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|
This is scm.info, produced by makeinfo version 4.7 from scm.texi.
INFO-DIR-SECTION The Algorithmic Language Scheme
START-INFO-DIR-ENTRY
* SCM: (scm). A Scheme interpreter.
END-INFO-DIR-ENTRY
File: scm.info, Node: Top, Next: Overview, Prev: (dir), Up: (dir)
This manual documents the SCM Scheme implementation. SCM version
5e2 was released February 2006. The most recent information about SCM |
can be found on SCM's "WWW" home page: |
`http://swiss.csail.mit.edu/~jaffer/SCM'
Copyright (C) 1990-1999 Free Software Foundation
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.
* Menu:
* Overview::
* Installing SCM:: How to
* Operational Features::
* The Language:: Reference.
* Packages:: Optional Capabilities.
* The Implementation:: How it works.
* Index::
File: scm.info, Node: Overview, Next: Installing SCM, Prev: Top, Up: Top
1 Overview
**********
Scm is a portable Scheme implementation written in C. Scm provides a
machine independent platform for [JACAL], a symbolic algebra system.
* Menu:
* SCM Features::
* SCM Authors::
* Copying::
* Bibliography::
File: scm.info, Node: SCM Features, Next: SCM Authors, Prev: Overview, Up: Overview
1.1 Features
============
* Conforms to Revised^5 Report on the Algorithmic Language Scheme
[R5RS] and the [IEEE] P1178 specification.
* Support for [SICP], [R2RS], [R3RS], and [R5RS] scheme code.
* Runs under Amiga, Atari-ST, MacOS, MS-DOS, OS/2, NOS/VE, Unicos,
VMS, Unix and similar systems. Supports ASCII and EBCDIC
character sets.
* Is fully documented in TeXinfo form, allowing documentation to be
generated in info, TeX, html, nroff, and troff formats.
* Supports inexact real and complex numbers, 30 bit immediate
integers and large precision integers.
* Many Common Lisp functions: `logand', `logor', `logxor', `lognot',
`ash', `logcount', `integer-length', `bit-extract', `defmacro',
`macroexpand', `macroexpand1', `gentemp', `defvar', `force-output',
`software-type', `get-decoded-time', `get-internal-run-time',
`get-internal-real-time', `delete-file', `rename-file',
`copy-tree', `acons', and `eval'.
* `Char-code-limit', `most-positive-fixnum', `most-negative-fixnum',
`and internal-time-units-per-second' constants. `*Features*' and
`*load-pathname*' variables.
* Arrays and bit-vectors. String ports and software emulation ports.
I/O extensions providing ANSI C and POSIX.1 facilities.
* Interfaces to standard libraries including REGEX string regular
expression matching and the CURSES screen management package.
* Available add-on packages including an interactive debugger,
database, X-window graphics, BGI graphics, Motif, and Open-Windows
packages.
* A compiler (HOBBIT, available separately) and dynamic linking of
compiled modules.
* User definable responses to interrupts and errors,
Process-syncronization primitives. Setable levels of monitoring
and timing information printed interactively (the `verbose'
function). `Restart', `quit', and `exec'.
File: scm.info, Node: SCM Authors, Next: Copying, Prev: SCM Features, Up: Overview
1.2 Authors
===========
Aubrey Jaffer (agj @ alum.mit.edu)
Most of SCM.
Radey Shouman
Arrays, `gsubr's, compiled closures, records, Ecache, syntax-rules
macros, and "safeport"s.
Jerry D. Hedden
Real and Complex functions. Fast mixed type arithmetics.
Hugh Secker-Walker
Syntax checking and memoization of special forms by evaluator.
Storage allocation strategy and parameters.
George Carrette
"Siod", written by George Carrette, was the starting point for SCM.
The major innovations taken from Siod are the evaluator's use of
the C-stack and being able to garbage collect off the C-stack
(*note Garbage Collection::).
There are many other contributors to SCM. They are acknowledged in the
file `ChangeLog', a log of changes that have been made to scm.
File: scm.info, Node: Copying, Next: Bibliography, Prev: SCM Authors, Up: Overview
1.3 Copyright
=============
Authors have assigned their SCM copyrights to:
Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111, USA
* Menu:
* The SCM License::
* SIOD copyright::
File: scm.info, Node: The SCM License, Next: SIOD copyright, Prev: Copying, Up: Copying
1.3.1 The SCM License
---------------------
The license of SCM consists of the GNU GPL plus a special statement
giving blanket permission to link with non-free software. This is the
license statement as found in any individual file that it applies to:
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2, or
(at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this software; see the file COPYING. If not, write to
the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA
As a special exception, the Free Software Foundation gives
permission for additional uses of the text contained in its
release of SCM.
The exception is that, if you link the SCM library with other
files to produce an executable, this does not by itself cause the
resulting executable to be covered by the GNU General Public
License. Your use of that executable is in no way restricted on
account of linking the SCM library code into it.
This exception does not however invalidate any other reasons why
the executable file might be covered by the GNU General Public
License.
This exception applies only to the code released by the Free
Software Foundation under the name SCM. If you copy code from
other Free Software Foundation releases into a copy of SCM, as the
General Public License permits, the exception does not apply to
the code that you add in this way. To avoid misleading anyone as
to the status of such modified files, you must delete this
exception notice from them.
If you write modifications of your own for SCM, it is your choice
whether to permit this exception to apply to your modifications.
If you do not wish that, delete this exception notice.
Permission to use, copy, modify, distribute, and sell this software and
its documentation for any purpose is hereby granted without fee,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation.
NO WARRANTY
BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR
THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH
YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
NECESSARY SERVICING, REPAIR OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR
DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL
DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM
(INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED
INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF
THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR
OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
File: scm.info, Node: SIOD copyright, Prev: The SCM License, Up: Copying
1.3.2 SIOD copyright
--------------------
COPYRIGHT (c) 1989 BY
PARADIGM ASSOCIATES INCORPORATED, CAMBRIDGE, MASSACHUSETTS.
ALL RIGHTS RESERVED
Permission to use, copy, modify, distribute and sell this software and
its documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of Paradigm Associates Inc
not be used in advertising or publicity pertaining to distribution of
the software without specific, written prior permission.
PARADIGM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
EVENT SHALL PARADIGM BE LIABLE FOR ANY SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
gjc@paradigm.com
Phone: 617-492-6079
Paradigm Associates Inc
29 Putnam Ave, Suite 6
Cambridge, MA 02138
File: scm.info, Node: Bibliography, Prev: Copying, Up: Overview
1.4 Bibliography
================
[IEEE]
`IEEE Standard 1178-1990. IEEE Standard for the Scheme
Programming Language.' IEEE, New York, 1991.
[R4RS]
William Clinger and Jonathan Rees, Editors. Revised(4) Report on
the Algorithmic Language Scheme. `ACM Lisp Pointers' Volume IV,
Number 3 (July-September 1991), pp. 1-55.
*Note Top: (r4rs)Top.
[R5RS]
Richard Kelsey and William Clinger and Jonathan (Rees, editors)
Revised(5) Report on the Algorithmic Language Scheme.
`Higher-Order and Symbolic Computation' Volume 11, Number 1 (1998),
pp. 7-105, and `ACM SIGPLAN Notices' 33(9), September 1998.
*Note Top: (r5rs)Top.
[Exrename]
William Clinger Hygienic Macros Through Explicit Renaming `Lisp
Pointers' Volume IV, Number 4 (December 1991), pp 17-23.
[SICP]
Harold Abelson and Gerald Jay Sussman with Julie Sussman.
`Structure and Interpretation of Computer Programs.' MIT Press,
Cambridge, 1985.
[Simply]
Brian Harvey and Matthew Wright. `Simply Scheme: Introducing
Computer Science' MIT Press, 1994 ISBN 0-262-08226-8
[SchemePrimer]
$B8$;tBg(B(Dai Inukai) `$BF~Lg(BScheme'
1999$BG/(B12$B7n=iHG(B ISBN4-87966-954-7
[SLIB]
Todd R. Eigenschink, Dave Love, and Aubrey Jaffer. SLIB, The
Portable Scheme Library. Version 2c8, June 2000.
*Note Top: (slib)Top.
[JACAL]
Aubrey Jaffer. JACAL Symbolic Mathematics System. Version 1b0,
Sep 1999.
*Note Top: (jacal)Top.
`scm.texi'
`scm.info'
Documentation of `scm' extensions (beyond Scheme standards).
Documentation on the internal representation and how to extend or
include `scm' in other programs.
`Xlibscm.texi'
`Xlibscm.info'
Documentation of the Xlib - SCM Language X Interface.
File: scm.info, Node: Installing SCM, Next: Operational Features, Prev: Overview, Up: Top
2 Installing SCM
****************
* Menu:
* Making SCM:: Bootstrapping.
* SLIB:: REQUIREd reading.
* Building SCM::
* Installing Dynamic Linking::
* Configure Module Catalog::
* Saving Images:: Make Fast-Booting Executables
* Automatic C Preprocessor Definitions::
* Problems Compiling::
* Problems Linking::
* Problems Running::
* Testing::
* Reporting Problems::
File: scm.info, Node: Making SCM, Next: SLIB, Prev: Installing SCM, Up: Installing SCM
2.1 Making SCM
==============
The SCM distribution has "Makefile" which contains rules for making
"scmlit", a "bare-bones" version of SCM sufficient for running `build'.
`build' is used to compile (or create scripts to compile) full
featured versions.
Makefiles are not portable to the majority of platforms. If `Makefile'
works for you, good; If not, I don't want to hear about it. If you
need to compile SCM without build, there are several ways to proceed:
* Use the build (http://swiss.csail.mit.edu/~jaffer/buildscm.html)
web page to create custom batch scripts for compiling SCM.
* Use SCM on a different platform to run `build' to create a script
to build SCM;
* Use another implementation of Scheme to run `build' to create a
script to build SCM;
* Create your own script or `Makefile'.
File: scm.info, Node: SLIB, Next: Building SCM, Prev: Making SCM, Up: Installing SCM
2.2 SLIB
========
[SLIB] is a portable Scheme library meant to provide compatibility and
utility functions for all standard Scheme implementations. Although
SLIB is not _neccessary_ to run SCM, I strongly suggest you obtain and
install it. Bug reports about running SCM without SLIB have very low
priority. SLIB is available from the same sites as SCM:
* swiss.csail.mit.edu:/pub/scm/slib3a3.tar.gz |
* ftp.gnu.org:/pub/gnu/jacal/slib3a3.tar.gz |
* ftp.cs.indiana.edu:/pub/scheme-repository/imp/slib3a3.tar.gz |
Unpack SLIB (`tar xzf slib3a3.tar.gz' or `unzip -ao slib3a3.zip') in an |
appropriate directory for your system; both `tar' and `unzip' will
create the directory `slib'.
Then create a file `require.scm' in the SCM "implementation-vicinity"
(this is the same directory as where the file `Init5e2.scm' is |
installed). `require.scm' should have the contents:
(define (library-vicinity) "/usr/local/lib/slib/")
where the pathname string `/usr/local/lib/slib/' is to be replaced by
the pathname into which you installed SLIB. Absolute pathnames are
recommended here; if you use a relative pathname, SLIB can get confused
when the working directory is changed (*note chmod: I/O-Extensions.).
The way to specify a relative pathname is to append it to the
implementation-vicinity, which is absolute:
(define library-vicinity
(let ((lv (string-append (implementation-vicinity) "../slib/")))
(lambda () lv)))
Alternatively, you can set the (shell) environment variable
`SCHEME_LIBRARY_PATH' to the pathname of the SLIB directory (*note
SCHEME_LIBRARY_PATH: SCM Variables.). If set, the environment variable
overrides `require.scm'. Again, absolute pathnames are recommended.
File: scm.info, Node: Building SCM, Next: Installing Dynamic Linking, Prev: SLIB, Up: Installing SCM
2.3 Building SCM
================
The file "build" loads the file "build.scm", which constructs a
relational database of how to compile and link SCM executables.
`build.scm' has information for the platforms which SCM has been ported
to (of which I have been notified). Some of this information is old,
incorrect, or incomplete. Send corrections and additions to jaffer @
ai.mit.edu.
* Menu:
* Invoking Build::
* Build Options::
* Compiling and Linking Custom Files::
File: scm.info, Node: Invoking Build, Next: Build Options, Prev: Building SCM, Up: Building SCM
2.3.1 Invoking Build
--------------------
The _all_ method will also work for MS-DOS and unix. Use the _all_
method if you encounter problems with `build'.
MS-DOS
From the SCM source directory, type `build' followed by up to 9
command line arguments.
unix
From the SCM source directory, type `./build' followed by command
line arguments.
_all_
From the SCM source directory, start `scm' or `scmlit' and type
`(load "build")'. Alternatively, start `scm' or `scmlit' with the
command line argument `-ilbuild'.
Invoking build without the `-F' option will build or create a shell
script with the `arrays', `inexact', and `bignums' options as defaults.
bash$ ./build
-|
#! /bin/sh
# unix (linux) script created by SLIB/batch
# ================ Write file with C defines
rm -f scmflags.h
echo '#define IMPLINIT "Init5e2.scm"'>>scmflags.h |
echo '#define BIGNUMS'>>scmflags.h
echo '#define FLOATS'>>scmflags.h
echo '#define ARRAYS'>>scmflags.h
# ================ Compile C source files
gcc -O2 -c continue.c scm.c scmmain.c findexec.c script.c time.c repl.c scl.c eval.c sys.c subr.c debug.c unif.c rope.c
# ================ Link C object files
gcc -rdynamic -o scm continue.o scm.o scmmain.o findexec.o script.o time.o repl.o scl.o eval.o sys.o subr.o debug.o unif.o rope.o -lm -lc
To cross compile for another platform, invoke build with the `-p' or
`--platform=' option. This will create a script for the platform named
in the `-p' or `--platform=' option.
bash$ ./build -o scmlit -p darwin -F lit
-|
#! /bin/sh
# unix (darwin) script created by SLIB/batch
# ================ Write file with C defines
rm -f scmflags.h
echo '#define IMPLINIT "Init5e2.scm"'>>scmflags.h |
# ================ Compile C source files
cc -O3 -c continue.c scm.c scmmain.c findexec.c script.c time.c repl.c scl.c eval.c sys.c subr.c debug.c unif.c rope.c
# ================ Link C object files
mv -f scmlit scmlit~
cc -o scmlit continue.o scm.o scmmain.o findexec.o script.o time.o repl.o scl.o eval.o sys.o subr.o debug.o unif.o rope.o
File: scm.info, Node: Build Options, Next: Compiling and Linking Custom Files, Prev: Invoking Build, Up: Building SCM
2.3.2 Build Options
-------------------
The options to "build" specify what, where, and how to build a SCM
program or dynamically linked module. These options are unrelated to
the SCM command line options.
-- Build Option: -p PLATFORM-NAME
-- Build Option: --platform=PLATFORM-NAME
specifies that the compilation should be for a
computer/operating-system combination called PLATFORM-NAME.
_Note_ The case of PLATFORM-NAME is distinguised. The current
PLATFORM-NAMEs are all lower-case.
The platforms defined by table "platform" in `build.scm' are:
Table: platform
name processor operating-system compiler
#f processor-family operating-system #f
symbol processor-family operating-system symbol
symbol symbol symbol symbol
================= ================= ================= =================
*unknown* *unknown* unix cc
acorn-unixlib acorn *unknown* cc
aix powerpc aix cc
alpha-elf alpha unix cc
alpha-linux alpha linux gcc
amiga-aztec m68000 amiga cc
amiga-dice-c m68000 amiga dcc
amiga-gcc m68000 amiga gcc
amiga-sas m68000 amiga lc
atari-st-gcc m68000 atari.st gcc
atari-st-turbo-c m68000 atari.st tcc
borland-c i8086 ms-dos bcc
darwin powerpc unix cc
djgpp i386 ms-dos gcc
freebsd i386 unix cc
gcc *unknown* unix gcc
gnu-win32 i386 unix gcc
highc i386 ms-dos hc386
hp-ux hp-risc hp-ux cc
irix mips irix gcc
linux i386 linux gcc
linux-aout i386 linux gcc
microsoft-c i8086 ms-dos cl
microsoft-c-nt i386 ms-dos cl
microsoft-quick-c i8086 ms-dos qcl
ms-dos i8086 ms-dos cc
netbsd *unknown* unix gcc
openbsd *unknown* unix gcc
os/2-cset i386 os/2 icc
os/2-emx i386 os/2 gcc
osf1 alpha unix cc
plan9-8 i386 plan9 8c
sunos sparc sunos cc
svr4 *unknown* unix cc
svr4-gcc-sun-ld sparc sunos gcc
turbo-c i8086 ms-dos tcc
unicos cray unicos cc
unix *unknown* unix cc
vms vax vms cc
vms-gcc vax vms gcc
watcom-9.0 i386 ms-dos wcc386p
-- Build Option: -f PATHNAME
specifies that the build options contained in PATHNAME be spliced
into the argument list at this point. The use of option files can
separate functional features from platform-specific ones.
The `Makefile' calls out builds with the options in `.opt' files:
`dlls.opt'
Options for Makefile targets mydlls, myturtle, and x.so.
`gdb.opt'
Options for udgdbscm and gdbscm.
`libscm.opt'
Options for libscm.a.
`pg.opt'
Options for pgscm, which instruments C functions.
`udscm4.opt'
Options for targets udscm4 and dscm4 (scm).
`udscm5.opt'
Options for targets udscm5 and dscm5 (scm).
The Makefile creates options files it depends on only if they do
not already exist.
-- Build Option: -o FILENAME
-- Build Option: --outname=FILENAME
specifies that the compilation should produce an executable or
object name of FILENAME. The default is `scm'. Executable
suffixes will be added if neccessary, e.g. `scm' => `scm.exe'.
-- Build Option: -l LIBNAME ...
-- Build Option: --libraries=LIBNAME
specifies that the LIBNAME should be linked with the executable
produced. If compile flags or include directories (`-I') are
needed, they are automatically supplied for compilations. The `c'
library is always included. SCM "features" specify any libraries
they need; so you shouldn't need this option often.
-- Build Option: -D DEFINITION ...
-- Build Option: --defines=DEFINITION
specifies that the DEFINITION should be made in any C source
compilations. If compile flags or include directories (`-I') are
needed, they are automatically supplied for compilations. SCM
"features" specify any flags they need; so you shouldn't need this
option often.
-- Build Option: --compiler-options=FLAG
specifies that that FLAG will be put on compiler command-lines.
-- Build Option: --linker-options=FLAG
specifies that that FLAG will be put on linker command-lines.
-- Build Option: -s PATHNAME
-- Build Option: --scheme-initial=PATHNAME
specifies that PATHNAME should be the default location of the SCM
initialization file `Init5e2.scm'. SCM tries several likely |
locations before resorting to PATHNAME (*note File-System
Habitat::). If not specified, the current directory (where build
is building) is used.
-- Build Option: -c PATHNAME ...
-- Build Option: --c-source-files=PATHNAME
specifies that the C source files PATHNAME ... are to be compiled.
-- Build Option: -j PATHNAME ...
-- Build Option: --object-files=PATHNAME
specifies that the object files PATHNAME ... are to be linked.
-- Build Option: -i CALL ...
-- Build Option: --initialization=CALL
specifies that the C functions CALL ... are to be invoked during
initialization.
-- Build Option: -t BUILD-WHAT
-- Build Option: --type=BUILD-WHAT
specifies in general terms what sort of thing to build. The
choices are:
`exe'
executable program.
`lib'
library module.
`dlls'
archived dynamically linked library object files.
`dll'
dynamically linked library object file.
The default is to build an executable.
-- Build Option: -h BATCH-SYNTAX
-- Build Option: -batch-dialect=BATCH-SYNTAX
specifies how to build. The default is to create a batch file for
the host system. The SLIB file `batch.scm' knows how to create
batch files for:
* unix
* dos
* vms
* amigaos (was amigados)
* system
This option executes the compilation and linking commands
through the use of the `system' procedure.
* *unknown*
This option outputs Scheme code.
-- Build Option: -w BATCH-FILENAME
-- Build Option: -script-name=BATCH-FILENAME
specifies where to write the build script. The default is to
display it on `(current-output-port)'.
-- Build Option: -F FEATURE ...
-- Build Option: --features=FEATURE
specifies to build the given features into the executable. The
defined features are:
"array"
Alias for ARRAYS
"array-for-each"
array-map! and array-for-each (arrays must also be featured).
"arrays"
Use if you want arrays, uniform-arrays and uniform-vectors.
"bignums"
Large precision integers.
"byte"
Treating strings as byte-vectors.
"careful-interrupt-masking"
Define this for extra checking of interrupt masking and some
simple checks for proper use of malloc and free. This is for
debugging C code in `sys.c', `eval.c', `repl.c' and makes the
interpreter several times slower than usual.
"cautious"
Normally, the number of arguments arguments to interpreted
closures (from LAMBDA) are checked if the function part of a
form is not a symbol or only the first time the form is
executed if the function part is a symbol. defining
`reckless' disables any checking. If you want to have SCM
always check the number of arguments to interpreted closures
define feature `cautious'.
"cheap-continuations"
If you only need straight stack continuations, executables
compile with this feature will run faster and use less
storage than not having it. Machines with unusual stacks
_need_ this. Also, if you incorporate new C code into scm
which uses VMS system services or library routines (which
need to unwind the stack in an ordrly manner) you may need to
use this feature.
"compiled-closure"
Use if you want to use compiled closures.
"curses"
For the "curses" screen management package.
"debug"
Turns on the features `cautious',
`careful-interrupt-masking', and `stack-limit'; uses `-g'
flags for debugging SCM source code.
"differ"
Sequence comparison
"dump"
Convert a running scheme program into an executable file.
"dynamic-linking"
Be able to load compiled files while running.
"edit-line"
interface to the editline or GNU readline library.
