. Backward compatible to most of the available Scheme format implementations. Returns @code{#t}, @code{#f} or a string; has side effect of printing according to @var{format-string}. If @var{destination} is @code{#t}, the output is to the current output port and @code{#t} is returned. If @var{destination} is @code{#f}, a formatted string is returned as the result of the call. NEW: If @var{destination} is a string, @var{destination} is regarded as the format string; @var{format-string} is then the first argument and the output is returned as a string. If @var{destination} is a number, the output is to the current error port if available by the implementation. Otherwise @var{destination} must be an output port and @code{#t} is returned.@refill @var{format-string} must be a string. In case of a formatting error format returns @code{#f} and prints a message on the current output or error port. Characters are output as if the string were output by the @code{display} function with the exception of those prefixed by a tilde (~). For a detailed description of the @var{format-string} syntax please consult a Common LISP format reference manual. For a test suite to verify this format implementation load @file{formatst.scm}. Please send bug reports to @code{lutzeb@@cs.tu-berlin.de}. Note: @code{format} is not reentrant, i.e. only one @code{format}-call may be executed at a time. @end defun @node Format Specification, , Format Interface, Format @subsection Format Specification (Format version 3.0) Please consult a Common LISP format reference manual for a detailed description of the format string syntax. For a demonstration of the implemented directives see @file{formatst.scm}.@refill This implementation supports directive parameters and modifiers (@code{:} and @code{@@} characters). Multiple parameters must be separated by a comma (@code{,}). Parameters can be numerical parameters (positive or negative), character parameters (prefixed by a quote character (@code{'}), variable parameters (@code{v}), number of rest arguments parameter (@code{#}), empty and default parameters. Directive characters are case independent. The general form of a directive is:@refill @noindent @var{directive} ::= ~@{@var{directive-parameter},@}[:][@@]@var{directive-character} @noindent @var{directive-parameter} ::= [ [-|+]@{0-9@}+ | '@var{character} | v | # ] @subsubsection Implemented CL Format Control Directives Documentation syntax: Uppercase characters represent the corresponding control directive characters. Lowercase characters represent control directive parameter descriptions. @table @asis @item @code{~A} Any (print as @code{display} does). @table @asis @item @code{~@@A} left pad. @item @code{~@var{mincol},@var{colinc},@var{minpad},@var{padchar}A} full padding. @end table @item @code{~S} S-expression (print as @code{write} does). @table @asis @item @code{~@@S} left pad. @item @code{~@var{mincol},@var{colinc},@var{minpad},@var{padchar}S} full padding. @end table @item @code{~D} Decimal. @table @asis @item @code{~@@D} print number sign always. @item @code{~:D} print comma separated. @item @code{~@var{mincol},@var{padchar},@var{commachar}D} padding. @end table @item @code{~X} Hexadecimal. @table @asis @item @code{~@@X} print number sign always. @item @code{~:X} print comma separated. @item @code{~@var{mincol},@var{padchar},@var{commachar}X} padding. @end table @item @code{~O} Octal. @table @asis @item @code{~@@O} print number sign always. @item @code{~:O} print comma separated. @item @code{~@var{mincol},@var{padchar},@var{commachar}O} padding. @end table @item @code{~B} Binary. @table @asis @item @code{~@@B} print number sign always. @item @code{~:B} print comma separated. @item @code{~@var{mincol},@var{padchar},@var{commachar}B} padding. @end table @item @code{~@var{n}R} Radix @var{n}. @table @asis @item @code{~@var{n},@var{mincol},@var{padchar},@var{commachar}R} padding. @end table @item @code{~@@R} print a number as a Roman numeral. @item @code{~:R} print a number as an ordinal English number. @item @code{~:@@R} print a number as a cardinal English number. @item @code{~P} Plural. @table @asis @item @code{~@@P} prints @code{y} and @code{ies}. @item @code{~:P} as @code{~P but jumps 1 argument backward.} @item @code{~:@@P} as @code{~@@P but jumps 1 argument backward.} @end table @item @code{~C} Character. @table @asis @item @code{~@@C} prints a character as the reader can understand it (i.e. @code{#\} prefixing). @item @code{~:C} prints a character as emacs does (eg. @code{^C} for ASCII 03). @end table @item @code{~F} Fixed-format floating-point (prints a flonum like @var{mmm.nnn}). @table @asis @item @code{~@var{width},@var{digits},@var{scale},@var{overflowchar},@var{padchar}F} @item @code{~@@F} If the number is positive a plus sign is printed. @end table @item @code{~E} Exponential floating-point (prints a flonum like @var{mmm.nnn}@code{E}@var{ee}). @table @asis @item @code{~@var{width},@var{digits},@var{exponentdigits},@var{scale},@var{overflowchar},@var{padchar},@var{exponentchar}E} @item @code{~@@E} If the number is positive a plus sign is printed. @end table @item @code{~G} General floating-point (prints a flonum either fixed or exponential). @table @asis @item @code{~@var{width},@var{digits},@var{exponentdigits},@var{scale},@var{overflowchar},@var{padchar},@var{exponentchar}G} @item @code{~@@G} If the number is positive a plus sign is printed. @end table @item @code{~$} Dollars floating-point (prints a flonum in fixed with signs separated). @table @asis @item @code{~@var{digits},@var{scale},@var{width},@var{padchar}$} @item @code{~@@$} If the number is positive a plus sign is printed. @item @code{~:@@$} A sign is always printed and appears before the padding. @item @code{~:$} The sign appears before the padding. @end table @item @code{~%} Newline. @table @asis @item @code{~@var{n}%} print @var{n} newlines. @end table @item @code{~&} print newline if not at the beginning of the output line. @table @asis @item @code{~@var{n}&} prints @code{~&} and then @var{n-1} newlines. @end table @item @code{~|} Page Separator. @table @asis @item @code{~@var{n}|} print @var{n} page separators. @end table @item @code{~~} Tilde. @table @asis @item @code{~@var{n}~} print @var{n} tildes. @end table @item @code{~} Continuation Line. @table @asis @item @code{~:} newline is ignored, white space left. @item @code{~@@} newline is left, white space ignored. @end table @item @code{~T} Tabulation. @table @asis @item @code{~@@T} relative tabulation. @item @code{~@var{colnum,colinc}T} full tabulation. @end table @item @code{~?} Indirection (expects indirect arguments as a list). @table @asis @item @code{~@@?} extracts indirect arguments from format arguments. @end table @item @code{~(@var{str}~)} Case conversion (converts by @code{string-downcase}). @table @asis @item @code{~:(@var{str}~)} converts by @code{string-capitalize}. @item @code{~@@(@var{str}~)} converts by @code{string-capitalize-first}. @item @code{~:@@(@var{str}~)} converts by @code{string-upcase}. @end table @item @code{~*} Argument Jumping (jumps 1 argument forward). @table @asis @item @code{~@var{n}*} jumps @var{n} arguments forward. @item @code{~:*} jumps 1 argument backward. @item @code{~@var{n}:*} jumps @var{n} arguments backward. @item @code{~@@*} jumps to the 0th argument. @item @code{~@var{n}@@*} jumps to the @var{n}th argument (beginning from 0) @end table @item @code{~[@var{str0}~;@var{str1}~;...~;@var{strn}~]} Conditional Expression (numerical clause conditional). @table @asis @item @code{~@var{n}[} take argument from @var{n}. @item @code{~@@[} true test conditional. @item @code{~:[} if-else-then conditional. @item @code{~;} clause separator. @item @code{~:;} default clause follows. @end table @item @code{~@{@var{str}~@}} Iteration (args come from the next argument (a list)). @table @asis @item @code{~@var{n}@{} at most @var{n} iterations. @item @code{~:@{} args from next arg (a list of lists). @item @code{~@@@{} args from the rest of arguments. @item @code{~:@@@{} args from the rest args (lists). @end table @item @code{~^} Up and out. @table @asis @item @code{~@var{n}^} aborts if @var{n} = 0 @item @code{~@var{n},@var{m}^} aborts if @var{n} = @var{m} @item @code{~@var{n},@var{m},@var{k}^} aborts if @var{n} <= @var{m} <= @var{k} @end table @end table @subsubsection Not Implemented CL Format Control Directives @table @asis @item @code{~:A} print @code{#f} as an empty list (see below). @item @code{~:S} print @code{#f} as an empty list (see below). @item @code{~<~>} Justification. @item @code{~:^} (sorry I don't understand its semantics completely) @end table @subsubsection Extended, Replaced and Additional Control Directives @table @asis @item @code{~@var{mincol},@var{padchar},@var{commachar},@var{commawidth}D} @item @code{~@var{mincol},@var{padchar},@var{commachar},@var{commawidth}X} @item @code{~@var{mincol},@var{padchar},@var{commachar},@var{commawidth}O} @item @code{~@var{mincol},@var{padchar},@var{commachar},@var{commawidth}B} @item @code{~@var{n},@var{mincol},@var{padchar},@var{commachar},@var{commawidth}R} @var{commawidth} is the number of characters between two comma characters. @end table @table @asis @item @code{~I} print a R4RS complex number as @code{~F~@@Fi} with passed parameters for @code{~F}. @item @code{~Y} Pretty print formatting of an argument for scheme code lists. @item @code{~K} Same as @code{~?.} @item @code{~!} Flushes the output if format @var{destination} is a port. @item @code{~_} Print a @code{#\space} character @table @asis @item @code{~@var{n}_} print @var{n} @code{#\space} characters. @end table @item @code{~/} Print a @code{#\tab} character @table @asis @item @code{~@var{n}/} print @var{n} @code{#\tab} characters. @end table @item @code{~@var{n}C} Takes @var{n} as an integer representation for a character. No arguments are consumed. @var{n} is converted to a character by @code{integer->char}. @var{n} must be a positive decimal number.@refill @item @code{~:S} Print out readproof. Prints out internal objects represented as @code{#<...>} as strings @code{"#<...>"} so that the format output can always be processed by @code{read}. @refill @item @code{~:A} Print out readproof. Prints out internal objects represented as @code{#<...>} as strings @code{"#<...>"} so that the format output can always be processed by @code{read}. @item @code{~Q} Prints information and a copyright notice on the format implementation. @table @asis @item @code{~:Q} prints format version. @end table @refill @item @code{~F, ~E, ~G, ~$} may also print number strings, i.e. passing a number as a string and format it accordingly. @end table @subsubsection Configuration Variables Format has some configuration variables at the beginning of @file{format.scm} to suit the systems and users needs. There should be no modification necessary for the configuration that comes with SLIB. If modification is desired the variable should be set after the format code is loaded. Format detects automatically if the running scheme system implements floating point numbers and complex numbers. @table @asis @item @var{format:symbol-case-conv} Symbols are converted by @code{symbol->string} so the case type of the printed symbols is implementation dependent. @code{format:symbol-case-conv} is a one arg closure which is either @code{#f} (no conversion), @code{string-upcase}, @code{string-downcase} or @code{string-capitalize}. (default @code{#f}) @item @var{format:iobj-case-conv} As @var{format:symbol-case-conv} but applies for the representation of implementation internal objects. (default @code{#f}) @item @var{format:expch} The character prefixing the exponent value in @code{~E} printing. (default @code{#\E}) @end table @subsubsection Compatibility With Other Format Implementations @table @asis @item SLIB format 2.x: See @file{format.doc}. @item SLIB format 1.4: Downward compatible except for padding support and @code{~A}, @code{~S}, @code{~P}, @code{~X} uppercase printing. SLIB format 1.4 uses C-style @code{printf} padding support which is completely replaced by the CL @code{format} padding style. @item MIT C-Scheme 7.1: Downward compatible except for @code{~}, which is not documented (ignores all characters inside the format string up to a newline character). (7.1 implements @code{~a}, @code{~s}, ~@var{newline}, @code{~~}, @code{~%}, numerical and variable parameters and @code{:/@@} modifiers in the CL sense).@refill @item Elk 1.5/2.0: Downward compatible except for @code{~A} and @code{~S} which print in uppercase. (Elk implements @code{~a}, @code{~s}, @code{~~}, and @code{~%} (no directive parameters or modifiers)).@refill @item Scheme->C 01nov91: Downward compatible except for an optional destination parameter: S2C accepts a format call without a destination which returns a formatted string. This is equivalent to a #f destination in S2C. (S2C implements @code{~a}, @code{~s}, @code{~c}, @code{~%}, and @code{~~} (no directive parameters or modifiers)).@refill @end table This implementation of format is solely useful in the SLIB context because it requires other components provided by SLIB.@refill @node Standard Formatted I/O, Program Arguments, Format, Textual Conversion Packages @section Standard Formatted I/O @menu * Standard Formatted Output:: 'printf * Standard Formatted Input:: 'scanf @end menu @subsection stdio @code{(require 'stdio)} @ftindex stdio @code{require}s @code{printf} and @code{scanf} and additionally defines the symbols: @defvar stdin Defined to be @code{(current-input-port)}. @end defvar @defvar stdout Defined to be @code{(current-output-port)}. @end defvar @defvar stderr Defined to be @code{(current-error-port)}. @end defvar @node Standard Formatted Output, Standard Formatted Input, Standard Formatted I/O, Standard Formatted I/O @subsection Standard Formatted Output @code{(require 'printf)} @ftindex printf @deffn Procedure printf format arg1 @dots{} @deffnx Procedure fprintf port format arg1 @dots{} @deffnx Procedure sprintf str format arg1 @dots{} Each function converts, formats, and outputs its @var{arg1} @dots{} arguments according to the control string @var{format} argument and returns the number of characters output. @code{printf} sends its output to the port @code{(current-output-port)}. @code{fprintf} sends its output to the port @var{port}. @code{sprintf} @code{string-set!}s locations of the non-constant string argument @var{str} to the output characters. @quotation @emph{Note:} sprintf should be changed to a macro so a @code{substring} expression could be used for the @var{str} argument. @end quotation The string @var{format} contains plain characters which are copied to the output stream, and conversion specifications, each of which results in fetching zero or more of the arguments @var{arg1} @dots{}. The results are undefined if there are an insufficient number of arguments for the format. If @var{format} is exhausted while some of the @var{arg1} @dots{} arguments remain unused, the excess @var{arg1} @dots{} arguments are ignored. The conversion specifications in a format string have the form: @example % @r{[} @var{flags} @r{]} @r{[} @var{width} @r{]} @r{[} . @var{precision} @r{]} @r{[} @var{type} @r{]} @var{conversion} @end example An output conversion specifications consist of an initial @samp{%} character followed in sequence by: @itemize @bullet @item Zero or more @dfn{flag characters} that modify the normal behavior of the conversion specification. @table @asis @item @samp{-} Left-justify the result in the field. Normally the result is right-justified. @item @samp{+} For the signed @samp{%d} and @samp{%i} conversions and all inexact conversions, prefix a plus sign if the value is positive. @item @samp{ } For the signed @samp{%d} and @samp{%i} conversions, if the result doesn't start with a plus or minus sign, prefix it with a space character instead. Since the @samp{+} flag ensures that the result includes a sign, this flag is ignored if both are specified. @item @samp{#} For inexact conversions, @samp{#} specifies that the result should always include a decimal point, even if no digits follow it. For the @samp{%g} and @samp{%G} conversions, this also forces trailing zeros after the decimal point to be printed where they would otherwise be elided. For the @samp{%o} conversion, force the leading digit to be @samp{0}, as if by increasing the precision. For @samp{%x} or @samp{%X}, prefix a leading @samp{0x} or @samp{0X} (respectively) to the result. This doesn't do anything useful for the @samp{%d}, @samp{%i}, or @samp{%u} conversions. Using this flag produces output which can be parsed by the @code{scanf} functions with the @samp{%i} conversion (@pxref{Standard Formatted Input}). @item @samp{0} Pad the field with zeros instead of spaces. The zeros are placed after any indication of sign or base. This flag is ignored if the @samp{-} flag is also specified, or if a precision is specified for an exact converson. @end table @item An optional decimal integer specifying the @dfn{minimum field width}. If the normal conversion produces fewer characters than this, the field is padded (with spaces or zeros per the @samp{0} flag) to the specified width. This is a @emph{minimum} width; if the normal conversion produces more characters than this, the field is @emph{not} truncated. @cindex minimum field width (@code{printf}) Alternatively, if the field width is @samp{*}, the next argument in the argument list (before the actual value to be printed) is used as the field width. The width value must be an integer. If the value is negative it is as though the @samp{-} flag is set (see above) and the absolute value is used as the field width. @item An optional @dfn{precision} to specify the number of digits to be written for numeric conversions and the maximum field width for string conversions. The precision is specified by a period (@samp{.}) followed optionally by a decimal integer (which defaults to zero if omitted). @cindex precision (@code{printf}) Alternatively, if the precision is @samp{.*}, the next argument in the argument list (before the actual value to be printed) is used as the precision. The value must be an integer, and is ignored if negative. If you specify @samp{*} for both the field width and precision, the field width argument precedes the precision argument. The @samp{.*} precision is an enhancement. C library versions may not accept this syntax. For the @samp{%f}, @samp{%e}, and @samp{%E} conversions, the precision specifies how many digits follow the decimal-point character. The default precision is @code{6}. If the precision is explicitly @code{0}, the decimal point character is suppressed. For the @samp{%g} and @samp{%G} conversions, the precision specifies how many significant digits to print. Significant digits are the first digit before the decimal point, and all the digits after it. If the precision is @code{0} or not specified for @samp{%g} or @samp{%G}, it is treated like a value of @code{1}. If the value being printed cannot be expressed accurately in the specified number of digits, the value is rounded to the nearest number that fits. For exact conversions, if a precision is supplied it specifies the minimum number of digits to appear; leading zeros are produced if necessary. If a precision is not supplied, the number is printed with as many digits as necessary. Converting an exact @samp{0} with an explicit precision of zero produces no characters. @item An optional one of @samp{l}, @samp{h} or @samp{L}, which is ignored for numeric conversions. It is an error to specify these modifiers for non-numeric conversions. @item A character that specifies the conversion to be applied. @end itemize @subsubsection Exact Conversions @table @asis @item @samp{d}, @samp{i} Print an integer as a signed decimal number. @samp{%d} and @samp{%i} are synonymous for output, but are different when used with @code{scanf} for input (@pxref{Standard Formatted Input}). @item @samp{o} Print an integer as an unsigned octal number. @item @samp{u} Print an integer as an unsigned decimal number. @item @samp{x}, @samp{X} Print an integer as an unsigned hexadecimal number. @samp{%x} prints using the digits @samp{0123456789abcdef}. @samp{%X} prints using the digits @samp{0123456789ABCDEF}. @end table @subsubsection Inexact Conversions @emph{Note:} Inexact conversions are not supported yet. @table @asis @item @samp{f} Print a floating-point number in fixed-point notation. @item @samp{e}, @samp{E} Print a floating-point number in exponential notation. @samp{%e} prints @samp{e} between mantissa and exponont. @samp{%E} prints @samp{E} between mantissa and exponont. @item @samp{g}, @samp{G} Print a floating-point number in either normal or exponential notation, whichever is more appropriate for its magnitude. @samp{%g} prints @samp{e} between mantissa and exponont. @samp{%G} prints @samp{E} between mantissa and exponont. @end table @subsubsection Other Conversions @table @asis @item @samp{c} Print a single character. The @samp{-} flag is the only one which can be specified. It is an error to specify a precision. @item @samp{s} Print a string. The @samp{-} flag is the only one which can be specified. A precision specifies the maximum number of characters to output; otherwise all characters in the string are output. @item @samp{a}, @samp{A} Print a scheme expression. The @samp{-} flag left-justifies the output. The @samp{#} flag specifies that strings and characters should be quoted as by @code{write} (which can be read using @code{read}); otherwise, output is as @code{display} prints. A precision specifies the maximum number of characters to output; otherwise as many characters as needed are output. @emph{Note:} @samp{%a} and @samp{%A} are SLIB extensions. @c @item @samp{p} @c Print the value of a pointer. @c @item @samp{n} @c Get the number of characters printed so far. @xref{Other Output Conversions}. @c Note that this conversion specification never produces any output. @c @item @samp{m} @c Print the string corresponding to the value of @code{errno}. @c (This is a GNU extension.) @c @xref{Other Output Conversions}. @item @samp{%} Print a literal @samp{%} character. No argument is consumed. It is an error to specifiy flags, field width, precision, or type modifiers with @samp{%%}. @end table @end deffn @node Standard Formatted Input, , Standard Formatted Output, Standard Formatted I/O @subsection Standard Formatted Input @code{(require 'scanf)} @ftindex scanf @deffn Function scanf-read-list format @deffnx Function scanf-read-list format port @deffnx Function scanf-read-list format string @end deffn @defmac scanf format arg1 @dots{} @defmacx fscanf port format arg1 @dots{} @defmacx sscanf str format arg1 @dots{} Each function reads characters, interpreting them according to the control string @var{format} argument. @code{scanf-read-list} returns a list of the items specified as far as the input matches @var{format}. @code{scanf}, @code{fscanf}, and @code{sscanf} return the number of items successfully matched and stored. @code{scanf}, @code{fscanf}, and @code{sscanf} also set the location corresponding to @var{arg1} @dots{} using the methods: @table @asis @item symbol @code{set!} @item car expression @code{set-car!} @item cdr expression @code{set-cdr!} @item vector-ref expression @code{vector-set!} @item substring expression @code{substring-move-left!} @end table The argument to a @code{substring} expression in @var{arg1} @dots{} must be a non-constant string. Characters will be stored starting at the position specified by the second argument to @code{substring}. The number of characters stored will be limited by either the position specified by the third argument to @code{substring} or the length of the matched string, whichever is less. The control string, @var{format}, contains conversion specifications and other characters used to direct interpretation of input sequences. The control string contains: @itemize @bullet @item White-space characters (blanks, tabs, newlines, or formfeeds) that cause input to be read (and discarded) up to the next non-white-space character. @item An ordinary character (not @samp{%}) that must match the next character of the input stream. @item Conversion specifications, consisting of the character @samp{%}, an optional assignment suppressing character @samp{*}, an optional numerical maximum-field width, an optional @samp{l}, @samp{h} or @samp{L} which is ignored, and a conversion code. @c @item The conversion specification can alternatively be prefixed by @c the character sequence @samp{%n$} instead of the character @samp{%}, @c where @var{n} is a decimal integer in the range. The @samp{%n$} @c construction indicates that the value of the next input field should be @c placed in the @var{n}th place in the return list, rather than to the next @c unused one. The two forms of introducing a conversion specification, @c @samp{%} and @samp{%n$}, must not be mixed within a single format string @c with the following exception: Skip fields (see below) can be designated @c as @samp{%*} or @samp{%n$*}. In the latter case, @var{n} is ignored. @end itemize Unless the specification contains the @samp{n} conversion character (described below), a conversion specification directs the conversion of the next input field. The result of a conversion specification is returned in the position of the corresponding argument points, unless @samp{*} indicates assignment suppression. Assignment suppression provides a way to describe an input field to be skipped. An input field is defined as a string of characters; it extends to the next inappropriate character or until the field width, if specified, is exhausted. @quotation @emph{Note:} This specification of format strings differs from the @cite{ANSI C} and @cite{POSIX} specifications. In SLIB, white space before an input field is not skipped unless white space appears before the conversion specification in the format string. In order to write format strings which work identically with @cite{ANSI C} and SLIB, prepend whitespace to all conversion specifications except @samp{[} and @samp{c}. @end quotation The conversion code indicates the interpretation of the input field; For a suppressed field, no value is returned. The following conversion codes are legal: @table @asis @item @samp{%} A single % is expected in the input at this point; no value is returned. @item @samp{d}, @samp{D} A decimal integer is expected. @item @samp{u}, @samp{U} An unsigned decimal integer is expected. @item @samp{o}, @samp{O} An octal integer is expected. @item @samp{x}, @samp{X} A hexadecimal integer is expected. @item @samp{i} An integer is expected. Returns the value of the next input item, interpreted according to C conventions; a leading @samp{0} implies octal, a leading @samp{0x} implies hexadecimal; otherwise, decimal is assumed. @item @samp{n} Returns the total number of bytes (including white space) read by @code{scanf}. No input is consumed by @code{%n}. @item @samp{f}, @samp{F}, @samp{e}, @samp{E}, @samp{g}, @samp{G} A floating-point number is expected. The input format for floating-point numbers is an optionally signed string of digits, possibly containing a radix character @samp{.