"engineering-notation"
Use if you want floats to display in engineering notation
(exponents always multiples of 3) instead of scientific
notation.
"generalized-c-arguments"
`make_gsubr' for arbitrary (< 11) arguments to C functions.
"i/o-extensions"
Commonly available I/O extensions: "exec", line I/O, file
positioning, file delete and rename, and directory functions.
"inexact"
Use if you want floating point numbers.
"lit"
Lightweight - no features
"macro"
C level support for hygienic and referentially transparent
macros (syntax-rules macros).
"mysql"
Client connections to the mysql databases.
"no-heap-shrink"
Use if you want segments of unused heap to not be freed up
after garbage collection. This may increase time in GC for
*very* large working sets.
"none"
No features
"posix"
Posix functions available on all "Unix-like" systems. fork
and process functions, user and group IDs, file permissions,
and "link".
"reckless"
If your scheme code runs without any errors you can disable
almost all error checking by compiling all files with
`reckless'.
"record"
The Record package provides a facility for user to define
their own record data types. See SLIB for documentation.
"regex"
String regular expression matching.
"rev2-procedures"
These procedures were specified in the `Revised^2 Report on
Scheme' but not in `R4RS'.
"sicp"
Use if you want to run code from:
Harold Abelson and Gerald Jay Sussman with Julie Sussman.
`Structure and Interpretation of Computer Programs.' The MIT
Press, Cambridge, Massachusetts, USA, 1985.
Differences from R5RS are:
* (eq? '() '#f)
* (define a 25) returns the symbol a.
* (set! a 36) returns 36.
"single-precision-only"
Use if you want all inexact real numbers to be single
precision. This only has an effect if SINGLES is also
defined (which is the default). This does not affect complex
numbers.
"socket"
BSD "socket" interface. Socket addr functions require
inexacts or bignums for 32-bit precision.
"stack-limit"
Use to enable checking for stack overflow. Define value of
the C preprocessor variable STACK_LIMIT to be the size to
which SCM should allow the stack to grow. STACK_LIMIT should
be less than the maximum size the hardware can support, as
not every routine checks the stack.
"tick-interrupts"
Use if you want the ticks and ticks-interrupt functions.
"turtlegr"
"Turtle" graphics calls for both Borland-C and X11 from
sjm@ee.tut.fi.
"unix"
Those unix features which have not made it into the Posix
specs: nice, acct, lstat, readlink, symlink, mknod and sync.
"wb"
WB database with relational wrapper.
"windows"
Microsoft Windows executable.
"x"
Alias for Xlib feature.
"xlib"
Interface to Xlib graphics routines.
File: scm.info, Node: Compiling and Linking Custom Files, Prev: Build Options, Up: Building SCM
2.3.3 Compiling and Linking Custom Files
----------------------------------------
A correspondent asks:
How can we link in our own c files to the SCM interpreter so that
we can add our own functionality? (e.g. we have a bunch of tcp
functions we want access to). Would this involve changing
build.scm or the Makefile or both?
(*note Changing Scm:: has instructions describing the C code format). Suppose
a C file "foo.c" has functions you wish to add to SCM. To compile and
link your file at compile time, use the `-c' and `-i' options to build:
bash$ ./build -c foo.c -i init_foo
-|
#! /bin/sh
rm -f scmflags.h
echo '#define IMPLINIT "/home/jaffer/scm/Init5e2.scm"'>>scmflags.h |
echo '#define COMPILED_INITS init_foo();'>>scmflags.h
echo '#define BIGNUMS'>>scmflags.h
echo '#define FLOATS'>>scmflags.h
echo '#define ARRAYS'>>scmflags.h
gcc -O2 -c continue.c scm.c findexec.c script.c time.c repl.c scl.c \
eval.c sys.c subr.c unif.c rope.c foo.c
gcc -rdynamic -o scm continue.o scm.o findexec.o script.o time.o \
repl.o scl.o eval.o sys.o subr.o unif.o rope.o foo.o -lm -lc
To make a dynamically loadable object file use the `-t dll' option:
bash$ ./build -t dll -c foo.c
-|
#! /bin/sh
rm -f scmflags.h
echo '#define IMPLINIT "/home/jaffer/scm/Init5e2.scm"'>>scmflags.h |
echo '#define BIGNUMS'>>scmflags.h
echo '#define FLOATS'>>scmflags.h
echo '#define ARRAYS'>>scmflags.h
echo '#define DLL'>>scmflags.h
gcc -O2 -fpic -c foo.c
gcc -shared -o foo.so foo.o -lm -lc
Once `foo.c' compiles correctly (and your SCM build supports
dynamic-loading), you can load the compiled file with the Scheme command
`(load "./foo.so")'. See *Note Configure Module Catalog:: for how to
add a compiled dll file to SLIB's catalog.
File: scm.info, Node: Installing Dynamic Linking, Next: Configure Module Catalog, Prev: Building SCM, Up: Installing SCM
2.4 Installing Dynamic Linking
==============================
Dynamic linking has not been ported to all platforms. Operating systems
in the BSD family (a.out binary format) can usually be ported to "DLD".
The "dl" library (`#define SUN_DL' for SCM) was a proposed POSIX
standard and may be available on other machines with "COFF" binary
format. For notes about porting to MS-Windows and finishing the port
to VMS *Note VMS Dynamic Linking::.
"DLD" is a library package of C functions that performs "dynamic link
editing" on Linux, VAX (Ultrix), Sun 3 (SunOS 3.4 and 4.0),
SPARCstation (SunOS 4.0), Sequent Symmetry (Dynix), and Atari ST. It is
available from:
* ftp.gnu.org:pub/gnu/dld-3.3.tar.gz
These notes about using libdl on SunOS are from `gcc.info':
On a Sun, linking using GNU CC fails to find a shared library and
reports that the library doesn't exist at all.
This happens if you are using the GNU linker, because it does only
static linking and looks only for unshared libraries. If you have
a shared library with no unshared counterpart, the GNU linker
won't find anything.
We hope to make a linker which supports Sun shared libraries, but
please don't ask when it will be finished-we don't know.
Sun forgot to include a static version of `libdl.a' with some
versions of SunOS (mainly 4.1). This results in undefined symbols
when linking static binaries (that is, if you use `-static'). If
you see undefined symbols `_dlclose', `_dlsym' or `_dlopen' when
linking, compile and link against the file `mit/util/misc/dlsym.c'
from the MIT version of X windows.
File: scm.info, Node: Configure Module Catalog, Next: Saving Images, Prev: Installing Dynamic Linking, Up: Installing SCM
2.5 Configure Module Catalog
============================
The SLIB module "catalog" can be extended to define other
`require'-able packages by adding calls to the Scheme source file
`mkimpcat.scm'. Within `mkimpcat.scm', the following procedures are
defined.
-- Function: add-link feature object-file lib1 ...
FEATURE should be a symbol. OBJECT-FILE should be a string naming
a file containing compiled "object-code". Each LIBn argument
should be either a string naming a library file or `#f'.
If OBJECT-FILE exists, the `add-link' procedure registers symbol
FEATURE so that the first time `require' is called with the symbol
FEATURE as its argument, OBJECT-FILE and the LIB1 ... are
dynamically linked into the executing SCM session.
If OBJECT-FILE exists, `add-link' returns `#t', otherwise it
returns `#f'.
For example, to install a compiled dll `foo', add these lines to
`mkimpcat.scm':
(add-link 'foo
(in-vicinity (implementation-vicinity) "foo"
link:able-suffix))
-- Function: add-alias alias feature
ALIAS and FEATURE are symbols. The procedure `add-alias'
registers ALIAS as an alias for FEATURE. An unspecified value is
returned.
`add-alias' causes `(require 'ALIAS)' to behave like `(require
'FEATURE)'.
-- Function: add-source feature filename
FEATURE is a symbol. FILENAME is a string naming a file
containing Scheme source code. The procedure `add-source'
registers FEATURE so that the first time `require' is called with
the symbol FEATURE as its argument, the file FILENAME will be
`load'ed. An unspecified value is returned.
Remember to delete the file `slibcat' after modifying the file
`mkimpcat.scm' in order to force SLIB to rebuild its cache.
File: scm.info, Node: Saving Images, Next: Automatic C Preprocessor Definitions, Prev: Configure Module Catalog, Up: Installing SCM
2.6 Saving Images
=================
In SCM, the ability to save running program images is called "dump"
(*note Dump::). In order to make `dump' available to SCM, build with
feature `dump'. `dump'ed executables are compatible with dynamic
linking.
Most of the code for "dump" is taken from `emacs-19.34/src/unex*.c'.
No modifications to the emacs source code were required to use
`unexelf.c'. Dump has not been ported to all platforms. If `unexec.c'
or `unexelf.c' don't work for you, try using the appropriate `unex*.c'
file from emacs.
File: scm.info, Node: Automatic C Preprocessor Definitions, Next: Problems Compiling, Prev: Saving Images, Up: Installing SCM
2.7 Automatic C Preprocessor Definitions
========================================
These `#defines' are automatically provided by preprocessors of various
C compilers. SCM uses the presence or absence of these definitions to
configure "include file" locations and aliases for library functions.
If the definition(s) corresponding to your system type is missing as
your system is configured, add `-DFLAG' to the compilation command
lines or add a `#define FLAG' line to `scmfig.h' or the beginning of
`scmfig.h'.
#define Platforms:
------- ----------
ARM_ULIB Huw Rogers free unix library for acorn archimedes
AZTEC_C Aztec_C 5.2a
__CYGWIN__ Cygwin
__CYGWIN32__ Cygwin |
_DCC Dice C on AMIGA
__GNUC__ Gnu CC (and DJGPP)
__EMX__ Gnu C port (gcc/emx 0.8e) to OS/2 2.0
__HIGHC__ MetaWare High C
__IBMC__ C-Set++ on OS/2 2.1
_MSC_VER MS VisualC++ 4.2
MWC Mark Williams C on COHERENT
__MWERKS__ Metrowerks Compiler; Macintosh and WIN32 (?)
_POSIX_SOURCE ??
_QC Microsoft QuickC
__STDC__ ANSI C compliant
__TURBOC__ Turbo C and Borland C
__USE_POSIX ??
__WATCOMC__ Watcom C on MS-DOS
__ZTC__ Zortech C
_AIX AIX operating system
__APPLE__ Apple Darwin
AMIGA SAS/C 5.10 or Dice C on AMIGA
__amigaos__ Gnu CC on AMIGA
atarist ATARI-ST under Gnu CC
__FreeBSD__ FreeBSD
GNUDOS DJGPP (obsolete in version 1.08)
__GO32__ DJGPP (future?)
hpux HP-UX
linux Linux
macintosh Macintosh (THINK_C and __MWERKS__ define)
MCH_AMIGA Aztec_c 5.2a on AMIGA
__MACH__ Apple Darwin
__MINGW32__ MinGW - Minimalist GNU for Windows |
MSDOS Microsoft C 5.10 and 6.00A
_MSDOS Microsoft CLARM and CLTHUMB compilers.
__MSDOS__ Turbo C, Borland C, and DJGPP
__NetBSD__ NetBSD
nosve Control Data NOS/VE
SVR2 System V Revision 2.
sun SunOS
__SVR4 SunOS
THINK_C developement environment for the Macintosh
ultrix VAX with ULTRIX operating system.
unix most Unix and similar systems and DJGPP (!?)
__unix__ Gnu CC and DJGPP
_UNICOS Cray operating system
vaxc VAX C compiler
VAXC VAX C compiler
vax11c VAX C compiler
VAX11 VAX C compiler
_Windows Borland C 3.1 compiling for Windows
_WIN32 MS VisualC++ 4.2 and Cygwin (Win32 API)
_WIN32_WCE MS Windows CE
vms (and VMS) VAX-11 C under VMS.
__alpha DEC Alpha processor
__alpha__ DEC Alpha processor
hp9000s800 HP RISC processor
__ia64 GCC on IA64
__ia64__ GCC on IA64
_LONGLONG GCC on IA64
__i386__ DJGPP
i386 DJGPP
_M_ARM Microsoft CLARM compiler defines as 4 for ARM.
_M_ARMT Microsoft CLTHUMB compiler defines as 4 for Thumb.
MULTIMAX Encore computer
ppc PowerPC
__ppc__ PowerPC
pyr Pyramid 9810 processor
__sgi__ Silicon Graphics Inc.
sparc SPARC processor
sequent Sequent computer
tahoe CCI Tahoe processor
vax VAX processor
__x86_64 AMD Opteron |
File: scm.info, Node: Problems Compiling, Next: Problems Linking, Prev: Automatic C Preprocessor Definitions, Up: Installing SCM
2.8 Problems Compiling
======================
FILE PROBLEM / MESSAGE HOW TO FIX
*.c include file not found. Correct the status of
STDC_HEADERS in scmfig.h.
fix #include statement or add
#define for system type to
scmfig.h.
*.c Function should return a value. Ignore.
Parameter is never used.
Condition is always false.
Unreachable code in function.
scm.c assignment between incompatible Change SIGRETTYPE in scm.c.
types.
time.c CLK_TCK redefined. incompatablility between
<stdlib.h> and <sys/types.h>.
Remove STDC_HEADERS in scmfig.h.
Edit <sys/types.h> to remove
incompatability.
subr.c Possibly incorrect assignment Ignore.
in function lgcd.
sys.c statement not reached. Ignore.
constant in conditional
expression.
sys.c undeclared, outside of #undef STDC_HEADERS in scmfig.h.
functions.
scl.c syntax error. #define SYSTNAME to your system
type in scl.c (softtype).
File: scm.info, Node: Problems Linking, Next: Problems Running, Prev: Problems Compiling, Up: Installing SCM
2.9 Problems Linking
====================
PROBLEM HOW TO FIX
_sin etc. missing. Uncomment LIBS in makefile.
File: scm.info, Node: Problems Running, Next: Testing, Prev: Problems Linking, Up: Installing SCM
2.10 Problems Running
=====================
PROBLEM HOW TO FIX
Opening message and then machine Change memory model option to C
crashes. compiler (or makefile).
Make sure sizet definition is
correct in scmfig.h.
Reduce the size of HEAP_SEG_SIZE in
setjump.h.
Input hangs. #define NOSETBUF
ERROR: heap: need larger initial. Increase initial heap allocation
using -a<kb> or INIT_HEAP_SIZE.
ERROR: Could not allocate. Check sizet definition.
Use 32 bit compiler mode.
Don't try to run as subproccess.
remove <FLAG> in scmfig.h and Do so and recompile files.
recompile scm.
add <FLAG> in scmfig.h and
recompile scm.
ERROR: Init5e2.scm not found. Assign correct IMPLINIT in makefile |
or scmfig.h.
Define environment variable
SCM_INIT_PATH to be the full
pathname of Init5e2.scm. |
WARNING: require.scm not found. Define environment variable
SCHEME_LIBRARY_PATH to be the full
pathname of the scheme library
[SLIB].
Change library-vicinity in
Init5e2.scm to point to library or |
remove.
Make sure the value of
(library-vicinity) has a trailing
file separator (like / or \).
File: scm.info, Node: Testing, Next: Reporting Problems, Prev: Problems Running, Up: Installing SCM
2.11 Testing
============
Loading `r4rstest.scm' in the distribution will run an [R4RS]
conformance test on `scm'.
> (load "r4rstest.scm")
-|
;loading "r4rstest.scm"
SECTION(2 1)
SECTION(3 4)
#<primitive-procedure boolean?>
#<primitive-procedure char?>
#<primitive-procedure null?>
#<primitive-procedure number?>
...
Loading `pi.scm' in the distribution will enable you to compute digits
of pi.
> (load "pi")
;loading "pi"
;done loading "pi.scm"
;Evaluation took 20 ms (0 in gc) 767 cells work, 233.B other
#<unspecified>
> (pi 100 5)
00003 14159 26535 89793 23846 26433 83279 50288 41971 69399
37510 58209 74944 59230 78164 06286 20899 86280 34825 34211
70679
;Evaluation took 550 ms (60 in gc) 36976 cells work, 1548.B other
#<unspecified>
Loading `bench.scm' will compute and display performance statistics of
SCM running `pi.scm'. `make bench' or `make benchlit' appends the
performance report to the file `BenchLog', facilitating tracking
effects of changes to SCM on performance.
PROBLEM HOW TO FIX
Runs some and then machine crashes. See above under machine crashes.
Runs some and then ERROR: ... Remove optimization option to C
(after a GC has happened). compiler and recompile.
#define SHORT_ALIGN in `scmfig.h'.
Some symbol names print incorrectly. Change memory model option to C
compiler (or makefile).
Check that HEAP_SEG_SIZE fits
within sizet.
Increase size of HEAP_SEG_SIZE (or
INIT_HEAP_SIZE if it is smaller
than HEAP_SEG_SIZE).
ERROR: Rogue pointer in Heap. See above under machine crashes.
Newlines don't appear correctly in Check file mode (define OPEN_... in
output files. `Init5e2.scm'). |
Spaces or control characters appear Check character defines in
in symbol names. `scmfig.h'.
Negative numbers turn positive. Check SRS in `scmfig.h'.
VMS: Couldn't unwind stack. #define CHEAP_CONTIUATIONS in
`scmfig.h'.
VAX: botched longjmp.
Sparc(SUN-4) heap is growing out of control
You are experiencing a GC problem peculiar to the Sparc. The
problem is that SCM doesn't know how to clear register windows.
Every location which is not reused still gets marked at GC time.
This causes lots of stuff which should be collected to not be.
This will be a problem with any _conservative_ GC until we find
what instruction will clear the register windows. This problem is
exacerbated by using lots of call-with-current-continuations. A
possible fix for dynthrow() is commented out in `continue.c'.
File: scm.info, Node: Reporting Problems, Prev: Testing, Up: Installing SCM
2.12 Reporting Problems
=======================
Reported problems and solutions are grouped under Compiling, Linking,
Running, and Testing. If you don't find your problem listed there, you
can send a bug report to `agj @ alum.mit.edu'. The bug report should
include:
1. The version of SCM (printed when SCM is invoked with no arguments).
2. The type of computer you are using.
3. The name and version of your computer's operating system.
4. The values of the environment variables `SCM_INIT_PATH' and
`SCHEME_LIBRARY_PATH'.
5. The name and version of your C compiler.
6. If you are using an executable from a distribution, the name,
vendor, and date of that distribution. In this case,
corresponding with the vendor is recommended.
File: scm.info, Node: Operational Features, Next: The Language, Prev: Installing SCM, Up: Top
3 Operational Features
**********************
* Menu:
* Invoking SCM::
* SCM Options::
* Invocation Examples::
* SCM Variables::
* SCM Session::
* Editing Scheme Code::
* Debugging Scheme Code::
* Debugging Continuations::
* Errors::
* Memoized Expressions::
* Internal State::
* Scripting::
File: scm.info, Node: Invoking SCM, Next: SCM Options, Prev: Operational Features, Up: Operational Features
3.1 Invoking SCM
================
scm [-a kbytes] [-muvbiq] [-version] [-help]
[[-]-no-init-file] [-p int] [-r feature] [-h feature]
[-d filename] [-f filename] [-l filename]
[-c expression] [-e expression] [-o dumpname]
[-- | - | -s] [filename] [arguments ...]
Upon startup `scm' loads the file specified by by the environment
variable SCM_INIT_PATH.
If SCM_INIT_PATH is not defined or if the file it names is not present,
`scm' tries to find the directory containing the executable file. If
it is able to locate the executable, `scm' looks for the initialization
file (usually `Init5e2.scm') in platform-dependent directories relative |
to this directory. See *Note File-System Habitat:: for a blow-by-blow
description.
As a last resort (if initialization file cannot be located), the C
compile parameter IMPLINIT (defined in the makefile or `scmfig.h') is
tried.
Unless the option `-no-init-file' or `--no-init-file' occurs in the
command line, `Init5e2.scm' checks to see if there is file |
`ScmInit.scm' in the path specified by the environment variable HOME
(or in the current directory if HOME is undefined). If it finds such a
file it is loaded.
`Init5e2.scm' then looks for command input from one of three sources: |
From an option on the command line, from a file named on the command
line, or from standard input.
This explanation applies to SCMLIT or other builds of SCM.
Scheme-code files can also invoke SCM and its variants. *Note #!:
Lexical Conventions.
File: scm.info, Node: SCM Options, Next: Invocation Examples, Prev: Invoking SCM, Up: Operational Features
3.2 Options
===========
The options are processed in the order specified on the command line.
-- Command Option: -a k
specifies that `scm' should allocate an initial heapsize of K
kilobytes. This option, if present, must be the first on the
command line. If not specified, the default is `INIT_HEAP_SIZE'
in source file `setjump.h' which the distribution sets at
`25000*sizeof(cell)'.
-- Command Option: -no-init-file
-- Command Option: --no-init-file
Inhibits the loading of `ScmInit.scm' as described above.
-- Command Option: --help
prints usage information and URI; then exit.
-- Command Option: --version
prints version information and exit.
-- Command Option: -r feature
requires FEATURE. This will load a file from [SLIB] if that
FEATURE is not already provided. If FEATURE is 2, 2rs, or r2rs;
3, 3rs, or r3rs; 4, 4rs, or r4rs; 5, 5rs, or r5rs; `scm' will
require the features neccessary to support [R2RS]; [R3RS]; [R4RS];
or [R5RS], respectively.
-- Command Option: -h feature
provides FEATURE.
-- Command Option: -l filename
-- Command Option: -f filename
loads FILENAME. `Scm' will load the first (unoptioned) file named
on the command line if no `-c', `-e', `-f', `-l', or `-s' option
preceeds it.
-- Command Option: -d filename
Loads SLIB `databases' feature and opens FILENAME as a database.
-- Command Option: -e expression
-- Command Option: -c expression
specifies that the scheme expression EXPRESSION is to be
evaluated. These options are inspired by `perl' and `sh'
respectively. On Amiga systems the entire option and argument
need to be enclosed in quotes. For instance `"-e(newline)"'.
-- Command Option: -o dumpname
saves the current SCM session as the executable program `dumpname'.
This option works only in SCM builds supporting `dump' (*note
Dump::).
If options appear on the command line after `-o DUMPNAME', then
the saved session will continue with processing those options when
it is invoked. Otherwise the (new) command line is processed as
usual when the saved image is invoked.
-- Command Option: -p level
sets the prolixity (verboseness) to LEVEL. This is the same as
the `scm' command (verobse LEVEL).
-- Command Option: -v
(verbose mode) specifies that `scm' will print prompts, evaluation
times, notice of loading files, and garbage collection statistics.
This is the same as `-p3'.
-- Command Option: -q
(quiet mode) specifies that `scm' will print no extra information.
This is the same as `-p0'.
-- Command Option: -m
specifies that subsequent loads, evaluations, and user
interactions will be with syntax-rules macro capability. To use a
specific syntax-rules macro implementation from [SLIB] (instead of
[SLIB]'s default) put `-r' MACROPACKAGE before `-m' on the command
line.
-- Command Option: -u
specifies that subsequent loads, evaluations, and user
interactions will be without syntax-rules macro capability.
Syntax-rules macro capability can be restored by a subsequent `-m'
on the command line or from Scheme code.
-- Command Option: -i
specifies that `scm' should run interactively. That means that
`scm' will not terminate until the `(quit)' or `(exit)' command is
given, even if there are errors. It also sets the prolixity level
to 2 if it is less than 2. This will print prompts, evaluation
times, and notice of loading files. The prolixity level can be
set by subsequent options. If `scm' is started from a tty, it
will assume that it should be interactive unless given a
subsequent `-b' option.
-- Command Option: -b
specifies that `scm' should run non-interactively. That means that
`scm' will terminate after processing the command line or if there
are errors.
-- Command Option: -s
specifies, by analogy with `sh', that `scm' should run
interactively and that further options are to be treated as program
aguments.
-- Command Option: -
-- Command Option: --
specifies that further options are to be treated as program
aguments.
File: scm.info, Node: Invocation Examples, Next: SCM Variables, Prev: SCM Options, Up: Operational Features
3.3 Invocation Examples
=======================
`% scm foo.scm'
Loads and executes the contents of `foo.scm' and then enters
interactive session.
`% scm -f foo.scm arg1 arg2 arg3'
Parameters `arg1', `arg2', and `arg3' are stored in the global
list `*argv*'; Loads and executes the contents of `foo.scm' and
exits.
`% scm -s foo.scm arg1 arg2'
Sets *argv* to `("foo.scm" "arg1" "arg2")' and enters interactive
session.
`% scm -e `(write (list-ref *argv* *optind*))' bar'
Prints `"bar"'.
`% scm -rpretty-print -r format -i'
Loads `pretty-print' and `format' and enters interactive session.
`% scm -r5'
Loads `dynamic-wind', `values', and syntax-rules macros and enters
interactive (with macros) session.
`% scm -r5 -r4'
Like above but `rev4-optional-procedures' are also loaded.
File: scm.info, Node: SCM Variables, Next: SCM Session, Prev: Invocation Examples, Up: Operational Features
3.4 Environment Variables
=========================
-- Environment Variable: SCM_INIT_PATH
is the pathname where `scm' will look for its initialization code.
The default is the file `Init5e2.scm' in the source directory. |
-- Environment Variable: SCHEME_LIBRARY_PATH
is the [SLIB] Scheme library directory.
-- Environment Variable: HOME
is the directory where `Init5e2.scm' will look for the user |
initialization file `ScmInit.scm'.
-- Environment Variable: EDITOR
is the name of the program which `ed' will call. If EDITOR is not
defined, the default is `ed'.
3.5 Scheme Variables
====================
-- Variable: *argv*
contains the list of arguments to the program. `*argv*' can change
during argument processing. This list is suitable for use as an
argument to [SLIB] `getopt'.
-- Variable: *syntax-rules*
controls whether loading and interaction support syntax-rules
macros. Define this in `ScmInit.scm' or files specified on the
command line. This can be overridden by subsequent `-m' and `-u'
options.
-- Variable: *interactive*
controls interactivity as explained for the `-i' and `-b' options.
Define this in `ScmInit.scm' or files specified on the command
line. This can be overridden by subsequent `-i' and `-b' options.
File: scm.info, Node: SCM Session, Next: Editing Scheme Code, Prev: SCM Variables, Up: Operational Features
3.6 SCM Session
===============
* Options, file loading and features can be specified from the
command line. *Note System interface: (scm)System interface.
*Note Require: (slib)Require.
* Typing the end-of-file character at the top level session (while
SCM is not waiting for parenthesis closure) causes SCM to exit.
* Typing the interrupt character aborts evaluation of the current
form and resumes the top level read-eval-print loop.
-- Function: quit
-- Function: quit n
-- Function: exit
-- Function: exit n
Aliases for `exit' (*note exit: (slib)System.). On many systems,
SCM can also tail-call another program. *Note execp:
I/O-Extensions.
-- Callback procedure: boot-tail dumped?
`boot-tail' is called by `scm_top_level' just before entering
interactive top-level. If `boot-tail' calls `quit', then
interactive top-level is not entered.
-- Function: program-arguments
Returns a list of strings of the arguments scm was called with.
-- Function: getlogin
Returns the (login) name of the user logged in on the controlling
terminal of the process, or #f if this information cannot be
determined.
For documentation of the procedures `getenv' and `system' *Note System
Interface: (slib)System Interface.
-- Function: vms-debug
If SCM is compiled under VMS this `vms-debug' will invoke the VMS
debugger.
File: scm.info, Node: Editing Scheme Code, Next: Debugging Scheme Code, Prev: SCM Session, Up: Operational Features
3.7 Editing Scheme Code
=======================
-- Function: ed arg1 ...
The value of the environment variable `EDITOR' (or just `ed' if it
isn't defined) is invoked as a command with arguments ARG1 ....
-- Function: ed filename
If SCM is compiled under VMS `ed' will invoke the editor with a
single the single argument FILENAME.
Gnu Emacs:
Editing of Scheme code is supported by emacs. Buffers holding
files ending in .scm are automatically put into scheme-mode.
If your Emacs can run a process in a buffer you can use the Emacs
command `M-x run-scheme' with SCM. Otherwise, use the emacs
command `M-x suspend-emacs'; or see "other systems" below.
Epsilon (MS-DOS):
There is lisp (and scheme) mode available by use of the package
`LISP.E'. It offers several different indentation formats. With
this package, buffers holding files ending in `.L', `.LSP', `.S',
and `.SCM' (my modification) are automatically put into lisp-mode.
It is possible to run a process in a buffer under Epsilon. With
Epsilon 5.0 the command line options `-e512 -m0' are neccessary to
manage RAM properly. It has been reported that when compiling SCM
with Turbo C, you need to `#define NOSETBUF' for proper operation
in a process buffer with Epsilon 5.0.
One can also call out to an editor from SCM if RAM is at a
premium; See "under other systems" below.
other systems:
Define the environment variable `EDITOR' to be the name of the
editing program you use. The SCM procedure `(ed arg1 ...)' will
invoke your editor and return to SCM when you exit the editor. The
following definition is convenient:
(define (e) (ed "work.scm") (load "work.scm"))
Typing `(e)' will invoke the editor with the file of interest.
After editing, the modified file will be loaded.
File: scm.info, Node: Debugging Scheme Code, Next: Debugging Continuations, Prev: Editing Scheme Code, Up: Operational Features
3.8 Debugging Scheme Code
=========================
The `cautious' and `stack-limit' options of `build' (*note Build
Options::) support debugging in Scheme.
"CAUTIOUS"
If SCM is built with the `CAUTIOUS' flag, then when an error
occurs, a "stack trace" of certain pending calls are printed as
part of the default error response. A (memoized) expression and
newline are printed for each partially evaluated combination whose
procedure is not builtin. See *Note Memoized Expressions:: for
how to read memoized expressions.
Also as the result of the `CAUTIOUS' flag, both `error' and
`user-interrupt' (invoked by <C-c>) to print stack traces and
conclude by calling `breakpoint' (*note Breakpoints:
(slib)Breakpoints.) instead of aborting to top level. Under
either condition, program execution can be resumed by `(continue)'.
In this configuration one can interrupt a running Scheme program
with <C-c>, inspect or modify top-level values, trace or untrace
procedures, and continue execution with `(continue)'.
"STACK_LIMIT"
If SCM is built with the `STACK_LIMIT' flag, the interpreter will
check stack size periodically. If the size of stack exceeds a
certain amount (default is `HEAP_SEG_SIZE/2'), SCM generates a
`segment violation' interrupt.
The usefulness of `STACK_LIMIT' depends on the user. I don't use
it; but the user I added this feature for got primarily this type
of error.
There are several SLIB macros which so useful that SCM automatically
loads the appropriate module from SLIB if they are invoked.
-- Macro: trace proc1 ...
Traces the top-level named procedures given as arguments.
-- Macro: 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.
-- Macro: untrace proc1 ...
Turns tracing off for its arguments.
-- Macro: untrace
With no arguments, untraces all currently traced identifiers and
returns a list of these formerly traced identifiers.
The routines I use most frequently for debugging are:
-- Function: print arg1 ...
`Print' writes all its arguments, separated by spaces. `Print'
outputs a `newline' at the end and returns the value of the last
argument.
One can just insert `(print '<label>' and `)' around an expression
in order to see its values as a program operates.
-- Function: pprint arg1 ...
`Pprint' pretty-prints (*note Pretty-Print: (slib)Pretty-Print.)
all its arguments, separated by newlines. `Pprint' returns the
value of the last argument.
One can just insert `(pprint '<label>' and `)' around an
expression in order to see its values as a program operates.
_Note_ `pretty-print' does _not_ format procedures.
When typing at top level, `pprint' is not a good way to see nested
structure because it will return the last object pretty-printed, which
could be large. `pp' is a better choice.
-- Procedure: pp arg1 ...
`Pprint' pretty-prints (*note Pretty-Print: (slib)Pretty-Print.)
all its arguments, separated by newlines. `pp' returns
`#<unspecified>'.
-- Syntax: print-args name
-- Syntax: print-args
Writes NAME if supplied; then writes the names and values of the
closest lexical bindings enclosing the call to `Print-args'.
(define (foo a b) (print-args foo) (+ a b))
(foo 3 6)
-| In foo: a = 3; b = 6;
=> 9
Sometimes more elaborate measures are needed to print values in a useful
manner. When the values to be printed may have very large (or infinite)
external representations, *Note Quick Print: (slib)Quick Print, can be
used.
When `trace' is not sufficient to find program flow problems, SLIB-PSD,
the Portable Scheme Debugger offers source code debugging from GNU
Emacs. PSD runs slowly, so start by instrumenting only a few functions
at a time.
http://swiss.csail.mit.edu/ftpdir/scm/slib-psd1-3.tar.gz
swiss.csail.mit.edu:/pub/scm/slib-psd1-3.tar.gz
ftp.maths.tcd.ie:pub/bosullvn/jacal/slib-psd1-3.tar.gz
ftp.cs.indiana.edu:/pub/scheme-repository/utl/slib-psd1-3.tar.gz
File: scm.info, Node: Debugging Continuations, Next: Errors, Prev: Debugging Scheme Code, Up: Operational Features
3.9 Debugging Continuations
===========================
These functions are defined in `debug.c', all operate on captured
continuations:
-- Procedure: frame-trace cont n
Prints information about the code being executed and the
environment scopes active for continuation frame N of continuation
CONT. A "continuation frame" is an entry in the environment
stack; a new frame is pushed when the environment is replaced or
extended in a non-tail call context. Frame 0 is the top of the
stack.
-- Procedure: frame->environment cont n
Prints the environment for continuation frame N of continuation
CONT. This contains just the names, not the values, of the
environment.
-- Procedure: scope-trace env
will print information about active lexical scopes for environment
ENV.
-- Procedure: frame-eval cont n expr
Evaluates EXPR in the environment defined by continuation frame N
of continuation CONT and returns the result. Values in the
environment may be returned or SET!.
*Note stack-trace: Errors. also now accepts an optional continuation
argument. `stack-trace' differs from `frame-trace' in that it
truncates long output using safeports and prints code from all
available frames.
(define k #f)
(define (foo x y)
(set! k (call-with-current-continuation identity))
#f)
(let ((a 3) (b 4))
(foo a b)
#f)
(stack-trace k)
-|
;STACK TRACE
1; ((#@set! #@k (#@call-with-current-continuation #@identity)) #f ...
2; (#@let ((a 3) (b 4)) (#@foo #@a #@b) #f)
...
#t
(frame-trace k 0)
-|
(#@call-with-current-continuation #@identity)
; in scope:
; (x y) procedure foo#<unspecified>
(frame-trace k 1)
-|
((#@set! #@k (#@call-with-current-continuation #@identity)) #f)
; in scope:
; (x y) procedure foo#<unspecified>
(frame-trace k 2)
-|
(#@let ((a 3) (b 4)) (#@foo #@a #@b) #f)
; in scope:
; (a b . #@let)#<unspecified>
(frame-trace k 3)
-|
(#@let ((a 3) (b 4)) (#@foo #@a #@b) #f)
; in top level environment.
(frame->environment k 0)
-|
((x y) 2 foo)
(scope-trace (frame->environment k 0))
-|
; in scope:
; (x y) procedure foo#<unspecified>
(frame-eval k 0 'x) => 3
(frame-eval k 0 '(set! x 8))
(frame-eval k 0 'x) => 8
File: scm.info, Node: Errors, Next: Memoized Expressions, Prev: Debugging Continuations, Up: Operational Features
3.10 Errors
===========
A computer-language implementation designer faces choices of how
reflexive to make the implementation in handling exceptions and errors;
that is, how much of the error and exception routines should be written
in the language itself. The design of a portable implementation is
further constrained by the need to have (almost) all errors print
meaningful messages, even when the implementation itself is not
functioning correctly. Therefore, SCM implements much of its error
response code in C.
The following common error and conditions are handled by C code. Those
with callback names after them can also be handled by Scheme code
(*note Interrupts::). If the callback identifier is not defined at top
level, the default error handler (C code) is invoked. There are many
other error messages which are not treated specially.
"ARGn"
Wrong type in argument
"ARG1"
Wrong type in argument 1
"ARG2"
Wrong type in argument 2
"ARG3"
Wrong type in argument 3
"ARG4"
Wrong type in argument 4
"ARG5"
Wrong type in argument 5
"WNA"
Wrong number of args
"OVFLOW"
numerical overflow
"OUTOFRANGE"
Argument out of range
"NALLOC"
`(out-of-storage)'
"THRASH"
GC is `(thrashing)'
"EXIT"
`(end-of-program)'
"HUP_SIGNAL"
`(hang-up)'
"INT_SIGNAL"
`(user-interrupt)'
"FPE_SIGNAL"
`(arithmetic-error)'
"BUS_SIGNAL"
bus error
"SEGV_SIGNAL"
segment violation
"ALRM_SIGNAL"
`(alarm-interrupt)'
"VTALRM_SIGNAL"
`(virtual-alarm-interrupt)'
"PROF_SIGNAL"
`(profile-alarm-interrupt)'
-- Variable: errobj
When SCM encounters a non-fatal error, it aborts evaluation of the
current form, prints a message explaining the error, and resumes
the top level read-eval-print loop. The value of ERROBJ is the
offending object if appropriate. The builtin procedure `error'
does _not_ set ERROBJ.
`errno' and `perror' report ANSI C errors encountered during a call to
a system or library function.
-- Function: errno
-- Function: errno n
With no argument returns the current value of the system variable
`errno'. When given an argument, `errno' sets the system variable
`errno' to N and returns the previous value of `errno'. `(errno
0)' will clear outstanding errors. This is recommended after
`try-load' returns `#f' since this occurs when the file could not
be opened.
-- Function: perror string
Prints on standard error output the argument STRING, a colon,
followed by a space, the error message corresponding to the current
value of `errno' and a newline. The value returned is unspecified.
`warn' and `error' provide a uniform way for Scheme code to signal
warnings and errors.
-- Function: warn arg1 arg2 arg3 ...
Alias for *Note slib:warn: (slib)System. Outputs an error message
containing the arguments. `warn' is defined in `Init5e2.scm'. |
-- Function: error arg1 arg2 arg3 ...
Alias for *Note slib:error: (slib)System. Outputs an error
message containing the arguments, aborts evaluation of the current
form and resumes the top level read-eval-print loop. `Error' is
defined in `Init5e2.scm'. |
If SCM is built with the `CAUTIOUS' flag, then when an error occurs, a
"stack trace" of certain pending calls are printed as part of the
default error response. A (memoized) expression and newline are
printed for each partially evaluated combination whose procedure is not
builtin. See *Note Memoized Expressions:: for how to read memoized
expressions.
Also as the result of the `CAUTIOUS' flag, both `error' and
`user-interrupt' (invoked by <C-c>) are defined to print stack traces
and conclude by calling `breakpoint' (*note Breakpoints:
(slib)Breakpoints.). This allows the user to interract with SCM as
with Lisp systems.
-- Function: stack-trace
Prints information describing the stack of partially evaluated
expressions. `stack-trace' returns `#t' if any lines were printed
and `#f' otherwise. See `Init5e2.scm' for an example of the use |
of `stack-trace'.
File: scm.info, Node: Memoized Expressions, Next: Internal State, Prev: Errors, Up: Operational Features
3.11 Memoized Expressions
=========================
SCM memoizes the address of each occurence of an identifier's value when
first encountering it in a source expression. Subsequent executions of
that memoized expression is faster because the memoized reference
encodes where in the top-level or local environment its value is.
When procedures are displayed, the memoized locations appear in a format
different from references which have not yet been executed. I find this
a convenient aid to locating bugs and untested expressions.
* The names of memoized lexically bound identifiers are replaced with
#@<m>-<n>, where <m> is the number of binding contours back and
<n> is the index of the value in that binding countour.
* The names of identifiers which are not lexiallly bound but defined
at top-level have #@ prepended.
For instance, `open-input-file' is defined as follows in `Init5e2.scm': |
(define (open-input-file str)
(or (open-file str OPEN_READ)
(and (procedure? could-not-open) (could-not-open) #f)
(error "OPEN-INPUT-FILE couldn't open file " str)))
If `open-input-file' has not yet been used, the displayed procedure is
similar to the original definition (lines wrapped for readability):
open-input-file =>
#<CLOSURE (str) (or (open-file str open_read)
(and (procedure? could-not-open) (could-not-open) #f)
(error "OPEN-INPUT-FILE couldn't open file " str))>
If we open a file using `open-input-file', the sections of code used
become memoized:
(open-input-file "r4rstest.scm") => #<input-port 3>
open-input-file =>
#<CLOSURE (str) (#@or (#@open-file #@0+0 #@open_read)
(and (procedure? could-not-open) (could-not-open) #f)
(error "OPEN-INPUT-FILE couldn't open file " str))>
If we cause `open-input-file' to execute other sections of code, they
too become memoized:
(open-input-file "foo.scm") =>
ERROR: No such file or directory
ERROR: OPEN-INPUT-FILE couldn't open file "foo.scm"
open-input-file =>
#<CLOSURE (str) (#@or (#@open-file #@0+0 #@open_read)
(#@and (#@procedure? #@could-not-open) (could-not-open) #f)
(#@error "OPEN-INPUT-FILE couldn't open file " #@0+0))>
File: scm.info, Node: Internal State, Next: Scripting, Prev: Memoized Expressions, Up: Operational Features
3.12 Internal State
===================
-- Variable: *interactive*
The variable *INTERACTIVE* determines whether the SCM session is
interactive, or should quit after the command line is processed.
*INTERACTIVE* is controlled directly by the command-line options
`-b', `-i', and `-s' (*note Invoking SCM::). If none of these
options are specified, the rules to determine interactivity are
more complicated; see `Init5e2.scm' for details. |
-- Function: abort
Resumes the top level Read-Eval-Print loop.
-- Function: restart
Restarts the SCM program with the same arguments as it was
originally invoked. All `-l' loaded files are loaded again; If
those files have changed, those changes will be reflected in the
new session.
_Note_ When running a saved executable (*note Dump::), `restart'
is redefined to be `exec-self'.
-- Function: exec-self
Exits and immediately re-invokes the same executable with the same
arguments. If the executable file has been changed or replaced
since the beginning of the current session, the _new_ executable
will be invoked. This differentiates `exec-self' from `restart'.
-- Function: verbose n
Controls how much monitoring information is printed. If N is:
0
no prompt or information is printed.
>= 1
a prompt is printed.
>= 2
messages bracketing file loading are printed.
>= 3
the CPU time is printed after each top level form evaluated;
notifications of heap growth printed.
>= 4
a garbage collection summary is printed after each top level
form evaluated;
>= 5
a message for each GC (*note Garbage Collection::) is printed;
warnings issued for top-level symbols redefined.
-- Function: gc
Scans all of SCM objects and reclaims for further use those that
are no longer accessible.
-- Function: room
-- Function: room #t
Prints out statistics about SCM's current use of storage. `(room
#t)' also gives the hexadecimal heap segment and stack bounds.
-- Constant: *scm-version*
Contains the version string (e.g. `5e2') of SCM. |
3.12.1 Executable path
----------------------
In order to dump a saved executable or to dynamically-link using DLD,
SCM must know where its executable file is. Sometimes SCM (*note
Executable Pathname::) guesses incorrectly the location of the
currently running executable. In that case, the correct path can be set
by calling `execpath' with the pathname.
-- Function: execpath
Returns the path (string) which SCM uses to find the executable
file whose invocation the currently running session is, or #f if
the path is not set.
-- Function: execpath #f
-- Function: execpath newpath
Sets the path to `#f' or NEWPATH, respectively. The old path is
returned.
For other configuration constants and procedures *Note Configuration:
(slib)Configuration.