}, followed by an optional exponent field consisting of an @samp{E} or an @samp{e}, followed by an optional @samp{+}, @samp{-}, or space, followed by an integer. @item @samp{c}, @samp{C} @var{Width} characters are expected. The normal skip-over-white-space is suppressed in this case; to read the next non-space character, use @samp{%1s}. If a field width is given, a string is returned; up to the indicated number of characters is read. @item @samp{s}, @samp{S} A character string is expected The input field is terminated by a white-space character. @code{scanf} cannot read a null string. @item @samp{[} Indicates string data and the normal skip-over-leading-white-space is suppressed. The left bracket is followed by a set of characters, called the scanset, and a right bracket; the input field is the maximal sequence of input characters consisting entirely of characters in the scanset. @samp{^}, when it appears as the first character in the scanset, serves as a complement operator and redefines the scanset as the set of all characters not contained in the remainder of the scanset string. Construction of the scanset follows certain conventions. A range of characters may be represented by the construct first-last, enabling @samp{[0123456789]} to be expressed @samp{[0-9]}. Using this convention, first must be lexically less than or equal to last; otherwise, the dash stands for itself. The dash also stands for itself when it is the first or the last character in the scanset. To include the right square bracket as an element of the scanset, it must appear as the first character (possibly preceded by a @samp{^}) of the scanset, in which case it will not be interpreted syntactically as the closing bracket. At least one character must match for this conversion to succeed. @end table The @code{scanf} functions terminate their conversions at end-of-file, at the end of the control string, or when an input character conflicts with the control string. In the latter case, the offending character is left unread in the input stream. @end defmac @node Program Arguments, Printing Scheme, Standard Formatted I/O, Textual Conversion Packages @section Program Arguments @menu * Getopt:: Command Line option parsing * Command Line:: A command line reader for Scheme shells * Parameter lists:: 'parameters * Batch:: 'batch @end menu @node Getopt, Command Line, Program Arguments, Program Arguments @subsection Getopt @code{(require 'getopt)} @ftindex getopt This routine implements Posix command line argument parsing. Notice that returning values through global variables means that @code{getopt} is @emph{not} reentrant. @defvar *optind* Is the index of the current element of the command line. It is initially one. In order to parse a new command line or reparse an old one, @var{*opting*} must be reset. @end defvar @defvar *optarg* Is set by getopt to the (string) option-argument of the current option. @end defvar @deffn Procedure getopt argc argv optstring Returns the next option letter in @var{argv} (starting from @code{(vector-ref argv *optind*)}) that matches a letter in @var{optstring}. @var{argv} is a vector or list of strings, the 0th of which getopt usually ignores. @var{argc} is the argument count, usually the length of @var{argv}. @var{optstring} is a string of recognized option characters; if a character is followed by a colon, the option takes an argument which may be immediately following it in the string or in the next element of @var{argv}. @var{*optind*} is the index of the next element of the @var{argv} vector to be processed. It is initialized to 1 by @file{getopt.scm}, and @code{getopt} updates it when it finishes with each element of @var{argv}. @code{getopt} returns the next option character from @var{argv} that matches a character in @var{optstring}, if there is one that matches. If the option takes an argument, @code{getopt} sets the variable @var{*optarg*} to the option-argument as follows: @itemize @bullet @item If the option was the last character in the string pointed to by an element of @var{argv}, then @var{*optarg*} contains the next element of @var{argv}, and @var{*optind*} is incremented by 2. If the resulting value of @var{*optind*} is greater than or equal to @var{argc}, this indicates a missing option argument, and @code{getopt} returns an error indication. @item Otherwise, @var{*optarg*} is set to the string following the option character in that element of @var{argv}, and @var{*optind*} is incremented by 1. @end itemize If, when @code{getopt} is called, the string @code{(vector-ref argv *optind*)} either does not begin with the character @code{#\-} or is just @code{"-"}, @code{getopt} returns @code{#f} without changing @var{*optind*}. If @code{(vector-ref argv *optind*)} is the string @code{"--"}, @code{getopt} returns @code{#f} after incrementing @var{*optind*}. If @code{getopt} encounters an option character that is not contained in @var{optstring}, it returns the question-mark @code{#\?} character. If it detects a missing option argument, it returns the colon character @code{#\:} if the first character of @var{optstring} was a colon, or a question-mark character otherwise. In either case, @code{getopt} sets the variable @var{getopt:opt} to the option character that caused the error. The special option @code{"--"} can be used to delimit the end of the options; @code{#f} is returned, and @code{"--"} is skipped. RETURN VALUE @code{getopt} returns the next option character specified on the command line. A colon @code{#\:} is returned if @code{getopt} detects a missing argument and the first character of @var{optstring} was a colon @code{#\:}. A question-mark @code{#\?} is returned if @code{getopt} encounters an option character not in @var{optstring} or detects a missing argument and the first character of @var{optstring} was not a colon @code{#\:}. Otherwise, @code{getopt} returns @code{#f} when all command line options have been parsed. Example: @lisp #! /usr/local/bin/scm ;;;This code is SCM specific. (define argv (program-arguments)) (require 'getopt) @ftindex getopt (define opts ":a:b:cd") (let loop ((opt (getopt (length argv) argv opts))) (case opt ((#\a) (print "option a: " *optarg*)) ((#\b) (print "option b: " *optarg*)) ((#\c) (print "option c")) ((#\d) (print "option d")) ((#\?) (print "error" getopt:opt)) ((#\:) (print "missing arg" getopt:opt)) ((#f) (if (< *optind* (length argv)) (print "argv[" *optind* "]=" (list-ref argv *optind*))) (set! *optind* (+ *optind* 1)))) (if (< *optind* (length argv)) (loop (getopt (length argv) argv opts)))) (slib:exit) @end lisp @end deffn @subsection Getopt-- @defun getopt-- argc argv optstring The procedure @code{getopt--} is an extended version of @code{getopt} which parses @dfn{long option names} of the form @samp{--hold-the-onions} and @samp{--verbosity-level=extreme}. @w{@code{Getopt--}} behaves as @code{getopt} except for non-empty options beginning with @samp{--}. Options beginning with @samp{--} are returned as strings rather than characters. If a value is assigned (using @samp{=}) to a long option, @code{*optarg*} is set to the value. The @samp{=} and value are not returned as part of the option string. No information is passed to @code{getopt--} concerning which long options should be accepted or whether such options can take arguments. If a long option did not have an argument, @code{*optarg} will be set to @code{#f}. The caller is responsible for detecting and reporting errors. @example (define opts ":-:b:") (define argc 5) (define argv '("foo" "-b9" "--f1" "--2=" "--g3=35234.342" "--")) (define *optind* 1) (define *optarg* #f) (require 'qp) @ftindex qp (do ((i 5 (+ -1 i))) ((zero? i)) (define opt (getopt-- argc argv opts)) (print *optind* opt *optarg*))) @print{} 2 #\b "9" 3 "f1" #f 4 "2" "" 5 "g3" "35234.342" 5 #f "35234.342" @end example @end defun @node Command Line, Parameter lists, Getopt, Program Arguments @subsection Command Line @code{(require 'read-command)} @ftindex read-command @defun read-command port @defunx read-command @code{read-command} converts a @dfn{command line} into a list of strings @cindex command line suitable for parsing by @code{getopt}. The syntax of command lines supported resembles that of popular @dfn{shell}s. @code{read-command} updates @var{port} to point to the first character past the command delimiter. If an end of file is encountered in the input before any characters are found that can begin an object or comment, then an end of file object is returned. The @var{port} argument may be omitted, in which case it defaults to the value returned by @code{current-input-port}. The fields into which the command line is split are delimited by whitespace as defined by @code{char-whitespace?}. The end of a command is delimited by end-of-file or unescaped semicolon (@key{;}) or @key{newline}. Any character can be literally included in a field by escaping it with a backslach (@key{\}). The initial character and types of fields recognized are: @table @asis @item @samp{\} The next character has is taken literally and not interpreted as a field delimiter. If @key{\} is the last character before a @key{newline}, that @key{newline} is just ignored. Processing continues from the characters after the @key{newline} as though the backslash and @key{newline} were not there. @item @samp{"} The characters up to the next unescaped @key{"} are taken literally, according to [R4RS] rules for literal strings (@pxref{Strings, , ,r4rs, Revised(4) Scheme}). @item @samp{(}, @samp{%'} One scheme expression is @code{read} starting with this character. The @code{read} expression is evaluated, converted to a string (using @code{display}), and replaces the expression in the returned field. @item @samp{;} Semicolon delimits a command. Using semicolons more than one command can appear on a line. Escaped semicolons and semicolons inside strings do not delimit commands. @end table @noindent The comment field differs from the previous fields in that it must be the first character of a command or appear after whitespace in order to be recognized. @key{#} can be part of fields if these conditions are not met. For instance, @code{ab#c} is just the field ab#c. @table @samp @item # Introduces a comment. The comment continues to the end of the line on which the semicolon appears. Comments are treated as whitespace by @code{read-dommand-line} and backslashes before @key{newline}s in comments are also ignored. @end table @end defun @defun read-options-file filename @code{read-options-file} converts an @dfn{options file} into a list of @cindex options file strings suitable for parsing by @code{getopt}. The syntax of options files is the same as the syntax for command lines, except that @key{newline}s do not terminate reading (only @key{;} or end of file). If an end of file is encountered before any characters are found that can begin an object or comment, then an end of file object is returned. @end defun @node Parameter lists, Batch, Command Line, Program Arguments @subsection Parameter lists @code{(require 'parameters)} @ftindex parameters @noindent Arguments to procedures in scheme are distinguished from each other by their position in the procedure call. This can be confusing when a procedure takes many arguments, many of which are not often used. @noindent A @dfn{parameter-list} is a way of passing named information to a procedure. Procedures are also defined to set unused parameters to default values, check parameters, and combine parameter lists. @noindent A @var{parameter} has the form @code{(@r{parameter-name} @r{value1} @dots{})}. This format allows for more than one value per parameter-name. @noindent A @var{parameter-list} is a list of @var{parameter}s, each with a different @var{parameter-name}. @deffn Function make-parameter-list parameter-names Returns an empty parameter-list with slots for @var{parameter-names}. @end deffn @deffn Function parameter-list-ref parameter-list parameter-name @var{parameter-name} must name a valid slot of @var{parameter-list}. @code{parameter-list-ref} returns the value of parameter @var{parameter-name} of @var{parameter-list}. @end deffn @deffn Procedure adjoin-parameters! parameter-list parameter1 @dots{} Returns @var{parameter-list} with @var{parameter1} @dots{} merged in. @end deffn @deffn Procedure parameter-list-expand expanders parameter-list @var{expanders} is a list of procedures whose order matches the order of the @var{parameter-name}s in the call to @code{make-parameter-list} which created @var{parameter-list}. For each non-false element of @var{expanders} that procedure is mapped over the corresponding parameter value and the returned parameter lists are merged into @var{parameter-list}. This process is repeated until @var{parameter-list} stops growing. The value returned from @code{parameter-list-expand} is unspecified. @end deffn @deffn Function fill-empty-parameters defaulters parameter-list @var{defaulters} is a list of procedures whose order matches the order of the @var{parameter-name}s in the call to @code{make-parameter-list} which created @var{parameter-list}. @code{fill-empty-parameters} returns a new parameter-list with each empty parameter replaced with the list returned by calling the corresponding @var{defaulter} with @var{parameter-list} as its argument. @end deffn @deffn Function check-parameters checks parameter-list @var{checks} is a list of procedures whose order matches the order of the @var{parameter-name}s in the call to @code{make-parameter-list} which created @var{parameter-list}. @code{check-parameters} returns @var{parameter-list} if each @var{check} of the corresponding @var{parameter-list} returns non-false. If some @var{check} returns @code{#f} an error is signaled. @end deffn @noindent In the following procedures @var{arities} is a list of symbols. The elements of @code{arities} can be: @table @code @item single Requires a single parameter. @item optional A single parameter or no parameter is acceptable. @item boolean A single boolean parameter or zero parameters is acceptable. @item nary Any number of parameters are acceptable. @item nary1 One or more of parameters are acceptable. @end table @deffn Function parameter-list->arglist positions arities types parameter-list Returns @var{parameter-list} converted to an argument list. Parameters of @var{arity} type @code{single} and @code{boolean} are converted to the single value associated with them. The other @var{arity} types are converted to lists of the value(s) of type @var{types}. @var{positions} is a list of positive integers whose order matches the order of the @var{parameter-name}s in the call to @code{make-parameter-list} which created @var{parameter-list}. The integers specify in which argument position the corresponding parameter should appear. @end deffn @deffn Function getopt->parameter-list argc argv optnames arities types aliases Returns @var{argv} converted to a parameter-list. @var{optnames} are the parameter-names. @var{aliases} is a list of lists of strings and elements of @var{optnames}. Each of these strings which have length of 1 will be treated as a single @key{-} option by @code{getopt}. Longer strings will be treated as long-named options (@pxref{Getopt, getopt--}). @end deffn @deffn Function getopt->arglist argc argv optnames positions arities types defaulters checks aliases Like @code{getopt->parameter-list}, but converts @var{argv} to an argument-list as specified by @var{optnames}, @var{positions}, @var{arities}, @var{types}, @var{defaulters}, @var{checks}, and @var{aliases}. @end deffn @noindent These @code{getopt} functions can be used with SLIB relational databases. For an example, @xref{Database Utilities, make-command-server}. @noindent If errors are encountered while processing options, directions for using the options are printed to @code{current-error-port}. @example (begin (set! *optind* 1) (getopt->parameter-list 2 '("cmd" "-?") '(flag number symbols symbols string flag2 flag3 num2 num3) '(boolean optional nary1 nary single boolean boolean nary nary) '(boolean integer symbol symbol string boolean boolean integer integer) '(("flag" flag) ("f" flag) ("Flag" flag2) ("B" flag3) ("optional" number) ("o" number) ("nary1" symbols) ("N" symbols) ("nary" symbols) ("n" symbols) ("single" string) ("s" string) ("a" num2) ("Abs" num3)))) @print{} Usage: cmd [OPTION ARGUMENT ...] ... -f, --flag -o, --optional= -n, --nary= ... -N, --nary1= ... -s, --single= --Flag -B -a ... --Abs= ... ERROR: getopt->parameter-list "unrecognized option" "-?" @end example @node Batch, , Parameter lists, Program Arguments @subsection Batch @code{(require 'batch)} @ftindex batch @noindent The batch procedures provide a way to write and execute portable scripts for a variety of operating systems. Each @code{batch:} procedure takes as its first argument a parameter-list (@pxref{Parameter lists}). This parameter-list argument @var{parms} contains named associations. Batch currently uses 2 of these: @table @code @item batch-port The port on which to write lines of the batch file. @item batch-dialect The syntax of batch file to generate. Currently supported are: @itemize @bullet @item unix @item dos @item vms @item system @item *unknown* @end itemize @end table @noindent @file{batch.scm} uses 2 enhanced relational tables (@pxref{Database Utilities}) to store information linking the names of @code{operating-system}s to @code{batch-dialect}es. @defun batch:initialize! database Defines @code{operating-system} and @code{batch-dialect} tables and adds the domain @code{operating-system} to the enhanced relational database @var{database}. @end defun @defvar batch:platform Is batch's best guess as to which operating-system it is running under. @code{batch:platform} is set to @code{(software-type)} (@pxref{Configuration}) unless @code{(software-type)} is @code{unix}, in which case finer distinctions are made. @end defvar @defun batch:call-with-output-script parms file proc @var{proc} should be a procedure of one argument. If @var{file} is an output-port, @code{batch:call-with-output-script} writes an appropriate header to @var{file} and then calls @var{proc} with @var{file} as the only argument. If @var{file} is a string, @code{batch:call-with-output-script} opens a output-file of name @var{file}, writes an appropriate header to @var{file}, and then calls @var{proc} with the newly opened port as the only argument. Otherwise, @code{batch:call-with-output-script} acts as if it was called with the result of @code{(current-output-port)} as its third argument. @end defun @defun batch:apply-chop-to-fit proc arg1 arg2 @dots{} list The procedure @var{proc} must accept at least one argument and return @code{#t} if successful, @code{#f} if not. @code{batch:apply-chop-to-fit} calls @var{proc} with @var{arg1}, @var{arg2}, @dots{}, and @var{chunk}, where @var{chunk} is a subset of @var{list}. @code{batch:apply-chop-to-fit} tries @var{proc} with successively smaller subsets of @var{list} until either @var{proc} returns non-false, or the @var{chunk}s become empty. @end defun @noindent The rest of the @code{batch:} procedures write (or execute if @code{batch-dialect} is @code{system}) commands to the batch port which has been added to @var{parms} or @code{(copy-tree @var{parms})} by the code: @example (adjoin-parameters! @var{parms} (list 'batch-port @var{port})) @end example @defun batch:system parms string1 string2 @dots{} Calls @code{batch:try-system} (below) with arguments, but signals an error if @code{batch:try-system} returns @code{#f}. @end defun @noindent These functions return a non-false value if the command was successfully translated into the batch dialect and @code{#f} if not. In the case of the @code{system} dialect, the value is non-false if the operation suceeded. @defun batch:try-system parms string1 string2 @dots{} Writes a command to the @code{batch-port} in @var{parms} which executes the program named @var{string1} with arguments @var{string2} @dots{}. @end defun @defun batch:run-script parms string1 string2 @dots{} Writes a command to the @code{batch-port} in @var{parms} which executes the batch script named @var{string1} with arguments @var{string2} @dots{}. @emph{Note:} @code{batch:run-script} and @code{batch:try-system} are not the same for some operating systems (VMS). @end defun @defun batch:comment parms line1 @dots{} Writes comment lines @var{line1} @dots{} to the @code{batch-port} in @var{parms}. @end defun @defun batch:lines->file parms file line1 @dots{} Writes commands to the @code{batch-port} in @var{parms} which create a file named @var{file} with contents @var{line1} @dots{}. @end defun @defun batch:delete-file parms file Writes a command to the @code{batch-port} in @var{parms} which deletes the file named @var{file}. @end defun @defun batch:rename-file parms old-name new-name Writes a command to the @code{batch-port} in @var{parms} which renames the file @var{old-name} to @var{new-name}. @end defun @noindent In addition, batch provides some small utilities very useful for writing scripts: @defun truncate-up-to path char @defunx truncate-up-to path string @defunx truncate-up-to path charlist @var{path} can be a string or a list of strings. Returns @var{path} sans any prefixes ending with a character of the second argument. This can be used to derive a filename moved locally from elsewhere. @example (truncate-up-to "/usr/local/lib/slib/batch.scm" "/") @result{} "batch.scm" @end example @end defun @defun replace-suffix str old new @var{str} can be a string or a list of strings. Returns a new string (or strings) similar to @code{str} but with the suffix string @var{old} removed and the suffix string @var{new} appended. If the end of @var{str} does not match @var{old}, an error is signaled. @example (replace-suffix "/usr/local/lib/slib/batch.scm" ".scm" ".c") @result{} "/usr/local/lib/slib/batch.c" @end example @end defun @defun string-join joiner string1 @dots{} Returns a new string consisting of all the strings @var{string1} @dots{} in order appended together with the string @var{joiner} between each adjacent pair. @end defun @defun must-be-first list1 list2 Returns a new list consisting of the elements of @var{list2} ordered so that if some elements of @var{list1} are @code{equal?} to elements of @var{list2}, then those elements will appear first and in the order of @var{list1}. @end defun @defun must-be-last list1 list2 Returns a new list consisting of the elements of @var{list1} ordered so that if some elements of @var{list2} are @code{equal?} to elements of @var{list1}, then those elements will appear last and in the order of @var{list2}. @end defun @defun os->batch-dialect osname Returns its best guess for the @code{batch-dialect} to be used for the operating-system named @var{osname}. @code{os->batch-dialect} uses the tables added to @var{database} by @code{batch:initialize!}. @end defun @noindent Here is an example of the use of most of batch's procedures: @example (require 'database-utilities) @ftindex database-utilities (require 'parameters) @ftindex parameters (require 'batch) @ftindex batch (define batch (create-database #f 'alist-table)) (batch:initialize! batch) (define my-parameters (list (list 'batch-dialect (os->batch-dialect batch:platform)) (list 'platform batch:platform) (list 'batch-port (current-output-port)))) ;gets filled in later (batch:call-with-output-script my-parameters "my-batch" (lambda (batch-port) (adjoin-parameters! my-parameters (list 'batch-port batch-port)) (and (batch:comment my-parameters "================ Write file with C program.") (batch:rename-file my-parameters "hello.c" "hello.c~") (batch:lines->file my-parameters "hello.c" "#include " "int main(int argc, char **argv)" "@{" " printf(\"hello world\\n\");" " return 0;" "@}" ) (batch:system my-parameters "cc" "-c" "hello.c") (batch:system my-parameters "cc" "-o" "hello" (replace-suffix "hello.c" ".c" ".o")) (batch:system my-parameters "hello") (batch:delete-file my-parameters "hello") (batch:delete-file my-parameters "hello.c") (batch:delete-file my-parameters "hello.o") (batch:delete-file my-parameters "my-batch") ))) @end example @noindent Produces the file @file{my-batch}: @example #!/bin/sh # "my-batch" build script created Sat Jun 10 21:20:37 1995 # ================ Write file with C program. mv -f hello.c hello.c~ rm -f hello.c echo '#include '>>hello.c echo 'int main(int argc, char **argv)'>>hello.c echo '@{'>>hello.c echo ' printf("hello world\n");'>>hello.c echo ' return 0;'>>hello.c echo '@}'>>hello.c cc -c hello.c cc -o hello hello.o hello rm -f hello rm -f hello.c rm -f hello.o rm -f my-batch @end example @noindent When run, @file{my-batch} prints: @example bash$ my-batch mv: hello.c: No such file or directory hello world @end example @node Printing Scheme, Time and Date, Program Arguments, Textual Conversion Packages @section Printing Scheme @menu * Generic-Write:: 'generic-write * Object-To-String:: 'object->string * Pretty-Print:: 'pretty-print, 'pprint-file @end menu @node Generic-Write, Object-To-String, Printing Scheme, Printing Scheme @subsection Generic-Write @code{(require 'generic-write)} @ftindex generic-write @code{generic-write} is a procedure that transforms a Scheme data value (or Scheme program expression) into its textual representation and prints it. The interface to the procedure is sufficiently general to easily implement other useful formatting procedures such as pretty printing, output to a string and truncated output.@refill @deffn Procedure generic-write obj display? width output @table @var @item obj Scheme data value to transform. @item display? Boolean, controls whether characters and strings are quoted. @item width Extended boolean, selects format: @table @asis @item #f single line format @item integer > 0 pretty-print (value = max nb of chars per line) @end table @item output Procedure of 1 argument of string type, called repeatedly with successive substrings of the textual representation. This procedure can return @code{#f} to stop the transformation. @end table The value returned by @code{generic-write} is undefined. Examples: @lisp (write obj) @equiv{} (generic-write obj #f #f @var{display-string}) (display obj) @equiv{} (generic-write obj #t #f @var{display-string}) @end lisp @noindent where @lisp @var{display-string} @equiv{} (lambda (s) (for-each write-char (string->list s)) #t) @end lisp @end deffn @node Object-To-String, Pretty-Print, Generic-Write, Printing Scheme @subsection Object-To-String @code{(require 'object->string)} @ftindex object->string @defun object->string obj Returns the textual representation of @var{obj} as a string. @end defun @node Pretty-Print, , Object-To-String, Printing Scheme @subsection Pretty-Print @code{(require 'pretty-print)} @ftindex pretty-print @deffn Procedure pretty-print obj @deffnx Procedure pretty-print obj port @code{pretty-print}s @var{obj} on @var{port}. If @var{port} is not specified, @code{current-output-port} is used. Example: @example @group (pretty-print '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15) (16 17 18 19 20) (21 22 23 24 25))) @print{} ((1 2 3 4 5) @print{} (6 7 8 9 10) @print{} (11 12 13 14 15) @print{} (16 17 18 19 20) @print{} (21 22 23 24 25)) @end group @end example @end deffn @code{(require 'pprint-file)} @ftindex pprint-file @deffn Procedure pprint-file infile @deffnx Procedure pprint-file infile outfile Pretty-prints all the code in @var{infile}. If @var{outfile} is specified, the output goes to @var{outfile}, otherwise it goes to @code{(current-output-port)}.@refill @end deffn @defun pprint-filter-file infile proc outfile @defunx pprint-filter-file infile proc @var{infile} is a port or a string naming an existing file. Scheme source code expressions and definitions are read from the port (or file) and @var{proc} is applied to them sequentially. @var{outfile} is a port or a string. If no @var{outfile} is specified then @code{current-output-port} is assumed. These expanded expressions are then @code{pretty-print}ed to this port. Whitepsace and comments (introduced by @code{;}) which are not part of scheme expressions are reproduced in the output. This procedure does not affect the values returned by @code{current-input-port} and @code{current-output-port}.