File: scm.info, Node: Scripting, Prev: Internal State, Up: Operational Features
3.13 Scripting
==============
* Menu:
* Unix Scheme Scripts:: From Olin Shivers' Scheme Shell
* MS-DOS Compatible Scripts:: Run in MS-DOS and Unix
* Unix Shell Scripts:: Use /bin/sh to run Scheme
File: scm.info, Node: Unix Scheme Scripts, Next: MS-DOS Compatible Scripts, Prev: Scripting, Up: Scripting
3.13.1 Unix Scheme Scripts
--------------------------
In reading this section, keep in mind that the first line of a script
file has (different) meanings to SCM and the operating system
(`execve').
-- file: #! interpreter \ ...
On unix systems, a "Shell-Script" is a file (with execute
permissions) whose first two characters are `#!'. The INTERPRETER
argument must be the pathname of the program to process the rest
of the file. The directories named by environment variable `PATH'
are _not_ searched to find INTERPRETER.
When executing a shell-script, the operating system invokes
INTERPRETER with a single argument encapsulating the rest of the
first line's contents (if not just whitespace), the pathname of the
Scheme Script file, and then any arguments which the shell-script
was invoked with.
Put one space character between `#!' and the first character of
INTERPRETER (`/'). The INTERPRETER name is followed by ` \'; SCM
substitutes the second line of FILE for `\' (and the rest of the
line), then appends any arguments given on the command line
invoking this Scheme-Script.
When SCM executes the script, the Scheme variable *SCRIPT* will be
set to the script pathname. The last argument before `!#' on the
second line should be `-'; SCM will load the script file, preserve
the unprocessed arguments, and set *ARGV* to a list of the script
pathname and the unprocessed arguments.
Note that the interpreter, not the operating system, provides the
`\' substitution; this will only take place if INTERPRETER is a
SCM or SCSH interpreter.
-- Read syntax: #! ignored !#
When the first two characters of the file being loaded are `#!' and
a `\' is present before a newline in the file, all characters up
to `!#' will be ignored by SCM `read'.
This combination of interpretatons allows SCM source files to be used as
POSIX shell-scripts if the first line is:
#! /usr/local/bin/scm \
The following Scheme-Script prints factorial of its argument:
#! /usr/local/bin/scm \ %0 %*
- !#
(define (fact.script args)
(cond ((and (= 1 (length args))
(string->number (car args)))
=> (lambda (n) (print (fact n)) #t))
(else (fact.usage))))
(define (fact.usage)
(print *argv*)
(display "\
Usage: fact N
Returns the factorial of N.
"
(current-error-port))
#f)
(define (fact n) (if (< n 2) 1 (* n (fact (+ -1 n)))))
(if *script* (exit (fact.script (list-tail *argv* *optind*))))
./fact 32
=>
263130836933693530167218012160000000
If the wrong number of arguments is given, `fact' prints its ARGV with
usage information.
./fact 3 2
-|
("./fact" "3" "2")
Usage: fact N
Returns the factorial of N.
File: scm.info, Node: MS-DOS Compatible Scripts, Next: Unix Shell Scripts, Prev: Unix Scheme Scripts, Up: Scripting
3.13.2 MS-DOS Compatible Scripts
--------------------------------
It turns out that we can create scheme-scripts which run both under unix
and MS-DOS. To implement this, I have written the MS-DOS programs:
`#!.bat' and `!#.exe', which are available from:
`http://swiss.csail.mit.edu/ftpdir/scm/sharpbang.zip'
With these two programs installed in a `PATH' directory, we have the
following syntax for <PROGRAM>.BAT files.
-- file: #! interpreter \ %0 %*
The first two characters of the Scheme-Script are `#!'. The
INTERPRETER can be either a unix style program path (using `/'
between filename components) or a DOS program name or path. The
rest of the first line of the Scheme-Script should be literally
`\ %0 %*', as shown.
If INTERPRETER has `/' in it, INTERPRETER is converted to a DOS
style filename (`/' => `\').
In looking for an executable named INTERPRETER, `#!' first checks
this (converted) filename; if INTERPRETER doesn't exist, it then
tries to find a program named like the string starting after the
last `\' (or `/') in INTERPRETER. When searching for executables,
`#!' tries all directories named by environment variable `PATH'.
Once the INTERPRETER executable path is found, arguments are
processed in the manner of scheme-shell, with all the text after
the `\' taken as part of the meta-argument. More precisely, `#!'
calls INTERPRETER with any options on the second line of the
Scheme-Script up to `!#', the name of the Scheme-Script file, and
then any of at most 8 arguments given on the command line invoking
this Scheme-Script.
The previous example Scheme-Script works in both MS-DOS and unix
systems.
File: scm.info, Node: Unix Shell Scripts, Prev: MS-DOS Compatible Scripts, Up: Scripting
3.13.3 Unix Shell Scripts
-------------------------
Scheme-scripts suffer from two drawbacks:
* Some Unixes limit the length of the `#!' interpreter line to the
size of an object file header, which can be as small as 32 bytes.
* A full, explicit pathname must be specified, perhaps requiring
more than 32 bytes and making scripts vulnerable to breakage when
programs are moved.
The following approach solves these problems at the expense of slower
startup. Make `#! /bin/sh' the first line and prepend every subsequent
line to be executed by the shell with `:;'. The last line to be
executed by the shell should contain an "exec" command; `exec'
tail-calls its argument.
`/bin/sh' is thus invoked with the name of the script file, which it
executes as a *sh script. Usually the second line starts `:;exec scm
-f$0', which executes scm, which in turn loads the script file. When
SCM loads the script file, it ignores the first and second lines, and
evaluates the rest of the file as Scheme source code.
The second line of the script file does not have the length restriction
mentioned above. Also, `/bin/sh' searches the directories listed in
the `PATH' environment variable for `scm', eliminating the need to use
absolute locations in order to invoke a program.
The following example additionally sets *SCRIPT* to the script
argument, making it compatible with the scheme code of the previous
example.
#! /bin/sh
:;exec scm -e"(set! *script* \"$0\")" -l$0 "$@"
(define (fact.script args)
(cond ((and (= 1 (length args))
(string->number (car args)))
=> (lambda (n) (print (fact n)) #t))
(else (fact.usage))))
(define (fact.usage)
(print *argv*)
(display "\
Usage: fact N
Returns the factorial of N.
"
(current-error-port))
#f)
(define (fact n) (if (< n 2) 1 (* n (fact (+ -1 n)))))
(if *script* (exit (fact.script (list-tail *argv* *optind*))))
./fact 6
=> 720
File: scm.info, Node: The Language, Next: Packages, Prev: Operational Features, Up: Top
4 The Language
**************
* Menu:
* Standards Compliance:: Links to sections in [R5RS] and [SLIB]
* Storage:: Finalizers, GC-hook, vector-set-length!
* Time:: Both real time and processor time
* Interrupts:: and exceptions
* Process Synchronization:: Because interrupts are preemptive
* Files and Ports::
* Eval and Load:: and line-numbers
* Lexical Conventions:: Also called read-syntax
* Syntax:: Macros
File: scm.info, Node: Standards Compliance, Next: Storage, Prev: The Language, Up: The Language
4.1 Standards Compliance
========================
Scm conforms to the `IEEE Standard 1178-1990. IEEE Standard for the
Scheme Programming Language.' (*note Bibliography::), and `Revised(5)
Report on the Algorithmic Language Scheme'. *Note Top: (r5rs)Top. All
the required features of these specifications are supported. Many of
the optional features are supported as well.
Optionals of [R5RS] Supported by SCM
------------------------------------
`-' and `/' of more than 2 arguments
`exp'
`log'
`sin'
`cos'
`tan'
`asin'
`acos'
`atan'
`sqrt'
`expt'
`make-rectangular'
`make-polar'
`real-part'
`imag-part'
`magnitude'
`angle'
`exact->inexact'
`inexact->exact'
*Note Numerical operations: (r5rs)Numerical operations.
`with-input-from-file'
`with-output-to-file'
*Note Ports: (r5rs)Ports.
`load'
`transcript-on'
`transcript-off'
*Note System interface: (r5rs)System interface.
Optionals of [R5RS] not Supported by SCM
----------------------------------------
`numerator'
`denominator'
`rationalize'
*Note Numerical operations: (r5rs)Numerical operations.
[SLIB] Features of SCM and SCMLIT
---------------------------------
`delay'
`full-continuation'
`ieee-p1178'
`object-hash'
`rev4-report'
`source'
See SLIB file `Template.scm'.
`current-time'
*Note Time and Date: (slib)Time and Date.
`defmacro'
*Note Defmacro: (slib)Defmacro.
`getenv'
`system'
*Note System Interface: (slib)System Interface.
`hash'
*Note Hashing: (slib)Hashing.
`logical'
*Note Bit-Twiddling: (slib)Bit-Twiddling.
`multiarg-apply'
*Note Multi-argument Apply: (slib)Multi-argument Apply.
`multiarg/and-'
*Note Multi-argument / and -: (slib)Multi-argument / and -.
`rev4-optional-procedures'
*Note Rev4 Optional Procedures: (slib)Rev4 Optional Procedures.
`string-port'
*Note String Ports: (slib)String Ports.
`tmpnam'
*Note Input/Output: (slib)Input/Output.
`transcript'
*Note Transcripts: (slib)Transcripts.
`vicinity'
*Note Vicinity: (slib)Vicinity.
`with-file'
*Note With-File: (slib)With-File.
[SLIB] Features of SCM
----------------------
`array'
*Note Arrays: (slib)Arrays.
`array-for-each'
*Note Array Mapping: (slib)Array Mapping.
`bignum'
`complex'
`inexact'
`rational'
`real'
*Note Require: (slib)Require.
File: scm.info, Node: Storage, Next: Time, Prev: Standards Compliance, Up: The Language
4.2 Storage
===========
-- Function: vector-set-length! object length
Change the length of string, vector, bit-vector, or uniform-array
OBJECT to LENGTH. If this shortens OBJECT then the remaining
contents are lost. If it enlarges OBJECT then the contents of the
extended part are undefined but the original part is unchanged.
It is an error to change the length of literal datums. The new
object is returned.
-- Function: copy-tree obj
-- Function: @copy-tree obj
*Note copy-tree: (slib)Tree Operations. This extends the SLIB
version by also copying vectors. Use `@copy-tree' if you depend
on this feature; `copy-tree' could get redefined.
-- Function: acons obj1 obj2 obj3
Returns (cons (cons obj1 obj2) obj3).
(set! a-list (acons key datum a-list))
Adds a new association to a-list.
-- Callback procedure: gc-hook ...
Allows a Scheme procedure to be run shortly after each garbage
collection. This procedure will not be run recursively. If it
runs long enough to cause a garbage collection before returning a
warning will be printed.
To remove the gc-hook, `(set! gc-hook #f)'.
-- Function: add-finalizer object finalizer
OBJECT may be any garbage collected object, that is, any object
other than an immediate integer, character, or special token such
as `#f' or `#t', *Note Immediates::. FINALIZER is a thunk, or
procedure taking no arguments.
FINALIZER will be invoked asynchronously exactly once some time
after OBJECT becomes eligible for garbage collection. A reference
to OBJECT in the environment of FINALIZER will not prevent
finalization, but will delay the reclamation of OBJECT at least
until the next garbage collection. A reference to OBJECT in some
other object's finalizer will necessarily prevent finalization
until both objects are eligible for garbage collection.
Finalizers are not run in any predictable order. All finalizers
will be run by the time the program ends.
This facility was based on the paper by Simon Peyton Jones, et al,
"Stretching the storage manager: weak pointers and stable names in
Haskell", Proc. 11th International Workshop on the Implementation
of Functional Languages, The Netherlands, September 7-10 1999,
Springer-Verlag LNCS.
File: scm.info, Node: Time, Next: Interrupts, Prev: Storage, Up: The Language
4.3 Time
========
-- Constant: internal-time-units-per-second
Is the integer number of internal time units in a second.
-- Function: get-internal-run-time
Returns the integer run time in internal time units from an
unspecified starting time. The difference of two calls to
`get-internal-run-time' divided by
`internal-time-units-per-second' will give elapsed run time in
seconds.
-- Function: get-internal-real-time
Returns the integer time in internal time units from an unspecified
starting time. The difference of two calls to
`get-internal-real-time' divided by
`interal-time-units-per-second' will give elapsed real time in
seconds.
-- Function: current-time
Returns the time since 00:00:00 GMT, January 1, 1970, measured in
seconds. *Note current-time: (slib)Time and Date. `current-time'
is used in *Note Time and Date: (slib)Time and Date.
File: scm.info, Node: Interrupts, Next: Process Synchronization, Prev: Time, Up: The Language
4.4 Interrupts
==============
-- Function: ticks n
Returns the number of ticks remaining till the next tick interrupt.
Ticks are an arbitrary unit of evaluation. Ticks can vary greatly
in the amount of time they represent.
If N is 0, any ticks request is canceled. Otherwise a
`ticks-interrupt' will be signaled N from the current time.
`ticks' is supported if SCM is compiled with the `ticks' flag
defined.
-- Callback procedure: ticks-interrupt ...
Establishes a response for tick interrupts. Another tick
interrupt will not occur unless `ticks' is called again. Program
execution will resume if the handler returns. This procedure
should (abort) or some other action which does not return if it
does not want processing to continue.
-- Function: alarm secs
Returns the number of seconds remaining till the next alarm
interrupt. If SECS is 0, any alarm request is canceled.
Otherwise an `alarm-interrupt' will be signaled SECS from the
current time. ALARM is not supported on all systems.
-- Function: milli-alarm millisecs interval
-- Function: virtual-alarm millisecs interval
-- Function: profile-alarm millisecs interval
`milli-alarm' is similar to `alarm', except that the first
argument MILLISECS, and the return value are measured in
milliseconds rather than seconds. If the optional argument
INTERVAL is supplied then alarm interrupts will be scheduled every
INTERVAL milliseconds until turned off by a call to `milli-alarm'
or `alarm'.
`virtual-alarm' and `profile-alarm' are similar. `virtual-alarm'
decrements process execution time rather than real time, and
causes `SIGVTALRM' to be signaled. `profile-alarm' decrements
both process execution time and system execution time on behalf
of the process, and causes `SIGPROF' to be signaled.
`milli-alarm', `virtual-alarm', and `profile-alarm' are supported
only on systems providing the `setitimer' system call.
-- Callback procedure: user-interrupt ...
-- Callback procedure: alarm-interrupt ...
-- Callback procedure: virtual-alarm-interrupt ...
-- Callback procedure: profile-alarm-interrupt ...
Establishes a response for `SIGINT' (control-C interrupt) and
`SIGALRM', `SIGVTALRM', and `SIGPROF' interrupts. Program
execution will resume if the handler returns. This procedure
should `(abort)' or some other action which does not return if it
does not want processing to continue after it returns.
Interrupt handlers are disabled during execution `system' and `ed'
procedures.
To unestablish a response for an interrupt set the handler symbol
to `#f'. For instance, `(set! user-interrupt #f)'.
-- Callback procedure: out-of-storage ...
-- Callback procedure: could-not-open ...
-- Callback procedure: end-of-program ...
-- Callback procedure: hang-up ...
-- Callback procedure: arithmetic-error ...
Establishes a response for storage allocation error, file opening
error, end of program, SIGHUP (hang up interrupt) and arithmetic
errors respectively. This procedure should (abort) or some other
action which does not return if it does not want the default error
message to also be displayed. If no procedure is defined for
HANG-UP then END-OF-PROGRAM (if defined) will be called.
To unestablish a response for an error set the handler symbol to
`#f'. For instance, `(set! could-not-open #f)'.
File: scm.info, Node: Process Synchronization, Next: Files and Ports, Prev: Interrupts, Up: The Language
4.5 Process Synchronization
===========================
An "exchanger" is a procedure of one argument regulating mutually exclusive
access to a resource. When a exchanger is called, its current content
is returned, while being replaced by its argument in an atomic
operation.
-- Function: make-exchanger obj
Returns a new exchanger with the argument OBJ as its initial
content.
(define queue (make-exchanger (list a)))
A queue implemented as an exchanger holding a list can be
protected from reentrant execution thus:
(define (pop queue)
(let ((lst #f))
(dynamic-wind
(lambda () (set! lst (queue #f)))
(lambda () (and lst (not (null? lst))
(let ((ret (car lst)))
(set! lst (cdr lst))
ret)))
(lambda () (and lst (queue lst))))))
(pop queue) => a
(pop queue) => #f
-- Function: make-arbiter name
Returns an object of type arbiter and name NAME. Its state is
initially unlocked.
-- Function: try-arbiter arbiter
Returns `#t' and locks ARBITER if ARBITER was unlocked.
Otherwise, returns `#f'.
-- Function: release-arbiter arbiter
Returns `#t' and unlocks ARBITER if ARBITER was locked.
Otherwise, returns `#f'.
File: scm.info, Node: Files and Ports, Next: Eval and Load, Prev: Process Synchronization, Up: The Language
4.6 Files and Ports
===================
These procedures generalize and extend the standard capabilities in
*Note Ports: (r5rs)Ports.
* Menu:
* Opening and Closing::
* Port Properties::
* Port Redirection::
* Soft Ports::
File: scm.info, Node: Opening and Closing, Next: Port Properties, Prev: Files and Ports, Up: Files and Ports
4.6.1 Opening and Closing
-------------------------
-- Function: open-file string modes
-- Function: try-open-file string modes
Returns a port capable of receiving or delivering characters as
specified by the MODES string. If a file cannot be opened `#f' is
returned.
Internal functions opening files "callback" to the SCM function
`open-file'. You can extend `open-file' by redefining it.
`try-open-file' is the primitive procedure; Do not redefine
`try-open-file'!
-- Constant: open_read
-- Constant: open_write
-- Constant: open_both
Contain modes strings specifying that a file is to be opened for
reading, writing, and both reading and writing respectively.
Both input and output functions can be used with io-ports. An end
of file must be read or a file-set-position done on the port
between a read operation and a write operation or vice-versa.
-- Function: _ionbf modestr
Returns a version of MODESTR which when `open-file' is called with
it as the second argument will return an unbuffered port. An
input-port must be unbuffered in order for `char-ready?' and
`wait-for-input' to work correctly on it. The initial value of
`(current-input-port)' is unbuffered if the platform supports it.
-- Function: _tracked modestr
Returns a version of MODESTR which when `open-file' is called with
it as the second argument will return a tracked port. A tracked
port maintains current line and column numbers, which may be
queried with `port-line' and `port-column'.
-- Function: _exclusive modestr
Returns a version of MODESTR which when `open-file' is called with
it as the second argument will return a port only if the named file
does not already exist. This functionality is provided by calling
`try-create-file' *Note I/O-Extensions::, which is not available
for all platforms.
-- Function: open-ports
Returns a list of all currently open ports, excluding string ports,
see *Note String Ports: (slib)String Ports. This may be useful
after a fork *Note Posix Extensions::, or for debugging. Bear in
mind that ports that would be closed by gc will be kept open by a
reference to this list.
-- Function: close-port port
Closes PORT. The same as close-input-port and close-output-port.
File: scm.info, Node: Port Properties, Next: Port Redirection, Prev: Opening and Closing, Up: Files and Ports
4.6.2 Port Properties
---------------------
-- Function: port-closed? port
Returns #t if PORT is closed.
-- Function: port-type obj
If OBJ is not a port returns false, otherwise returns a symbol
describing the port type, for example string or pipe.
-- Function: port-filename port
Returns the filename PORT was opened with. If PORT is not open to
a file the result is unspecified.
-- Function: port-line port
-- Function: port-column port
If PORT is a tracked port, return the current line (column) number,
otherwise return `#f'. Line and column numbers begin with 1. The
column number applies to the next character to be read; if that
character is a newline, then the column number will be one more
than the length of the line.
-- Function: freshline port
Outputs a newline to optional argument PORT unless the current
output column number of PORT is known to be zero, ie output will
start at the beginning of a new line. PORT defaults to
`current-output-port'. If PORT is not a tracked port `freshline'
is equivalent to `newline'.
-- Function: isatty? port
Returns `#t' if PORT is input or output to a serial non-file
device.
-- procedure: char-ready?
-- procedure: char-ready? port
Returns `#t' if a character is ready on the input PORT and returns
`#f' otherwise. If `char-ready?' returns `#t' then the next
`read-char' operation on the given PORT is guaranteed not to hang.
If the PORT is at end of file then `char-ready?' returns `#t'. PORT
may be omitted, in which case it defaults to the value returned by
`current-input-port'.
_Rationale_ `Char-ready?' exists to make it possible for a program
to accept characters from interactive ports without getting stuck
waiting for input. Any input editors associated with such ports
must ensure that characters whose existence has been asserted by
`char-ready?' cannot be rubbed out. If `char-ready?' were to
return `#f' at end of file, a port at end of file would be
indistinguishable from an interactive port that has no ready
characters.
-- procedure: wait-for-input x
-- procedure: wait-for-input x port1 ...
Returns a list those ports PORT1 ... which are `char-ready?'. If
none of PORT1 ... become `char-ready?' within the time interval of
X seconds, then #f is returned. The PORT1 ... arguments may be
omitted, in which case they default to the list of the value
returned by `current-input-port'.
File: scm.info, Node: Port Redirection, Next: Soft Ports, Prev: Port Properties, Up: Files and Ports
4.6.3 Port Redirection
----------------------
-- Function: current-error-port
Returns the current port to which diagnostic output is directed.
-- Function: with-error-to-file string thunk
THUNK must be a procedure of no arguments, and string must be a
string naming a file. The file is opened for output, an output
port connected to it is made the default value returned by
current-error-port, and the THUNK is called with no arguments.
When the thunk returns, the port is closed and the previous
default is restored. With-error-to-file returns the value yielded
by THUNK.
-- Function: with-input-from-port port thunk
-- Function: with-output-to-port port thunk
-- Function: with-error-to-port port thunk
These routines differ from with-input-from-file,
with-output-to-file, and with-error-to-file in that the first
argument is a port, rather than a string naming a file.
-- Function: call-with-outputs thunk proc
Calls the THUNK procedure while the current-output-port and
current-error-port are directed to string-ports. If THUNK
returns, the PROC procedure is called with the output-string, the
error-string, and the value returned by THUNK. If THUNK does not
return a value (perhaps because of error), PROC is called with
just the output-string and the error-string as arguments.
File: scm.info, Node: Soft Ports, Prev: Port Redirection, Up: Files and Ports
4.6.4 Soft Ports
----------------
A "soft-port" is a port based on a vector of procedures capable of
accepting or delivering characters. It allows emulation of I/O ports.
-- Function: make-soft-port vector modes
Returns a port capable of receiving or delivering characters as
specified by the MODES string (*note open-file: Files and Ports.).
VECTOR must be a vector of length 5. Its components are as
follows:
0. procedure accepting one character for output
1. procedure accepting a string for output
2. thunk for flushing output
3. thunk for getting one character
4. thunk for closing port (not by garbage collection)
For an output-only port only elements 0, 1, 2, and 4 need be
procedures. For an input-only port only elements 3 and 4 need be
procedures. Thunks 2 and 4 can instead be `#f' if there is no
useful operation for them to perform.
If thunk 3 returns `#f' or an `eof-object' (*note eof-object?:
(r5rs)Input.) it indicates that the port has reached end-of-file.
For example:
If it is necessary to explicitly close the port when it is garbage
collected, (*note add-finalizer: Interrupts.).
(define stdout (current-output-port))
(define p (make-soft-port
(vector
(lambda (c) (write c stdout))
(lambda (s) (display s stdout))
(lambda () (display "." stdout))
(lambda () (char-upcase (read-char)))
(lambda () (display "@" stdout)))
"rw"))
(write p p) => #<input-output-soft#\space45d10#\>
File: scm.info, Node: Eval and Load, Next: Lexical Conventions, Prev: Files and Ports, Up: The Language
4.7 Eval and Load
=================
-- Function: try-load filename
If the string FILENAME names an existing file, the try-load
procedure reads Scheme source code expressions and definitions
from the file and evaluates them sequentially and returns `#t'.
If not, try-load returns `#f'. The try-load procedure does not
affect the values returned by `current-input-port' and
`current-output-port'.
-- Variable: *load-pathname*
Is set to the pathname given as argument to `load', `try-load',
and `dyn:link' (*note Compiling And Linking: (hobbit)Compiling And
Linking.). `*load-pathname*' is used to compute the value of
*Note program-vicinity: (slib)Vicinity.
-- Function: eval obj
Alias for *Note eval: (slib)System.
-- Function: eval-string str
Returns the result of reading an expression from STR and
evaluating it. `eval-string' does not change `*load-pathname*' or
`line-number'.
-- Function: load-string str
Reads and evaluates all the expressions from STR. As with `load',
the value returned is unspecified. `load-string' does not change
`*load-pathname*' or `line-number'.
-- Function: line-number
Returns the current line number of the file currently being loaded.
* Menu:
* Line Numbers::
File: scm.info, Node: Line Numbers, Prev: Eval and Load, Up: Eval and Load
4.7.1 Line Numbers
------------------
Scheme code defined by load may optionally contain line number
information. Currently this information is used only for reporting
expansion time errors, but in the future run-time error messages may
also include line number information.
-- Function: try-load pathname reader
This is the primitive for loading, PATHNAME is the name of a file
containing Scheme code, and optional argument READER is a function
of one argument, a port. READER should read and return Scheme
code as list structure. The default value is `read', which is
used if READER is not supplied or is false.
Line number objects are disjoint from integers or other Scheme types.
When evaluated or loaded as Scheme code, an s-expression containing a
line-number in the car is equivalent to the cdr of the s-expression. A
pair consisting of a line-number in the car and a vector in the cdr is
equivalent to the vector. The meaning of s-expressions with
line-numbers in other positions is undefined.
-- Function: read-numbered port
Behaves like `read', except that
bullet Load (read) sytnaxes are enabled.
bullet every s-expression read will be replaced with a cons of
a line-number object and the sexp actually read. This
replacement is done only if PORT is a tracked port See *Note
Files and Ports::.
-- Function: integer->line-number int
Returns a line-number object with value INT. INT should be an
exact non-negative integer.
-- Function: line-number->integer linum
Returns the value of line-number object LINUM as an integer.
-- Function: line-number? obj
Returns true if and only if OBJ is a line-number object.
-- Function: read-for-load port
Behaves like `read', except that load syntaxes are enabled.
-- Variable: *load-reader*
-- Variable: *slib-load-reader*
The value of `*load-reader*' should be a value acceptable as the
second argument to `try-load' (note that #f is acceptable). This
value will be used to read code during calls to `scm:load'. The
value of `*slib-load-reader*' will similarly be used during calls
to `slib:load' and `require'.
In order to disable all line-numbering, it is sufficient to set!
`*load-reader*' and `*slib-load-reader*' to #f.
File: scm.info, Node: Lexical Conventions, Next: Syntax, Prev: Eval and Load, Up: The Language
4.8 Lexical Conventions
=======================
* Menu:
* Common-Lisp Read Syntax::
* Load Syntax::
* Documentation and Comments::
* Modifying Read Syntax::
File: scm.info, Node: Common-Lisp Read Syntax, Next: Load Syntax, Prev: Lexical Conventions, Up: Lexical Conventions
4.8.1 Common-Lisp Read Syntax
-----------------------------
-- Read syntax: #\token
If TOKEN is a sequence of two or more digits, then this syntax is
equivalent to `#.(integer->char (string->number token 8))'.
If TOKEN is `C-', `c-', or `^' followed by a character, then this
syntax is read as a control character. If TOKEN is `M-' or `m-'
followed by a character, then a meta character is read. `c-' and
`m-' prefixes may be combined.
-- Read syntax: #+ feature form
If feature is `provided?' (by `*features*') then FORM is read as a
scheme expression. If not, then FORM is treated as whitespace.
Feature is a boolean expression composed of symbols and `and',
`or', and `not' of boolean expressions.
For more information on `provided?' and `*features*', *Note
Require: (slib)Require.
-- Read syntax: #- feature form
is equivalent to `#+(not feature) expression'.
-- Read syntax: #| any thing |#
Is a balanced comment. Everything up to the matching `|#' is
ignored by the `read'. Nested `#|...|#' can occur inside ANY
THING.
"Load sytax" is Read syntax enabled for `read' only when that `read' is
part of loading a file or string. This distinction was made so that
reading from a datafile would not be able to corrupt a scheme program
using `#.'.
-- Load syntax: #. expression
Is read as the object resulting from the evaluation of EXPRESSION.
This substitution occurs even inside quoted structure.
In order to allow compiled code to work with `#.' it is good
practice to define those symbols used inside of EXPRESSION with
`#.(define ...)'. For example:
#.(define foo 9) => #<unspecified>
'(#.foo #.(+ foo foo)) => (9 18)
-- Load syntax: #' form
is equivalent to FORM (for compatibility with common-lisp).
File: scm.info, Node: Load Syntax, Next: Documentation and Comments, Prev: Common-Lisp Read Syntax, Up: Lexical Conventions
4.8.2 Load Syntax
-----------------
"#!" is the unix mechanism for executing scripts. See *Note Unix
Scheme Scripts:: for the full description of how this comment supports
scripting.
-- Load syntax: #?line
-- Load syntax: #?column
Return integers for the current line and column being read during a
load.
-- Load syntax: #?file
Returns the string naming the file currently being loaded. This
path is the string passed to `load', possibly with `.scm' appended.
File: scm.info, Node: Documentation and Comments, Next: Modifying Read Syntax, Prev: Load Syntax, Up: Lexical Conventions
4.8.3 Documentation and Comments
--------------------------------
-- procedure: procedure-documentation proc
Returns the documentation string of PROC if it exists, or `#f' if
not.
If the body of a `lambda' (or the definition of a procedure) has
more than one expression, and the first expression (preceeding any
internal definitions) is a string, then that string is the
"documentation string" of that procedure.
(procedure-documentation (lambda (x) "Identity" x)) => "Identity"
(define (square x)
"Return the square of X."
(* x x))
=> #<unspecified>
(procedure-documentation square) => "Return the square of X."
-- Function: comment string1 ...
Appends STRING1 ... to the strings given as arguments to previous
calls `comment'.
-- Function: comment
Returns the (appended) strings given as arguments to previous calls
`comment' and empties the current string collection.
-- Load syntax: #;text-till-end-of-line
Behaves as `(comment "TEXT-TILL-END-OF-LINE")'.
File: scm.info, Node: Modifying Read Syntax, Prev: Documentation and Comments, Up: Lexical Conventions
4.8.4 Modifying Read Syntax
---------------------------
-- Callback procedure: read:sharp c port
If a <#> followed by a character (for a non-standard syntax) is
encountered by `read', `read' will call the value of the symbol
`read:sharp' with arguments the character and the port being read
from. The value returned by this function will be the value of
`read' for this expression unless the function returns
`#<unspecified>' in which case the expression will be treated as
whitespace. `#<unspecified>' is the value returned by the
expression `(if #f #f)'.
-- Callback procedure: load:sharp c port
Dispatches like `read:sharp', but only during `load's. The
read-syntaxes handled by `load:sharp' are a superset of those
handled by `read:sharp'. `load:sharp' calls `read:sharp' if none
of its syntaxes match C.
-- Callback procedure: char:sharp token
If the sequence <#\> followed by a non-standard character name is
encountered by `read', `read' will call the value of the symbol
`char:sharp' with the token (a string of length at least two) as
argument. If the value returned is a character, then that will be
the value of `read' for this expression, otherwise an error will
be signaled.
_Note_ When adding new <#> syntaxes, have your code save the previous
value of `load:sharp', `read:sharp', or `char:sharp' when defining it.
Call this saved value if an invocation's syntax is not recognized.
This will allow `#+', `#-', and *Note Uniform Array::s to still be
supported (as they dispatch from `read:sharp').
File: scm.info, Node: Syntax, Prev: Lexical Conventions, Up: The Language
4.9 Syntax
==========
SCM provides a native implementation of "defmacro". *Note Defmacro:
(slib)Defmacro.
When built with `-F macro' build option (*note Build Options::) and
`*syntax-rules*' is non-false, SCM also supports [R5RS] `syntax-rules'
macros. *Note Macros: (r5rs)Macros.
Other Scheme Syntax Extension Packages from SLIB can be employed through
the use of `macro:eval' and `macro:load'; Or by using the SLIB
read-eval-print-loop:
(require 'repl)
(repl:top-level macro:eval)
With the appropriate catalog entries (*note Library Catalogs:
(slib)Library Catalogs.), files using macro packages will automatically
use the correct macro loader when `require'd.
* Menu:
* Define and Set::
* Defmacro::
* Syntax-Rules::
* Macro Primitives::
* Environment Frames::
* Syntactic Hooks for Hygienic Macros::
File: scm.info, Node: Define and Set, Next: Defmacro, Prev: Syntax, Up: Syntax
4.9.1 Define and Set
--------------------
-- Special Form: defined? symbol
Equivalent to `#t' if SYMBOL is a syntactic keyword (such as `if')
or a symbol with a value in the top level environment (*note
Variables and regions: (r5rs)Variables and regions.). Otherwise
equivalent to `#f'.
-- Special Form: defvar identifier initial-value
If IDENTIFIER is unbound in the top level environment, then
IDENTIFIER is `define'd to the result of evaluating the form
INITIAL-VALUE as if the `defvar' form were instead the form
`(define identifier initial-value)' . If IDENTIFIER already has a
value, then INITIAL-VALUE is _not_ evaluated and IDENTIFIER's
value is not changed. `defvar' is valid only when used at
top-level.
-- Special Form: defconst identifier value
If IDENTIFIER is unbound in the top level environment, then
IDENTIFIER is `define'd to the result of evaluating the form VALUE
as if the `defconst' form were instead the form `(define
identifier value)' . If IDENTIFIER already has a value, then
VALUE is _not_ evaluated, IDENTIFIER's value is not changed, and
an error is signaled. `defconst' is valid only when used at
top-level.
-- Special Form: set! (variable1 variable2 ...) <expression>
The identifiers VARIABLE1, VARIABLE2, ... must be bound either in
some region enclosing the `set!' expression or at top level.
<Expression> is evaluated, and the elements of the resulting list
are stored in the locations to which each corresponding VARIABLE
is bound. The result of the `set!' expression is unspecified.
(define x 2)
(define y 3)
(+ x y) => 5
(set! (x y) (list 4 5)) => _unspecified_
(+ x y) => 9
-- Special Form: qase key clause1 clause2 ...
`qase' is an extension of standard Scheme `case': Each CLAUSE of a
`qase' statement must have as first element a list containing
elements which are:
* literal datums, or
* a comma followed by the name of a symbolic constant, or
* a comma followed by an at-sign (@) followed by the name of a
symbolic constant whose value is a list.
A `qase' statement is equivalent to a `case' statement in which
these symbolic constants preceded by commas have been replaced by
the values of the constants, and all symbolic constants preceded by
comma-at-signs have been replaced by the elements of the list
values of the constants. This use of comma, (or, equivalently,
`unquote') is similar to that of `quasiquote' except that the
unquoted expressions must be "symbolic constants".
Symbolic constants are defined using `defconst', their values are
substituted in the head of each `qase' clause during macro
expansion. `defconst' constants should be defined before use.
`qase' can be substituted for any correct use of `case'.
(defconst unit '1)
(defconst semivowels '(w y))
(qase (* 2 3)
((2 3 5 7) 'prime)
((,unit 4 6 8 9) 'composite)) ==> composite
(qase (car '(c d))
((a) 'a)
((b) 'b)) ==> _unspecified_
(qase (car '(c d))
((a e i o u) 'vowel)
((,@semivowels) 'semivowel)
(else 'consonant)) ==> consonant
File: scm.info, Node: Defmacro, Next: Syntax-Rules, Prev: Define and Set, Up: Syntax
4.9.2 Defmacro
--------------
SCM supports the following constructs from Common Lisp: `defmacro',
`macroexpand', `macroexpand-1', and `gentemp'. *Note Defmacro:
(slib)Defmacro.
SCM `defmacro' is extended over that described for SLIB:
(defmacro (macro-name . arguments) body)
is equivalent to
(defmacro macro-name arguments body)
As in Common Lisp, an element of the formal argument list for
`defmacro' may be a possibly nested list, in which case the
corresponding actual argument must be a list with as many members as the
formal argument. Rest arguments are indicated by improper lists, as in
Scheme. It is an error if the actual argument list does not have the
tree structure required by the formal argument list.
For example:
(defmacro (let1 ((name value)) . body)
`((lambda (,name) ,@body) ,value))
(let1 ((x (foo))) (print x) x) == ((lambda (x) (print x) x) (foo))
(let1 not legal syntax) error--> not "does not match" ((name value))
File: scm.info, Node: Syntax-Rules, Next: Macro Primitives, Prev: Defmacro, Up: Syntax
4.9.3 Syntax-Rules
------------------
SCM supports [R5RS] `syntax-rules' macros *Note Macros: (r5rs)Macros.
The pattern language is extended by the syntax `(... <obj>)', which is
identical to `<obj>' except that ellipses in `<obj>' are treated as
ordinary identifiers in a template, or as literals in a pattern. In
particular, `(... ...)' quotes the ellipsis token `...' in a pattern or
template.
For example:
(define-syntax check-tree
(syntax-rules ()
((_ (?pattern (... ...)) ?obj)
(let loop ((obj ?obj))
(or (null? obj)
(and (pair? obj)
(check-tree ?pattern (car obj))
(loop (cdr obj))))))
((_ (?first . ?rest) ?obj)
(let ((obj ?obj))
(and (pair? obj)
(check-tree ?first (car obj))
(check-tree ?rest (cdr obj)))))
((_ ?atom ?obj) #t)))
(check-tree ((a b) ...) '((1 2) (3 4) (5 6))) => #t
(check-tree ((a b) ...) '((1 2) (3 4) not-a-2list) => #f
Note that although the ellipsis is matched as a literal token in the
defined macro it is not included in the literals list for
`syntax-rules'.
The pattern language is also extended to support identifier macros. A
reference to an identifier macro keyword that is not the first
identifier in a form may expand into Scheme code, rather than raising a
"keyword as variable" error. The pattern for expansion of such a bare
macro keyword is a single identifier, as in other syntax rules the
identifier is ignored.
For example:
(define-syntax eight
(syntax-rules ()
(_ 8)))
(+ 3 eight) => 11
(eight) => ERROR
(set! eight 9) => ERROR
File: scm.info, Node: Macro Primitives, Next: Environment Frames, Prev: Syntax-Rules, Up: Syntax
4.9.4 Macro Primitives
----------------------
-- Function: procedure->syntax proc
Returns a "macro" which, when a symbol defined to this value
appears as the first symbol in an expression, returns the result
of applying PROC to the expression and the environment.
-- Function: procedure->macro proc
-- Function: procedure->memoizing-macro proc
-- Function: procedure->identifier-macro
Returns a "macro" which, when a symbol defined to this value
appears as the first symbol in an expression, evaluates the result
of applying PROC to the expression and the environment. The value
returned from PROC which has been passed to
`PROCEDURE->MEMOIZING-MACRO' replaces the form passed to PROC.
For example:
(defsyntax trace
(procedure->macro
(lambda (x env) `(set! ,(cadr x) (tracef ,(cadr x) ',(cadr x))))))
(trace foo) == (set! foo (tracef foo 'foo)).
`PROCEDURE->IDENTIFIER-MACRO' is similar to
`PROCEDURE->MEMOIZING-MACRO' except that PROC is also called in
case the symbol bound to the macro appears in an expression but
_not_ as the first symbol, that is, when it looks like a variable
reference. In that case, the form passed to PROC is a single
identifier.
-- Special Form: defsyntax name expr
Defines NAME as a macro keyword bound to the result of evaluating
EXPR, which should be a macro. Using `define' for this purpose
may not result in NAME being interpreted as a macro keyword.
File: scm.info, Node: Environment Frames, Next: Syntactic Hooks for Hygienic Macros, Prev: Macro Primitives, Up: Syntax
4.9.5 Environment Frames
------------------------
An "environment" is a list of frames representing lexical bindings.
Only the names and scope of the bindings are included in environments
passed to macro expanders - run-time values are not included.
There are several types of environment frames:
`((lambda (variable1 ...) ...) value1 ...)'
`(let ((variable1 value1) (variable2 value2) ...) ...)'
`(letrec ((variable1 value1) ...) ...)'
result in a single enviroment frame:
(variable1 variable2 ...)
`(let ((variable1 value1)) ...)'
`(let* ((variable1 value1) ...) ...)'
result in an environment frame for each variable:
variable1 variable2 ...
`(let-syntax ((key1 macro1) (key2 macro2)) ...)'
`(letrec-syntax ((key1 value1) (key2 value2)) ...)'
Lexically bound macros result in environment frames consisting of
a marker and an alist of keywords and macro objects:
(<env-syntax-marker> (key1 . value1) (key2 . value2))
Currently <env-syntax-marker> is the integer 6.
`line numbers'
Line numbers (*note Line Numbers::) may be included in the
environment as frame entries to indicate the line number on which
a function is defined. They are ignored for variable lookup.
#<line 8>
`miscellaneous'
Debugging information is stored in environments in a plist format:
Any exact integer stored as an environment frame may be followed
by any value. The two frame entries are ignored when doing
variable lookup. Load file names, procedure names, and closure
documentation strings are stored in this format.
<env-filename-marker> "foo.scm" <env-procedure-name-marker> foo ...
Currently <env-filename-marker> is the integer 1 and
<env-procedure-name-marker> the integer 2.
-- Special Form: @apply procedure argument-list
Returns the result of applying PROCEDURE to ARGUMENT-LIST.
`@apply' differs from `apply' when the identifiers bound by the
closure being applied are `set!'; setting affects ARGUMENT-LIST.
(define lst (list 'a 'b 'c))
(@apply (lambda (v1 v2 v3) (set! v1 (cons v2 v3))) lst)
lst => ((b . c) b c)
Thus a mutable environment can be treated as both a list and local
bindings.
File: scm.info, Node: Syntactic Hooks for Hygienic Macros, Prev: Environment Frames, Up: Syntax
4.9.6 Syntactic Hooks for Hygienic Macros
-----------------------------------------
SCM provides a synthetic identifier type for efficient implementation of
hygienic macros (for example, `syntax-rules' *note Macros:
(r5rs)Macros.) A synthetic identifier may be inserted in Scheme code by
a macro expander in any context where a symbol would normally be used.
Collectively, symbols and synthetic identifiers are _identifiers_.
-- Function: identifier? obj
Returns `#t' if OBJ is a symbol or a synthetic identifier, and
`#f' otherwise.
If it is necessary to distinguish between symbols and synthetic
identifiers, use the predicate `symbol?'.
A synthetic identifier includes two data: a parent, which is an
identifier, and an environment, which is either `#f' or a lexical
environment which has been passed to a "macro expander" (a procedure
passed as an argument to `procedure->macro',
`procedure->memoizing-macro', or `procedure->syntax').
-- Function: renamed-identifier parent env
Returns a synthetic identifier. PARENT must be an identifier, and
ENV must either be `#f' or a lexical environment passed to a macro
expander. `renamed-identifier' returns a distinct object for each
call, even if passed identical arguments.
There is no direct way to access all of the data internal to a synthetic
identifier, those data are used during variable lookup. If a synthetic
identifier is inserted as quoted data then during macro expansion it
will be repeatedly replaced by its parent, until a symbol is obtained.
-- Function: identifier->symbol id
Returns the symbol obtained by recursively extracting the parent of
ID, which must be an identifier.