@refill @end defun @code{pprint-filter-file} can be used to pre-compile macro-expansion and thus can reduce loading time. The following will write into @file{exp-code.scm} the result of expanding all defmacros in @file{code.scm}. @lisp (require 'pprint-file) @ftindex pprint-file (require 'defmacroexpand) @ftindex defmacroexpand (defmacro:load "my-macros.scm") (pprint-filter-file "code.scm" defmacro:expand* "exp-code.scm") @end lisp @node Time and Date, Vector Graphics, Printing Scheme, Textual Conversion Packages @section Time and Date @menu * Posix Time:: 'posix-time * Common-Lisp Time:: 'common-lisp-time @end menu @node Posix Time, Common-Lisp Time, Time and Date, Time and Date @subsection Posix Time @example (require 'posix-time) @ftindex posix-time @end example @deftp {Data Type} {Calendar-Time} @cindex calendar time @cindex caltime is a datatype encapsulating time. @end deftp @deftp {Data Type} {Coordinated Universal Time} @cindex Coordinated Universal Time @cindex UTC (abbreviated @dfn{UTC}) is a vector of integers representing time: @enumerate 0 @item seconds (0 - 61) @item minutes (0 - 59) @item hours since midnight (0 - 23) @item day of month (1 - 31) @item month (0 - 11). Note difference from @code{decode-universal-time}. @item the number of years since 1900. Note difference from @code{decode-universal-time}. @item day of week (0 - 6) @item day of year (0 - 365) @item 1 for daylight savings, 0 for regular time @end enumerate @end deftp @defun gmtime caltime Converts the calendar time @var{caltime} to UTC and returns it. @defunx localtime caltime tz Returns @var{caltime} converted to UTC relative to timezone @var{tz}. @defunx localtime caltime converts the calendar time @var{caltime} to a vector of integers expressed relative to the user's time zone. @code{localtime} sets the variable @var{*timezone*} with the difference between Coordinated Universal Time (UTC) and local standard time in seconds (@pxref{Time Zone,tzset}). @end defun @defun gmktime univtime Converts a vector of integers in GMT Coordinated Universal Time (UTC) format to a calendar time. @defunx mktime univtime Converts a vector of integers in local Coordinated Universal Time (UTC) format to a calendar time. @defunx mktime univtime tz Converts a vector of integers in Coordinated Universal Time (UTC) format (relative to time-zone @var{tz}) to calendar time. @end defun @defun asctime univtime Converts the vector of integers @var{caltime} in Coordinated Universal Time (UTC) format into a string of the form @code{"Wed Jun 30 21:49:08 1993"}. @end defun @defun gtime caltime @defunx ctime caltime @defunx ctime caltime tz Equivalent to @code{(asctime (gmtime @var{caltime}))}, @code{(asctime (localtime @var{caltime}))}, and @code{(asctime (localtime @var{caltime} @var{tz}))}, respectively. @end defun @node Common-Lisp Time, , Posix Time, Time and Date @subsection Common-Lisp Time @defun get-decoded-time Equivalent to @code{(decode-universal-time (get-universal-time))}. @end defun @defun get-universal-time Returns the current time as @dfn{Universal Time}, number of seconds since 00:00:00 Jan 1, 1900 GMT. Note that the reference time is different from @code{current-time}. @end defun @defun decode-universal-time univtime Converts @var{univtime} to @dfn{Decoded Time} format. Nine values are returned: @enumerate 0 @item seconds (0 - 61) @item minutes (0 - 59) @item hours since midnight @item day of month @item month (1 - 12). Note difference from @code{gmtime} and @code{localtime}. @item year (A.D.). Note difference from @code{gmtime} and @code{localtime}. @item day of week (0 - 6) @item #t for daylight savings, #f otherwise @item hours west of GMT (-24 - +24) @end enumerate Notice that the values returned by @code{decode-universal-time} do not match the arguments to @code{encode-universal-time}. @end defun @defun encode-universal-time second minute hour date month year @defunx encode-universal-time second minute hour date month year time-zone Converts the arguments in Decoded Time format to Universal Time format. If @var{time-zone} is not specified, the returned time is adjusted for daylight saving time. Otherwise, no adjustment is performed. Notice that the values returned by @code{decode-universal-time} do not match the arguments to @code{encode-universal-time}. @end defun @node Vector Graphics, , Time and Date, Textual Conversion Packages @section Vector Graphics @menu * Tektronix Graphics Support:: @end menu @node Tektronix Graphics Support, , Vector Graphics, Vector Graphics @subsection Tektronix Graphics Support @emph{Note:} The Tektronix graphics support files need more work, and are not complete. @subsubsection Tektronix 4000 Series Graphics The Tektronix 4000 series graphics protocol gives the user a 1024 by 1024 square drawing area. The origin is in the lower left corner of the screen. Increasing y is up and increasing x is to the right. The graphics control codes are sent over the current-output-port and can be mixed with regular text and ANSI or other terminal control sequences. @deffn Procedure tek40:init @end deffn @deffn Procedure tek40:graphics @end deffn @deffn Procedure tek40:text @end deffn @deffn Procedure tek40:linetype linetype @end deffn @deffn Procedure tek40:move x y @end deffn @deffn Procedure tek40:draw x y @end deffn @deffn Procedure tek40:put-text x y str @end deffn @deffn Procedure tek40:reset @end deffn @subsubsection Tektronix 4100 Series Graphics The graphics control codes are sent over the current-output-port and can be mixed with regular text and ANSI or other terminal control sequences. @deffn Procedure tek41:init @end deffn @deffn Procedure tek41:reset @end deffn @deffn Procedure tek41:graphics @end deffn @deffn Procedure tek41:move x y @end deffn @deffn Procedure tek41:draw x y @end deffn @deffn Procedure tek41:point x y number @end deffn @deffn Procedure tek41:encode-x-y x y @end deffn @deffn Procedure tek41:encode-int number @end deffn @node Mathematical Packages, Database Packages, Textual Conversion Packages, Top @chapter Mathematical Packages @menu * Bit-Twiddling:: 'logical * Modular Arithmetic:: 'modular * Prime Testing and Generation:: 'primes * Prime Factorization:: 'factor * Random Numbers:: 'random * Cyclic Checksum:: 'make-crc * Plotting:: 'charplot * Root Finding:: 'root * Commutative Rings:: 'commutative-ring * Determinant:: @end menu @node Bit-Twiddling, Modular Arithmetic, Mathematical Packages, Mathematical Packages @section Bit-Twiddling @code{(require 'logical)} @ftindex logical The bit-twiddling functions are made available through the use of the @code{logical} package. @code{logical} is loaded by inserting @code{(require 'logical)} before the code that uses these @ftindex logical functions.@refill @defun logand n1 n1 Returns the integer which is the bit-wise AND of the two integer arguments. Example: @lisp (number->string (logand #b1100 #b1010) 2) @result{} "1000" @end lisp @end defun @defun logior n1 n2 Returns the integer which is the bit-wise OR of the two integer arguments. Example: @lisp (number->string (logior #b1100 #b1010) 2) @result{} "1110" @end lisp @end defun @defun logxor n1 n2 Returns the integer which is the bit-wise XOR of the two integer arguments. Example: @lisp (number->string (logxor #b1100 #b1010) 2) @result{} "110" @end lisp @end defun @defun lognot n Returns the integer which is the 2s-complement of the integer argument. Example: @lisp (number->string (lognot #b10000000) 2) @result{} "-10000001" (number->string (lognot #b0) 2) @result{} "-1" @end lisp @end defun @defun logtest j k @example (logtest j k) @equiv{} (not (zero? (logand j k))) (logtest #b0100 #b1011) @result{} #f (logtest #b0100 #b0111) @result{} #t @end example @end defun @defun logbit? index j @example (logbit? index j) @equiv{} (logtest (integer-expt 2 index) j) (logbit? 0 #b1101) @result{} #t (logbit? 1 #b1101) @result{} #f (logbit? 2 #b1101) @result{} #t (logbit? 3 #b1101) @result{} #t (logbit? 4 #b1101) @result{} #f @end example @end defun @defun ash int count Returns an integer equivalent to @code{(inexact->exact (floor (* @var{int} (expt 2 @var{count}))))}.@refill Example: @lisp (number->string (ash #b1 3) 2) @result{} "1000" (number->string (ash #b1010 -1) 2) @result{} "101" @end lisp @end defun @defun logcount n Returns the number of bits in integer @var{n}. If integer is positive, the 1-bits in its binary representation are counted. If negative, the 0-bits in its two's-complement binary representation are counted. If 0, 0 is returned. Example: @lisp (logcount #b10101010) @result{} 4 (logcount 0) @result{} 0 (logcount -2) @result{} 1 @end lisp @end defun @defun integer-length n Returns the number of bits neccessary to represent @var{n}. Example: @lisp (integer-length #b10101010) @result{} 8 (integer-length 0) @result{} 0 (integer-length #b1111) @result{} 4 @end lisp @end defun @defun integer-expt n k Returns @var{n} raised to the non-negative integer exponent @var{k}. Example: @lisp (integer-expt 2 5) @result{} 32 (integer-expt -3 3) @result{} -27 @end lisp @end defun @defun bit-extract n start end Returns the integer composed of the @var{start} (inclusive) through @var{end} (exclusive) bits of @var{n}. The @var{start}th bit becomes the 0-th bit in the result.@refill Example: @lisp (number->string (bit-extract #b1101101010 0 4) 2) @result{} "1010" (number->string (bit-extract #b1101101010 4 9) 2) @result{} "10110" @end lisp @end defun @node Modular Arithmetic, Prime Testing and Generation, Bit-Twiddling, Mathematical Packages @section Modular Arithmetic @code{(require 'modular)} @ftindex modular @defun extended-euclid n1 n2 Returns a list of 3 integers @code{(d x y)} such that d = gcd(@var{n1}, @var{n2}) = @var{n1} * x + @var{n2} * y.@refill @end defun @defun symmetric:modulus n Returns @code{(quotient (+ -1 n) -2)} for positive odd integer @var{n}. @end defun @defun modulus->integer modulus Returns the non-negative integer characteristic of the ring formed when @var{modulus} is used with @code{modular:} procedures. @end defun @defun modular:normalize modulus n Returns the integer @code{(modulo @var{n} (modulus->integer @var{modulus}))} in the representation specified by @var{modulus}. @end defun @noindent The rest of these functions assume normalized arguments; That is, the arguments are constrained by the following table: @noindent For all of these functions, if the first argument (@var{modulus}) is: @table @code @item positive? Work as before. The result is between 0 and @var{modulus}. @item zero? The arguments are treated as integers. An integer is returned. @item negative? The arguments and result are treated as members of the integers modulo @code{(+ 1 (* -2 @var{modulus}))}, but with @dfn{symmetric} representation; i.e. @code{(<= (- @var{modulus}) @var{n} @var{modulus})}. @end table @noindent If all the arguments are fixnums the computation will use only fixnums. @defun modular:invertable? modulus k Returns @code{#t} if there exists an integer n such that @var{k} * n @equiv{} 1 mod @var{modulus}, and @code{#f} otherwise. @end defun @defun modular:invert modulus k2 Returns an integer n such that 1 = (n * @var{k2}) mod @var{modulus}. If @var{k2} has no inverse mod @var{modulus} an error is signaled. @end defun @defun modular:negate modulus k2 Returns (@minus{}@var{k2}) mod @var{modulus}. @end defun @defun modular:+ modulus k2 k3 Returns (@var{k2} + @var{k3}) mod @var{modulus}. @end defun @defun modular:@minus{} modulus k2 k3 Returns (@var{k2} @minus{} @var{k3}) mod @var{modulus}. @end defun @defun modular:* modulus k2 k3 Returns (@var{k2} * @var{k3}) mod @var{modulus}. The Scheme code for @code{modular:*} with negative @var{modulus} is not completed for fixnum-only implementations. @end defun @defun modular:expt modulus k2 k3 Returns (@var{k2} ^ @var{k3}) mod @var{modulus}. @end defun @node Prime Testing and Generation, Prime Factorization, Modular Arithmetic, Mathematical Packages @section Prime Testing and Generation @code{(require 'primes)} @ftindex primes This package tests and generates prime numbers. The strategy used is as follows: @itemize @bullet @item First, use trial division by small primes (primes less than 1000) to quickly weed out composites with small factors. As a side benefit, this makes the test precise for numbers up to one million. @item Second, apply the Miller-Rabin primality test to detect (with high probability) any remaining composites. @end itemize The Miller-Rabin test is a Monte-Carlo test---in other words, it's fast and it gets the right answer with high probability. For a candidate that @emph{is} prime, the Miller-Rabin test is certain to report "prime"; it will never report "composite". However, for a candidate that is composite, there is a (small) probability that the Miller-Rabin test will erroneously report "prime". This probability can be made arbitarily small by adjusting the number of iterations of the Miller-Rabin test. @defun probably-prime? candidate @defunx probably-prime? candidate iter Returns @code{#t} if @code{candidate} is probably prime. The optional parameter @code{iter} controls the number of iterations of the Miller-Rabin test. The probability of a composite candidate being mistaken for a prime is at most @code{(1/4)^iter}. The default value of @code{iter} is 15, which makes the probability less than 1 in 10^9. @end defun @defun primes< start count @defunx primes< start count iter @defunx primes> start count @defunx primes> start count iter Returns a list of the first @code{count} odd probable primes less (more) than or equal to @code{start}. The optional parameter @code{iter} controls the number of iterations of the Miller-Rabin test for each candidate. The probability of a composite candidate being mistaken for a prime is at most @code{(1/4)^iter}. The default value of @code{iter} is 15, which makes the probability less than 1 in 10^9. @end defun @menu * The Miller-Rabin Test:: How the Miller-Rabin test works @end menu @node The Miller-Rabin Test, , Prime Testing and Generation, Prime Testing and Generation @subsection Theory Rabin and Miller's result can be summarized as follows. Let @code{p} (the candidate prime) be any odd integer greater than 2. Let @code{b} (the "base") be an integer in the range @code{2 ... p-1}. There is a fairly simple Boolean function---call it @code{C}, for "Composite"---with the following properties: @itemize @bullet @item If @code{p} is prime, @code{C(p, b)} is false for all @code{b} in the range @code{2 ... p-1}. @item If @code{p} is composite, @code{C(p, b)} is false for at most 1/4 of all @code{b} in the range @code{ 2 ... p-1}. (If the test fails for base @code{b}, @code{p} is called a @emph{strong pseudo-prime to base @code{b}}.) @end itemize For details of @code{C}, and why it fails for at most 1/4 of the potential bases, please consult a book on number theory or cryptography such as "A Course in Number Theory and Cryptography" by Neal Koblitz, published by Springer-Verlag 1994. There is nothing probablistic about this result. It's true for all @code{p}. If we had time to test @code{(1/4)p + 1} different bases, we could definitively determine the primality of @code{p}. For large candidates, that would take much too long---much longer than the simple approach of dividing by all numbers up to @code{sqrt(p)}. This is where probability enters the picture. Suppose we have some candidate prime @code{p}. Pick a random integer @code{b} in the range @code{2 ... p-1}. Compute @code{C(p,b)}. If @code{p} is prime, the result will certainly be false. If @code{p} is composite, the probability is at most 1/4 that the result will be false (demonstrating that @code{p} is a strong pseudoprime to base @code{b}). The test can be repeated with other random bases. If @code{p} is prime, each test is certain to return false. If @code{p} is composite, the probability of @code{C(p,b)} returning false is at most 1/4 for each test. Since the @code{b} are chosen at random, the tests outcomes are independent. So if @code{p} is composite and the test is repeated, say, 15 times, the probability of it returning false all fifteen times is at most (1/4)^15, or about 10^-9. If the test is repeated 30 times, the probability of failure drops to at most 8.3e-25. Rabin and Miller's result holds for @emph{all} candidates @code{p}. However, if the candidate @code{p} is picked at random, the probability of the Miller-Rabin test failing is much less than the computed bound. This is because, for @emph{most} composite numbers, the fraction of bases that cause the test to fail is much less than 1/4. For example, if you pick a random odd number less than 1000 and apply the Miller-Rabin test with only 3 random bases, the computed failure bound is (1/4)^3, or about 1.6e-2. However, the actual probability of failure is much less---about 7.2e-5. If you accidentally pick 703 to test for primality, the probability of failure is (161/703)^3, or about 1.2e-2, which is almost as high as the computed bound. This is because 703 is a strong pseudoprime to 161 bases. But if you pick at random there is only a small chance of picking 703, and no other number less than 1000 has that high a percentage of pseudoprime bases. The Miller-Rabin test is sometimes used in a slightly different fashion, where it can, at least in principle, cause problems. The weaker version uses small prime bases instead of random bases. If you are picking candidates at random and testing for primality, this works well since very few composites are strong pseudo-primes to small prime bases. (For example, there is only one composite less than 2.5e10 that is a strong pseudo-prime to the bases 2, 3, 5, and 7.) The problem with this approach is that once a candidate has been picked, the test is deterministic. This distinction is subtle, but real. With the randomized test, for @emph{any} candidate you pick---even if your candidate-picking procedure is strongly biased towards troublesome numbers, the test will work with high probability. With the deterministic version, for any particular candidate, the test will either work (with probability 1), or fail (with probability 1). It won't fail for very many candidates, but that won't be much consolation if your candidate-picking procedure is somehow biased toward troublesome numbers. @node Prime Factorization, Random Numbers, Prime Testing and Generation, Mathematical Packages @section Prime Factorization @code{(require 'factor)} @ftindex factor @defun factor k Returns a list of the prime factors of @var{k}. The order of the factors is unspecified. In order to obtain a sorted list do @code{(sort! (factor k) <)}.@refill @end defun @emph{Note:} The rest of these procedures implement the Solovay-Strassen primality test. This test has been superseeded by the faster @xref{Prime Testing and Generation, probably-prime?}. However these are left here as they take up little space and may be of use to an implementation without bignums. See Robert Solovay and Volker Strassen, @cite{A Fast Monte-Carlo Test for Primality}, SIAM Journal on Computing, 1977, pp 84-85. @defun jacobi-symbol p q Returns the value (+1, @minus{}1, or 0) of the Jacobi-Symbol of exact non-negative integer @var{p} and exact positive odd integer @var{q}.@refill @end defun @defun prime? p Returns @code{#f} if @var{p} is composite; @code{#t} if @var{p} is prime. There is a slight chance @code{(expt 2 (- prime:trials))} that a composite will return @code{#t}.@refill @end defun @defun prime:trials Is the maxinum number of iterations of Solovay-Strassen that will be done to test a number for primality. @end defun @node Random Numbers, Cyclic Checksum, Prime Factorization, Mathematical Packages @section Random Numbers @code{(require 'random)} @ftindex random @deffn Procedure random n @deffnx Procedure random n state Accepts a positive integer or real @var{n} and returns a number of the same type between zero (inclusive) and @var{n} (exclusive). The values returned have a uniform distribution.@refill The optional argument @var{state} must be of the type produced by @code{(make-random-state)}. It defaults to the value of the variable @code{*random-state*}. This object is used to maintain the state of the pseudo-random-number generator and is altered as a side effect of the @code{random} operation.@refill @end deffn @defvar *random-state* Holds a data structure that encodes the internal state of the random-number generator that @code{random} uses by default. The nature of this data structure is implementation-dependent. It may be printed out and successfully read back in, but may or may not function correctly as a random-number state object in another implementation.@refill @end defvar @deffn Procedure make-random-state @deffnx Procedure make-random-state state Returns a new object of type suitable for use as the value of the variable @code{*random-state*} and as a second argument to @code{random}. If argument @var{state} is given, a copy of it is returned. Otherwise a copy of @code{*random-state*} is returned.@refill @end deffn If inexact numbers are support by the Scheme implementation, @file{randinex.scm} will be loaded as well. @file{randinex.scm} contains procedures for generating inexact distributions.@refill @deffn Procedure random:uniform state Returns an uniformly distributed inexact real random number in the range between 0 and 1. @end deffn @deffn Procedure random:solid-sphere! vect @deffnx Procedure random:solid-sphere! vect state Fills @var{vect} with inexact real random numbers the sum of whose squares is less than 1.0. Thinking of @var{vect} as coordinates in space of dimension @var{n} = @code{(vector-length @var{vect})}, the coordinates are uniformly distributed within the unit @var{n}-shere. The sum of the squares of the numbers is returned.@refill @end deffn @deffn Procedure random:hollow-sphere! vect @deffnx Procedure random:hollow-sphere! vect state Fills @var{vect} with inexact real random numbers the sum of whose squares is equal to 1.0. Thinking of @var{vect} as coordinates in space of dimension n = @code{(vector-length @var{vect})}, the coordinates are uniformly distributed over the surface of the unit n-shere.@refill @end deffn @deffn Procedure random:normal @deffnx Procedure random:normal state Returns an inexact real in a normal distribution with mean 0 and standard deviation 1. For a normal distribution with mean @var{m} and standard deviation @var{d} use @code{(+ @var{m} (* @var{d} (random:normal)))}.@refill @end deffn @deffn Procedure random:normal-vector! vect @deffnx Procedure random:normal-vector! vect state Fills @var{vect} with inexact real random numbers which are independent and standard normally distributed (i.e., with mean 0 and variance 1). @end deffn @deffn Procedure random:exp @deffnx Procedure random:exp state Returns an inexact real in an exponential distribution with mean 1. For an exponential distribution with mean @var{u} use (* @var{u} (random:exp)).@refill @end deffn @node Cyclic Checksum, Plotting, Random Numbers, Mathematical Packages @section Cyclic Checksum @code{(require 'make-crc)} @ftindex make-crc @defun make-port-crc @defunx make-port-crc degree @defunx make-port-crc degree generator Returns an expression for a procedure of one argument, a port. This procedure reads characters from the port until the end of file and returns the integer checksum of the bytes read. The integer @var{degree}, if given, specifies the degree of the polynomial being computed -- which is also the number of bits computed in the checksums. The default value is 32. The integer @var{generator} specifies the polynomial being computed. The power of 2 generating each 1 bit is the exponent of a term of the polynomial. The bit at position @var{degree} is implicit and should not be part of @var{generator}. This allows systems with numbers limited to 32 bits to calculate 32 bit checksums. The default value of @var{generator} when @var{degree} is 32 (its default) is: @example (make-port-crc 32 #b00000100110000010001110110110111) @end example Creates a procedure to calculate the P1003.2/D11.2 (POSIX.2) 32-bit checksum from the polynomial: @example 32 26 23 22 16 12 11 ( x + x + x + x + x + x + x + 10 8 7 5 4 2 1 x + x + x + x + x + x + x + 1 ) mod 2 @end example @end defun @example (require 'make-crc) @ftindex make-crc (define crc32 (slib:eval (make-port-crc))) (define (file-check-sum file) (call-with-input-file file crc32)) (file-check-sum (in-vicinity (library-vicinity) "ratize.scm")) @result{} 3553047446 @end example @node Plotting, Root Finding, Cyclic Checksum, Mathematical Packages @section Plotting on Character Devices @code{(require 'charplot)} @ftindex charplot The plotting procedure is made available through the use of the @code{charplot} package. @code{charplot} is loaded by inserting @code{(require 'charplot)} before the code that uses this @ftindex charplot procedure.@refill @defvar charplot:height The number of rows to make the plot vertically. @end defvar @defvar charplot:width The number of columns to make the plot horizontally. @end defvar @deffn Procedure plot! coords x-label y-label @var{coords} is a list of pairs of x and y coordinates. @var{x-label} and @var{y-label} are strings with which to label the x and y axes.@refill Example: @example (require 'charplot) @ftindex charplot (set! charplot:height 19) (set! charplot:width 45) (define (make-points n) (if (zero? n) '() (cons (cons (/ n 6) (sin (/ n 6))) (make-points (1- n))))) (plot! (make-points 37) "x" "Sin(x)") @print{} @group Sin(x) ______________________________________________ 1.25|- | | | 1|- **** | | ** ** | 750.0e-3|- * * | | * * | 500.0e-3|- * * | | * | 250.0e-3|- * | | * * | 0|-------------------*--------------------------| | * | -250.0e-3|- * * | | * * | -500.0e-3|- * | | * * | -750.0e-3|- * * | | ** ** | -1|- **** | |____________:_____._____:_____._____:_________| x 2 4 @end group @end example @end deffn @node Root Finding, Commutative Rings, Plotting, Mathematical Packages @section Root Finding @code{(require 'root)} @ftindex root @defun newtown:find-integer-root f df/dx x0 Given integer valued procedure @var{f}, its derivative (with respect to its argument) @var{df/dx}, and initial integer value @var{x0} for which @var{df/dx}(@var{x0}) is non-zero, returns an integer @var{x} for which @var{f}(@var{x}) is closer to zero than either of the integers adjacent to @var{x}; or returns @code{#f} if such an integer can't be found. To find the closest integer to a given integers square root: @example (define (integer-sqrt y) (newton:find-integer-root (lambda (x) (- (* x x) y)) (lambda (x) (* 2 x)) (ash 1 (quotient (integer-length y) 2)))) (integer-sqrt 15) @result{} 4 @end example @end defun @defun integer-sqrt y Given a non-negative integer @var{y}, returns the rounded square-root of @var{y}. @end defun @defun newton:find-root f df/dx x0 prec Given real valued procedures @var{f}, @var{df/dx} of one (real) argument, initial real value @var{x0} for which @var{df/dx}(@var{x0}) is non-zero, and positive real number @var{prec}, returns a real @var{x} for which @code{abs}(@var{f}(@var{x})) is less than @var{prec}; or returns @code{#f} if such a real can't be found. If @code{prec} is instead a negative integer, @code{newton:find-root} returns the result of -@var{prec} iterations. @end defun @noindent H. J. Orchard, @cite{The Laguerre Method for Finding the Zeros of Polynomials}, IEEE Transactions on Circuits and Systems, Vol. 36, No. 11, November 1989, pp 1377-1381. @quotation There are 2 errors in Orchard's Table II. Line k=2 for starting value of 1000+j0 should have Z_k of 1.0475 + j4.1036 and line k=2 for starting value of 0+j1000 should have Z_k of 1.0988 + j4.0833. @end quotation @defun laguerre:find-root f df/dz ddf/dz^2 z0 prec Given complex valued procedure @var{f} of one (complex) argument, its derivative (with respect to its argument) @var{df/dx}, its second derivative @var{ddf/dz^2}, initial complex value @var{z0}, and positive real number @var{prec}, returns a complex number @var{z} for which @code{magnitude}(@var{f}(@var{z})) is less than @var{prec}; or returns @code{#f} if such a number can't be found. If @code{prec} is instead a negative integer, @code{laguerre:find-root} returns the result of -@var{prec} iterations. @end defun @defun laguerre:find-polynomial-root deg f df/dz ddf/dz^2 z0 prec Given polynomial procedure @var{f} of integer degree @var{deg} of one argument, its derivative (with respect to its argument) @var{df/dx}, its second derivative @var{ddf/dz^2}, initial complex value @var{z0}, and positive real number @var{prec}, returns a complex number @var{z} for which @code{magnitude}(@var{f}(@var{z})) is less than @var{prec}; or returns @code{#f} if such a number can't be found. If @code{prec} is instead a negative integer, @code{laguerre:find-polynomial-root} returns the result of -@var{prec} iterations. @end defun @node Commutative Rings, Determinant, Root Finding, Mathematical Packages @section Commutative Rings Scheme provides a consistent and capable set of numeric functions. Inexacts implement a field; integers a commutative ring (and Euclidean domain). This package allows the user to use basic Scheme numeric functions with symbols and non-numeric elements of commutative rings. @code{(require 'commutative-ring)} @ftindex commutative-ring @cindex ring, commutative The @dfn{commutative-ring} package makes @code{+}, @code{-}, @code{*}, @code{/}, and @code{^} @dfn{careful} in the sense that any non-numeric @cindex careful arguments which it cannot reduce appear in the expression output. In order to see what working with this package is like, self-set all the single letter identifiers (to their corresponding symbols). @example (define a 'a) @dots{} (define z 'z) @end example Or just @code{(require 'self-set)}. Now for some sample expressions: @example (* (+ a b) (+ a b)) @result{} (+ (* 2 a b) (^ a 2) (^ b 2)) (* (+ a b) (- a b)) @result{} (- (^ a 2) (^ b 2)) (* (- a b) (- a b)) @result{} (- (+ (^ a 2) (^ b 2)) (* 2 a b)) (* (- a b) (+ a b)) @result{} (- (^ a 2) (^ b 2)) (/ (+ a b) (+ c d)) @result{} (+ (/ a (+ c d)) (/ b (+ c d))) (/ (+ a b) (- c d)) @result{} (+ (/ a (- c d)) (/ b (- c d))) (/ (- a b) (- c d)) @result{} (- (/ a (- c d)) (/ b (- c d))) (/ (- a b) (+ c d)) @result{} (- (/ a (+ c d)) (/ b (+ c d))) (^ (+ a b) 3) @result{} (+ (* 3 a (^ b 2)) (* 3 b (^ a 2)) (^ a 3) (^ b 3)) (^ (+ a 2) 3) @result{} (+ 8 (* a 12) (* (^ a 2) 6) (^ a 3)) @end example Use of this package is not restricted to simple arithmetic expressions: @example (require 'determinant) (determinant '((a b c) (d e f) (g h i))) @result{} (- (+ (* a e i) (* b f g) (* c d h)) (* a f h) (* b d i) (* c e g)) @end example The @dfn{commutative-ring} package differs from other extension mechanisms in that it automatically, using properties true of all commutative rings, simplifies sum and product expressions containing non-numeric elements. One need only specify behavior for @code{+} or @code{*} for cases where expressions involving objects reduce to numbers or to expressions involving different non-numeric elements. Currently, only @code{+}, @code{-}, @code{*}, @code{/}, and @code{^} support non-numeric elements. Expressions with @code{-} are converted to equivalent expressions without @code{-}, so behavior for @code{-} is not defined separately. @code{/} expressions are handled similarly. This list might be extended to include @code{quotient}, @code{modulo}, @code{remainder}, @code{lcm}, and @code{gcd}; but these work only for the more restrictive Euclidean (Unique Factorization) Domain. @cindex Unique Factorization @cindex Euclidean Domain @defun cring:define-rule op sub-op1 sub-op2 reduction Defines a rule for the case when the operation represented by symbol @var{op} is applied to lists whose @code{car}s are @var{sub-op1} and @var{sub-op2}, respectively. The argument @var{reduction} is a procedure accepting 2 arguments which will be lists whose @code{car}s are @var{sub-op1} and @var{sub-op2}. @defunx cring:define-rule op sub-op1 'identity reduction Defines a rule for the case when the operation represented by symbol @var{op} is applied to a list whose @code{car} is @var{sub-op1}, and some other argument. @var{Reduction} will be called with the list whose @code{car} is @var{sub-op1} and some other argument. If @var{reduction} returns @code{#f}, the reduction has failed and other reductions will be tried. If @var{reduction} returns a non-false value, that value will replace the two arguments in arithmetic (@code{+}, @code{-}, and @code{*}) calculations involving non-numeric elements. The operations @code{+} and @code{*} are assumed commutative; hence both orders of arguments to @var{reduction} will be tried if necessary. The following rule is the built-in definition for distributing @code{*} over @code{+}. @example (cring:define-rule '* '+ 'identity (lambda (exp1 exp2) (apply + (map (lambda (trm) (* trm exp2)) (cdr exp1)))))) @end example @end defun @heading How to Create a Commutative Ring The first step in creating your commutative ring is to write procedures to create elements of the ring. A non-numeric element of the ring must be represented as a list whose first element is a symbol or string. This first element identifies the type of the object. A convenient and clear convention is to make the type-identifying element be the same symbol whose top-level value is the procedure to create it. @example (define (n . list1) (cond ((and (= 2 (length list1)) (eq? (car list1) (cadr list1))) 0) ((not (term< (first list1) (last1 list1))) (apply n (reverse list1))) (else (cons 'n list1)))) (define (s x y) (n x y)) (define (m . list1) (cond ((neq? (first list1) (term_min list1)) (apply m (cyclicrotate list1))) ((term< (last1 list1) (cadr list1)) (apply m (reverse (cyclicrotate list1)))) (else (cons 'm list1)))) @end example Define a procedure to multiply 2 non-numeric elements of the ring. Other multiplicatons are handled automatically. Objects for which rules have @emph{not} been defined are not changed. @example (define (n*n ni nj) (let ((list1 (cdr ni)) (list2 (cdr nj))) (cond ((null? (intersection list1 list2)) #f) ((and (eq? (last1 list1) (first list2)) (neq? (first list1) (last1 list2))) (apply n (splice list1 list2))) ((and (eq? (first list1) (first list2)) (neq? (last1 list1) (last1 list2))) (apply n (splice (reverse list1) list2))) ((and (eq? (last1 list1) (last1 list2)) (neq? (first list1) (first list2))) (apply n (splice list1 (reverse list2)))) ((and (eq? (last1 list1) (first list2)) (eq? (first list1) (last1 list2))) (apply m (cyclicsplice list1 list2))) ((and (eq? (first list1) (first list2)) (eq? (last1 list1) (last1 list2))) (apply m (cyclicsplice (reverse list1) list2))) (else #f)))) @end example Test the procedures to see if they work. @example ;;; where cyclicrotate(list) is cyclic rotation of the list one step ;;; by putting the first element at the end (define (cyclicrotate list1) (append (rest list1) (list (first list1)))) ;;; and where term_min(list) is the element of the list which is ;;; first in the term ordering. (define (term_min list1) (car (sort list1 term<))) (define (term< sym1 sym2) (stringstring sym1) (symbol->string sym2))) (define first car) (define rest cdr) (define (last1 list1) (car (last-pair list1))) (define (neq? obj1 obj2) (not (eq? obj1 obj2))) ;;; where splice is the concatenation of list1 and list2 except that their ;;; common element is not repeated. (define (splice list1 list2) (cond ((eq? (last1 list1) (first list2)) (append list1 (cdr list2))) (else (error 'splice list1 list2)))) ;;; where cyclicsplice is the result of leaving off the last element of ;;; splice(list1,list2). (define (cyclicsplice list1 list2) (cond ((and (eq? (last1 list1) (first list2)) (eq? (first list1) (last1 list2))) (butlast (splice list1 list2) 1)) (else (error 'cyclicsplice list1 list2)))) (N*N (S a b) (S a b)) @result{} (m a b) @end example Then register the rule for multiplying type N objects by type N objects. @example (cring:define-rule '* 'N 'N N*N)) @end example Now we are ready to compute! @example (define (t) (define detM (+ (* (S g b) (+ (* (S f d) (- (* (S a f) (S d g)) (* (S a g) (S d f)))) (* (S f f) (- (* (S a g) (S d d)) (* (S a d) (S d g)))) (* (S f g) (- (* (S a d) (S d f)) (* (S a f) (S d d)))))) (* (S g d) (+ (* (S f b) (- (* (S a g) (S d f)) (* (S a f) (S d g)))) (* (S f f) (- (* (S a b) (S d g)) (* (S a g) (S d b)))) (* (S f g) (- (* (S a f) (S d b)) (* (S a b) (S d f)))))) (* (S g f) (+ (* (S f b) (- (* (S a d) (S d g)) (* (S a g) (S d d)))) (* (S f d) (- (* (S a g) (S d b)) (* (S a b) (S d g)))) (* (S f g) (- (* (S a b) (S d d)) (* (S a d) (S d b)))))) (* (S g g) (+ (* (S f b) (- (* (S a f) (S d d)) (* (S a d) (S d f)))) (* (S f d) (- (* (S a b) (S d f)) (* (S a f) (S d b)))) (* (S f f) (- (* (S a d) (S d b)) (* (S a b) (S d d)))))))) (* (S b e) (S c a) (S e c) detM )) (pretty-print (t)) @print{} (- (+ (m a c e b d f g) (m a c e b d g f) (m a c e b f d g) (m a c e b f g d) (m a c e b g d f) (m a c e b g f d)) (* 2 (m a b e c) (m d f g)) (* (m a c e b d) (m f g)) (* (m a c e b f) (m d g)) (* (m a c e b g) (m d f))) @end example @node Determinant, , Commutative Rings, Mathematical Packages @section Determinant @example (require 'determinant) (determinant '((1 2) (3 4))) @result{} -2 (determinant '((1 2 3) (4 5 6) (7 8 9))) @result{} 0 (determinant '((1 2 3 4) (5 6 7 8) (9 10 11 12))) @result{} 0 @end example @node Database Packages, Other Packages, Mathematical Packages, Top @chapter Database Packages @menu * Base Table:: * Relational Database:: 'relational-database * Weight-Balanced Trees:: 'wt-tree @end menu @node Base Table, Relational Database, Database Packages, Database Packages @section Base Table A base table implementation using Scheme association lists is available as the value of the identifier @code{alist-table} after doing: @code{(require 'alist-table)} @ftindex alist-table Association list base tables are suitable for small databases and support all Scheme types when temporary and readable/writeable Scheme types when saved. I hope support for other base table implementations will be added in the future. This rest of this section documents the interface for a base table implementation from which the @ref{Relational Database} package constructs a Relational system. It will be of interest primarily to those wishing to port or write new base-table implementations. All of these functions are accessed through a single procedure by calling that procedure with the symbol name of the operation. A procedure will be returned if that operation is supported and @code{#f} otherwise. For example: @example @group (require 'alist-table) @ftindex alist-table (define open-base (alist-table 'make-base)) make-base @result{} *a procedure* (define foo (alist-table 'foo)) foo @result{} #f @end group @end example @defun make-base filename key-dimension column-types Returns a new, open, low-level database (collection of tables) associated with @var{filename}. This returned database has an empty table associated with @var{catalog-id}. The positive integer @var{key-dimension} is the number of keys composed to make a @var{primary-key} for the catalog table. The list of symbols @var{column-types} describes the types of each column for that table. If the database cannot be created as specified, @code{#f} is returned. Calling the @code{close-base} method on this database and possibly other operations will cause @var{filename} to be written to. If @var{filename} is @code{#f} a temporary, non-disk based database will be created if such can be supported by the base table implelentation. @end defun @defun open-base filename mutable Returns an open low-level database associated with @var{filename}. If @var{mutable?} is @code{#t}, this database will have methods capable of effecting change to the database. If @var{mutable?} is @code{#f}, only methods for inquiring the database will be available. If the database cannot be opened as specified @code{#f} is returned. Calling the @code{close-base} (and possibly other) method on a @var{mutable?} database will cause @var{filename} to be written to. @end defun @defun write-base lldb filename Causes the low-level database @var{lldb} to be written to @var{filename}. If the write is successful, also causes @var{lldb} to henceforth be associated with @var{filename}. Calling the @code{close-database} (and possibly other) method on @var{lldb} may cause @var{filename} to be written to. If @var{filename} is @code{#f} this database will be changed to a temporary, non-disk based database if such can be supported by the underlying base table implelentation. If the operations completed successfully, @code{#t} is returned. Otherwise, @code{#f} is returned. @end defun @defun sync-base lldb Causes the file associated with the low-level database @var{lldb} to be updated to reflect its current state. If the associated filename is @code{#f}, no action is taken and @code{#f} is returned. If this operation completes successfully, @code{#t} is returned. Otherwise, @code{#f} is returned. @end defun @defun close-base lldb Causes the low-level database @var{lldb} to be written to its associated file (if any). If the write is successful, subsequent operations to @var{lldb} will signal an error. If the operations complete successfully, @code{#t} is returned. Otherwise, @code{#f} is returned. @end defun @defun make-table lldb key-dimension column-types Returns the @var{base-id} for a new base table, otherwise returns @code{#f}. The base table can then be opened using @code{(open-table @var{lldb} @var{base-id})}. The positive integer @var{key-dimension} is the number of keys composed to make a @var{primary-key} for this table. The list of symbols @var{column-types} describes the types of each column. @end defun @defvr Constant catalog-id A constant @var{base-id} suitable for passing as a parameter to @code{open-table}. @var{catalog-id} will be used as the base table for the system catalog. @end defvr @defun open-table lldb base-id key-dimension column-types Returns a @var{handle} for an existing base table in the low-level database @var{lldb} if that table exists and can be opened in the mode indicated by @var{mutable?}, otherwise returns @code{#f}. As with @code{make-table}, the positive integer @var{key-dimension} is the number of keys composed to make a @var{primary-key} for this table. The list of symbols @var{column-types} describes the types of each column. @end defun @defun kill-table lldb base-id key-dimension column-types Returns @code{#t} if the base table associated with @var{base-id} was removed from the low level database @var{lldb}, and @code{#f} otherwise. @end defun @defun make-keyifier-1 type Returns a procedure which accepts a single argument which must be of type @var{type}. This returned procedure returns an object suitable for being a @var{key} argument in the functions whose descriptions follow. Any 2 arguments of the supported type passed to the returned function which are not @code{equal?} must result in returned values which are not @code{equal?}. @end defun @defun make-list-keyifier key-dimension types The list of symbols @var{types} must have at least @var{key-dimension} elements. Returns a procedure which accepts a list of length @var{key-dimension} and whose types must corresopond to the types named by @var{types}. This returned procedure combines the elements of its list argument into an object suitable for being a @var{key} argument in the functions whose descriptions follow. Any 2 lists of supported types (which must at least include symbols and non-negative integers) passed to the returned function which are not @code{equal?} must result in returned values which are not @code{equal?}. @end defun @defun make-key-extractor key-dimension types column-number Returns a procedure which accepts objects produced by application of the result of @code{(make-list-keyifier @var{key-dimension} @var{types})}. This procedure returns a @var{key} which is @code{equal?} to the @var{column-number}th element of the list which was passed to create @var{combined-key}. The list @var{types} must have at least @var{key-dimension} elements. @end defun @defun make-key->list key-dimension types Returns a procedure which accepts objects produced by application of the result of @code{(make-list-keyifier @var{key-dimension} @var{types})}. This procedure returns a list of @var{key}s which are elementwise @code{equal?} to the list which was passed to create @var{combined-key}. @end defun @noindent In the following functions, the @var{key} argument can always be assumed to be the value returned by a call to a @emph{keyify} routine. @noindent @cindex match-key @cindex match @cindex wild-card In contrast, a @var{match-key} argument is a list of length equal to the number of primary keys. The @var{match-key} restricts the actions of the table command to those records whose primary keys all satisfy the corresponding element of the @var{match-key} list. The elements and their actions are: @quotation @table @asis @item @code{#f} The false value matches any key in the corresponding position. @item an object of type procedure This procedure must take a single argument, the key in the corresponding position. Any key for which the procedure returns a non-false value is a match; Any key for which the procedure returns a @code{#f} is not. @item other values Any other value matches only those keys @code{equal?} to it. @end table @end quotation @defun for-each-key handle procedure match-key Calls @var{procedure} once with each @var{key} in the table opened in @var{handle} which satisfies @var{match-key} in an unspecified order. An unspecified value is returned. @end defun @defun map-key handle procedure match-key Returns a list of the values returned by calling @var{procedure} once with each @var{key} in the table opened in @var{handle} which satisfies @var{match-key} in an unspecified order. @end defun @defun ordered-for-each-key handle procedure match-key Calls @var{procedure} once with each @var{key} in the table opened in @var{handle} which satisfies @var{match-key} in the natural order for the types of the primary key fields of that table. An unspecified value is returned. @end defun @defun delete* handle match-key Removes all rows which satisfy @var{match-key} from the table opened in @var{handle}. An unspecified value is returned. @end defun @defun present? handle key Returns a non-@code{#f} value if there is a row associated with @var{key} in the table opened in @var{handle} and @code{#f} otherwise. @end defun @defun delete handle key Removes the row associated with @var{key} from the table opened in @var{handle}. An unspecified value is returned. @end defun @defun make-getter key-dimension types Returns a procedure which takes arguments @var{handle} and @var{key}. This procedure returns a list of the non-primary values of the relation (in the base table opened in @var{handle}) whose primary key is @var{key} if it exists, and @code{#f} otherwise. @end defun @defun make-putter key-dimension types Returns a procedure which takes arguments @var{handle} and @var{key} and @var{value-list}. This procedure associates the primary key @var{key} with the values in @var{value-list} (in the base table opened in @var{handle}) and returns an unspecified value. @end defun @defun supported-type? symbol Returns @code{#t} if @var{symbol} names a type allowed as a column value by the implementation, and @code{#f} otherwise. At a minimum, an implementation must support the types @code{integer}, @code{symbol}, @code{string}, @code{boolean}, and @code{base-id}. @end defun @defun supported-key-type? symbol Returns @code{#t} if @var{symbol} names a type allowed as a key value by the implementation, and @code{#f} otherwise. At a minimum, an implementation must support the types @code{integer}, and @code{symbol}. @end defun @table @code @item integer Scheme exact integer. @item symbol Scheme symbol. @item boolean @code{#t} or @code{#f}. @item base-id Objects suitable for passing as the @var{base-id} parameter to @code{open-table}. The value of @var{catalog-id} must be an acceptable @code{base-id}. @end table @node Relational Database, Weight-Balanced Trees, Base Table, Database Packages @section Relational Database @code{(require 'relational-database)} @ftindex relational-database This package implements a database system inspired by the Relational Model (@cite{E. F. Codd, A Relational Model of Data for Large Shared Data Banks}). An SLIB relational database implementation can be created from any @ref{Base Table} implementation. @menu * Motivations:: Database Manifesto * Creating and Opening Relational Databases:: * Relational Database Operations:: * Table Operations:: * Catalog Representation:: * Unresolved Issues:: * Database Utilities:: 'database-utilities @end menu @node Motivations, Creating and Opening Relational Databases, Relational Database, Relational Database @subsection Motivations Most nontrivial programs contain databases: Makefiles, configure scripts, file backup, calendars, editors, source revision control, CAD systems, display managers, menu GUIs, games, parsers, debuggers, profilers, and even error reporting are all rife with databases. Coding databases is such a common activity in programming that many may not be aware of how often they do it. A database often starts as a dispatch in a program. The author, perhaps because of the need to make the dispatch configurable, the need for correlating dispatch in other routines, or because of changes or growth, devises a data structure to contain the information, a routine for interpreting that data structure, and perhaps routines for augmenting and modifying the stored data. The dispatch must be converted into this form and tested. The programmer may need to devise an interactive program for enabling easy examination and modification of the information contained in this database. Often, in an attempt to foster modularity and avoid delays in release, intermediate file formats for the database information are devised. It often turns out that users prefer modifying these intermediate files with a text editor to using the interactive program in order to do operations (such as global changes) not forseen by the program's author. In order to address this need, the concientous software engineer may even provide a scripting language to allow users to make repetitive database changes. Users will grumble that they need to read a large manual and learn yet another programming language (even if it @emph{almost} has language "xyz" syntax) in order to do simple configuration. All of these facilities need to be designed, coded, debugged, documented, and supported; often causing what was very simple in concept to become a major developement project. This view of databases just outlined is somewhat the reverse of the view of the originators of the @dfn{Relational Model} of database abstraction. The relational model was devised to unify and allow interoperation of large multi-user databases running on diverse platforms. A fairly general purpose "Comprehensive Language" for database manipulations is mandated (but not specified) as part of the relational model for databases. One aspect of the Relational Model of some importance is that the "Comprehensive Language" must be expressible in some form which can be stored in the database. This frees the programmer from having to make programs data-driven in order to use a database. This package includes as one of its basic supported types Scheme @dfn{expression}s. This type allows expressions as defined by the Scheme standards to be stored in the database. Using @code{slib:eval} retrieved expressions can be evaluated (in the top-level environment). Scheme's @code{lambda} facilitates closure of environments, modularity, etc. so that procedures (which could not be stored directly most databases) can still be effectively retrieved. Since @code{slib:eval} evaluates expressions in the top-level environment, built-in and user defined procedures can be easily accessed by name. This package's purpose is to standardize (through a common interface) database creation and usage in Scheme programs. The relational model's provision for inclusion of language expressions as data as well as the description (in tables, of course) of all of its tables assures that relational databases are powerful enough to assume the roles currently played by thousands of ad-hoc routines and data formats. @noindent Such standardization to a relational-like model brings many benefits: @itemize @bullet @item Tables, fields, domains, and types can be dealt with by name in programs. @item The underlying database implementation can be changed (for performance or other reasons) by changing a single line of code. @item The formats of tables can be easily extended or changed without altering code. @item Consistency checks are specified as part of the table descriptions. Changes in checks need only occur in one place. @item All the configuration information which the developer wishes to group together is easily grouped, without needing to change programs aware of only some of these tables. @item Generalized report generators, interactive entry programs, and other database utilities can be part of a shared library. The burden of adding configurability to a program is greatly reduced. @item Scheme is the "comprehensive language" for these databases. Scripting for configuration no longer needs to be in a separate language with additional documentation. @item Scheme's latent types mesh well with the strict typing and logical requirements of the relational model. @item Portable formats allow easy interchange of data. The included table descriptions help prevent misinterpretation of format. @end itemize @node Creating and Opening Relational Databases, Relational Database Operations, Motivations, Relational Database @subsection Creating and Opening Relational Databases @defun make-relational-system base-table-implementation Returns a procedure implementing a relational database using the @var{base-table-implementation}. All of the operations of a base table implementation are accessed through a procedure defined by @code{require}ing that implementation. Similarly, all of the operations of the relational database implementation are accessed through the procedure returned by @code{make-relational-system}. For instance, a new relational database could be created from the procedure returned by @code{make-relational-system} by: @example (require 'alist-table) @ftindex alist-table (define relational-alist-system (make-relational-system alist-table)) (define create-alist-database (relational-alist-system 'create-database)) (define my-database (create-alist-database "mydata.db")) @end example @end defun @noindent What follows are the descriptions of the methods available from relational system returned by a call to @code{make-relational-system}. @defun create-database filename Returns an open, nearly empty relational database associated with @var{filename}. The only tables defined are the system catalog and domain table. Calling the @code{close-database} method on this database and possibly other operations will cause @var{filename} to be written to. If @var{filename} is @code{#f} a temporary, non-disk based database will be created if such can be supported by the underlying base table implelentation. If the database cannot be created as specified @code{#f} is returned. For the fields and layout of descriptor tables, @xref{Catalog Representation} @end defun @defun open-database filename mutable? Returns an open relational database associated with @var{filename}. If @var{mutable?} is @code{#t}, this database will have methods capable of effecting change to the database. If @var{mutable?} is @code{#f}, only methods for inquiring the database will be available. Calling the @code{close-database} (and possibly other) method on a @var{mutable?} database will cause @var{filename} to be written to. If the database cannot be opened as specified @code{#f} is returned. @end defun @node Relational Database Operations, Table Operations, Creating and Opening Relational Databases, Relational Database @subsection Relational Database Operations @noindent These are the descriptions of the methods available from an open relational database. A method is retrieved from a database by calling the database with the symbol name of the operation. For example: @example (define my-database (create-alist-database "mydata.db")) (define telephone-table-desc ((my-database 'create-table) 'telephone-table-desc)) @end example @defun close-database Causes the relational database to be written to its associated file (if any). If the write is successful, subsequent operations to this database will signal an error. If the operations completed successfully, @code{#t} is returned. Otherwise, @code{#f} is returned. @end defun @defun write-database filename Causes the relational database to be written to @var{filename}. If the write is successful, also causes the database to henceforth be associated with @var{filename}. Calling the @code{close-database} (and possibly other) method on this database will cause @var{filename} to be written to. If @var{filename} is @code{#f} this database will be changed to a temporary, non-disk based database if such can be supported by the underlying base table implelentation. If the operations completed successfully, @code{#t} is returned. Otherwise, @code{#f} is returned. @end defun @defun table-exists? table-name Returns @code{#t} if @var{table-name} exists in the system catalog, otherwise returns @code{#f}. @end defun @defun open-table table-name mutable? Returns a @dfn{methods} procedure for an existing relational table in this database if it exists and can be opened in the mode indicated by @var{mutable?}, otherwise returns @code{#f}. @end defun @noindent These methods will be present only in databases which are @var{mutable?