4.9.7 Use of Synthetic Identifiers
----------------------------------
`renamed-identifier' may be used as a replacement for `gentemp':
(define gentemp
(let ((name (string->symbol "An unlikely variable")))
(lambda ()
(renamed-identifier name #f))))
If an identifier returned by this version of `gentemp' is inserted in a
binding position as the name of a variable then it is guaranteed that
no other identifier (except one produced by passing the first to
`renamed-identifier') may denote that variable. If an identifier
returned by `gentemp' is inserted free, then it will denote the
top-level value bound to its parent, the symbol named "An unlikely
variable". This behavior, of course, is meant to be put to good use:
(define top-level-foo
(procedure->memoizing-macro
(lambda (exp env)
(renamed-identifier 'foo #f))))
Defines a macro which may always be used to refer to the top-level
binding of `foo'.
(define foo 'top-level)
(let ((foo 'local))
(top-level-foo)) => top-level
In other words, we can avoid capturing `foo'.
If a lexical environment is passed as the second argument to
`renamed-identifier' then if the identifier is inserted free its parent
will be looked up in that environment, rather than in the top-level
environment. The use of such an identifier _must_ be restricted to the
lexical scope of its environment.
There is another restriction imposed for implementation convenience:
Macros passing their lexical environments to `renamed-identifier' may
be lexically bound only by the special forms `let-syntax' or
`letrec-syntax'. No error is signaled if this restriction is not met,
but synthetic identifier lookup will not work properly.
In order to maintain referential transparency it is necessary to
determine whether two identifiers have the same denotation. With
synthetic identifiers it is not necessary that two identifiers be `eq?'
in order to denote the same binding.
-- Function: identifier-equal? id1 id2 env
Returns `#t' if identifiers ID1 and ID2 denote the same binding in
lexical environment ENV, and `#f' otherwise. ENV must either be a
lexical environment passed to a macro transformer during macro
expansion or the empty list.
For example,
(define top-level-foo?
(procedure->memoizing-macro
(let ((foo-name (renamed-identifier 'foo #f)))
(lambda (exp env)
(identifier-equal? (cadr exp) foo-name env)))))
(top-level-foo? foo) => #t
(let ((foo 'local))
(top-level-foo? foo)) => #f
-- Function: @macroexpand1 expr env
If the `car' of EXPR denotes a macro in ENV, then if that macro is
a primitive, EXPR will be returned, if the macro was defined in
Scheme, then a macro expansion will be returned. If the `car' of
EXPR does not denote a macro, the `#f' is returned.
-- Function: extended-environment names values env
Returns a new environment object, equivalent to ENV, which must
either be an environment object or null, extended by one frame.
NAMES must be an identifier, or an improper list of identifiers,
usable as a formals list in a `lambda' expression. VALUES must be
a list of objects long enough to provide a binding for each of the
identifiers in NAMES. If NAMES is an identifier or an improper
list then VALS may be, respectively, any object or an improper
list of objects.
-- Special Form: syntax-quote obj
Synthetic identifiers are converted to their parent symbols by
`quote' and `quasiquote' so that literal data in macro definitions
will be properly transcribed. `syntax-quote' behaves like
`quote', but preserves synthetic identifier intact.
-- Special Form: the-macro mac
`the-macro' is the simplest of all possible macro transformers:
MAC may be a syntactic keyword (macro name) or an expression
evaluating to a macro, otherwise an error is signaled. MAC is
evaluated and returned once only, after which the same memoizied
value is returned.
`the-macro' may be used to protect local copies of macros against
redefinition, for example:
(@let-syntax ((let (the-macro let)))
;; code that will continue to work even if LET is redefined.
...)
-- Special Form: renaming-transformer proc
A low-level "explicit renaming" macro facility very similar to that
proposed by W. Clinger [Exrename] is supported. Syntax may be
defined in `define-syntax', `let-syntax', and `letrec-syntax'
using `renaming-transformer' instead of `syntax-rules'. PROC
should evaluate to a procedure accepting three arguments: EXPR,
RENAME, and COMPARE. EXPR is a representation of Scheme code to
be expanded, as list structure. RENAME is a procedure accepting
an identifier and returning an identifier renamed in the
definition environment of the new syntax. COMPARE accepts two
identifiers and returns true if and only if both denote the same
binding in the usage environment of the new syntax.
File: scm.info, Node: Packages, Next: The Implementation, Prev: The Language, Up: Top
5 Packages
**********
* Menu:
* Dynamic Linking::
* Dump:: Create Fast-Booting Executables
* Numeric:: Numeric Language Extensions
* Arrays:: As in APL
* Records:: Define new aggregate data types
* I/O-Extensions:: i/o-extensions
* Posix Extensions:: posix
* Unix Extensions:: non-posix unix
* Sequence Comparison::
* Regular Expression Pattern Matching:: regex
* Line Editing:: edit-line
* Curses:: Screen Control
* Sockets:: Cruise the Net
* SCMDB:: interface to MySQL
* Menu:
* Xlib: (Xlibscm). X Window Graphics.
* Hobbit: (hobbit). Scheme-to-C Compiler
File: scm.info, Node: Dynamic Linking, Next: Dump, Prev: Packages, Up: Packages
5.1 Dynamic Linking
===================
If SCM has been compiled with `dynl.c' then the additional properties
of load and ([SLIB]) require specified here are supported. The
`require' form is preferred.
-- Function: require feature
If the symbol FEATURE has not already been given as an argument to
`require', then the object and library files associated with
FEATURE will be dynamically-linked, and an unspecified value
returned. If FEATURE is not found in `*catalog*', then an error
is signaled.
-- Function: usr:lib lib
Returns the pathname of the C library named LIB. For example:
`(usr:lib "m")' returns `"/usr/lib/libm.a"', the path of the C
math library.
-- Function: x:lib lib
Returns the pathname of the X library named LIB. For example:
`(x:lib "X11")' returns `"/usr/X11/lib/libX11.sa"', the path of
the X11 library.
-- Function: load filename lib1 ...
In addition to the [R5RS] requirement of loading Scheme
expressions if FILENAME is a Scheme source file, `load' will also
dynamically load/link object files (produced by `compile-file', for
instance). The object-suffix need not be given to load. For
example,
(load (in-vicinity (implementation-vicinity) "sc2"))
or (load (in-vicinity (implementation-vicinity) "sc2.o"))
or (require 'rev2-procedures)
or (require 'rev3-procedures)
will load/link `sc2.o' if it exists.
The LIB1 ... pathnames specify additional libraries which may be
needed for object files not produced by the Hobbit compiler. For
instance, crs is linked on Linux by
(load (in-vicinity (implementation-vicinity) "crs.o")
(usr:lib "ncurses") (usr:lib "c"))
or (require 'curses)
Turtlegr graphics library is linked by:
(load (in-vicinity (implementation-vicinity) "turtlegr")
(usr:lib "X11") (usr:lib "c") (usr:lib "m"))
or (require 'turtle-graphics)
And the string regular expression (*note Regular Expression
Pattern Matching::) package is linked by:
(load (in-vicinity (implementation-vicinity) "rgx") (usr:lib "c"))
or
(require 'regex)
The following functions comprise the low-level Scheme interface to
dynamic linking. See the file `Link.scm' in the SCM distribution for
an example of their use.
-- Function: dyn:link filename
FILENAME should be a string naming an "object" or "archive" file,
the result of C-compiling. The `dyn:link' procedure links and
loads FILENAME into the current SCM session. If successfull,
`dyn:link' returns a "link-token" suitable for passing as the
second argument to `dyn:call'. If not successful, `#f' is
returned.
-- Function: dyn:call name link-token
LINK-TOKEN should be the value returned by a call to `dyn:link'.
NAME should be the name of C function of no arguments defined in
the file named FILENAME which was succesfully `dyn:link'ed in the
current SCM session. The `dyn:call' procedure calls the C
function corresponding to NAME. If successful, `dyn:call' returns
`#t'; If not successful, `#f' is returned.
`dyn:call' is used to call the "init_..." function after loading
SCM object files. The init_... function then makes the
identifiers defined in the file accessible as Scheme procedures.
-- Function: dyn:main-call name link-token arg1 ...
LINK-TOKEN should be the value returned by a call to `dyn:link'.
NAME should be the name of C function of 2 arguments, `(int argc,
const char **argv)', defined in the file named FILENAME which was |
succesfully `dyn:link'ed in the current SCM session. The
`dyn:main-call' procedure calls the C function corresponding to
NAME with `argv' style arguments, such as are given to C `main'
functions. If successful, `dyn:main-call' returns the integer
returned from the call to NAME.
`dyn:main-call' can be used to call a `main' procedure from SCM.
For example, I link in and `dyn:main-call' a large C program, the
low level routines of which callback (*note Callbacks::) into SCM
(which emulates PCI hardware).
-- Function: dyn:unlink link-token
LINK-TOKEN should be the value returned by a call to `dyn:link'.
The `dyn:unlink' procedure removes the previously loaded file from
the current SCM session. If successful, `dyn:unlink' returns
`#t'; If not successful, `#f' is returned.
File: scm.info, Node: Dump, Next: Numeric, Prev: Dynamic Linking, Up: Packages
5.2 Dump
========
"Dump", (also known as "unexec"), saves the continuation of an entire
SCM session to an executable file, which can then be invoked as a
program. Dumped executables start very quickly, since no Scheme code
has to be loaded.
There are constraints on which sessions are savable using `dump'
* Saved continuations are invalid in subsequent invocations; they
cause segmentation faults and other unpleasant side effects.
* Although DLD (*note Dynamic Linking::) can be used to load compiled
modules both before and after dumping, `SUN_DL' ELF systems can
load compiled modules only after dumping. This can be worked
around by compiling in those features you wish to `dump'.
* Ports (other than `current-input-port', `current-output-port',
`current-error-port'), X windows, etc. are invalid in subsequent
invocations.
This restriction could be removed; *Note Improvements To Make::.
* `Dump' should only be called from a loading file when the call to
dump is the last expression in that file.
* `Dump' can be called from the command line.
-- Function: dump newpath
-- Function: dump newpath #f
-- Function: dump newpath #t
-- Function: dump newpath thunk
* Calls `gc'.
* Creates an executable program named NEWPATH which continues
the state of the current SCM session when invoked. The
optional argument THUNK, if provided, should be a procedure
of no arguments; BOOT-TAIL will be set to this procedure,
causing it to be called in the restored executable.
If the optional argument is missing or a boolean, SCM's
standard command line processing will be called in the
restored executable.
If the second argument to `dump' is `#t', argument processing
will continue from the command line passed to the dumping
session. If the second argument is missing or `#f' then the
command line arguments of the restoring invocation will be
processed.
* Resumes the top level Read-Eval-Print loop. This is done
instead of continuing normally to avoid creating a saved
continuation in the dumped executable.
`dump' may set the values of `boot-tail', `*argv*', `restart', and
*INTERACTIVE*. `dump' returns an unspecified value.
When a dumped executable is invoked, the variable *INTERACTIVE* (*note
Internal State::) has the value it possessed when `dump' created it.
Calling `dump' with a single argument sets *INTERACTIVE* to `#f', which
is the state it has at the beginning of command line processing.
The procedure `program-arguments' returns the command line arguments
for the curent invocation. More specifically, `program-arguments' for
the restored session are _not_ saved from the dumping session. Command
line processing is done on the value of the identifier `*argv*'.
The following example shows how to create `rscm', which is like regular
scm, but which loads faster and has the `random' package alreadly
provided.
bash$ scm -rrandom
> (dump "rscm")
#<unspecified>
> (quit)
bash$ ./rscm -lpi.scm -e"(pi (random 200) 5)"
00003 14159 26535 89793 23846 26433 83279 50288 41971 69399
37510 58209 74944 59230 78164 06286 20899 86280 34825 34211
70679 82148 08651 32823 06647 09384 46095 50582 23172 53594
08128 48111 74502 84102 70193 85211 05559 64462 29489
bash$
This task can also be accomplished using the `-o' command line option
(*note SCM Options::).
bash$ scm -rrandom -o rscm
> (quit)
bash$ ./rscm -lpi.scm -e"(pi (random 200) 5)"
00003 14159 26535 89793 23846 26433 83279 50288 41971 69399
37510 58209 74944 59230 78164 06286 20899 86280 34825 34211
70679 82148 08651 32823 06647 09384 46095 50582 23172 53594
08128 48111 74502 84102 70193 85211 05559 64462 29489
bash$
File: scm.info, Node: Numeric, Next: Arrays, Prev: Dump, Up: Packages
5.3 Numeric
===========
-- Constant: most-positive-fixnum
The immediate integer closest to positive infinity. *Note
Configuration: (slib)Configuration.
-- Constant: most-negative-fixnum
The immediate integer closest to negative infinity.
-- Constant: $pi
-- Constant: pi
The ratio of the circumference to the diameter of a circle.
These procedures augment the standard capabilities in *Note Numerical
operations: (r5rs)Numerical operations.
-- Function: pi* z
`(* pi Z)'
-- Function: pi/ z
`(/ pi Z)'
-- Function: sinh z
-- Function: cosh z
-- Function: tanh z
Return the hyperbolic sine, cosine, and tangent of Z
-- Function: asinh z
-- Function: acosh z
-- Function: atanh z
Return the inverse hyperbolic sine, cosine, and tangent of Z
-- Function: $sqrt x
-- Function: $abs x
-- Function: $exp x
-- Function: $log x
-- Function: $sin x
-- Function: $cos x
-- Function: $tan x
-- Function: $asin x
-- Function: $acos x
-- Function: $atan x
-- Function: $sinh x
-- Function: $cosh x
-- Function: $tanh x
-- Function: $asinh x
-- Function: $acosh x
-- Function: $atanh x
Real-only versions of these popular functions. The argument X
must be a real number. It is an error if the value which should be
returned by a call to these procedures is _not_ real.
-- Function: $log10 x
Real-only base 10 logarithm.
-- Function: $atan2 y x
Computes `(angle (make-rectangular x y))' for real numbers Y and X.
-- Function: $expt x1 x2
Returns real number X1 raised to the real power X2. It is an
error if the value which should be returned by a call to `$expt'
is not real.
File: scm.info, Node: Arrays, Next: Records, Prev: Numeric, Up: Packages
5.4 Arrays
==========
* Menu:
* Conventional Arrays::
* Uniform Array::
* Bit Vectors::
* Array Mapping:: array-for-each
File: scm.info, Node: Conventional Arrays, Next: Uniform Array, Prev: Arrays, Up: Arrays
5.4.1 Conventional Arrays
-------------------------
The following syntax and procedures are SCM extensions to feature
`array' in *Note Arrays: (slib)Arrays.
"Arrays" read and write as a `#' followed by the "rank" (number of
dimensions) followed by the character #\a or #\A and what appear as
lists (of lists) of elements. The lists must be nested to the depth of
the rank. For each depth, all lists must be the same length.
(make-array '#(ho) 4 3) =>
#2A((ho ho ho) (ho ho ho) (ho ho ho) (ho ho ho))
Unshared, conventional (not uniform) 0-based arrays of rank 1 are
equivalent to (and can't be distinguished from) scheme vectors.
(make-array '#(ho) 3) => #(ho ho ho)
-- Function: transpose-array array dim0 dim1 ...
Returns an array sharing contents with ARRAY, but with dimensions
arranged in a different order. There must be one DIM argument for
each dimension of ARRAY. DIM0, DIM1, ... should be integers
between 0 and the rank of the array to be returned. Each integer
in that range must appear at least once in the argument list.
The values of DIM0, DIM1, ... correspond to dimensions in the
array to be returned, their positions in the argument list to
dimensions of ARRAY. Several DIMs may have the same value, in
which case the returned array will have smaller rank than ARRAY.
examples:
(transpose-array '#2A((a b) (c d)) 1 0) => #2A((a c) (b d))
(transpose-array '#2A((a b) (c d)) 0 0) => #1A(a d)
(transpose-array '#3A(((a b c) (d e f)) ((1 2 3) (4 5 6))) 1 1 0) =>
#2A((a 4) (b 5) (c 6))
-- Function: enclose-array array dim0 dim1 ...
DIM0, DIM1 ... should be nonnegative integers less than the rank
of ARRAY. ENCLOSE-ARRAY returns an array resembling an array of
shared arrays. The dimensions of each shared array are the same
as the DIMth dimensions of the original array, the dimensions of
the outer array are the same as those of the original array that
did not match a DIM.
An enclosed array is not a general Scheme array. Its elements may
not be set using `array-set!'. Two references to the same element
of an enclosed array will be `equal?' but will not in general be
`eq?'. The value returned by ARRAY-PROTOTYPE when given an
enclosed array is unspecified.
examples:
(enclose-array '#3A(((a b c) (d e f)) ((1 2 3) (4 5 6))) 1) =>
#<enclosed-array (#1A(a d) #1A(b e) #1A(c f)) (#1A(1 4) #1A(2 5) #1A(3 6))>
(enclose-array '#3A(((a b c) (d e f)) ((1 2 3) (4 5 6))) 1 0) =>
#<enclosed-array #2A((a 1) (d 4)) #2A((b 2) (e 5)) #2A((c 3) (f 6))>
-- Function: array->list array
Returns a list consisting of all the elements, in order, of ARRAY.
In the case of a rank-0 array, returns the single element.
-- Function: array-contents array
-- Function: array-contents array strict
If ARRAY may be "unrolled" into a one dimensional shared array
without changing their order (last subscript changing fastest),
then `array-contents' returns that shared array, otherwise it
returns `#f'. All arrays made by MAKE-ARRAY may be unrolled, some
arrays made by MAKE-SHARED-ARRAY may not be.
If the optional argument STRICT is provided, a shared array will
be returned only if its elements are stored internally contiguous
in memory.
File: scm.info, Node: Uniform Array, Next: Bit Vectors, Prev: Conventional Arrays, Up: Arrays
5.4.2 Uniform Array
-------------------
"Uniform Arrays" and vectors are arrays whose elements are all of the
same type. Uniform vectors occupy less storage than conventional
vectors. Uniform Array procedures also work on vectors,
uniform-vectors, bit-vectors, and strings.
SLIB now supports uniform arrys. The primary array creation procedure
is `make-array', detailed in *Note Arrays: (slib)Arrays.
Unshared uniform character 0-based arrays of rank 1 (dimension) are
equivalent to (and can't be distinguished from) strings.
(make-array "" 3) => "$q2"
Unshared uniform boolean 0-based arrays of rank 1 (dimension) are
equivalent to (and can't be distinguished from) *Note bit-vectors: Bit
Vectors.
(make-array '#1at() 3) => #*000
==
#1At(#f #f #f) => #*000
PROTOTYPE arguments in the following procedures are interpreted
according to the table:
prototype type display prefix
() conventional vector #A
+64i complex (double precision) #A:floC64b
64.0 double (double precision) #A:floR64b
32.0 float (single precision) #A:floR32b
32 unsigned integer (32-bit) #A:fixN32b
-32 signed integer (32-bit) #A:fixZ32b
-16 signed integer (16-bit) #A:fixZ16b
#\a char (string) #A:char
#t boolean (bit-vector) #A:bool
Other uniform vectors are written in a form similar to that of general
arrays, except that one or more modifying characters are put between the
#\A character and the contents list. For example, `'#1A:fixZ32b(3 5 9)'
returns a uniform vector of signed integers.
-- Function: array? obj prototype
Returns `#t' if the OBJ is an array of type corresponding to
PROTOTYPE, and `#f' if not.
-- Function: array-prototype array
Returns an object that would produce an array of the same type as
ARRAY, if used as the PROTOTYPE for `list->uniform-array'.
-- Function: list->uniform-array rank prot lst
Returns a uniform array of the type indicated by prototype PROT
with elements the same as those of LST. Elements must be of the
appropriate type, no coercions are done.
In, for example, the case of a rank-2 array, LST must be a list of
lists, all of the same length. The length of LST will be the
first dimension of the result array, and the length of each
element the second dimension.
If RANK is zero, LST, which need not be a list, is the single
element of the returned array.
-- Function: uniform-array-read! ura
-- Function: uniform-array-read! ura port
Attempts to read all elements of URA, in lexicographic order, as
binary objects from PORT. If an end of file is encountered during
uniform-array-read! the objects up to that point only are put into
URA (starting at the beginning) and the remainder of the array is
unchanged.
`uniform-array-read!' returns the number of objects read. PORT
may be omitted, in which case it defaults to the value returned by
`(current-input-port)'.
-- Function: uniform-array-write ura
-- Function: uniform-array-write ura port
Writes all elements of URA as binary objects to PORT. The number
of of objects actually written is returned. PORT may be omitted,
in which case it defaults to the value returned by
`(current-output-port)'.
-- Function: logaref array index1 index2 ...
If an INDEX is provided for each dimension of ARRAY returns the
INDEX1, INDEX2, ...'th element of ARRAY. If one more INDEX is
provided, then the last index specifies bit position of the
twos-complement representation of the array element indexed by the
other INDEXs returning `#t' if the bit is 1, and `#f' if 0. It is
an error if this element is not an exact integer.
(logaref '#(#b1101 #b0010) 0) => #b1101
(logaref '#(#b1101 #b0010) 0 1) => #f
(logaref '#2((#b1101 #b0010)) 0 0) => #b1101
-- Function: logaset! array val index1 index2 ...
If an INDEX is provided for each dimension of ARRAY sets the
INDEX1, INDEX2, ...'th element of ARRAY to VAL. If one more INDEX
is provided, then the last index specifies bit position of the
twos-complement representation of an exact integer array element,
setting the bit to 1 if VAL is `#t' and to 0 if VAL is `#f'. In
this case it is an error if the array element is not an exact
integer or if VAL is not boolean.
File: scm.info, Node: Bit Vectors, Next: Array Mapping, Prev: Uniform Array, Up: Arrays
5.4.3 Bit Vectors
-----------------
Bit vectors can be written and read as a sequence of `0's and `1's
prefixed by `#*'.
#1At(#f #f #f #t #f #t #f) => #*0001010
Some of these operations will eventually be generalized to other
uniform-arrays.