}. @defun delete-table table-name Removes and returns the @var{table-name} row from the system catalog if the table or view associated with @var{table-name} gets removed from the database, and @code{#f} otherwise. @end defun @defun create-table table-desc-name Returns a methods procedure for a new (open) relational table for describing the columns of a new base table in this database, otherwise returns @code{#f}. For the fields and layout of descriptor tables, @xref{Catalog Representation}. @defunx create-table table-name table-desc-name Returns a methods procedure for a new (open) relational table with columns as described by @var{table-desc-name}, otherwise returns @code{#f}. @end defun @defun create-view ?? @defunx project-table ?? @defunx restrict-table ?? @defunx cart-prod-tables ?? Not yet implemented. @end defun @node Table Operations, Catalog Representation, Relational Database Operations, Relational Database @subsection Table Operations @noindent These are the descriptions of the methods available from an open relational table. A method is retrieved from a table by calling the table with the symbol name of the operation. For example: @example @group (define telephone-table-desc ((my-database 'create-table) 'telephone-table-desc)) (require 'common-list-functions) (define ndrp (telephone-table-desc 'row:insert)) (ndrp '(1 #t name #f string)) (ndrp '(2 #f telephone (lambda (d) (and (string? d) (> (string-length d) 2) (every (lambda (c) (memv c '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9 #\+ #\( #\ #\) #\-))) (string->list d)))) string)) @end group @end example @noindent Some operations described below require primary key arguments. Primary keys arguments are denoted @var{key1} @var{key2} @dots{}. It is an error to call an operation for a table which takes primary key arguments with the wrong number of primary keys for that table. @noindent The term @dfn{row} used below refers to a Scheme list of values (one for each column) in the order specified in the descriptor (table) for this table. Missing values appear as @code{#f}. Primary keys must not be missing. @defun get column-name Returns a procedure of arguments @var{key1} @var{key2} @dots{} which returns the value for the @var{column-name} column of the row associated with primary keys @var{key1}, @var{key2} @dots{} if that row exists in the table, or @code{#f} otherwise. @example ((plat 'get 'processor) 'djgpp) @result{} i386 ((plat 'get 'processor) 'be-os) @result{} #f @end example @defunx get* column-name Returns a procedure of optional arguments @var{match-key1} @dots{} which returns a list of the values for the specified column for all rows in this table. The optional @var{match-key1} @dots{} arguments restrict actions to a subset of the table. See the match-key description below for details. @example ((plat 'get* 'processor)) @result{} (i386 8086 i386 8086 i386 i386 8086 m68000 m68000 m68000 m68000 m68000 powerpc) ((plat 'get* 'processor) #f) @result{} (i386 8086 i386 8086 i386 i386 8086 m68000 m68000 m68000 m68000 m68000 powerpc) (define (a-key? key) (char=? #\a (string-ref (symbol->string key) 0))) ((plat 'get* 'processor) a-key?) @result{} (m68000 m68000 m68000 m68000 m68000 powerpc) ((plat 'get* 'name) a-key?) @result{} (atari-st-turbo-c atari-st-gcc amiga-sas/c-5.10 amiga-aztec amiga-dice-c aix) @end example @end defun @defun row:retrieve Returns a procedure of arguments @var{key1} @var{key2} @dots{} which returns the row associated with primary keys @var{key1}, @var{key2} @dots{} if it exists, or @code{#f} otherwise. @example ((plat 'row:retrieve) 'linux) @result{} (linux i386 linux gcc) ((plat 'row:retrieve) 'multics) @result{} #f @end example @defunx row:retrieve* Returns a procedure of optional arguments @var{match-key1} @dots{} which returns a list of all rows in this table. The optional @var{match-key1} @dots{} arguments restrict actions to a subset of the table. See the match-key description below for details. @end defun @example ((plat 'row:retrieve*) a-key?) @result{} ((atari-st-turbo-c m68000 atari turbo-c) (atari-st-gcc m68000 atari gcc) (amiga-sas/c-5.10 m68000 amiga sas/c) (amiga-aztec m68000 amiga aztec) (amiga-dice-c m68000 amiga dice-c) (aix powerpc aix -)) @end example @defun row:remove Returns a procedure of arguments @var{key1} @var{key2} @dots{} which removes and returns the row associated with primary keys @var{key1}, @var{key2} @dots{} if it exists, or @code{#f} otherwise. @defunx row:remove* Returns a procedure of optional arguments @var{match-key1} @dots{} which removes and returns a list of all rows in this table. The optional @var{match-key1} @dots{} arguments restrict actions to a subset of the table. See the match-key description below for details. @end defun @defun row:delete Returns a procedure of arguments @var{key1} @var{key2} @dots{} which deletes the row associated with primary keys @var{key1}, @var{key2} @dots{} if it exists. The value returned is unspecified. @defunx row:delete* Returns a procedure of optional arguments @var{match-key1} @dots{} which Deletes all rows from this table. The optional @var{match-key1} @dots{} arguments restrict deletions to a subset of the table. See the match-key description below for details. The value returned is unspecified. The descriptor table and catalog entry for this table are not affected. @end defun @defun row:update Returns a procedure of one argument, @var{row}, which adds the row, @var{row}, to this table. If a row for the primary key(s) specified by @var{row} already exists in this table, it will be overwritten. The value returned is unspecified. @defunx row:update* Returns a procedure of one argument, @var{rows}, which adds each row in the list of rows, @var{rows}, to this table. If a row for the primary key specified by an element of @var{rows} already exists in this table, it will be overwritten. The value returned is unspecified. @end defun @defun row:insert Adds the row @var{row} to this table. If a row for the primary key(s) specified by @var{row} already exists in this table an error is signaled. The value returned is unspecified. @defunx row:insert* Returns a procedure of one argument, @var{rows}, which adds each row in the list of rows, @var{rows}, to this table. If a row for the primary key specified by an element of @var{rows} already exists in this table, an error is signaled. The value returned is unspecified. @end defun @defun for-each-row Returns a procedure of arguments @var{proc} @var{match-key1} @dots{} which calls @var{proc} with each @var{row} in this table in the (implementation-dependent) natural ordering for rows. The optional @var{match-key1} @dots{} arguments restrict actions to a subset of the table. See the match-key description below for details. @emph{Real} relational programmers would use some least-upper-bound join for every row to get them in order; But we don't have joins yet. @end defun @noindent @cindex match-keys The (optional) @var{match-key1} @dots{} arguments are used to restrict actions of a whole-table operation to a subset of that table. Those procedures (returned by methods) which accept match-key arguments will accept any number of match-key arguments between zero and the number of primary keys in the table. Any unspecified @var{match-key} arguments default to @code{#f}. @noindent The @var{match-key1} @dots{} restrict the actions of the table command to those records whose primary keys each satisfy the corresponding @var{match-key} argument. The arguments and their actions are: @quotation @table @asis @item @code{#f} The false value matches any key in the corresponding position. @item an object of type procedure This procedure must take a single argument, the key in the corresponding position. Any key for which the procedure returns a non-false value is a match; Any key for which the procedure returns a @code{#f} is not. @item other values Any other value matches only those keys @code{equal?} to it. @end table @end quotation @defun close-table Subsequent operations to this table will signal an error. @end defun @defvr Constant column-names @defvrx Constant column-foreigns @defvrx Constant column-domains @defvrx Constant column-types Return a list of the column names, foreign-key table names, domain names, or type names respectively for this table. These 4 methods are different from the others in that the list is returned, rather than a procedure to obtain the list. @defvrx Constant primary-limit Returns the number of primary keys fields in the relations in this table. @end defvr @node Catalog Representation, Unresolved Issues, Table Operations, Relational Database @subsection Catalog Representation @noindent Each database (in an implementation) has a @dfn{system catalog} which describes all the user accessible tables in that database (including itself). @noindent The system catalog base table has the following fields. @code{PRI} indicates a primary key for that table. @example @group PRI table-name column-limit the highest column number coltab-name descriptor table name bastab-id data base table identifier user-integrity-rule view-procedure A scheme thunk which, when called, produces a handle for the view. coltab and bastab are specified if and only if view-procedure is not. @end group @end example @noindent Descriptors for base tables (not views) are tables (pointed to by system catalog). Descriptor (base) tables have the fields: @example @group PRI column-number sequential integers from 1 primary-key? boolean TRUE for primary key components column-name column-integrity-rule domain-name @end group @end example @noindent A @dfn{primary key} is any column marked as @code{primary-key?} in the corresponding descriptor table. All the @code{primary-key?} columns must have lower column numbers than any non-@code{primary-key?} columns. Every table must have at least one primary key. Primary keys must be sufficient to distinguish all rows from each other in the table. All of the system defined tables have a single primary key. @noindent This package currently supports tables having from 1 to 4 primary keys if there are non-primary columns, and any (natural) number if @emph{all} columns are primary keys. If you need more than 4 primary keys, I would like to hear what you are doing! @noindent A @dfn{domain} is a category describing the allowable values to occur in a column. It is described by a (base) table with the fields: @example @group PRI domain-name foreign-table domain-integrity-rule type-id type-param @end group @end example @noindent The @dfn{type-id} field value is a symbol. This symbol may be used by the underlying base table implementation in storing that field. @noindent If the @code{foreign-table} field is non-@code{#f} then that field names a table from the catalog. The values for that domain must match a primary key of the table referenced by the @var{type-param} (or @code{#f}, if allowed). This package currently does not support composite foreign-keys. @noindent The types for which support is planned are: @example @group atom symbol string [] number [] money date-time boolean foreign-key expression virtual @end group @end example @node Unresolved Issues, Database Utilities, Catalog Representation, Relational Database @subsection Unresolved Issues Although @file{rdms.scm} is not large, I found it very difficult to write (six rewrites). I am not aware of any other examples of a generalized relational system (although there is little new in CS). I left out several aspects of the Relational model in order to simplify the job. The major features lacking (which might be addressed portably) are views, transaction boundaries, and protection. Protection needs a model for specifying priveledges. Given how operations are accessed from handles it should not be difficult to restrict table accesses to those allowed for that user. The system catalog has a field called @code{view-procedure}. This should allow a purely functional implementation of views. This will work but is unsatisfying for views resulting from a @dfn{select}ion (subset of rows); for whole table operations it will not be possible to reduce the number of keys scanned over when the selection is specified only by an opaque procedure. Transaction boundaries present the most intriguing area. Transaction boundaries are actually a feature of the "Comprehensive Language" of the Relational database and not of the database. Scheme would seem to provide the opportunity for an extremely clean semantics for transaction boundaries since the builtin procedures with side effects are small in number and easily identified. These side-effect builtin procedures might all be portably redefined to versions which properly handled transactions. Compiled library routines would need to be recompiled as well. Many system extensions (delete-file, system, etc.) would also need to be redefined. @noindent There are 2 scope issues that must be resolved for multiprocess transaction boundaries: @table @asis @item Process scope The actions captured by a transaction should be only for the process which invoked the start of transaction. Although standard Scheme does not provide process primitives as such, @code{dynamic-wind} would provide a workable hook into process switching for many implementations. @item Shared utilities with state Some shared utilities have state which should @emph{not} be part of a transaction. An example would be calling a pseudo-random number generator. If the success of a transaction depended on the pseudo-random number and failed, the state of the generator would be set back. Subsequent calls would keep returning the same number and keep failing. Pseudo-random number generators are not reentrant; thus they would require locks in order to operate properly in a multiprocess environment. Are all examples of utilities whose state should not be part of transactions also non-reentrant? If so, perhaps suspending transaction capture for the duration of locks would solve this problem. @end table @node Database Utilities, , Unresolved Issues, Relational Database @subsection Database Utilities @code{(require 'database-utilities)} @ftindex database-utilities @noindent This enhancement wraps a utility layer on @code{relational-database} which provides: @itemize @bullet @item Automatic loading of the appropriate base-table package when opening a database. @item Automatic execution of initialization commands stored in database. @item Transparent execution of database commands stored in @code{*commands*} table in database. @end itemize @noindent Also included are utilities which provide: @itemize @bullet @item Data definition from Scheme lists and @item Report generation @end itemize @noindent for any SLIB relational database. @defun create-database filename base-table-type Returns an open, nearly empty enhanced (with @code{*commands*} table) relational database (with base-table type @var{base-table-type}) associated with @var{filename}. @end defun @defun open-database filename @defunx open-database filename base-table-type Returns an open enchanced relational database associated with @var{filename}. The database will be opened with base-table type @var{base-table-type}) if supplied. If @var{base-table-type} is not supplied, @code{open-database} will attempt to deduce the correct base-table-type. If the database can not be opened or if it lacks the @code{*commands*} table, @code{#f} is returned. @defunx open-database! filename @defunx open-database! filename base-table-type Returns @emph{mutable} open enchanced relational database @dots{} @end defun @noindent The table @code{*commands*} in an @dfn{enhanced} relational-database has the fields (with domains): @example @group PRI name symbol parameters parameter-list procedure expression documentation string @end group @end example The @code{parameters} field is a foreign key (domain @code{parameter-list}) of the @code{*catalog-data*} table and should have the value of a table described by @code{*parameter-columns*}. This @code{parameter-list} table describes the arguments suitable for passing to the associated command. The intent of this table is to be of a form such that different user-interfaces (for instance, pull-down menus or plain-text queries) can operate from the same table. A @code{parameter-list} table has the following fields: @example @group PRI index uint name symbol arity parameter-arity domain domain defaulter expression expander expression documentation string @end group @end example The @code{arity} field can take the values: @table @code @item single Requires a single parameter of the specified domain. @item optional A single parameter of the specified domain or zero parameters is acceptable. @item boolean A single boolean parameter or zero parameters (in which case @code{#f} is substituted) is acceptable. @item nary Any number of parameters of the specified domain are acceptable. The argument passed to the command function is always a list of the parameters. @item nary1 One or more of parameters of the specified domain are acceptable. The argument passed to the command function is always a list of the parameters. @end table The @code{domain} field specifies the domain which a parameter or parameters in the @code{index}th field must satisfy. The @code{defaulter} field is an expression whose value is either @code{#f} or a procedure of one argument (the parameter-list) which returns a @emph{list} of the default value or values as appropriate. Note that since the @code{defaulter} procedure is called every time a default parameter is needed for this column, @dfn{sticky} defaults can be implemented using shared state with the domain-integrity-rule. @subsubheading Invoking Commands When an enhanced relational-database is called with a symbol which matches a @var{name} in the @code{*commands*} table, the associated procedure expression is evaluated and applied to the enhanced relational-database. A procedure should then be returned which the user can invoke on (optional) arguments. The command @code{*initialize*} is special. If present in the @code{*commands*} table, @code{open-database} or @code{open-database!} will return the value of the @code{*initialize*} command. Notice that arbitrary code can be run when the @code{*initialize*} procedure is automatically applied to the enhanced relational-database. Note also that if you wish to shadow or hide from the user relational-database methods described in @ref{Relational Database Operations}, this can be done by a dispatch in the closure returned by the @code{*initialize*} expression rather than by entries in the @code{*commands*} table if it is desired that the underlying methods remain accessible to code in the @code{*commands*} table. @defun make-command-server rdb table-name Returns a procedure of 2 arguments, a (symbol) command and a call-back procedure. When this returned procedure is called, it looks up @var{command} in table @var{table-name} and calls the call-back procedure with arguments: @table @var @item command The @var{command} @item command-value The result of evaluating the expression in the @var{procedure} field of @var{table-name} and calling it with @var{rdb}. @item parameter-name A list of the @dfn{official} name of each parameter. Corresponds to the @code{name} field of the @var{command}'s parameter-table. @item positions A list of the positive integer index of each parameter. Corresponds to the @code{index} field of the @var{command}'s parameter-table. @item arities A list of the arities of each parameter. Corresponds to the @code{arity} field of the @var{command}'s parameter-table. For a description of @code{arity} see table above. @item types A list of the type name of each parameter. Correspnds to the @code{type-id} field of the contents of the @code{domain} of the @var{command}'s parameter-table. @item defaulters A list of the defaulters for each parameter. Corresponds to the @code{defaulters} field of the @var{command}'s parameter-table. @item domain-integrity-rules A list of procedures (one for each parameter) which tests whether a value for a parameter is acceptable for that parameter. The procedure should be called with each datum in the list for @code{nary} arity parameters. @item aliases A list of lists of @code{(@r{alias} @r{parameter-name})}. There can be more than one alias per @var{parameter-name}. @end table @end defun For information about parameters, @xref{Parameter lists}. Here is an example of setting up a command with arguments and parsing those arguments from a @code{getopt} style argument list (@pxref{Getopt}). @example (require 'database-utilities) @ftindex database-utilities (require 'fluid-let) @ftindex fluid-let (require 'parameters) @ftindex parameters (require 'getopt) @ftindex getopt (define my-rdb (create-database #f 'alist-table)) (define-tables my-rdb '(foo-params *parameter-columns* *parameter-columns* ((1 single-string single string (lambda (pl) '("str")) #f "single string") (2 nary-symbols nary symbol (lambda (pl) '()) #f "zero or more symbols") (3 nary1-symbols nary1 symbol (lambda (pl) '(symb)) #f "one or more symbols") (4 optional-number optional uint (lambda (pl) '()) #f "zero or one number") (5 flag boolean boolean (lambda (pl) '(#f)) #f "a boolean flag"))) '(foo-pnames ((name string)) ((parameter-index uint)) (("s" 1) ("single-string" 1) ("n" 2) ("nary-symbols" 2) ("N" 3) ("nary1-symbols" 3) ("o" 4) ("optional-number" 4) ("f" 5) ("flag" 5))) '(my-commands ((name symbol)) ((parameters parameter-list) (parameter-names parameter-name-translation) (procedure expression) (documentation string)) ((foo foo-params foo-pnames (lambda (rdb) (lambda args (print args))) "test command arguments")))) (define (dbutil:serve-command-line rdb command-table command argc argv) (set! argv (if (vector? argv) (vector->list argv) argv)) ((make-command-server rdb command-table) command (lambda (comname comval options positions arities types defaulters dirs aliases) (apply comval (getopt->arglist argc argv options positions arities types defaulters dirs aliases))))) (define (cmd . opts) (fluid-let ((*optind* 1)) (printf "%-34s @result{} " (call-with-output-string (lambda (pt) (write (cons 'cmd opts) pt))) ;;(apply string-append (map (lambda (x) (string-append x " ")) opts)) ) (set! opts (cons "cmd" opts)) (force-output) (dbutil:serve-command-line my-rdb 'my-commands 'foo (length opts) opts))) (cmd) @result{} ("str" () (symb) () #f) (cmd "-f") @result{} ("str" () (symb) () #t) (cmd "--flag") @result{} ("str" () (symb) () #t) (cmd "-o177") @result{} ("str" () (symb) (177) #f) (cmd "-o" "177") @result{} ("str" () (symb) (177) #f) (cmd "--optional" "621") @result{} ("str" () (symb) (621) #f) (cmd "--optional=621") @result{} ("str" () (symb) (621) #f) (cmd "-s" "speciality") @result{} ("speciality" () (symb) () #f) (cmd "-sspeciality") @result{} ("speciality" () (symb) () #f) (cmd "--single" "serendipity") @result{} ("serendipity" () (symb) () #f) (cmd "--single=serendipity") @result{} ("serendipity" () (symb) () #f) (cmd "-n" "gravity" "piety") @result{} ("str" () (piety gravity) () #f) (cmd "-ngravity" "piety") @result{} ("str" () (piety gravity) () #f) (cmd "--nary" "chastity") @result{} ("str" () (chastity) () #f) (cmd "--nary=chastity" "") @result{} ("str" () ( chastity) () #f) (cmd "-N" "calamity") @result{} ("str" () (calamity) () #f) (cmd "-Ncalamity") @result{} ("str" () (calamity) () #f) (cmd "--nary1" "surety") @result{} ("str" () (surety) () #f) (cmd "--nary1=surety") @result{} ("str" () (surety) () #f) (cmd "-N" "levity" "fealty") @result{} ("str" () (fealty levity) () #f) (cmd "-Nlevity" "fealty") @result{} ("str" () (fealty levity) () #f) (cmd "--nary1" "surety" "brevity") @result{} ("str" () (brevity surety) () #f) (cmd "--nary1=surety" "brevity") @result{} ("str" () (brevity surety) () #f) (cmd "-?") @print{} Usage: cmd [OPTION ARGUMENT ...] ... -f, --flag -o, --optional[=] -n, --nary[=] ... -N, --nary1[=] ... -s, --single[=] ERROR: getopt->parameter-list "unrecognized option" "-?" @end example Some commands are defined in all extended relational-databases. The are called just like @ref{Relational Database Operations}. @defun add-domain domain-row Adds @var{domain-row} to the @dfn{domains} table if there is no row in the domains table associated with key @code{(car @var{domain-row})} and returns @code{#t}. Otherwise returns @code{#f}. For the fields and layout of the domain table, @xref{Catalog Representation}. Currently, these fields are @itemize @bullet @item domain-name @item foreign-table @item domain-integrity-rule @item type-id @item type-param @end itemize The following example adds 3 domains to the @samp{build} database. @samp{Optstring} is either a string or @code{#f}. @code{filename} is a string and @code{build-whats} is a symbol. @example (for-each (build 'add-domain) '((optstring #f (lambda (x) (or (not x) (string? x))) string #f) (filename #f #f string #f) (build-whats #f #f symbol #f))) @end example @end defun @defun delete-domain domain-name Removes and returns the @var{domain-name} row from the @dfn{domains} table. @end defun @defun domain-checker domain Returns a procedure to check an argument for conformance to domain @var{domain}. @end defun @subsubheading Defining Tables @deffn Procedure define-tables rdb spec-0 @dots{} Adds tables as specified in @var{spec-0} @dots{} to the open relational-database @var{rdb}. Each @var{spec} has the form: @lisp (@r{} @r{} @r{} @r{}) @end lisp or @lisp (@r{} @r{} @r{} @r{}) @end lisp where @r{} is the table name, @r{} is the symbol name of a descriptor table, @r{} and @r{} describe the primary keys and other fields respectively, and @r{} is a list of data rows to be added to the table. @r{} and @r{} are lists of field descriptors of the form: @lisp (@r{} @r{}) @end lisp or @lisp (@r{} @r{} @r{}) @end lisp where @r{} is the column name, @r{} is the domain of the column, and @r{} is an expression whose value is a procedure of one argument (which returns @code{#f} to signal an error). If @r{} is not a defined domain name and it matches the name of this table or an already defined (in one of @var{spec-0} @dots{}) single key field table, a foriegn-key domain will be created for it. @end deffn @deffn Procedure create-report rdb destination report-name table @deffnx Procedure create-report rdb destination report-name The symbol @var{report-name} must be primary key in the table named @code{*reports*} in the relational database @var{rdb}. @var{destination} is a port, string, or symbol. If @var{destination} is a: @table @asis @item port The table is created as ascii text and written to that port. @item string The table is created as ascii text and written to the file named by @var{destination}. @item symbol @var{destination} is the primary key for a row in the table named *printers*. @end table Each row in the table *reports* has the fields: @table @asis @item name The report name. @item default-table The table to report on if none is specified. @item header, footer A @code{format} string. At the beginning and end of each page respectively, @code{format} is called with this string and the (list of) column-names of this table. @item reporter A @code{format} string. For each row in the table, @code{format} is called with this string and the row. @item minimum-break The minimum number of lines into which the report lines for a row can be broken. Use @code{0} if a row's lines should not be broken over page boundaries. @end table Each row in the table *printers* has the fields: @table @asis @item name The printer name. @item print-procedure The procedure to call to actually print. @end table The report is prepared as follows: @itemize @bullet @item @code{Format} (@pxref{Format}) is called with the @code{header} field and the (list of) @code{column-names} of the table. @item @code{Format} is called with the @code{reporter} field and (on successive calls) each record in the natural order for the table. A count is kept of the number of newlines output by format. When the number of newlines to be output exceeds the number of lines per page, the set of lines will be broken if there are more than @code{minimum-break} left on this page and the number of lines for this row is larger or equal to twice @code{minimum-break}. @item @code{Format} is called with the @code{footer} field and the (list of) @code{column-names} of the table. The footer field should not output a newline. @item A new page is output. @item This entire process repeats until all the rows are output. @end itemize @end deffn @noindent The following example shows a new database with the name of @file{foo.db} being created with tables describing processor families and processor/os/compiler combinations. @noindent The database command @code{define-tables} is defined to call @code{define-tables} with its arguments. The database is also configured to print @samp{Welcome} when the database is opened. The database is then closed and reopened. @example (require 'database-utilities) @ftindex database-utilities (define my-rdb (create-database "foo.db" 'alist-table)) (define-tables my-rdb '(*commands* ((name symbol)) ((parameters parameter-list) (procedure expression) (documentation string)) ((define-tables no-parameters no-parameter-names (lambda (rdb) (lambda specs (apply define-tables rdb specs))) "Create or Augment tables from list of specs") (*initialize* no-parameters no-parameter-names (lambda (rdb) (display "Welcome") (newline) rdb) "Print Welcome")))) ((my-rdb 'define-tables) '(processor-family ((family atom)) ((also-ran processor-family)) ((m68000 #f) (m68030 m68000) (i386 8086) (8086 #f) (powerpc #f))) '(platform ((name symbol)) ((processor processor-family) (os symbol) (compiler symbol)) ((aix powerpc aix -) (amiga-dice-c m68000 amiga dice-c) (amiga-aztec m68000 amiga aztec) (amiga-sas/c-5.10 m68000 amiga sas/c) (atari-st-gcc m68000 atari gcc) (atari-st-turbo-c m68000 atari turbo-c) (borland-c-3.1 8086 ms-dos borland-c) (djgpp i386 ms-dos gcc) (linux i386 linux gcc) (microsoft-c 8086 ms-dos microsoft-c) (os/2-emx i386 os/2 gcc) (turbo-c-2 8086 ms-dos turbo-c) (watcom-9.0 i386 ms-dos watcom)))) ((my-rdb 'close-database)) (set! my-rdb (open-database "foo.db" 'alist-table)) @print{} Welcome @end example @node Weight-Balanced Trees, , Relational Database, Database Packages @section Weight-Balanced Trees @code{(require 'wt-tree)} @ftindex wt-tree @cindex trees, balanced binary @cindex balanced binary trees @cindex binary trees @cindex weight-balanced binary trees Balanced binary trees are a useful data structure for maintaining large sets of ordered objects or sets of associations whose keys are ordered. MIT Scheme has an comprehensive implementation of weight-balanced binary trees which has several advantages over the other data structures for large aggregates: @itemize @bullet @item In addition to the usual element-level operations like insertion, deletion and lookup, there is a full complement of collection-level operations, like set intersection, set union and subset test, all of which are implemented with good orders of growth in time and space. This makes weight balanced trees ideal for rapid prototyping of functionally derived specifications. @item An element in a tree may be indexed by its position under the ordering of the keys, and the ordinal position of an element may be determined, both with reasonable efficiency. @item Operations to find and remove minimum element make weight balanced trees simple to use for priority queues. @item The implementation is @emph{functional} rather than @emph{imperative}. This means that operations like `inserting' an association in a tree do not destroy the old tree, in much the same way that @code{(+ 1 x)} modifies neither the constant 1 nor the value bound to @code{x}. The trees are referentially transparent thus the programmer need not worry about copying the trees. Referential transparency allows space efficiency to be achieved by sharing subtrees. @end itemize These features make weight-balanced trees suitable for a wide range of applications, especially those that require large numbers of sets or discrete maps. Applications that have a few global databases and/or concentrate on element-level operations like insertion and lookup are probably better off using hash-tables or red-black trees. The @emph{size} of a tree is the number of associations that it contains. Weight balanced binary trees are balanced to keep the sizes of the subtrees of each node within a constant factor of each other. This ensures logarithmic times for single-path operations (like lookup and insertion). A weight balanced tree takes space that is proportional to the number of associations in the tree. For the current implementation, the constant of proportionality is six words per association. @cindex binary trees, as sets @cindex binary trees, as discrete maps @cindex sets, using binary trees @cindex discrete maps, using binary trees Weight balanced trees can be used as an implementation for either discrete sets or discrete maps (associations). Sets are implemented by ignoring the datum that is associated with the key. Under this scheme if an associations exists in the tree this indicates that the key of the association is a member of the set. Typically a value such as @code{()}, @code{#t} or @code{#f} is associated with the key. Many operations can be viewed as computing a result that, depending on whether the tree arguments are thought of as sets or maps, is known by two different names. An example is @code{wt-tree/member?