-- Function: bit-count bool bv
Returns the number of occurrences of BOOL in BV.
-- Function: bit-position bool bv k
Returns the minimum index of an occurrence of BOOL in BV which is
at least K. If no BOOL occurs within the specified range `#f' is
returned.
-- Function: bit-invert! bv
Modifies BV by replacing each element with its negation.
-- Function: bit-set*! bv uve bool
If uve is a bit-vector BV and uve must be of the same length. If
BOOL is `#t', uve is OR'ed into BV; If BOOL is `#f', the inversion
of uve is AND'ed into BV.
If uve is a unsigned integer vector all the elements of uve must be
between 0 and the `LENGTH' of BV. The bits of BV corresponding to
the indexes in uve are set to BOOL.
The return value is unspecified.
-- Function: bit-count* bv uve bool
Returns
(bit-count (bit-set*! (if bool bv (bit-invert! bv)) uve #t) #t).
BV is not modified.
File: scm.info, Node: Array Mapping, Prev: Bit Vectors, Up: Arrays
5.4.4 Array Mapping
-------------------
`(require 'array-for-each)'
SCM has some extra functions in feature `array-for-each':
-- Function: array-fill! array fill
Stores FILL in every element of ARRAY. The value returned is
unspecified.
-- Function: serial-array:copy! destination source
Same as `array:copy!' but guaranteed to copy in row-major order.
-- Function: array-equal? array0 array1 ...
Returns `#t' iff all arguments are arrays with the same shape, the
same type, and have corresponding elements which are either
`equal?' or `array-equal?'. This function differs from `equal?'
in that a one dimensional shared array may be ARRAY-EQUAL? but not
EQUAL? to a vector or uniform vector.
-- Function: array-map! array0 proc array1 ...
If ARRAY1, ... are arrays, they must have the same number of
dimensions as ARRAY0 and have a range for each index which
includes the range for the corresponding index in ARRAY0. If they
are scalars, that is, not arrays, vectors, or strings, then they
will be converted internally to arrays of the appropriate shape.
PROC is applied to each tuple of elements of ARRAY1 ... and the
result is stored as the corresponding element in ARRAY0. The
value returned is unspecified. The order of application is
unspecified.
Handling non-array arguments is a SCM extension of *Note
array-map!: (slib)Array Mapping.
-- Function: serial-array-map! array0 proc array1 ...
Same as ARRAY-MAP!, but guaranteed to apply PROC in row-major
order.
-- Function: array-map prototype proc array1 array2 ...
ARRAY2, ... must have the same number of dimensions as ARRAY1 and
have a range for each index which includes the range for the
corresponding index in ARRAY1. PROC is applied to each tuple of
elements of ARRAY1, ARRAY2, ... and the result is stored as the
corresponding element in a new array of type PROTOTYPE. The new
array is returned. The order of application is unspecified.
-- Function: scalar->array scalar array prototype
-- Function: scalar->array scalar array
Returns a uniform array of the same shape as ARRAY, having only
one shared element, which is `eqv?' to SCALAR. If the optional
argument PROTOTYPE is supplied it will be used as the prototype
for the returned array. Otherwise the returned array will be of
the same type as `array' if that is possible, and a conventional
array if it is not. This function is used internally by
`array-map!' and friends to handle scalar arguments.
File: scm.info, Node: Records, Next: I/O-Extensions, Prev: Arrays, Up: Packages
5.5 Records
===========
SCM provides user-definable datatypes with the same interface as SLIB,
see *Note Records: (slib)Records, with the following extension.
-- Function: record-printer-set! rtd printer
Causes records of type RTD to be printed in a user-specified
format. RTD must be a record type descriptor returned by
`make-record-type', PRINTER a procedure accepting three arguments:
the record to be printed, the port to print to, and a boolean
which is true if the record is being written on behalf of `write'
and false if for `display'. If PRINTER returns #f, the default
record printer will be called.
A PRINTER value of #f means use the default printer.
Only the default printer will be used when printing error messages.
File: scm.info, Node: I/O-Extensions, Next: Posix Extensions, Prev: Records, Up: Packages
5.6 I/O-Extensions
==================
If `'i/o-extensions' is provided (by linking in `ioext.o'), *Note Line
I/O: (slib)Line I/O, and the following functions are defined:
-- Function: stat <port-or-string>
Returns a vector of integers describing the argument. The argument
can be either a string or an open input port. If the argument is
an open port then the returned vector describes the file to which
the port is opened; If the argument is a string then the returned
vector describes the file named by that string. If there exists
no file with the name string, or if the file cannot be accessed
`#f' is returned. The elements of the returned vector are as
follows:
0 st_dev
ID of device containing a directory entry for this file
1 st_ino
Inode number
2 st_mode
File type, attributes, and access control summary
3 st_nlink
Number of links
4 st_uid
User ID of file owner
5 st_gid
Group ID of file group
6 st_rdev
Device ID; this entry defined only for char or blk spec files
7 st_size
File size (bytes)
8 st_atime
Time of last access
9 st_mtime
Last modification time
10 st_ctime
Last file status change time
-- Function: getpid
Returns the process ID of the current process.
-- Function: file-position port
Returns the current position of the character in PORT which will
next be read or written. If PORT is not open to a file the result
is unspecified.
-- Function: file-set-position port integer
Sets the current position in PORT which will next be read or
written. If PORT is not open to a file the action of
`file-set-position' is unspecified. The result of
`file-set-position' is unspecified.
-- Function: try-create-file name modes perms
If the file with name NAME already exists, return `#f', otherwise
try to create and open the file like `try-open-file', *Note Files
and Ports::. If the optional integer argument PERMS is provided,
it is used as the permissions of the new file (modified by the
current umask).
-- Function: reopen-file filename modes port
Closes port PORT and reopens it with FILENAME and MODES.
`reopen-file' returns `#t' if successful, `#f' if not.
-- Function: duplicate-port port modes
Creates and returns a "duplicate" port from PORT. Duplicate
_unbuffered_ ports share one file position. MODES are as for
*Note open-file: Files and Ports.
-- Function: redirect-port! from-port to-port
Closes TO-PORT and makes TO-PORT be a duplicate of FROM-PORT.
`redirect-port!' returns TO-PORT if successful, `#f' if not. If
unsuccessful, TO-PORT is not closed.
-- Function: opendir dirname
Returns a "directory" object corresponding to the file system
directory named DIRNAME. If unsuccessful, returns `#f'.
-- Function: readdir dir
Returns the string name of the next entry from the directory DIR.
If there are no more entries in the directory, `readdir' returns a
`#f'.
-- Function: rewinddir dir
Reinitializes DIR so that the next call to `readdir' with DIR will
return the first entry in the directory again.
-- Function: closedir dir
Closes DIR and returns `#t'. If DIR is already closed,,
`closedir' returns a `#f'.
-- Function: directory-for-each proc directory
PROC must be a procedure taking one argument.
`Directory-For-Each' applies PROC to the (string) name of each
file in DIRECTORY. The dynamic order in which PROC is applied to
the filenames is unspecified. The value returned by
`directory-for-each' is unspecified.
-- Function: directory-for-each proc directory pred
Applies PROC only to those filenames for which the procedure PRED
returns a non-false value.
-- Function: directory-for-each proc directory match
Applies PROC only to those filenames for which `(filename:match??
MATCH)' would return a non-false value (*note Filenames:
(slib)Filenames.).
(require 'directory)
(directory-for-each print "." "[A-Z]*.scm")
-|
"Init.scm"
"Iedline.scm"
"Link.scm"
"Macro.scm"
"Transcen.scm"
"Init5e2.scm" |
-- Function: mkdir path mode
The `mkdir' function creates a new, empty directory whose name is
PATH. The integer argument MODE specifies the file permissions
for the new directory. *Note The Mode Bits for Access Permission:
(libc)The Mode Bits for Access Permission, for more information
about this.
`mkdir' returns if successful, `#f' if not.
-- Function: rmdir path
The `rmdir' function deletes the directory PATH. The directory
must be empty before it can be removed. `rmdir' returns if
successful, `#f' if not.
-- Function: chdir filename
Changes the current directory to FILENAME. If FILENAME does not
exist or is not a directory, `#f' is returned. Otherwise, `#t' is
returned.
-- Function: getcwd
The function `getcwd' returns a string containing the absolute file
name representing the current working directory. If this string
cannot be obtained, `#f' is returned.
-- Function: rename-file oldfilename newfilename
Renames the file specified by OLDFILENAME to NEWFILENAME. If the
renaming is successful, `#t' is returned. Otherwise, `#f' is
returned.
-- Function: chmod file mode
The function `chmod' sets the access permission bits for the file
named by FILE to MODE. The FILE argument may be a string
containing the filename or a port open to the file.
`chmod' returns if successful, `#f' if not.
-- Function: utime pathname acctime modtime
Sets the file times associated with the file named PATHNAME to
have access time ACCTIME and modification time MODTIME. `utime'
returns if successful, `#f' if not.
-- Function: umask mode
The function `umask' sets the file creation mask of the current
process to MASK, and returns the previous value of the file
creation mask.
-- Function: fileno port
Returns the integer file descriptor associated with the port PORT.
If an error is detected, `#f' is returned.
-- Function: access pathname how
Returns `#t' if the file named by PATHNAME can be accessed in the
way specified by the HOW argument. The HOW argument can be the
`logior' of the flags:
0. File-exists?
1. File-is-executable?
2. File-is-writable?
4. File-is-readable?
Or the HOW argument can be a string of 0 to 3 of the following
characters in any order. The test performed is the `and' of the
associated tests and `file-exists?'.
<x>
File-is-executable?
<w>
File-is-writable?
<r>
File-is-readable?
-- Function: execl command arg0 ...
-- Function: execlp command arg0 ...
Transfers control to program COMMAND called with arguments ARG0
.... For `execl', COMMAND must be an exact pathname of an
executable file. `execlp' searches for COMMAND in the list of
directories specified by the environment variable PATH. The
convention is that ARG0 is the same name as COMMAND.
If successful, this procedure does not return. Otherwise an error
message is printed and the integer `errno' is returned.
-- Function: execv command arglist
-- Function: execvp command arglist
Like `execl' and `execlp' except that the set of arguments to
COMMAND is ARGLIST.
-- Function: putenv string
adds or removes definitions from the "environment". If the STRING
is of the form `NAME=VALUE', the definition is added to the
environment. Otherwise, the STRING is interpreted as the name of
an environment variable, and any definition for this variable in
the environment is removed.
Names of environment variables are case-sensitive and must not
contain the character `='. System-defined environment variables
are invariably uppercase.
`Putenv' is used to set up the environment before calls to
`execl', `execlp', `execv', `execvp', `system', or `open-pipe'
(*note open-pipe: Posix Extensions.).
To access environment variables, use `getenv' (*note getenv:
(slib)System Interface.).
File: scm.info, Node: Posix Extensions, Next: Unix Extensions, Prev: I/O-Extensions, Up: Packages
5.7 Posix Extensions
====================
If `'posix' is provided (by linking in `posix.o'), the following
functions are defined:
-- Function: open-pipe string modes
If the string MODES contains an <r>, returns an input port capable
of delivering characters from the standard output of the system
command STRING. Otherwise, returns an output port capable of
receiving characters which become the standard input of the system
command STRING. If a pipe cannot be created `#f' is returned.
-- Function: open-input-pipe string
Returns an input port capable of delivering characters from the
standard output of the system command STRING. If a pipe cannot be
created `#f' is returned.
-- Function: open-output-pipe string
Returns an output port capable of receiving characters which become
the standard input of the system command STRING. If a pipe cannot
be created `#f' is returned.
-- Function: broken-pipe port
If this function is defined at top level, it will be called when an
output pipe is closed from the other side (this is the condition
under which a SIGPIPE is sent). The already closed PORT will be
passed so that any necessary cleanup may be done. An error is not
signaled when output to a pipe fails in this way, but any further
output to the closed pipe will cause an error to be signaled.
-- Function: close-port pipe
Closes the PIPE, rendering it incapable of delivering or accepting
characters. This routine has no effect if the pipe has already
been closed. The value returned is unspecified.
-- Function: pipe
Returns `(cons RD WD)' where RD and WD are the read and write
(port) ends of a "pipe" respectively.
-- Function: fork
Creates a copy of the process calling `fork'. Both processes
return from `fork', but the calling ("parent") process's `fork'
returns the "child" process's ID whereas the child process's
`fork' returns 0.
For a discussion of "ID"s *Note Process Persona: (GNU C Library)Process
Persona.
-- Function: getppid
Returns the process ID of the parent of the current process. For
a process's own ID *Note getpid: I/O-Extensions.
-- Function: getuid
Returns the real user ID of this process.
-- Function: getgid
Returns the real group ID of this process.
-- Function: getegid
Returns the effective group ID of this process.
-- Function: geteuid
Returns the effective user ID of this process.
-- Function: setuid id
Sets the real user ID of this process to ID. Returns `#t' if
successful, `#f' if not.
-- Function: setgid id
Sets the real group ID of this process to ID. Returns `#t' if
successful, `#f' if not.
-- Function: setegid id
Sets the effective group ID of this process to ID. Returns `#t'
if successful, `#f' if not.
-- Function: seteuid id
Sets the effective user ID of this process to ID. Returns `#t' if
successful, `#f' if not.
-- Function: kill pid sig
The `kill' function sends the signal SIGNUM to the process or
process group specified by PID. Besides the signals listed in
*Note Standard Signals: (libc)Standard Signals, SIGNUM can also
have a value of zero to check the validity of the PID.
The PID specifies the process or process group to receive the
signal:
> 0
The process whose identifier is PID.
0
All processes in the same process group as the sender. The
sender itself does not receive the signal.
-1
If the process is privileged, send the signal to all
processes except for some special system processes.
Otherwise, send the signal to all processes with the same
effective user ID.
< -1
The process group whose identifier is `(abs PID)'.
A process can send a signal to itself with `(kill (getpid)
SIGNUM)'. If `kill' is used by a process to send a signal to
itself, and the signal is not blocked, then `kill' delivers at
least one signal (which might be some other pending unblocked
signal instead of the signal SIGNUM) to that process before it
returns.
The return value from `kill' is zero if the signal can be sent
successfully. Otherwise, no signal is sent, and a value of `-1' is
returned. If PID specifies sending a signal to several processes,
`kill' succeeds if it can send the signal to at least one of them.
There's no way you can tell which of the processes got the signal
or whether all of them did.
-- Function: waitpid pid options
The `waitpid' function suspends execution of the current process
until a child as specified by the PID argument has exited, or
until a signal is delivered whose action is to terminate the
current process or to call a signal handling function. If a child
as requested by PID has already exited by the time of the call (a
so-called "zombie" process), the function returns immediately.
Any system resources used by the child are freed.
The value of PID can be:
< -1
which means to wait for any child process whose process group
ID is equal to the absolute value of PID.
-1
which means to wait for any child process; this is the same
behaviour which wait exhibits.
0
which means to wait for any child process whose process group
ID is equal to that of the calling process.
> 0
which means to wait for the child whose process ID is equal
to the value of PID.
The value of OPTIONS is one of the following:
0. Nothing special.
1. (`WNOHANG') which means to return immediately if no child is
there to be waited for.
2. (`WUNTRACED') which means to also return for children which
are stopped, and whose status has not been reported.
3. Which means both of the above.
The return value normally is the exit status of the child process,
including the exit value along with flags indicating whether a
coredump was generated or the child terminated as a result of a
signal. If the `WNOHANG' option was specified and no child
process is waiting to be noticed, the value is zero. A value of
`#f' is returned in case of error and `errno' is set. For
information about the `errno' codes *Note Process Completion: (GNU
C Library)Process Completion.
-- Function: uname
You can use the `uname' procedure to find out some information
about the type of computer your program is running on.
Returns a vector of strings. These strings are:
0. The name of the operating system in use.
1. The network name of this particular computer.
2. The current release level of the operating system
implementation.
3. The current version level within the release of the operating
system.
4. Description of the type of hardware that is in use.
Some examples are `"i386-ANYTHING"', `"m68k-hp"',
`"sparc-sun"', `"m68k-sun"', `"m68k-sony"' and `"mips-dec"'.
-- Function: getpw name
-- Function: getpw uid
-- Function: getpw
Returns a vector of information for the entry for `NAME', `UID',
or the next entry if no argument is given. The information is:
0. The user's login name.
1. The encrypted password string.
2. The user ID number.
3. The user's default group ID number.
4. A string typically containing the user's real name, and
possibly other information such as a phone number.
5. The user's home directory, initial working directory, or
`#f', in which case the interpretation is system-dependent.
6. The user's default shell, the initial program run when the
user logs in, or `#f', indicating that the system default
should be used.
-- Function: setpwent #t
Rewinds the pw entry table back to the begining.
-- Function: setpwent #f
-- Function: setpwent
Closes the pw table.
-- Function: getgr name
-- Function: getgr uid
-- Function: getgr
Returns a vector of information for the entry for `NAME', `UID',
or the next entry if no argument is given. The information is:
0. The name of the group.
1. The encrypted password string.
2. The group ID number.
3. A list of (string) names of users in the group.
-- Function: setgrent #t
Rewinds the group entry table back to the begining.
-- Function: setgrent #f
-- Function: setgrent
Closes the group table.
-- Function: getgroups
Returns a vector of all the supplementary group IDs of the process.
-- Function: link oldname newname
The `link' function makes a new link to the existing file named by
OLDNAME, under the new name NEWNAME.
`link' returns a value of `#t' if it is successful and `#f' on
failure.
-- Function: chown filename owner group
The `chown' function changes the owner of the file FILENAME to
OWNER, and its group owner to GROUP.
`chown' returns a value of `#t' if it is successful and `#f' on
failure.
-- Function: ttyname port
If port PORT is associated with a terminal device, returns a
string containing the file name of termainal device; otherwise
`#f'.
File: scm.info, Node: Unix Extensions, Next: Sequence Comparison, Prev: Posix Extensions, Up: Packages
5.8 Unix Extensions
===================
If `'unix' is provided (by linking in `unix.o'), the following
functions are defined:
These "privileged" and symbolic link functions are not in Posix:
-- Function: symlink oldname newname
The `symlink' function makes a symbolic link to OLDNAME named
NEWNAME.
`symlink' returns a value of `#t' if it is successful and `#f' on
failure.
-- Function: readlink filename
Returns the value of the symbolic link FILENAME or `#f' for
failure.
-- Function: lstat filename
The `lstat' function is like `stat', except that it does not
follow symbolic links. If FILENAME is the name of a symbolic
link, `lstat' returns information about the link itself; otherwise,
`lstat' works like `stat'. *Note I/O-Extensions::.
-- Function: nice increment
Increment the priority of the current process by INCREMENT.
`chown' returns a value of `#t' if it is successful and `#f' on
failure.
-- Function: acct filename
When called with the name of an exisitng file as argument,
accounting is turned on, records for each terminating process are
appended to FILENAME as it terminates. An argument of `#f' causes
accounting to be turned off.
`acct' returns a value of `#t' if it is successful and `#f' on
failure.
-- Function: mknod filename mode dev
The `mknod' function makes a special file with name FILENAME and
modes MODE for device number DEV.
`mknod' returns a value of `#t' if it is successful and `#f' on
failure.
-- Function: sync
`sync' first commits inodes to buffers, and then buffers to disk.
sync() only schedules the writes, so it may return before the
actual writing is done. The value returned is unspecified.
File: scm.info, Node: Sequence Comparison, Next: Regular Expression Pattern Matching, Prev: Unix Extensions, Up: Packages
5.9 Sequence Comparison
=======================
`(require 'diff)'
A blazing fast implementation of the sequence-comparison module in
SLIB, see *Note Sequence Comparison: (slib)Sequence Comparison.
File: scm.info, Node: Regular Expression Pattern Matching, Next: Line Editing, Prev: Sequence Comparison, Up: Packages
5.10 Regular Expression Pattern Matching
========================================
These functions are defined in `rgx.c' using a POSIX or GNU "regex"
library. If your computer does not support regex, a package is
available via ftp from `ftp.gnu.org:/pub/gnu/regex-0.12.tar.gz'. For a
description of regular expressions, *Note syntax: (regex)syntax.
-- Function: regcomp PATTERN [FLAGS]
Compile a "regular expression". Return a compiled regular
expression, or an integer error code suitable as an argument to
`regerror'.
FLAGS in `regcomp' is a string of option letters used to control
the compilation of the regular expression. The letters may
consist of:
`n'
newlines won't be matched by `.' or hat lists; ( `[^...]' )
`i'
ignore case.only when compiled with _GNU_SOURCE:
`0'
allows dot to match a null character.
`f'
enable GNU fastmaps.
-- Function: regerror ERRNO
Returns a string describing the integer ERRNO returned when
`regcomp' fails.
-- Function: regexec RE STRING
Returns `#f' or a vector of integers. These integers are in
doublets. The first of each doublet is the index of STRING of the
start of the matching expression or sub-expression (delimited by
parentheses in the pattern). The last of each doublet is index of
STRING of the end of that expression. `#f' is returned if the
string does not match.
-- Function: regmatch? RE STRING
Returns `#t' if the PATTERN such that REGEXP = (regcomp PATTERN)
matches STRING as a POSIX extended regular expressions. Returns
`#f' otherwise.
-- Function: regsearch RE STRING [START [LEN]]
-- Function: regsearchv RE STRING [START [LEN]]
-- Function: regmatch RE STRING [START [LEN]]
-- Function: regmatchv RE STRING [START [LEN]]
`Regsearch' searches for the pattern within the string.
`Regmatch' anchors the pattern and begins matching it against
string.
`Regsearch' returns the character position where RE starts, or
`#f' if not found.
`Regmatch' returns the number of characters matched, `#f' if not
matched.
`Regsearchv' and `regmatchv' return the match vector is returned
if RE is found, `#f' otherwise.