}, which, when regarding the tree argument as a set, computes the set membership operation, but, when regarding the tree as a discrete map, @code{wt-tree/member?} is the predicate testing if the map is defined at an element in its domain. Most names in this package have been chosen based on interpreting the trees as sets, hence the name @code{wt-tree/member?} rather than @code{wt-tree/defined-at?}. @cindex run-time-loadable option @cindex option, run-time-loadable The weight balanced tree implementation is a run-time-loadable option. To use weight balanced trees, execute @example (load-option 'wt-tree) @end example @findex load-option @noindent once before calling any of the procedures defined here. @menu * Construction of Weight-Balanced Trees:: * Basic Operations on Weight-Balanced Trees:: * Advanced Operations on Weight-Balanced Trees:: * Indexing Operations on Weight-Balanced Trees:: @end menu @node Construction of Weight-Balanced Trees, Basic Operations on Weight-Balanced Trees, Weight-Balanced Trees, Weight-Balanced Trees @subsection Construction of Weight-Balanced Trees Binary trees require there to be a total order on the keys used to arrange the elements in the tree. Weight balanced trees are organized by @emph{types}, where the type is an object encapsulating the ordering relation. Creating a tree is a two-stage process. First a tree type must be created from the predicate which gives the ordering. The tree type is then used for making trees, either empty or singleton trees or trees from other aggregate structures like association lists. Once created, a tree `knows' its type and the type is used to test compatibility between trees in operations taking two trees. Usually a small number of tree types are created at the beginning of a program and used many times throughout the program's execution. @deffn {procedure+} make-wt-tree-type keywt-tree tree-type alist Returns a newly allocated weight-balanced tree that contains the same associations as @var{alist}. This procedure is equivalent to: @example (lambda (type alist) (let ((tree (make-wt-tree type))) (for-each (lambda (association) (wt-tree/add! tree (car association) (cdr association))) alist) tree)) @end example @end deffn @node Basic Operations on Weight-Balanced Trees, Advanced Operations on Weight-Balanced Trees, Construction of Weight-Balanced Trees, Weight-Balanced Trees @subsection Basic Operations on Weight-Balanced Trees This section describes the basic tree operations on weight balanced trees. These operations are the usual tree operations for insertion, deletion and lookup, some predicates and a procedure for determining the number of associations in a tree. @deffn {procedure+} wt-tree? object Returns @code{#t} if @var{object} is a weight-balanced tree, otherwise returns @code{#f}. @end deffn @deffn {procedure+} wt-tree/empty? wt-tree Returns @code{#t} if @var{wt-tree} contains no associations, otherwise returns @code{#f}. @end deffn @deffn {procedure+} wt-tree/size wt-tree Returns the number of associations in @var{wt-tree}, an exact non-negative integer. This operation takes constant time. @end deffn @deffn {procedure+} wt-tree/add wt-tree key datum Returns a new tree containing all the associations in @var{wt-tree} and the association of @var{datum} with @var{key}. If @var{wt-tree} already had an association for @var{key}, the new association overrides the old. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in @var{wt-tree}. @end deffn @deffn {procedure+} wt-tree/add! wt-tree key datum Associates @var{datum} with @var{key} in @var{wt-tree} and returns an unspecified value. If @var{wt-tree} already has an association for @var{key}, that association is replaced. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in @var{wt-tree}. @end deffn @deffn {procedure+} wt-tree/member? key wt-tree Returns @code{#t} if @var{wt-tree} contains an association for @var{key}, otherwise returns @code{#f}. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in @var{wt-tree}. @end deffn @deffn {procedure+} wt-tree/lookup wt-tree key default Returns the datum associated with @var{key} in @var{wt-tree}. If @var{wt-tree} doesn't contain an association for @var{key}, @var{default} is returned. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in @var{wt-tree}. @end deffn @deffn {procedure+} wt-tree/delete wt-tree key Returns a new tree containing all the associations in @var{wt-tree}, except that if @var{wt-tree} contains an association for @var{key}, it is removed from the result. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in @var{wt-tree}. @end deffn @deffn {procedure+} wt-tree/delete! wt-tree key If @var{wt-tree} contains an association for @var{key} the association is removed. Returns an unspecified value. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in @var{wt-tree}. @end deffn @node Advanced Operations on Weight-Balanced Trees, Indexing Operations on Weight-Balanced Trees, Basic Operations on Weight-Balanced Trees, Weight-Balanced Trees @subsection Advanced Operations on Weight-Balanced Trees In the following the @emph{size} of a tree is the number of associations that the tree contains, and a @emph{smaller} tree contains fewer associations. @deffn {procedure+} wt-tree/split< wt-tree bound Returns a new tree containing all and only the associations in @var{wt-tree} which have a key that is less than @var{bound} in the ordering relation of the tree type of @var{wt-tree}. The average and worst-case times required by this operation are proportional to the logarithm of the size of @var{wt-tree}. @end deffn @deffn {procedure+} wt-tree/split> wt-tree bound Returns a new tree containing all and only the associations in @var{wt-tree} which have a key that is greater than @var{bound} in the ordering relation of the tree type of @var{wt-tree}. The average and worst-case times required by this operation are proportional to the logarithm of size of @var{wt-tree}. @end deffn @deffn {procedure+} wt-tree/union wt-tree-1 wt-tree-2 Returns a new tree containing all the associations from both trees. This operation is asymmetric: when both trees have an association for the same key, the returned tree associates the datum from @var{wt-tree-2} with the key. Thus if the trees are viewed as discrete maps then @code{wt-tree/union} computes the map override of @var{wt-tree-1} by @var{wt-tree-2}. If the trees are viewed as sets the result is the set union of the arguments. The worst-case time required by this operation is proportional to the sum of the sizes of both trees. If the minimum key of one tree is greater than the maximum key of the other tree then the time required is at worst proportional to the logarithm of the size of the larger tree. @end deffn @deffn {procedure+} wt-tree/intersection wt-tree-1 wt-tree-2 Returns a new tree containing all and only those associations from @var{wt-tree-1} which have keys appearing as the key of an association in @var{wt-tree-2}. Thus the associated data in the result are those from @var{wt-tree-1}. If the trees are being used as sets the result is the set intersection of the arguments. As a discrete map operation, @code{wt-tree/intersection} computes the domain restriction of @var{wt-tree-1} to (the domain of) @var{wt-tree-2}. The time required by this operation is never worse that proportional to the sum of the sizes of the trees. @end deffn @deffn {procedure+} wt-tree/difference wt-tree-1 wt-tree-2 Returns a new tree containing all and only those associations from @var{wt-tree-1} which have keys that @emph{do not} appear as the key of an association in @var{wt-tree-2}. If the trees are viewed as sets the result is the asymmetric set difference of the arguments. As a discrete map operation, it computes the domain restriction of @var{wt-tree-1} to the complement of (the domain of) @var{wt-tree-2}. The time required by this operation is never worse that proportional to the sum of the sizes of the trees. @end deffn @deffn {procedure+} wt-tree/subset? wt-tree-1 wt-tree-2 Returns @code{#t} iff the key of each association in @var{wt-tree-1} is the key of some association in @var{wt-tree-2}, otherwise returns @code{#f}. Viewed as a set operation, @code{wt-tree/subset?} is the improper subset predicate. A proper subset predicate can be constructed: @example (define (proper-subset? s1 s2) (and (wt-tree/subset? s1 s2) (< (wt-tree/size s1) (wt-tree/size s2)))) @end example As a discrete map operation, @code{wt-tree/subset?} is the subset test on the domain(s) of the map(s). In the worst-case the time required by this operation is proportional to the size of @var{wt-tree-1}. @end deffn @deffn {procedure+} wt-tree/set-equal? wt-tree-1 wt-tree-2 Returns @code{#t} iff for every association in @var{wt-tree-1} there is an association in @var{wt-tree-2} that has the same key, and @emph{vice versa}. Viewing the arguments as sets @code{wt-tree/set-equal?} is the set equality predicate. As a map operation it determines if two maps are defined on the same domain. This procedure is equivalent to @example (lambda (wt-tree-1 wt-tree-2) (and (wt-tree/subset? wt-tree-1 wt-tree-2 (wt-tree/subset? wt-tree-2 wt-tree-1))) @end example In the worst-case the time required by this operation is proportional to the size of the smaller tree. @end deffn @deffn {procedure+} wt-tree/fold combiner initial wt-tree This procedure reduces @var{wt-tree} by combining all the associations, using an reverse in-order traversal, so the associations are visited in reverse order. @var{Combiner} is a procedure of three arguments: a key, a datum and the accumulated result so far. Provided @var{combiner} takes time bounded by a constant, @code{wt-tree/fold} takes time proportional to the size of @var{wt-tree}. A sorted association list can be derived simply: @example (wt-tree/fold (lambda (key datum list) (cons (cons key datum) list)) '() @var{wt-tree})) @end example The data in the associations can be summed like this: @example (wt-tree/fold (lambda (key datum sum) (+ sum datum)) 0 @var{wt-tree}) @end example @end deffn @deffn {procedure+} wt-tree/for-each action wt-tree This procedure traverses the tree in-order, applying @var{action} to each association. The associations are processed in increasing order of their keys. @var{Action} is a procedure of two arguments which take the key and datum respectively of the association. Provided @var{action} takes time bounded by a constant, @code{wt-tree/for-each} takes time proportional to in the size of @var{wt-tree}. The example prints the tree: @example (wt-tree/for-each (lambda (key value) (display (list key value))) @var{wt-tree})) @end example @end deffn @node Indexing Operations on Weight-Balanced Trees, , Advanced Operations on Weight-Balanced Trees, Weight-Balanced Trees @subsection Indexing Operations on Weight-Balanced Trees Weight balanced trees support operations that view the tree as sorted sequence of associations. Elements of the sequence can be accessed by position, and the position of an element in the sequence can be determined, both in logarthmic time. @deffn {procedure+} wt-tree/index wt-tree index @deffnx {procedure+} wt-tree/index-datum wt-tree index @deffnx {procedure+} wt-tree/index-pair wt-tree index Returns the 0-based @var{index}th association of @var{wt-tree} in the sorted sequence under the tree's ordering relation on the keys. @code{wt-tree/index} returns the @var{index}th key, @code{wt-tree/index-datum} returns the datum associated with the @var{index}th key and @code{wt-tree/index-pair} returns a new pair @code{(@var{key} . @var{datum})} which is the @code{cons} of the @var{index}th key and its datum. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. These operations signal an error if the tree is empty, if @var{index}@code{<0}, or if @var{index} is greater than or equal to the number of associations in the tree. Indexing can be used to find the median and maximum keys in the tree as follows: @example median: (wt-tree/index @var{wt-tree} (quotient (wt-tree/size @var{wt-tree}) 2)) maximum: (wt-tree/index @var{wt-tree} (-1+ (wt-tree/size @var{wt-tree}))) @end example @end deffn @deffn {procedure+} wt-tree/rank wt-tree key Determines the 0-based position of @var{key} in the sorted sequence of the keys under the tree's ordering relation, or @code{#f} if the tree has no association with for @var{key}. This procedure returns either an exact non-negative integer or @code{#f}. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. @end deffn @deffn {procedure+} wt-tree/min wt-tree @deffnx {procedure+} wt-tree/min-datum wt-tree @deffnx {procedure+} wt-tree/min-pair wt-tree Returns the association of @var{wt-tree} that has the least key under the tree's ordering relation. @code{wt-tree/min} returns the least key, @code{wt-tree/min-datum} returns the datum associated with the least key and @code{wt-tree/min-pair} returns a new pair @code{(key . datum)} which is the @code{cons} of the minimum key and its datum. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. These operations signal an error if the tree is empty. They could be written @example (define (wt-tree/min tree) (wt-tree/index tree 0)) (define (wt-tree/min-datum tree) (wt-tree/index-datum tree 0)) (define (wt-tree/min-pair tree) (wt-tree/index-pair tree 0)) @end example @end deffn @deffn {procedure+} wt-tree/delete-min wt-tree Returns a new tree containing all of the associations in @var{wt-tree} except the association with the least key under the @var{wt-tree}'s ordering relation. An error is signalled if the tree is empty. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. This operation is equivalent to @example (wt-tree/delete @var{wt-tree} (wt-tree/min @var{wt-tree})) @end example @end deffn @deffn {procedure+} wt-tree/delete-min! wt-tree Removes the association with the least key under the @var{wt-tree}'s ordering relation. An error is signalled if the tree is empty. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. This operation is equivalent to @example (wt-tree/delete! @var{wt-tree} (wt-tree/min @var{wt-tree})) @end example @end deffn @node Other Packages, About SLIB, Database Packages, Top @chapter Other Packages @menu * Data Structures:: Various data structures. * Procedures:: Miscellaneous utility procedures. * Standards Support:: Support for Scheme Standards. * Session Support:: REPL and Debugging. * Extra-SLIB Packages:: @end menu @node Data Structures, Procedures, Other Packages, Other Packages @section Data Structures @menu * Arrays:: 'array * Array Mapping:: 'array-for-each * Association Lists:: 'alist * Byte:: 'byte * Collections:: 'collect * Dynamic Data Type:: 'dynamic * Hash Tables:: 'hash-table * Hashing:: 'hash, 'sierpinski, 'soundex * Priority Queues:: 'priority-queue * Queues:: 'queue * Records:: 'record * Structures:: 'struct, 'structure @end menu @node Arrays, Array Mapping, Data Structures, Data Structures @subsection Arrays @code{(require 'array)} @ftindex array @defun array? obj Returns @code{#t} if the @var{obj} is an array, and @code{#f} if not. @end defun @defun make-array initial-value bound1 bound2 @dots{} Creates and returns an array that has as many dimensins as there are @var{bound}s and fills it with @var{initial-value}.@refill @end defun When constructing an array, @var{bound} is either an inclusive range of indices expressed as a two element list, or an upper bound expressed as a single integer. So@refill @lisp (make-array 'foo 3 3) @equiv{} (make-array 'foo '(0 2) '(0 2)) @end lisp @defun make-shared-array array mapper bound1 bound2 @dots{} @code{make-shared-array} can be used to create shared subarrays of other arrays. The @var{mapper} is a function that translates coordinates in the new array into coordinates in the old array. A @var{mapper} must be linear, and its range must stay within the bounds of the old array, but it can be otherwise arbitrary. A simple example:@refill @lisp (define fred (make-array #f 8 8)) (define freds-diagonal (make-shared-array fred (lambda (i) (list i i)) 8)) (array-set! freds-diagonal 'foo 3) (array-ref fred 3 3) @result{} FOO (define freds-center (make-shared-array fred (lambda (i j) (list (+ 3 i) (+ 3 j))) 2 2)) (array-ref freds-center 0 0) @result{} FOO @end lisp @end defun @defun array-rank obj Returns the number of dimensions of @var{obj}. If @var{obj} is not an array, 0 is returned. @end defun @defun array-shape array @code{array-shape} returns a list of inclusive bounds. So: @lisp (array-shape (make-array 'foo 3 5)) @result{} ((0 2) (0 4)) @end lisp @end defun @defun array-dimensions array @code{array-dimensions} is similar to @code{array-shape} but replaces elements with a 0 minimum with one greater than the maximum. So: @lisp (array-dimensions (make-array 'foo 3 5)) @result{} (3 5) @end lisp @end defun @deffn Procedure array-in-bounds? array index1 index2 @dots{} Returns @code{#t} if its arguments would be acceptable to @code{array-ref}. @end deffn @defun array-ref array index1 index2 @dots{} Returns the element at the @code{(@var{index1}, @var{index2})} element in @var{array}.@refill @end defun @deffn Procedure array-set! array new-value index1 index2 @dots{} @end deffn @defun array-1d-ref array index @defunx array-2d-ref array index index @defunx array-3d-ref array index index index @end defun @deffn Procedure array-1d-set! array new-value index @deffnx Procedure array-2d-set! array new-value index index @deffnx Procedure array-3d-set! array new-value index index index @end deffn The functions are just fast versions of @code{array-ref} and @code{array-set!} that take a fixed number of arguments, and perform no bounds checking.@refill If you comment out the bounds checking code, this is about as efficient as you could ask for without help from the compiler. An exercise left to the reader: implement the rest of APL. @node Array Mapping, Association Lists, Arrays, Data Structures @subsection Array Mapping @code{(require 'array-for-each)} @ftindex array-for-each @defun array-map! array0 proc array1 @dots{} @var{array1}, @dots{} must have the same number of dimensions as @var{array0} and have a range for each index which includes the range for the corresponding index in @var{array0}. @var{proc} is applied to each tuple of elements of @var{array1} @dots{} and the result is stored as the corresponding element in @var{array0}. The value returned is unspecified. The order of application is unspecified. @end defun @defun array-for-each @var{proc} @var{array0} @dots{} @var{proc} is applied to each tuple of elements of @var{array0} @dots{} in row-major order. The value returned is unspecified. @end defun @defun array-indexes @var{array} Returns an array of lists of indexes for @var{array} such that, if @var{li} is a list of indexes for which @var{array} is defined, (equal? @var{li} (apply array-ref (array-indexes @var{array}) @var{li})). @end defun @defun array-index-map! array proc applies @var{proc} to the indices of each element of @var{array} in turn, storing the result in the corresponding element. The value returned and the order of application are unspecified. One can implement @var{array-indexes} as @example (define (array-indexes array) (let ((ra (apply make-array #f (array-shape array)))) (array-index-map! ra (lambda x x)) ra)) @end example Another example: @example (define (apl:index-generator n) (let ((v (make-uniform-vector n 1))) (array-index-map! v (lambda (i) i)) v)) @end example @end defun @defun array-copy! source destination Copies every element from vector or array @var{source} to the corresponding element of @var{destination}. @var{destination} must have the same rank as @var{source}, and be at least as large in each dimension. The order of copying is unspecified. @end defun @node Association Lists, Byte, Array Mapping, Data Structures @subsection Association Lists @code{(require 'alist)} @ftindex alist Alist functions provide utilities for treating a list of key-value pairs as an associative database. These functions take an equality predicate, @var{pred}, as an argument. This predicate should be repeatable, symmetric, and transitive.@refill Alist functions can be used with a secondary index method such as hash tables for improved performance. @defun predicate->asso pred Returns an @dfn{association function} (like @code{assq}, @code{assv}, or @code{assoc}) corresponding to @var{pred}. The returned function returns a key-value pair whose key is @code{pred}-equal to its first argument or @code{#f} if no key in the alist is @var{pred}-equal to the first argument.@refill @end defun @defun alist-inquirer pred Returns a procedure of 2 arguments, @var{alist} and @var{key}, which returns the value associated with @var{key} in @var{alist} or @code{#f} if @var{key} does not appear in @var{alist}.@refill @end defun @defun alist-associator pred Returns a procedure of 3 arguments, @var{alist}, @var{key}, and @var{value}, which returns an alist with @var{key} and @var{value} associated. Any previous value associated with @var{key} will be lost. This returned procedure may or may not have side effects on its @var{alist} argument. An example of correct usage is:@refill @lisp (define put (alist-associator string-ci=?)) (define alist '()) (set! alist (put alist "Foo" 9)) @end lisp @end defun @defun alist-remover pred Returns a procedure of 2 arguments, @var{alist} and @var{key}, which returns an alist with an association whose @var{key} is key removed. This returned procedure may or may not have side effects on its @var{alist} argument. An example of correct usage is:@refill @lisp (define rem (alist-remover string-ci=?)) (set! alist (rem alist "foo")) @end lisp @end defun @defun alist-map proc alist Returns a new association list formed by mapping @var{proc} over the keys and values of @var{alist}. @var{proc} must be a function of 2 arguments which returns the new value part. @end defun @defun alist-for-each proc alist Applies @var{proc} to each pair of keys and values of @var{alist}. @var{proc} must be a function of 2 arguments. The returned value is unspecified. @end defun @node Byte, Collections, Association Lists, Data Structures @subsection Byte @code{(require 'byte)} Some algorithms are expressed in terms of arrays of small integers. Using Scheme strings to implement these arrays is not portable vis-a-vis the correspondence between integers and characters and non-ascii character sets. These functions abstract the notion of a @dfn{byte}. @cindex byte @deffn Function byte-ref bytes k @var{k} must be a valid index of @var{bytes}. @code{byte-ref} returns byte @var{k} of @var{bytes} using zero-origin indexing. @findex byte-ref @end deffn @deffn Procedure byte-set! bytes k byte @var{k} must be a valid index of @var{bytes}%, and @var{byte} must be a small integer. @code{Byte-set!} stores @var{byte} in element @var{k} of @var{bytes} @findex byte-set! and returns an unspecified value. @c @end deffn @deffn Function make-bytes k @deffnx Function make-bytes k byte @code{Make-bytes} returns a newly allocated byte-array of @findex make-bytes length @var{k}. If @var{byte} is given, then all elements of the byte-array are initialized to @var{byte}, otherwise the contents of the byte-array are unspecified. @end deffn @deffn Function write-byte byte @deffnx Function write-byte byte port Writes the byte @var{byte} (not an external representation of the byte) to the given @var{port} and returns an unspecified value. The @var{port} argument may be omitted, in which case it defaults to the value returned by @code{current-output-port}. @findex current-output-port @end deffn @deffn Function read-byte @deffnx Function read-byte port Returns the next byte available from the input @var{port}, updating the @var{port} to point to the following byte. If no more bytes are available, an end of file object is returned. @var{Port} may be omitted, in which case it defaults to the value returned by @code{current-input-port}. @findex current-input-port @end deffn @deffn Function bytes byte @dots{} Returns a newly allocated byte-array composed of the arguments. @end deffn @deffn Function bytes->list bytes @deffnx Function list->bytes bytes @code{Bytes->list} returns a newly allocated list of the @findex bytes->list bytes that make up the given byte-array. @code{List->bytes} @findex list->bytes returns a newly allocated byte-array formed from the small integers in the list @var{bytes}. @code{Bytes->list} and @code{list->bytes} are @findex list->bytes @findex bytes->list inverses so far as @code{equal?} is concerned. @findex equal? @end deffn @node Collections, Dynamic Data Type, Byte, Data Structures @subsection Collections @c Much of the documentation in this section was written by Dave Love @c (d.love@dl.ac.uk) -- don't blame Ken Dickey for its faults. @c but we can blame him for not writing it! @code{(require 'collect)} @ftindex collect Routines for managing collections. Collections are aggregate data structures supporting iteration over their elements, similar to the Dylan(TM) language, but with a different interface. They have @dfn{elements} indexed by corresponding @dfn{keys}, although the keys may be implicit (as with lists).@refill New types of collections may be defined as YASOS objects (@xref{Yasos}). They must support the following operations: @itemize @bullet @item @code{(collection? @var{self})} (always returns @code{#t}); @item @code{(size @var{self})} returns the number of elements in the collection; @item @code{(print @var{self} @var{port})} is a specialized print operation for the collection which prints a suitable representation on the given @var{port} or returns it as a string if @var{port} is @code{#t};@refill @item @code{(gen-elts @var{self})} returns a thunk which on successive invocations yields elements of @var{self} in order or gives an error if it is invoked more than @code{(size @var{self})} times;@refill @item @code{(gen-keys @var{self})} is like @code{gen-elts}, but yields the collection's keys in order. @end itemize They might support specialized @code{for-each-key} and @code{for-each-elt} operations.@refill @defun collection? obj A predicate, true initially of lists, vectors and strings. New sorts of collections must answer @code{#t} to @code{collection?}.@refill @end defun @deffn Procedure map-elts proc . collections @deffnx Procedure do-elts proc . collections @var{proc} is a procedure taking as many arguments as there are @var{collections} (at least one). The @var{collections} are iterated over in their natural order and @var{proc} is applied to the elements yielded by each iteration in turn. The order in which the arguments are supplied corresponds to te order in which the @var{collections} appear. @code{do-elts} is used when only side-effects of @var{proc} are of interest and its return value is unspecified. @code{map-elts} returns a collection (actually a vector) of the results of the applications of @var{proc}.@refill Example: @lisp (map-elts + (list 1 2 3) (vector 1 2 3)) @result{} #(2 4 6) @end lisp @end deffn @deffn Procedure map-keys proc . collections @deffnx Procedure do-keys proc . collections These are analogous to @code{map-elts} and @code{do-elts}, but each iteration is over the @var{collections}' @emph{keys} rather than their elements.@refill Example: @lisp (map-keys + (list 1 2 3) (vector 1 2 3)) @result{} #(0 2 4) @end lisp @end deffn @deffn Procedure for-each-key collection proc @deffnx Procedure for-each-elt collection proc These are like @code{do-keys} and @code{do-elts} but only for a single collection; they are potentially more efficient. @end deffn @defun reduce proc seed . collections A generalization of the list-based @code{comlist:reduce-init} (@xref{Lists as sequences}) to collections which will shadow the list-based version if @code{(require 'collect)} follows @ftindex collect @code{(require 'common-list-functions)} (@xref{Common List Functions}).@refill @ftindex common-list-functions Examples: @lisp (reduce + 0 (vector 1 2 3)) @result{} 6 (reduce union '() '((a b c) (b c d) (d a))) @result{} (c b d a). @end lisp @end defun @defun any? pred . collections A generalization of the list-based @code{some} (@xref{Lists as sequences}) to collections.@refill Example: @lisp (any? odd? (list 2 3 4 5)) @result{} #t @end lisp @end defun @defun every? pred . collections A generalization of the list-based @code{every} (@xref{Lists as sequences}) to collections.@refill Example: @lisp (every? collection? '((1 2) #(1 2))) @result{} #t @end lisp @end defun @defun empty? collection Returns @code{#t} iff there are no elements in @var{collection}. @code{(empty? @var{collection}) @equiv{} (zero? (size @var{collection}))} @end defun @defun size collection Returns the number of elements in @var{collection}. @end defun @defun Setter list-ref See @xref{Setters} for a definition of @dfn{setter}. N.B. @code{(setter list-ref)} doesn't work properly for element 0 of a list.@refill @end defun Here is a sample collection: @code{simple-table} which is also a @code{table}.@refill @lisp (define-predicate TABLE?) (define-operation (LOOKUP table key failure-object)) (define-operation (ASSOCIATE! table key value)) ;; returns key (define-operation (REMOVE! table key)) ;; returns value (define (MAKE-SIMPLE-TABLE) (let ( (table (list)) ) (object ;; table behaviors ((TABLE? self) #t) ((SIZE self) (size table)) ((PRINT self port) (format port "#")) ((LOOKUP self key failure-object) (cond ((assq key table) => cdr) (else failure-object) )) ((ASSOCIATE! self key value) (cond ((assq key table) => (lambda (bucket) (set-cdr! bucket value) key)) (else (set! table (cons (cons key value) table)) key) )) ((REMOVE! self key);; returns old value (cond ((null? table) (slib:error "TABLE:REMOVE! Key not found: " key)) ((eq? key (caar table)) (let ( (value (cdar table)) ) (set! table (cdr table)) value) ) (else (let loop ( (last table) (this (cdr table)) ) (cond ((null? this) (slib:error "TABLE:REMOVE! Key not found: " key)) ((eq? key (caar this)) (let ( (value (cdar this)) ) (set-cdr! last (cdr this)) value) ) (else (loop (cdr last) (cdr this))) ) ) ) )) ;; collection behaviors ((COLLECTION? self) #t) ((GEN-KEYS self) (collect:list-gen-elts (map car table))) ((GEN-ELTS self) (collect:list-gen-elts (map cdr table))) ((FOR-EACH-KEY self proc) (for-each (lambda (bucket) (proc (car bucket))) table) ) ((FOR-EACH-ELT self proc) (for-each (lambda (bucket) (proc (cdr bucket))) table) ) ) ) ) @end lisp @node Dynamic Data Type, Hash Tables, Collections, Data Structures @subsection Dynamic Data Type @code{(require 'dynamic)} @ftindex dynamic @defun make-dynamic obj Create and returns a new @dfn{dynamic} whose global value is @var{obj}. @end defun @defun dynamic? obj Returns true if and only if @var{obj} is a dynamic. No object satisfying @code{dynamic?} satisfies any of the other standard type predicates.@refill @end defun @defun dynamic-ref dyn Return the value of the given dynamic in the current dynamic environment. @end defun @deffn Procedure dynamic-set! dyn obj Change the value of the given dynamic to @var{obj} in the current dynamic environment. The returned value is unspecified.@refill @end deffn @defun call-with-dynamic-binding dyn obj thunk Invoke and return the value of the given thunk in a new, nested dynamic environment in which the given dynamic has been bound to a new location whose initial contents are the value @var{obj}. This dynamic environment has precisely the same extent as the invocation of the thunk and is thus captured by continuations created within that invocation and re-established by those continuations when they are invoked.@refill @end defun The @code{dynamic-bind} macro is not implemented. @node Hash Tables, Hashing, Dynamic Data Type, Data Structures @subsection Hash Tables @code{(require 'hash-table)} @ftindex hash-table @defun predicate->hash pred Returns a hash function (like @code{hashq}, @code{hashv}, or @code{hash}) corresponding to the equality predicate @var{pred}. @var{pred} should be @code{eq?}, @code{eqv?}, @code{equal?}, @code{=}, @code{char=?}, @code{char-ci=?}, @code{string=?}, or @code{string-ci=?}.@refill @end defun A hash table is a vector of association lists. @defun make-hash-table k Returns a vector of @var{k} empty (association) lists. @end defun Hash table functions provide utilities for an associative database. These functions take an equality predicate, @var{pred}, as an argument. @var{pred} should be @code{eq?}, @code{eqv?}, @code{equal?}, @code{=}, @code{char=?}, @code{char-ci=?}, @code{string=?}, or @code{string-ci=?}.@refill @defun predicate->hash-asso pred Returns a hash association function of 2 arguments, @var{key} and @var{hashtab}, corresponding to @var{pred}. The returned function returns a key-value pair whose key is @var{pred}-equal to its first argument or @code{#f} if no key in @var{hashtab} is @var{pred}-equal to the first argument.@refill @end defun @defun hash-inquirer pred Returns a procedure of 3 arguments, @code{hashtab} and @code{key}, which returns the value associated with @code{key} in @code{hashtab} or @code{#f} if key does not appear in @code{hashtab}.@refill @end defun @defun hash-associator pred Returns a procedure of 3 arguments, @var{hashtab}, @var{key}, and @var{value}, which modifies @var{hashtab} so that @var{key} and @var{value} associated. Any previous value associated with @var{key} will be lost.@refill @end defun @defun hash-remover pred Returns a procedure of 2 arguments, @var{hashtab} and @var{key}, which modifies @var{hashtab} so that the association whose key is @var{key} is removed.@refill @end defun @defun hash-map proc hash-table Returns a new hash table formed by mapping @var{proc} over the keys and values of @var{hash-table}. @var{proc} must be a function of 2 arguments which returns the new value part. @end defun @defun hash-for-each proc hash-table Applies @var{proc} to each pair of keys and values of @var{hash-table}. @var{proc} must be a function of 2 arguments. The returned value is unspecified. @end defun @node Hashing, Priority Queues, Hash Tables, Data Structures @subsection Hashing @code{(require 'hash)} @ftindex hash These hashing functions are for use in quickly classifying objects. Hash tables use these functions. @defun hashq obj k @defunx hashv obj k @defunx hash obj k Returns an exact non-negative integer less than @var{k}. For each non-negative integer less than @var{k} there are arguments @var{obj} for which the hashing functions applied to @var{obj} and @var{k} returns that integer.@refill For @code{hashq}, @code{(eq? obj1 obj2)} implies @code{(= (hashq obj1 k) (hashq obj2))}.@refill For @code{hashv}, @code{(eqv? obj1 obj2)} implies @code{(= (hashv obj1 k) (hashv obj2))}.@refill For @code{hash}, @code{(equal? obj1 obj2)} implies @code{(= (hash obj1 k) (hash obj2))}.@refill @code{hash}, @code{hashv}, and @code{hashq} return in time bounded by a constant. Notice that items having the same @code{hash} implies the items have the same @code{hashv} implies the items have the same @code{hashq}.@refill @end defun @code{(require 'sierpinski)} @ftindex sierpinski @defun make-sierpinski-indexer max-coordinate Returns a procedure (eg hash-function) of 2 numeric arguments which preserves @emph{nearness} in its mapping from NxN to N. @var{max-coordinate} is the maximum coordinate (a positive integer) of a population of points. The returned procedures is a function that takes the x and y coordinates of a point, (non-negative integers) and returns an integer corresponding to the relative position of that point along a Sierpinski curve. (You can think of this as computing a (pseudo-) inverse of the Sierpinski spacefilling curve.) Example use: Make an indexer (hash-function) for integer points lying in square of integer grid points [0,99]x[0,99]: @example (define space-key (make-sierpinski-indexer 100)) @end example Now let's compute the index of some points: @example (space-key 24 78) @result{} 9206 (space-key 23 80) @result{} 9172 @end example Note that locations (24, 78) and (23, 80) are near in index and therefore, because the Sierpinski spacefilling curve is continuous, we know they must also be near in the plane. Nearness in the plane does not, however, necessarily correspond to nearness in index, although it @emph{tends} to be so. Example applications: @itemize @bullet @item Sort points by Sierpinski index to get heuristic solution to @emph{travelling salesman problem}. For details of performance, see L. Platzman and J. Bartholdi, "Spacefilling curves and the Euclidean travelling salesman problem", JACM 36(4):719--737 (October 1989) and references therein. @item Use Sierpinski index as key by which to store 2-dimensional data in a 1-dimensional data structure (such as a table). Then locations that are near each other in 2-d space will tend to be near each other in 1-d data structure; and locations that are near in 1-d data structure will be near in 2-d space. This can significantly speed retrieval from secondary storage because contiguous regions in the plane will tend to correspond to contiguous regions in secondary storage. (This is a standard technique for managing CAD/CAM or geographic data.) @end itemize @end defun @code{(require 'soundex)} @ftindex soundex @defun soundex name Computes the @emph{soundex} hash of @var{name}. Returns a string of an initial letter and up to three digits between 0 and 6. Soundex supposedly has the property that names that sound similar in normal English pronunciation tend to map to the same key. Soundex was a classic algorithm used for manual filing of personal records before the advent of computers. It performs adequately for English names but has trouble with other nationalities. See Knuth, Vol. 3 @cite{Sorting and searching}, pp 391--2 To manage unusual inputs, @code{soundex} omits all non-alphabetic characters. Consequently, in this implementation: @example (soundex ) @result{} "" (soundex "") @result{} "" @end example Examples from Knuth: @example (map soundex '("Euler" "Gauss" "Hilbert" "Knuth" "Lloyd" "Lukasiewicz")) @result{} ("E460" "G200" "H416" "K530" "L300" "L222") (map soundex '("Ellery" "Ghosh" "Heilbronn" "Kant" "Ladd" "Lissajous")) @result{} ("E460" "G200" "H416" "K530" "L300" "L222") @end example Some cases in which the algorithm fails (Knuth): @example (map soundex '("Rogers" "Rodgers")) @result{} ("R262" "R326") (map soundex '("Sinclair" "St. Clair")) @result{} ("S524" "S324") (map soundex '("Tchebysheff" "Chebyshev")) @result{} ("T212" "C121") @end example @end defun @node Priority Queues, Queues, Hashing, Data Structures @subsection Priority Queues @code{(require 'priority-queue)} @ftindex priority-queue @defun make-heap pred added field setters. @defmac define-record tag (var1 var2 @dots{}) Defines several functions pertaining to record-name @var{tag}: @defun make-@var{tag} var1 var2 @dots{} @end defun @defun @var{tag}? obj @end defun @defun @var{tag}->var1 obj @end defun @defun @var{tag}->var2 obj @end defun @dots{} @defun set-@var{tag}-var1! obj val @end defun @defun set-@var{tag}-var2! obj val @end defun @dots{} Here is an example of its use. @example (define-record term (operator left right)) @result{} # (define foo (make-term 'plus 1 2)) @result{} foo (term->left foo) @result{} 1 (set-term-left! foo 2345) @result{} # (term->left foo) @result{} 2345 @end example @end defmac @defmac variant-case exp (tag (var1 var2 @dots{}) body) @dots{} executes the following for the matching clause: @example ((lambda (@var{var1} @var{var} @dots{}) @var{body}) (@var{tag->var1} @var{exp}) (@var{tag->var2} @var{exp}) @dots{}) @end example @end defmac @node Procedures, Standards Support, Data Structures, Other Packages @section Procedures Anything that doesn't fall neatly into any of the other categories winds up here. @menu * Common List Functions:: 'common-list-functions * Tree Operations:: 'tree * Chapter Ordering:: 'chapter-order * Sorting:: 'sort * Topological Sort:: Keep your socks on. * String-Case:: 'string-case * String Ports:: 'string-port * String Search:: Also Search from a Port. * Line I/O:: 'line-i/o * Multi-Processing:: 'process @end menu @node Common List Functions, Tree Operations, Procedures, Procedures @subsection Common List Functions @code{(require 'common-list-functions)} @ftindex common-list-functions The procedures below follow the Common LISP equivalents apart from optional arguments in some cases. @menu * List construction:: * Lists as sets:: * Lists as sequences:: * Destructive list operations:: * Non-List functions:: @end menu @node List construction, Lists as sets, Common List Functions, Common List Functions @subsubsection List construction @defun make-list k . init @code{make-list} creates and returns a list of @var{k} elements. If @var{init} is included, all elements in the list are initialized to @var{init}.@refill Example: @lisp (make-list 3) @result{} (# # #) (make-list 5 'foo) @result{} (foo foo foo foo foo) @end lisp @end defun @defun list* x . y Works like @code{list} except that the cdr of the last pair is the last argument unless there is only one argument, when the result is just that argument. Sometimes called @code{cons*}. E.g.:@refill @lisp (list* 1) @result{} 1 (list* 1 2 3) @result{} (1 2 . 3) (list* 1 2 '(3 4)) @result{} (1 2 3 4) (list* @var{args} '()) @equiv{} (list @var{args}) @end lisp @end defun @defun copy-list lst @code{copy-list} makes a copy of @var{lst} using new pairs and returns it. Only the top level of the list is copied, i.e., pairs forming elements of the copied list remain @code{eq?} to the corresponding elements of the original; the copy is, however, not @code{eq?} to the original, but is @code{equal?} to it.@refill Example: @lisp (copy-list '(foo foo foo)) @result{} (foo foo foo) (define q '(foo bar baz bang)) (define p q) (eq? p q) @result{} #t (define r (copy-list q)) (eq? q r) @result{} #f (equal? q r) @result{} #t (define bar '(bar)) (eq? bar (car (copy-list (list bar 'foo)))) @result{} #t @end lisp @end defun @node Lists as sets, Lists as sequences, List construction, Common List Functions @subsubsection Lists as sets @code{eq?} is used to test for membership by all the procedures below which treat lists as sets.@refill @defun adjoin e l @code{adjoin} returns the adjoint of the element @var{e} and the list @var{l}. That is, if @var{e} is in @var{l}, @code{adjoin} returns @var{l}, otherwise, it returns @code{(cons @var{e} @var{l})}.@refill Example: @lisp (adjoin 'baz '(bar baz bang)) @result{} (bar baz bang) (adjoin 'foo '(bar baz bang)) @result{} (foo bar baz bang) @end lisp @end defun @defun union l1 l2 @code{union} returns the combination of @var{l1} and @var{l2}. Duplicates between @var{l1} and @var{l2} are culled. Duplicates within @var{l1} or within @var{l2} may or may not be removed.@refill Example: @lisp (union '(1 2 3 4) '(5 6 7 8)) @result{} (4 3 2 1 5 6 7 8) (union '(1 2 3 4) '(3 4 5 6)) @result{} (2 1 3 4 5 6) @end lisp @end defun @defun intersection l1 l2 @code{intersection} returns all elements that are in both @var{l1} and @var{l2}.@refill Example: @lisp (intersection '(1 2 3 4) '(3 4 5 6)) @result{} (3 4) (intersection '(1 2 3 4) '(5 6 7 8)) @result{} () @end lisp @end defun @defun set-difference l1 l2 @code{set-difference} returns the union of all elements that are in @var{l1} but not in @var{l2}.@refill Example: @lisp (set-difference '(1 2 3 4) '(3 4 5 6)) @result{} (1 2) (set-difference '(1 2 3 4) '(1 2 3 4 5 6)) @result{} () @end lisp @end defun @defun member-if pred lst @code{member-if} returns @var{lst} if @code{(@var{pred} @var{element})} is @code{#t} for any @var{element} in @var{lst}. Returns @code{#f} if @var{pred} does not apply to any @var{element} in @var{lst}.@refill Example: @lisp (member-if vector? '(1 2 3 4)) @result{} #f (member-if number? '(1 2 3 4)) @result{} (1 2 3 4) @end lisp @end defun @defun some pred lst . more-lsts @var{pred} is a boolean function of as many arguments as there are list arguments to @code{some} i.e., @var{lst} plus any optional arguments. @var{pred} is applied to successive elements of the list arguments in order. @code{some} returns @code{#t} as soon as one of these applications returns @code{#t}, and is @code{#f} if none returns @code{#t}. All the lists should have the same length.@refill Example: @lisp (some odd? '(1 2 3 4)) @result{} #t (some odd? '(2 4 6 8)) @result{} #f (some > '(2 3) '(1 4)) @result{} #f @end lisp @end defun @defun every pred lst . more-lsts @code{every} is analogous to @code{some} except it returns @code{#t} if every application of @var{pred} is @code{#t} and @code{#f} otherwise.@refill Example: @lisp (every even? '(1 2 3 4)) @result{} #f (every even? '(2 4 6 8)) @result{} #t (every > '(2 3) '(1 4)) @result{} #f @end lisp @end defun @defun notany pred . lst @code{notany} is analogous to @code{some} but returns @code{#t} if no application of @var{pred} returns @code{#t} or @code{#f} as soon as any one does.@refill @end defun @defun notevery pred . lst @code{notevery} is analogous to @code{some} but returns @code{#t} as soon as an application of @var{pred} returns @code{#f}, and @code{#f} otherwise.@refill Example: @lisp (notevery even? '(1 2 3 4)) @result{} #t (notevery even? '(2 4 6 8)) @result{} #f @end lisp @end defun @defun find-if pred lst @code{find-if} searches for the first @var{element} in @var{lst} such that @code{(@var{pred} @var{element})} returns @code{#t}. If it finds any such @var{element} in @var{lst}, @var{element} is returned. Otherwise, @code{#f} is returned.@refill Example: @lisp (find-if number? '(foo 1 bar 2)) @result{} 1 (find-if number? '(foo bar baz bang)) @result{} #f (find-if symbol? '(1 2 foo bar)) @result{} foo @end lisp @end defun @defun remove elt lst @code{remove} removes all occurrences of @var{elt} from @var{lst} using @code{eqv?} to test for equality and returns everything that's left. N.B.: other implementations (Chez, Scheme->C and T, at least) use @code{equal?} as the equality test.@refill Example: @lisp (remove 1 '(1 2 1 3 1 4 1 5)) @result{} (2 3 4 5) (remove 'foo '(bar baz bang)) @result{} (bar baz bang) @end lisp @end defun @defun remove-if pred lst @code{remove-if} removes all @var{element}s from @var{lst} where @code{(@var{pred} @var{element})} is @code{#t} and returns everything that's left.@refill Example: @lisp (remove-if number? '(1 2 3 4)) @result{} () (remove-if even? '(1 2 3 4 5 6 7 8)) @result{} (1 3 5 7) @end lisp @end defun @defun remove-if-not pred lst @code{remove-if-not} removes all @var{element}s from @var{lst} for which @code{(@var{pred} @var{element})} is @code{#f} and returns everything that's left.@refill Example: @lisp (remove-if-not number? '(foo bar baz)) @result{} () (remove-if-not odd? '(1 2 3 4 5 6 7 8)) @result{} (1 3 5 7) @end lisp @end defun @defun has-duplicates? lst returns @code{#t} if 2 members of @var{lst} are @code{equal?}, @code{#f} otherwise. Example: @lisp (has-duplicates? '(1 2 3 4)) @result{} #f (has-duplicates? '(2 4 3 4)) @result{} #t @end lisp @end defun @node Lists as sequences, Destructive list operations, Lists as sets, Common List Functions @subsubsection Lists as sequences @defun position obj lst @code{position} returns the 0-based position of @var{obj} in @var{lst}, or @code{#f} if @var{obj} does not occur in @var{lst}.@refill Example: @lisp (position 'foo '(foo bar baz bang)) @result{} 0 (position 'baz '(foo bar baz bang)) @result{} 2 (position 'oops '(foo bar baz bang)) @result{} #f @end lisp @end defun @defun reduce p lst @code{reduce} combines all the elements of a sequence using a binary operation (the combination is left-associative). For example, using @code{+}, one can add up all the elements. @code{reduce} allows you to apply a function which accepts only two arguments to more than 2 objects. Functional programmers usually refer to this as @dfn{foldl}. @code{collect:reduce} (@xref{Collections}) provides a version of @code{collect} generalized to collections.@refill Example: @lisp (reduce + '(1 2 3 4)) @result{} 10 (define (bad-sum . l) (reduce + l)) (bad-sum 1 2 3 4) @equiv{} (reduce + (1 2 3 4)) @equiv{} (+ (+ (+ 1 2) 3) 4) @result{} 10 (bad-sum) @equiv{} (reduce + ()) @result{} () (reduce string-append '("hello" "cruel" "world")) @equiv{} (string-append (string-append "hello" "cruel") "world") @result{} "hellocruelworld" (reduce anything '()) @result{} () (reduce anything '(x)) @result{} x @end lisp What follows is a rather non-standard implementation of @code{reverse} in terms of @code{reduce} and a combinator elsewhere called @dfn{C}.@refill @lisp ;;; Contributed by Jussi Piitulainen (jpiitula@@ling.helsinki.fi) (define commute (lambda (f) (lambda (x y) (f y x)))) (define reverse (lambda (args) (reduce-init (commute cons) '() args))) @end lisp @end defun @defun reduce-init p init lst @code{reduce-init} is the same as reduce, except that it implicitly inserts @var{init} at the start of the list. @code{reduce-init} is preferred if you want to handle the null list, the one-element, and lists with two or more elements consistently. It is common to use the operator's idempotent as the initializer. Functional programmers usually call this @dfn{foldl}.@refill Example: @lisp (define (sum . l) (reduce-init + 0 l)) (sum 1 2 3 4) @equiv{} (reduce-init + 0 (1 2 3 4)) @equiv{} (+ (+ (+ (+ 0 1) 2) 3) 4) @result{} 10 (sum) @equiv{} (reduce-init + 0 '()) @result{} 0 (reduce-init string-append "@@" '("hello" "cruel" "world")) @equiv{} (string-append (string-append (string-append "@@" "hello") "cruel") "world") @result{} "@@hellocruelworld" @end lisp Given a differentiation of 2 arguments, @code{diff}, the following will differentiate by any number of variables. @lisp (define (diff* exp . vars) (reduce-init diff exp vars)) @end lisp Example: @lisp ;;; Real-world example: Insertion sort using reduce-init. (define (insert l item) (if (null? l) (list item) (if (< (car l) item) (cons (car l) (insert (cdr l) item)) (cons item l)))) (define (insertion-sort l) (reduce-init insert '() l)) (insertion-sort '(3 1 4 1 5) @equiv{} (reduce-init insert () (3 1 4 1 5)) @equiv{} (insert (insert (insert (insert (insert () 3) 1) 4) 1) 5) @equiv{} (insert (insert (insert (insert (3)) 1) 4) 1) 5) @equiv{} (insert (insert (insert (1 3) 4) 1) 5) @equiv{} (insert (insert (1 3 4) 1) 5) @equiv{} (insert (1 1 3 4) 5) @result{} (1 1 3 4 5) @end lisp @end defun @defun last lst n @code{last} returns the last @var{n} elements of @var{lst}. @var{n} must be a non-negative integer. Example: @lisp (last '(foo bar baz bang) 2) @result{} (baz bang) (last '(1 2 3) 0) @result{} 0 @end lisp @end defun @defun butlast lst n @code{butlast} returns all but the last @var{n} elements of @var{lst}.@refill Example: @lisp (butlast '(a b c d) 3) @result{} (a) (butlast '(a b c d) 4) @result{} () @end lisp @end defun @noindent @code{last} and @code{butlast} split a list into two parts when given identical arugments. @example (last '(a b c d e) 2) @result{} (d e) (butlast '(a b c d e) 2) @result{} (a b c) @end example @defun nthcdr n lst @code{nthcdr} takes @var{n} @code{cdr}s of @var{lst} and returns the result. Thus @code{(nthcdr 3 @var{lst})} @equiv{} @code{(cdddr @var{lst})} Example: @lisp (nthcdr 2 '(a b c d)) @result{} (c d) (nthcdr 0 '(a b c d)) @result{} (a b c d) @end lisp @end defun @defun butnthcdr n lst @code{butnthcdr} returns all but the nthcdr @var{n} elements of @var{lst}.@refill Example: @lisp (butnthcdr 3 '(a b c d)) @result{} (a b c) (butnthcdr 4 '(a b c d)) @result{} () @end lisp @end defun @noindent @code{nthcdr} and @code{butnthcdr} split a list into two parts when given identical arugments. @example (nthcdr 2 '(a b c d e)) @result{} (c d e) (butnthcdr 2 '(a b c d e)) @result{} (a b) @end example @node Destructive list operations, Non-List functions, Lists as sequences, Common List Functions @subsubsection Destructive list operations These procedures may mutate the list they operate on, but any such mutation is undefined. @deffn Procedure nconc args @code{nconc} destructively concatenates its arguments. (Compare this with @code{append}, which copies arguments rather than destroying them.) Sometimes called @code{append!} (@xref{Rev2 Procedures}).@refill Example: You want to find the subsets of a set. Here's the obvious way: @lisp (define (subsets set) (if (null? set) '(()) (append (mapcar (lambda (sub) (cons (car set) sub)) (subsets (cdr set))) (subsets (cdr set))))) @end lisp But that does way more consing than you need. Instead, you could replace the @code{append} with @code{nconc}, since you don't have any need for all the intermediate results.@refill Example: @lisp (define x '(a b c)) (define y '(d e f)) (nconc x y) @result{} (a b c d e f) x @result{} (a b c d e f) @end lisp @code{nconc} is the same as @code{append!} in @file{sc2.scm}. @end deffn @deffn Procedure nreverse lst @code{nreverse} reverses the order of elements in @var{lst} by mutating @code{cdr}s of the list. Sometimes called @code{reverse!}.@refill Example: @lisp (define foo '(a b c)) (nreverse foo) @result{} (c b a) foo @result{} (a) @end lisp Some people have been confused about how to use @code{nreverse}, thinking that it doesn't return a value. It needs to be pointed out that@refill @lisp (set! lst (nreverse lst)) @end lisp @noindent is the proper usage, not @lisp (nreverse lst) @end lisp The example should suffice to show why this is the case. @end deffn @deffn Procedure delete elt lst @deffnx Procedure delete-if pred lst @deffnx Procedure delete-if-not pred lst Destructive versions of @code{remove} @code{remove-if}, and @code{remove-if-not}.@refill Example: @lisp (define lst '(foo bar baz bang)) (delete 'foo lst) @result{} (bar baz bang) lst @result{} (foo bar baz bang) (define lst '(1 2 3 4 5 6 7 8 9)) (delete-if odd? lst) @result{} (2 4 6 8) lst @result{} (1 2 4 6 8) @end lisp Some people have been confused about how to use @code{delete}, @code{delete-if}, and @code{delete-if}, thinking that they dont' return a value. It needs to be pointed out that@refill @lisp (set! lst (delete el lst)) @end lisp @noindent is the proper usage, not @lisp (delete el lst) @end lisp The examples should suffice to show why this is the case. @end deffn @node Non-List functions, , Destructive list operations, Common List Functions @subsubsection Non-List functions @defun and? . args @code{and?} checks to see if all its arguments are true. If they are, @code{and?} returns @code{#t}, otherwise, @code{#f}. (In contrast to @code{and}, this is a function, so all arguments are always evaluated and in an unspecified order.)@refill Example: @lisp (and? 1 2 3) @result{} #t (and #f 1 2) @result{} #f @end lisp @end defun @defun or? . args @code{or?} checks to see if any of its arguments are true. If any is true, @code{or?} returns @code{#t}, and @code{#f} otherwise. (To @code{or} as @code{and?} is to @code{and}.)@refill Example: @lisp (or? 1 2 #f) @result{} #t (or? #f #f #f) @result{} #f @end lisp @end defun @defun atom? object Returns @code{#t} if @var{object} is not a pair and @code{#f} if it is pair. (Called @code{atom} in Common LISP.) @lisp (atom? 1) @result{} #t (atom? '(1 2)) @result{} #f (atom? #(1 2)) ; dubious! @result{} #t @end lisp @end defun @defun type-of object Returns a symbol name for the type of @var{object}. @end defun @defun coerce object result-type Converts and returns @var{object} of type @code{char}, @code{number}, @code{string}, @code{symbol}, @code{list}, or @code{vector} to @var{result-type} (which must be one of these symbols). @end defun @node Tree Operations, Chapter Ordering, Common List Functions, Procedures @subsection Tree operations @code{(require 'tree)} @ftindex tree These are operations that treat lists a representations of trees. @defun subst new old tree @defunx substq new old tree @defunx substv new old tree @code{subst} makes a copy of @var{tree}, substituting @var{new} for every subtree or leaf of @var{tree} which is @code{equal?} to @var{old} and returns a modified tree. The original @var{tree} is unchanged, but may share parts with the result.@refill @code{substq} and @code{substv} are similar, but test against @var{old} using @code{eq?} and @code{eqv?} respectively.@refill Examples: @lisp (substq 'tempest 'hurricane '(shakespeare wrote (the hurricane))) @result{} (shakespeare wrote (the tempest)) (substq 'foo '() '(shakespeare wrote (twelfth night))) @result{} (shakespeare wrote (twelfth night . foo) . foo) (subst '(a . cons) '(old . pair) '((old . spice) ((old . shoes) old . pair) (old . pair))) @result{} ((old . spice) ((old . shoes) a . cons) (a . cons)) @end lisp @end defun @defun copy-tree tree Makes a copy of the nested list structure @var{tree} using new pairs and returns it. All levels are copied, so that none of the pairs in the tree are @code{eq?} to the original ones -- only the leaves are.@refill Example: @lisp (define bar '(bar)) (copy-tree (list bar 'foo)) @result{} ((bar) foo) (eq? bar (car (copy-tree (list bar 'foo)))) @result{} #f @end lisp @end defun @node Chapter Ordering, Sorting, Tree Operations, Procedures @subsection Chapter Ordering @code{(require 'chapter-order)} @ftindex chapter-order The @samp{chap:} functions deal with strings which are ordered like chapter numbers (or letters) in a book. Each section of the string consists of consecutive numeric or consecutive aphabetic characters of like case. @defun chap:string? string1 string2 @defunx chap:string<=? string1 string2 @defunx chap:string>=? string1 string2 Implement the corresponding chapter-order predicates. @end defun @defun chap:next-string string Returns the next string in the @emph{chapter order}. If @var{string} has no alphabetic or numeric characters, @code{(string-append @var{string} "0")} is returnd. The argument to chap:next-string will always be @code{chap:string}, @code{char?}, @code{char-ci?}, @code{string?}, @code{string-ci?} are suitable for use as comparison functions. Think of @code{(less? x y)} as saying when @code{x} must @emph{not} precede @code{y}.@refill @defun sorted? sequence less? Returns @code{#t} when the sequence argument is in non-decreasing order according to @var{less?} (that is, there is no adjacent pair @code{@dots{} x y @dots{}} for which @code{(less? y x)}).@refill Returns @code{#f} when the sequence contains at least one out-of-order pair. It is an error if the sequence is neither a list nor a vector. @end defun @defun merge list1 list2 less? This merges two lists, producing a completely new list as result. I gave serious consideration to producing a Common-LISP-compatible version. However, Common LISP's @code{sort} is our @code{sort!} (well, in fact Common LISP's @code{stable-sort} is our @code{sort!}, merge sort is @emph{fast} as well as stable!) so adapting CL code to Scheme takes a bit of work anyway. I did, however, appeal to CL to determine the @emph{order} of the arguments. @end defun @deffn Procedure merge! list1 list2 less? Merges two lists, re-using the pairs of @var{list1} and @var{list2} to build the result. If the code is compiled, and @var{less?} constructs no new pairs, no pairs at all will be allocated. The first pair of the result will be either the first pair of @var{list1} or the first pair of @var{list2}, but you can't predict which. The code of @code{merge} and @code{merge!} could have been quite a bit simpler, but they have been coded to reduce the amount of work done per iteration. (For example, we only have one @code{null?} test per iteration.)@refill @end deffn @defun sort sequence less? Accepts either a list or a vector, and returns a new sequence which is sorted. The new sequence is the same type as the input. Always @code{(sorted? (sort sequence less?) less?)}. The original sequence is not altered in any way. The new sequence shares its @emph{elements} with the old one; no elements are copied.@refill @end defun @deffn Procedure sort! sequence less? Returns its sorted result in the original boxes. If the original sequence is a list, no new storage is allocated at all. If the original sequence is a vector, the sorted elements are put back in the same vector. Some people have been confused about how to use @code{sort!}, thinking that it doesn't return a value. It needs to be pointed out that @lisp (set! slist (sort! slist <)) @end lisp @noindent is the proper usage, not @lisp (sort! slist <) @end lisp @end deffn Note that these functions do @emph{not} accept a CL-style @samp{:key} argument. A simple device for obtaining the same expressiveness is to define@refill @lisp (define (keyed less? key) (lambda (x y) (less? (key x) (key y)))) @end lisp @noindent and then, when you would have written @lisp (sort a-sequence #'my-less :key #'my-key) @end lisp @noindent in Common LISP, just write @lisp (sort! a-sequence (keyed my-less? my-key)) @end lisp @noindent in Scheme. @node Topological Sort, String-Case, Sorting, Procedures @subsection Topological Sort @code{(require 'topological-sort)} or @code{(require 'tsort)} @ftindex topological-sort @ftindex tsort @noindent The algorithm is inspired by Cormen, Leiserson and Rivest (1990) @cite{Introduction to Algorithms}, chapter 23. @defun tsort dag pred @defunx topological-sort dag pred where @table @var @item dag is a list of sublists. The car of each sublist is a vertex. The cdr is the adjacency list of that vertex, i.e. a list of all vertices to which there exists an edge from the car vertex. @item pred is one of @code{eq?}, @code{eqv?}, @code{equal?}, @code{=}, @code{char=?}, @code{char-ci=?}, @code{string=?}, or @code{string-ci=?}. @end table Sort the directed acyclic graph @var{dag} so that for every edge from vertex @var{u} to @var{v}, @var{u} will come before @var{v} in the resulting list of vertices. Time complexity: O (|V| + |E|) Example (from Cormen): @quotation Prof. Bumstead topologically sorts his clothing when getting dressed. The first argument to `tsort' describes which garments he needs to put on before others. (For example, Prof Bumstead needs to put on his shirt before he puts on his tie or his belt.) `tsort' gives the correct order of dressing: @end quotation @example (require 'tsort) @ftindex tsort (tsort '((shirt tie belt) (tie jacket) (belt jacket) (watch) (pants shoes belt) (undershorts pants shoes) (socks shoes)) eq?) @result{} (socks undershorts pants shoes watch shirt belt tie jacket) @end example @end defun @node String-Case, String Ports, Topological Sort, Procedures @subsection String-Case @code{(require 'string-case)} @ftindex string-case @deffn Procedure string-upcase str @deffnx Procedure string-downcase str @deffnx Procedure string-capitalize str The obvious string conversion routines. These are non-destructive. @end deffn @defun string-upcase! str @defunx string-downcase! str @defunx string-captialize! str The destructive versions of the functions above. @end defun @node String Ports, String Search, String-Case, Procedures @subsection String Ports @code{(require 'string-port)} @ftindex string-port @deffn Procedure call-with-output-string proc @var{proc} must be a procedure of one argument. This procedure calls @var{proc} with one argument: a (newly created) output port. When the function returns, the string composed of the characters written into the port is returned.@refill @end deffn @deffn Procedure call-with-input-string string proc @var{proc} must be a procedure of one argument. This procedure calls @var{proc} with one argument: an (newly created) input port from which @var{string}'s contents may be read. When @var{proc} returns, the port is closed and the value yielded by the procedure @var{proc} is returned.@refill @end deffn @node String Search, Line I/O, String Ports, Procedures @subsection String Search @code{(require 'string-search)} @ftindex string-search @deffn Procedure string-index string char @deffnx Procedure string-index-ci string char Returns the index of the first occurence of @var{char} within @var{string}, or @code{#f} if the @var{string} does not contain a character @var{char}. @end deffn @deffn Procedure string-reverse-index string char @deffnx Procedure string-reverse-index-ci string char Returns the index of the last occurence of @var{char} within @var{string}, or @code{#f} if the @var{string} does not contain a character @var{char}. @end deffn @deffn procedure substring? pattern string @deffnx procedure substring-ci? pattern string Searches @var{string} to see if some substring of @var{string} is equal to @var{pattern}. @code{substring?} returns the index of the first character of the first substring of @var{string} that is equal to @var{pattern}; or @code{#f} if @var{string} does not contain @var{pattern}. @example (substring? "rat" "pirate") @result{} 2 (substring? "rat" "outrage") @result{} #f (substring? "" any-string) @result{} 0 @end example @end deffn @deffn Procedure find-string-from-port? str in-port max-no-chars Looks for a string @var{str} within the first @var{max-no-chars} chars of the input port @var{in-port}. @deffnx Procedure find-string-from-port? str in-port When called with two arguments, the search span is limited by the end of the input stream. @deffnx Procedure find-string-from-port? str in-port char Searches up to the first occurrence of character @var{char} in @var{str}. @deffnx Procedure find-string-from-port? str in-port proc Searches up to the first occurrence of the procedure @var{proc} returning non-false when called with a character (from @var{in-port}) argument. When the @var{str} is found, @code{find-string-from-port?} returns the number of characters it has read from the port, and the port is set to read the first char after that (that is, after the @var{str}) The function returns @code{#f} when the @var{str} isn't found. @code{find-string-from-port?} reads the port @emph{strictly} sequentially, and does not perform any buffering. So @code{find-string-from-port?} can be used even if the @var{in-port} is open to a pipe or other communication channel. @end deffn @node Line I/O, Multi-Processing, String Search, Procedures @subsection Line I/O @code{(require 'line-i/o)} @ftindex line-i @defun read-line @defunx read-line port Returns a string of the characters up to, but not including a newline or end of file, updating @var{port} to point to the character following the newline. If no characters are available, an end of file object is returned. @var{port} may be omitted, in which case it defaults to the value returned by @code{current-input-port}.@refill @end defun @defun read-line! string @defunx read-line! string port Fills @var{string} with characters up to, but not including a newline or end of file, updating the port to point to the last character read or following the newline if it was read. If no characters are available, an end of file object is returned. If a newline or end of file was found, the number of characters read is returned. Otherwise, @code{#f} is returned. @var{port} may be omitted, in which case it defaults to the value returned by @code{current-input-port}.@refill @end defun @defun write-line string @defunx write-line string port Writes @var{string} followed by a newline to the given port and returns an unspecified value. Port may be omited, in which case it defaults to the value returned by @code{current-input-port}.@refill @end defun @node Multi-Processing, , Line I/O, Procedures @subsection Multi-Processing @code{(require 'process)} @ftindex process This module implements asynchronous (non-polled) time-sliced multi-processing in the SCM Scheme implementation using procedures @code{alarm} and @code{alarm-interrupt}. @findex alarm @findex alarm-interrupt Until this is ported to another implementation, consider it an example of writing schedulers in Scheme. @deffn Procedure add-process! proc Adds proc, which must be a procedure (or continuation) capable of accepting accepting one argument, to the @code{process:queue}. The value returned is unspecified. The argument to @var{proc} should be ignored. If @var{proc} returns, the process is killed.@refill @end deffn @deffn Procedure process:schedule! Saves the current process on @code{process:queue} and runs the next process from @code{process:queue}. The value returned is unspecified.@refill @end deffn @deffn Procedure kill-process! Kills the current process and runs the next process from @code{process:queue}. If there are no more processes on @code{process:queue}, @code{(slib:exit)} is called (@xref{System}). @end deffn @node Standards Support, Session Support, Procedures, Other Packages @section Standards Support @menu * With-File:: 'with-file * Transcripts:: 'transcript * Rev2 Procedures:: 'rev2-procedures * Rev4 Optional Procedures:: 'rev4-optional-procedures * Multi-argument / and -:: 'multiarg/and- * Multi-argument Apply:: 'multiarg-apply * Rationalize:: 'rationalize * Promises:: 'promise * Dynamic-Wind:: 'dynamic-wind * Values:: 'values @end menu @node With-File, Transcripts, Standards Support, Standards Support @subsection With-File @code{(require 'with-file)} @ftindex with-file @defun with-input-from-file file thunk @defunx with-output-to-file file thunk Description found in R4RS. @end defun @node Transcripts, Rev2 Procedures, With-File, Standards Support @subsection Transcripts @code{(require 'transcript)} @ftindex transcript @defun transcript-on filename @defunx transcript-off filename Redefines @code{read-char}, @code{read}, @code{write-char}, @code{write}, @code{display}, and @code{newline}.@refill @end defun @node Rev2 Procedures, Rev4 Optional Procedures, Transcripts, Standards Support @subsection Rev2 Procedures @code{(require 'rev2-procedures)} @ftindex rev2-procedures The procedures below were specified in the @cite{Revised^2 Report on Scheme}. @strong{N.B.}: The symbols @code{1+} and @code{-1+} are not @cite{R4RS} syntax. Scheme->C, for instance, barfs on this module.@refill @deffn Procedure substring-move-left! string1 start1 end1 string2 start2 @deffnx Procedure substring-move-right! string1 start1 end1 string2 start2 @var{string1} and @var{string2} must be a strings, and @var{start1}, @var{start2} and @var{end1} must be exact integers satisfying@refill @display 0 <= @var{start1} <= @var{end1} <= (string-length @var{string1}) 0 <= @var{start2} <= @var{end1} - @var{start1} + @var{start2} <= (string-length @var{string2}) @end display @code{substring-move-left!} and @code{substring-move-right!} store characters of @var{string1} beginning with index @var{start1} (inclusive) and ending with index @var{end1} (exclusive) into @var{string2} beginning with index @var{start2} (inclusive).@refill @code{substring-move-left!} stores characters in time order of increasing indices. @code{substring-move-right!} stores characters in time order of increasing indeces.@refill @end deffn @deffn Procedure substring-fill! string start end char Fills the elements @var{start}--@var{end} of @var{string} with the character @var{char}.@refill @end deffn @defun string-null? str @equiv{} @code{(= 0 (string-length @var{str}))} @end defun @deffn Procedure append! . pairs Destructively appends its arguments. Equivalent to @code{nconc}. @end deffn @defun 1+ n Adds 1 to @var{n}. @end defun @defun -1+ n Subtracts 1 from @var{n}. @end defun @defun ? @defunx >=? These are equivalent to the procedures of the same name but without the trailing @samp{?}. @end defun @node Rev4 Optional Procedures, Multi-argument / and -, Rev2 Procedures, Standards Support @subsection Rev4 Optional Procedures @code{(require 'rev4-optional-procedures)} @ftindex rev4-optional-procedures For the specification of these optional procedures, @xref{Standard procedures, , ,r4rs, Revised(4) Scheme}. @defun list-tail l p @end defun @defun string->list s @end defun @defun list->string l @end defun @defun string-copy @end defun @deffn Procedure string-fill! s obj @end deffn @defun list->vector l @end defun @defun vector->list s @end defun @deffn Procedure vector-fill! s obj @end deffn @node Multi-argument / and -, Multi-argument Apply, Rev4 Optional Procedures, Standards Support @subsection Multi-argument / and - @code{(require 'mutliarg/and-)} @ftindex mutliarg For the specification of these optional forms, @xref{Numerical operations, , ,r4rs, Revised(4) Scheme}. The @code{two-arg:}* forms are only defined if the implementation does not support the many-argument forms.@refill @defun two-arg:/ n1 n2 The original two-argument version of @code{/}. @end defun @defun / divident . divisors @end defun @defun two-arg:- n1 n2 The original two-argument version of @code{-}. @end defun @defun - minuend . subtrahends @end defun @node Multi-argument Apply, Rationalize, Multi-argument / and -, Standards Support @subsection Multi-argument Apply @code{(require 'multiarg-apply)} @ftindex multiarg-apply @noindent For the specification of this optional form, @xref{Control features, , ,r4rs, Revised(4) Scheme}. @defun two-arg:apply proc l The implementation's native @code{apply}. Only defined for implementations which don't support the many-argument version. @end defun @defun apply proc . args @end defun @node Rationalize, Promises, Multi-argument Apply, Standards Support @subsection Rationalize @code{(require 'rationalize)} @ftindex rationalize The procedure rationalize is interesting because most programming languages do not provide anything analogous to it. For simplicity, we present an algorithm which computes the correct result for exact arguments (provided the implementation supports exact rational numbers of unlimited precision), and produces a reasonable answer for inexact arguments when inexact arithmetic is implemented using floating-point. We thank Alan Bawden for contributing this algorithm. @defun rationalize x e @end defun @node Promises, Dynamic-Wind, Rationalize, Standards Support @subsection Promises @code{(require 'promise)} @ftindex promise @defun make-promise proc @end defun Change occurrences of @code{(delay @var{expression})} to @code{(make-promise (lambda () @var{expression}))} and @code{(define force promise:force)} to implement promises if your implementation doesn't support them (@pxref{Control features, , ,r4rs, Revised(4) Scheme}). @node Dynamic-Wind, Values, Promises, Standards Support @subsection Dynamic-Wind @code{(require 'dynamic-wind)} @ftindex dynamic-wind This facility is a generalization of Common LISP @code{unwind-protect}, designed to take into account the fact that continuations produced by @code{call-with-current-continuation} may be reentered.@refill @deffn Procedure dynamic-wind thunk1 thunk2 thunk3 The arguments @var{thunk1}, @var{thunk2}, and @var{thunk3} must all be procedures of no arguments (thunks).@refill @code{dynamic-wind} calls @var{thunk1}, @var{thunk2}, and then @var{thunk3}. The value returned by @var{thunk2} is returned as the result of @code{dynamic-wind}. @var{thunk3} is also called just before control leaves the dynamic context of @var{thunk2} by calling a continuation created outside that context. Furthermore, @var{thunk1} is called before reentering the dynamic context of @var{thunk2} by calling a continuation created inside that context. (Control is inside the context of @var{thunk2} if @var{thunk2} is on the current return stack). @strong{Warning:} There is no provision for dealing with errors or interrupts. If an error or interrupt occurs while using @code{dynamic-wind}, the dynamic environment will be that in effect at the time of the error or interrupt.@refill @end deffn @node Values, , Dynamic-Wind, Standards Support @subsection Values @code{(require 'values)} @ftindex values @defun values obj @dots{} @code{values} takes any number of arguments, and passes (returns) them to its continuation.@refill @end defun @defun call-with-values thunk proc @var{thunk} must be a procedure of no arguments, and @var{proc} must be a procedure. @code{call-with-values} calls @var{thunk} with a continuation that, when passed some values, calls @var{proc} with those values as arguments.@refill Except for continuations created by the @code{call-with-values} procedure, all continuations take exactly one value, as now; the effect of passing no value or more than one value to continuations that were not created by the @code{call-with-values} procedure is unspecified.@refill @end defun @node Session Support, Extra-SLIB Packages, Standards Support, Other Packages @section Session Support @menu * Repl:: Macros at top-level * Quick Print:: Loop-safe Output * Debug:: To err is human ... * Breakpoints:: Pause execution * Trace:: 'trace * System Interface:: 'system and 'getenv * Time Zone:: @end menu @node Repl, Quick Print, Session Support, Session Support @subsection Repl @code{(require 'repl)} @ftindex repl Here is a read-eval-print-loop which, given an eval, evaluates forms. @deffn Procedure repl:top-level repl:eval @code{read}s, @code{repl:eval}s and @code{write}s expressions from @code{(current-input-port)} to @code{(current-output-port)} until an end-of-file is encountered. @code{load}, @code{slib:eval}, @code{slib:error}, and @code{repl:quit} dynamically bound during @code{repl:top-level}.@refill @end deffn @deffn Procedure repl:quit Exits from the invocation of @code{repl:top-level}. @end deffn The @code{repl:} procedures establish, as much as is possible to do portably, a top level environment supporting macros. @code{repl:top-level} uses @code{dynamic-wind} to catch error conditions and interrupts. If your implementation supports this you are all set. Otherwise, if there is some way your implementation can catch error conditions and interrupts, then have them call @code{slib:error}. It will display its arguments and reenter @code{repl:top-level}. @code{slib:error} dynamically bound by @code{repl:top-level}.@refill To have your top level loop always use macros, add any interrupt catching lines and the following lines to your Scheme init file: @lisp (require 'macro) @ftindex macro (require 'repl) @ftindex repl (repl:top-level macro:eval) @end lisp @node Quick Print, Debug, Repl, Session Support @subsection Quick Print @code{(require 'qp)} @ftindex qp @noindent When displaying error messages and warnings, it is paramount that the output generated for circular lists and large data structures be limited. This section supplies a procedure to do this. It could be much improved. @quotation Notice that the neccessity for truncating output eliminates Common-Lisp's @xref{Format} from consideration; even when variables @code{*print-level*} and @code{*print-level*} are set, huge strings and bit-vectors are @emph{not} limited. @end quotation @deffn Procedure qp arg1 @dots{} @deffnx Procedure qpn arg1 @dots{} @deffnx Procedure qpr arg1 @dots{} @code{qp} writes its arguments, separated by spaces, to @code{(current-output-port)}. @code{qp} compresses printing by substituting @samp{...} for substructure it does not have sufficient room to print. @code{qpn} is like @code{qp} but outputs a newline before returning. @code{qpr} is like @code{qpn} except that it returns its last argument.@refill @end deffn @defvar *qp-width* @code{*qp-width*} is the largest number of characters that @code{qp} should use.@refill @end defvar @node Debug, Breakpoints, Quick Print, Session Support @subsection Debug @code{(require 'debug)} @ftindex debug @noindent Requiring @code{debug} automatically requires @code{trace} and @code{break}. @noindent An application with its own datatypes may want to substitute its own printer for @code{qp}. This example shows how to do this: @example (define qpn (lambda args) @dots{}) (provide 'qp) (require 'debug) @ftindex debug @end example @deffn Procedure trace-all file Traces (@pxref{Trace}) all procedures @code{define}d at top-level in file @file{file}. @end deffn @deffn Procedure break-all file Breakpoints (@pxref{Breakpoints}) all procedures @code{define}d at top-level in file @file{file}. @end deffn @node Breakpoints, Trace, Debug, Session Support @subsection Breakpoints @code{(require 'break)} @ftindex break @defun init-debug If your Scheme implementation does not support @code{break} or @code{abort}, a message will appear when you @code{(require 'break)} or @ftindex break @code{(require 'debug)} telling you to type @code{(init-debug)}. This @ftindex debug is in order to establish a top-level continuation. Typing @code{(init-debug)} at top level sets up a continuation for @code{break}. @end defun @defun breakpoint arg1 @dots{} Returns from the top level continuation and pushes the continuation from which it was called on a continuation stack. @end defun @defun continue Pops the topmost continuation off of the continuation stack and returns an unspecified value to it. @defunx continue arg1 @dots{} Pops the topmost continuation off of the continuation stack and returns @var{arg1} @dots{} to it. @end defun @defmac break proc1 @dots{} Redefines the top-level named procedures given as arguments so that @code{breakpoint} is called before calling @var{proc1} @dots{}. @defmacx break With no arguments, makes sure that all the currently broken identifiers are broken (even if those identifiers have been redefined) and returns a list of the broken identifiers. @end defmac @defmac unbreak proc1 @dots{} Turns breakpoints off for its arguments. @defmacx unbreak With no arguments, unbreaks all currently broken identifiers and returns a list of these formerly broken identifiers. @end defmac The following routines are the procedures which actually do the tracing when this module is supplied by SLIB, rather than natively. If defmacros are not natively supported by your implementation, these might be more convenient to use. @defun breakf proc @defunx breakf proc name @defunx debug:breakf proc @defunx debug:breakf proc name To break, type @lisp (set! @var{symbol} (breakf @var{symbol})) @end lisp @noindent or @lisp (set! @var{symbol} (breakf @var{symbol} '@var{symbol})) @end lisp @noindent or @lisp (define @var{symbol} (breakf @var{function})) @end lisp @noindent or @lisp (define @var{symbol} (breakf @var{function} '@var{symbol})) @end lisp @end defun @defun unbreakf proc @defunx debug:unbreakf proc To unbreak, type @lisp (set! @var{symbol} (unbreakf @var{symbol})) @end lisp @end defun @node Trace, System Interface, Breakpoints, Session Support @subsection Tracing @code{(require 'trace)} @ftindex trace @defmac trace proc1 @dots{} Traces the top-level named procedures given as arguments. @defmacx trace With no arguments, makes sure that all the currently traced identifiers are traced (even if those identifiers have been redefined) and returns a list of the traced identifiers. @end defmac @defmac untrace proc1 @dots{} Turns tracing off for its arguments. @defmacx untrace With no arguments, untraces all currently traced identifiers and returns a list of these formerly traced identifiers. @end defmac The following routines are the procedures which actually do the tracing when this module is supplied by SLIB, rather than natively. If defmacros are not natively supported by your implementation, these might be more convenient to use. @defun tracef proc @defunx tracef proc name @defunx debug:tracef proc @defunx debug:tracef proc name To trace, type @lisp (set! @var{symbol} (tracef @var{symbol})) @end lisp @noindent or @lisp (set! @var{symbol} (tracef @var{symbol} '@var{symbol})) @end lisp @noindent or @lisp (define @var{symbol} (tracef @var{function})) @end lisp @noindent or @lisp (define @var{symbol} (tracef @var{function} '@var{symbol})) @end lisp @end defun @defun untracef proc @defunx debug:untracef proc To untrace, type @lisp (set! @var{symbol} (untracef @var{symbol})) @end lisp @end defun @node System Interface, Time Zone, Trace, Session Support @subsection System Interface @noindent If @code{(provided? 'getenv)}: @defun getenv name Looks up @var{name}, a string, in the program environment. If @var{name} is found a string of its value is returned. Otherwise, @code{#f} is returned. @end defun @noindent If @code{(provided? 'system)}: @defun system command-string Executes the @var{command-string} on the computer and returns the integer status code. @end defun @noindent If @code{(provided? 'current-time)}: @noindent The procedures @code{current-time}, @code{difftime}, and @code{offset-time} deal with a @dfn{calendar time} datatype @cindex time @cindex calendar time which may or may not be disjoint from other Scheme datatypes. @defun current-time Returns the time since 00:00:00 GMT, January 1, 1970, measured in seconds. Note that the reference time is different from the reference time for @code{get-universal-time} in @ref{Common-Lisp Time}. @end defun @defun difftime caltime1 caltime0 Returns the difference (number of seconds) between twe calendar times: @var{caltime1} - @var{caltime0}. @var{caltime0} may also be a number. @end defun @defun offset-time caltime offset Returns the calendar time of @var{caltime} offset by @var{offset} number of seconds @code{(+ caltime offset)}. @end defun @node Time Zone, , System Interface, Session Support @subsection Time Zone (require 'time-zone) @deftp {Data Format} TZ-string POSIX standards specify several formats for encoding time-zone rules. @table @t @item :@i{} If the first character of @i{} is @samp{/}, then @i{} specifies the absolute pathname of a tzfile(5) format time-zone file. Otherwise, @i{} is interpreted as a pathname within @var{tzfile:vicinity} (/usr/lib/zoneinfo/) naming a tzfile(5) format time-zone file. @item @i{}@i{} The string @i{} consists of 3 or more alphabetic characters. @i{} specifies the time difference from GMT. The @i{} is positive if the local time zone is west of the Prime Meridian and negative if it is east. @i{} can be the number of hours or hours and minutes (and optionally seconds) separated by @samp{:}. For example, @code{-4:30}. @item @i{}@i{}@i{} @i{} is the at least 3 alphabetic characters naming the local daylight-savings-time. @item @i{}@i{}@i{}@i{} @i{} specifies the offset from the Prime Meridian when daylight-savings-time is in effect. @end table The non-tzfile formats can optionally be followed by transition times specifying the day and time when a zone changes from standard to daylight-savings and back again. @table @t @item ,@i{}/@i{