RE
may be either:
1. a compiled regular expression returned by `regcomp';
2. a string representing a regular expression;
3. a list of a string and a set of option letters.
STRING
The string to be operated upon.
START
The character position at which to begin the search or match.
If absent, the default is zero.
_Compiled _GNU_SOURCE and using GNU libregex only_
When searching, if START is negative, the absolute value of
START will be used as the start location and reverse searching
will be performed.
LEN
The search is allowed to examine only the first LEN
characters of STRING. If absent, the entire string may be
examined.
-- Function: string-split RE STRING
-- Function: string-splitv RE STRING
`String-split' splits a string into substrings that are separated
by RE, returning a vector of substrings.
`String-splitv' returns a vector of string positions that indicate
where the substrings are located.
-- Function: string-edit RE EDIT-SPEC STRING [COUNT]
Returns the edited string.
EDIT-SPEC
Is a string used to replace occurances of RE. Backquoted
integers in the range of 1-9 may be used to insert
subexpressions in RE, as in `sed'.
COUNT
The number of substitutions for `string-edit' to perform. If
`#t', all occurances of RE will be replaced. The default is
to perform one substitution.
File: scm.info, Node: Line Editing, Next: Curses, Prev: Regular Expression Pattern Matching, Up: Packages
5.11 Line Editing
=================
These procedures provide input line editing and recall.
These functions are defined in `edline.c' and `Iedline.scm' using the
"editline" or GNU "readline" (*note Overview: (readline)Top.) libraries
available from:
* `ftp.sys.toronto.edu:/pub/rc/editline.shar'
* `ftp.gnu.org:/pub/gnu/readline-2.0.tar.gz'
When `Iedline.scm' is loaded, if the current input port is the default
input port and the environment variable EMACS is not defined,
line-editing mode will be entered.
-- Function: default-input-port
Returns the initial `current-input-port' SCM was invoked with
(stdin).
-- Function: default-output-port
Returns the initial `current-output-port' SCM was invoked with
(stdout).
-- Function: make-edited-line-port
Returns an input/output port that allows command line editing and
retrieval of history.
-- Function: line-editing
Returns the current edited line port or `#f'.
-- Function: line-editing bool
If BOOL is false, exits line-editing mode and returns the previous
value of `(line-editing)'. If BOOL is true, sets the current
input and output ports to an edited line port and returns the
previous value of `(line-editing)'.
File: scm.info, Node: Curses, Next: Sockets, Prev: Line Editing, Up: Packages
5.12 Curses
===========
These functions are defined in `crs.c' using the "curses" library.
Unless otherwise noted these routines return `#t' for successful
completion and `#f' for failure.
-- Function: initscr
Returns a port for a full screen window. This routine must be
called to initialize curses.
-- Function: endwin
A program should call `endwin' before exiting or escaping from
curses mode temporarily, to do a system call, for example. This
routine will restore termio modes, move the cursor to the lower
left corner of the screen and reset the terminal into the proper
non-visual mode. To resume after a temporary escape, call *Note
refresh: Window Manipulation.
* Menu:
* Output Options Setting::
* Terminal Mode Setting::
* Window Manipulation::
* Output::
* Input::
* Curses Miscellany::
File: scm.info, Node: Output Options Setting, Next: Terminal Mode Setting, Prev: Curses, Up: Curses
5.12.1 Output Options Setting
-----------------------------
These routines set options within curses that deal with output. All
options are initially `#f', unless otherwise stated. It is not
necessary to turn these options off before calling `endwin'.
-- Function: clearok win bf
If enabled (BF is `#t'), the next call to `force-output' or
`refresh' with WIN will clear the screen completely and redraw the
entire screen from scratch. This is useful when the contents of
the screen are uncertain, or in some cases for a more pleasing
visual effect.
-- Function: idlok win bf
If enabled (BF is `#t'), curses will consider using the hardware
"insert/delete-line" feature of terminals so equipped. If
disabled (BF is `#f'), curses will very seldom use this feature.
The "insert/delete-character" feature is always considered. This
option should be enabled only if your application needs
"insert/delete-line", for example, for a screen editor. It is
disabled by default because
"insert/delete-line" tends to be visually annoying when used in
applications where it is not really needed. If
"insert/delete-line" cannot be used, curses will redraw the
changed portions of all lines.
-- Function: leaveok win bf
Normally, the hardware cursor is left at the location of the window
cursor being refreshed. This option allows the cursor to be left
wherever the update happens to leave it. It is useful for
applications where the cursor is not used, since it reduces the
need for cursor motions. If possible, the cursor is made
invisible when this option is enabled.
-- Function: scrollok win bf
This option controls what happens when the cursor of window WIN is
moved off the edge of the window or scrolling region, either from a
newline on the bottom line, or typing the last character of the
last line. If disabled (BF is `#f'), the cursor is left on the
bottom line at the location where the offending character was
entered. If enabled (BF is `#t'), `force-output' is called on the
window WIN, and then the physical terminal and window WIN are
scrolled up one line.
_Note_ in order to get the physical scrolling effect on the
terminal, it is also necessary to call `idlok'.
-- Function: nodelay win bf
This option causes wgetch to be a non-blocking call. If no input
is ready, wgetch will return an eof-object. If disabled, wgetch
will hang until a key is pressed.
File: scm.info, Node: Terminal Mode Setting, Next: Window Manipulation, Prev: Output Options Setting, Up: Curses
5.12.2 Terminal Mode Setting
----------------------------
These routines set options within curses that deal with input. The
options involve using ioctl(2) and therefore interact with curses
routines. It is not necessary to turn these options off before calling
`endwin'. The routines in this section all return an unspecified value.
-- Function: cbreak
-- Function: nocbreak
These two routines put the terminal into and out of `CBREAK' mode,
respectively. In `CBREAK' mode, characters typed by the user are
immediately available to the program and erase/kill character
processing is not performed. When in `NOCBREAK' mode, the tty
driver will buffer characters typed until a <LFD> or <RET> is
typed. Interrupt and flowcontrol characters are unaffected by
this mode. Initially the terminal may or may not be in `CBREAK'
mode, as it is inherited, therefore, a program should call
`cbreak' or `nocbreak' explicitly. Most interactive programs
using curses will set `CBREAK' mode.
_Note_ `cbreak' overrides `raw'. For a discussion of how these
routines interact with `echo' and `noecho' *Note read-char: Input.
-- Function: raw
-- Function: noraw
The terminal is placed into or out of `RAW' mode. `RAW' mode is
similar to `CBREAK' mode, in that characters typed are immediately
passed through to the user program. The differences are that in
`RAW' mode, the interrupt, quit, suspend, and flow control
characters are passed through uninterpreted, instead of generating
a signal. `RAW' mode also causes 8-bit input and output. The
behavior of the `BREAK' key depends on other bits in the terminal
driver that are not set by curses.
-- Function: echo
-- Function: noecho
These routines control whether characters typed by the user are
echoed by `read-char' as they are typed. Echoing by the tty
driver is always disabled, but initially `read-char' is in `ECHO'
mode, so characters typed are echoed. Authors of most interactive
programs prefer to do their own echoing in a controlled area of
the screen, or not to echo at all, so they disable echoing by
calling `noecho'. For a discussion of how these routines interact
with `echo' and `noecho' *Note read-char: Input.
-- Function: nl
-- Function: nonl
These routines control whether <LFD> is translated into <RET> and
`LFD' on output, and whether <RET> is translated into <LFD> on
input. Initially, the translations do occur. By disabling these
translations using `nonl', curses is able to make better use of
the linefeed capability, resulting in faster cursor motion.
-- Function: resetty
-- Function: savetty
These routines save and restore the state of the terminal modes.
`savetty' saves the current state of the terminal in a buffer and
`resetty' restores the state to what it was at the last call to
`savetty'.
File: scm.info, Node: Window Manipulation, Next: Output, Prev: Terminal Mode Setting, Up: Curses
5.12.3 Window Manipulation
--------------------------
-- Function: newwin nlines ncols begy begx
Create and return a new window with the given number of lines (or
rows), NLINES, and columns, NCOLS. The upper left corner of the
window is at line BEGY, column BEGX. If either NLINES or NCOLS is
0, they will be set to the value of `LINES'-BEGY and `COLS'-BEGX.
A new full-screen window is created by calling `newwin(0,0,0,0)'.
-- Function: subwin orig nlines ncols begy begx
Create and return a pointer to a new window with the given number
of lines (or rows), NLINES, and columns, NCOLS. The window is at
position (BEGY, BEGX) on the screen. This position is relative to
the screen, and not to the window ORIG. The window is made in the
middle of the window ORIG, so that changes made to one window will
affect both windows. When using this routine, often it will be
necessary to call `touchwin' or `touchline' on ORIG before calling
`force-output'.
-- Function: close-port win
Deletes the window WIN, freeing up all memory associated with it.
In the case of sub-windows, they should be deleted before the main
window WIN.
-- Function: refresh
-- Function: force-output win
These routines are called to write output to the terminal, as most
other routines merely manipulate data structures. `force-output'
copies the window WIN to the physical terminal screen, taking into
account what is already there in order to minimize the amount of
information that's sent to the terminal (called optimization).
Unless `leaveok' has been enabled, the physical cursor of the
terminal is left at the location of window WIN's cursor. With
`refresh', the number of characters output to the terminal is
returned.
-- Function: mvwin win y x
Move the window WIN so that the upper left corner will be at
position (Y, X). If the move would cause the window WIN to be off
the screen, it is an error and the window WIN is not moved.
-- Function: overlay srcwin dstwin
-- Function: overwrite srcwin dstwin
These routines overlay SRCWIN on top of DSTWIN; that is, all text
in SRCWIN is copied into DSTWIN. SRCWIN and DSTWIN need not be
the same size; only text where the two windows overlap is copied.
The difference is that `overlay' is non-destructive (blanks are
not copied), while `overwrite' is destructive.
-- Function: touchwin win
-- Function: touchline win start count
Throw away all optimization information about which parts of the
window WIN have been touched, by pretending that the entire window
WIN has been drawn on. This is sometimes necessary when using
overlapping windows, since a change to one window will affect the
other window, but the records of which lines have been changed in
the other window will not reflect the change. `touchline' only
pretends that COUNT lines have been changed, beginning with line
START.
-- Function: wmove win y x
The cursor associated with the window WIN is moved to line (row) Y,
column X. This does not move the physical cursor of the terminal
until `refresh' (or `force-output') is called. The position
specified is relative to the upper left corner of the window WIN,
which is (0, 0).
File: scm.info, Node: Output, Next: Input, Prev: Window Manipulation, Up: Curses
5.12.4 Output
-------------
These routines are used to "draw" text on windows
-- Function: display ch win
-- Function: display str win
-- Function: wadd win ch
-- Function: wadd win str
The character CH or characters in STR are put into the window WIN
at the current cursor position of the window and the position of
WIN's cursor is advanced. At the right margin, an automatic
newline is performed. At the bottom of the scrolling region, if
scrollok is enabled, the scrolling region will be scrolled up one
line.
If CH is a <TAB>, <LFD>, or backspace, the cursor will be moved
appropriately within the window WIN. A <LFD> also does a
`wclrtoeol' before moving. <TAB> characters are considered to be
at every eighth column. If CH is another control character, it
will be drawn in the `C-x' notation. (Calling `winch' after
adding a control character will not return the control character,
but instead will return the representation of the control
character.)
Video attributes can be combined with a character by or-ing them
into the parameter. This will result in these attributes also
being set. The intent here is that text, including attributes,
can be copied from one place to another using inch and display.
See `standout', below.
_Note_ For `wadd' CH can be an integer and will insert the
character of the corresponding value.
-- Function: werase win
This routine copies blanks to every position in the window WIN.
-- Function: wclear win
This routine is like `werase', but it also calls *Note clearok:
Output Options Setting, arranging that the screen will be cleared
completely on the next call to `refresh' or `force-output' for
window WIN, and repainted from scratch.
-- Function: wclrtobot win
All lines below the cursor in window WIN are erased. Also, the
current line to the right of the cursor, inclusive, is erased.
-- Function: wclrtoeol win
The current line to the right of the cursor, inclusive, is erased.
-- Function: wdelch win
The character under the cursor in the window WIN is deleted. All
characters to the right on the same line are moved to the left one
position and the last character on the line is filled with a
blank. The cursor position does not change. This does not imply
use of the hardware "delete-character" feature.
-- Function: wdeleteln win
The line under the cursor in the window WIN is deleted. All lines
below the current line are moved up one line. The bottom line WIN
is cleared. The cursor position does not change. This does not
imply use of the hardware "deleteline" feature.
-- Function: winsch win ch
The character CH is inserted before the character under the
cursor. All characters to the right are moved one <SPC> to the
right, possibly losing the rightmost character of the line. The
cursor position does not change . This does not imply use of the
hardware "insertcharacter" feature.
-- Function: winsertln win
A blank line is inserted above the current line and the bottom
line is lost. This does not imply use of the hardware
"insert-line" feature.
-- Function: scroll win
The window WIN is scrolled up one line. This involves moving the
lines in WIN's data structure. As an optimization, if WIN is
stdscr and the scrolling region is the entire window, the physical
screen will be scrolled at the same time.
File: scm.info, Node: Input, Next: Curses Miscellany, Prev: Output, Up: Curses
5.12.5 Input
------------
-- Function: read-char win
A character is read from the terminal associated with the window
WIN. Depending on the setting of `cbreak', this will be after one
character (`CBREAK' mode), or after the first newline (`NOCBREAK'
mode). Unless `noecho' has been set, the character will also be
echoed into WIN.
When using `read-char', do not set both `NOCBREAK' mode
(`nocbreak') and `ECHO' mode (`echo') at the same time. Depending
on the state of the terminal driver when each character is typed,
the program may produce undesirable results.
-- Function: winch win
The character, of type chtype, at the current position in window
WIN is returned. If any attributes are set for that position,
their values will be OR'ed into the value returned.
-- Function: getyx win
A list of the y and x coordinates of the cursor position of the
window WIN is returned
File: scm.info, Node: Curses Miscellany, Prev: Input, Up: Curses
5.12.6 Curses Miscellany
------------------------
-- Function: wstandout win
-- Function: wstandend win
These functions set the current attributes of the window WIN. The
current attributes of WIN are applied to all characters that are
written into it. Attributes are a property of the character, and
move with the character through any scrolling and insert/delete
line/character operations. To the extent possible on the
particular terminal, they will be displayed as the graphic
rendition of characters put on the screen.
`wstandout' sets the current attributes of the window WIN to be
visibly different from other text. `wstandend' turns off the
attributes.
-- Function: box win vertch horch
A box is drawn around the edge of the window WIN. VERTCH and
HORCH are the characters the box is to be drawn with. If VERTCH
and HORCH are 0, then appropriate default characters, `ACS_VLINE'
and `ACS_HLINE', will be used.
_Note_ VERTCH and HORCH can be an integers and will insert the
character (with attributes) of the corresponding values.
-- Function: unctrl c
This macro expands to a character string which is a printable
representation of the character C. Control characters are
displayed in the `C-x' notation. Printing characters are displayed
as is.
File: scm.info, Node: Sockets, Next: SCMDB, Prev: Curses, Up: Packages
5.13 Sockets
============
These procedures (defined in `socket.c') provide a Scheme interface to
most of the C "socket" library. For more information on sockets, *Note
Sockets: (libc)Sockets.
* Menu:
* Host and Other Inquiries::
* Internet Addresses and Socket Names::
* Socket::
File: scm.info, Node: Host and Other Inquiries, Next: Internet Addresses and Socket Names, Prev: Sockets, Up: Sockets
5.13.1 Host and Other Inquiries
-------------------------------
-- Constant: af_inet
-- Constant: af_unix
Integer family codes for Internet and Unix sockets, respectively.
-- Function: gethost host-spec
-- Function: gethost
Returns a vector of information for the entry for `HOST-SPEC' or
the next entry if `HOST-SPEC' isn't given. The information is:
0. host name string
1. list of host aliases strings
2. integer address type (`AF_INET')
3. integer size of address entries (in bytes)
4. list of integer addresses
-- Function: sethostent stay-open
-- Function: sethostent
Rewinds the host entry table back to the begining if given an
argument. If the argument STAY-OPEN is `#f' queries will be be
done using `UDP' datagrams. Otherwise, a connected `TCP' socket
will be used. When called without an argument, the host table is
closed.
-- Function: getnet name-or-number
-- Function: getnet
Returns a vector of information for the entry for NAME-OR-NUMBER or
the next entry if an argument isn't given. The information is:
0. official network name string
1. list of network aliases strings
2. integer network address type (`AF_INET')
3. integer network number
-- Function: setnetent stay-open
-- Function: setnetent
Rewinds the network entry table back to the begining if given an
argument. If the argument STAY-OPEN is `#f' the table will be
closed between calls to getnet. Otherwise, the table stays open.
When called without an argument, the network table is closed.
-- Function: getproto name-or-number
-- Function: getproto
Returns a vector of information for the entry for NAME-OR-NUMBER or
the next entry if an argument isn't given. The information is:
1. official protocol name string
2. list of protocol aliases strings
3. integer protocol number
-- Function: setprotoent stay-open
-- Function: setprotoent
Rewinds the protocol entry table back to the begining if given an
argument. If the argument STAY-OPEN is `#f' the table will be
closed between calls to getproto. Otherwise, the table stays
open. When called without an argument, the protocol table is
closed.
-- Function: getserv name-or-port-number protocol
-- Function: getserv
Returns a vector of information for the entry for
NAME-OR-PORT-NUMBER and PROTOCOL or the next entry if arguments
aren't given. The information is:
0. official service name string
1. list of service aliases strings
2. integer port number
3. protocol
-- Function: setservent stay-open
-- Function: setservent
Rewinds the service entry table back to the begining if given an
argument. If the argument STAY-OPEN is `#f' the table will be
closed between calls to getserv. Otherwise, the table stays open.
When called without an argument, the service table is closed.
File: scm.info, Node: Internet Addresses and Socket Names, Next: Socket, Prev: Host and Other Inquiries, Up: Sockets
5.13.2 Internet Addresses and Socket Names
------------------------------------------
-- Function: inet:string->address string
Returns the host address number (integer) for host STRING or `#f'
if not found.
-- Function: inet:address->string address
Converts an internet (integer) address to a string in numbers and
dots notation.
-- Function: inet:network address
Returns the network number (integer) specified from ADDRESS or
`#f' if not found.
-- Function: inet:local-network-address address
Returns the integer for the address of ADDRESS within its local
network or `#f' if not found.
-- Function: inet:make-address network local-address
Returns the Internet address of LOCAL-ADDRESS in NETWORK.
The type "socket-name" is used for inquiries about open sockets in the
following procedures:
-- Function: getsockname socket
Returns the socket-name of SOCKET. Returns `#f' if unsuccessful
or SOCKET is closed.
-- Function: getpeername socket
Returns the socket-name of the socket connected to SOCKET.
Returns `#f' if unsuccessful or SOCKET is closed.
-- Function: socket-name:family socket-name
Returns the integer code for the family of SOCKET-NAME.
-- Function: socket-name:port-number socket-name
Returns the integer port number of SOCKET-NAME.
-- Function: socket-name:address socket-name
Returns the integer Internet address for SOCKET-NAME.
File: scm.info, Node: Socket, Prev: Internet Addresses and Socket Names, Up: Sockets
5.13.3 Socket
-------------
When a port is returned from one of these calls it is unbuffered. This
allows both reading and writing to the same port to work. If you want
buffered ports you can (assuming sock-port is a socket i/o port):
(require 'i/o-extensions)
(define i-port (duplicate-port sock-port "r"))
(define o-port (duplicate-port sock-port "w"))
-- Function: make-stream-socket family
-- Function: make-stream-socket family protocol
Returns a `SOCK_STREAM' socket of type FAMILY using PROTOCOL. If
FAMILY has the value `AF_INET', `SO_REUSEADDR' will be set. The
integer argument PROTOCOL corresponds to the integer protocol
numbers returned (as vector elements) from `(getproto)'. If the
PROTOCOL argument is not supplied, the default (0) for the
specified FAMILY is used. SCM sockets look like ports opened for
neither reading nor writing.
-- Function: make-stream-socketpair family
-- Function: make-stream-socketpair family protocol
Returns a pair (cons) of connected `SOCK_STREAM' (socket) ports of
type FAMILY using PROTOCOL. Many systems support only socketpairs
of the `af-unix' FAMILY. The integer argument PROTOCOL
corresponds to the integer protocol numbers returned (as vector
elements) from (getproto). If the PROTOCOL argument is not
supplied, the default (0) for the specified FAMILY is used.
-- Function: socket:shutdown socket how
Makes SOCKET no longer respond to some or all operations depending
on the integer argument HOW:
0. Further input is disallowed.
1. Further output is disallowed.
2. Further input or output is disallowed.
`Socket:shutdown' returns SOCKET if successful, `#f' if not.
-- Function: socket:connect inet-socket host-number port-number
-- Function: socket:connect unix-socket pathname
Returns SOCKET (changed to a read/write port) connected to the
Internet socket on host HOST-NUMBER, port PORT-NUMBER or the Unix
socket specified by PATHNAME. Returns `#f' if not successful.
-- Function: socket:bind inet-socket port-number
-- Function: socket:bind unix-socket pathname
Returns INET-SOCKET bound to the integer PORT-NUMBER or the
UNIX-SOCKET bound to new socket in the file system at location
PATHNAME. Returns `#f' if not successful. Binding a UNIX-SOCKET
creates a socket in the file system that must be deleted by the
caller when it is no longer needed (using `delete-file').
-- Function: socket:listen socket backlog
The bound (*note bind: Socket.) SOCKET is readied to accept
connections. The positive integer BACKLOG specifies how many
pending connections will be allowed before further connection
requests are refused. Returns SOCKET (changed to a read-only
port) if successful, `#f' if not.
-- Function: char-ready? listen-socket
The input port returned by a successful call to `socket:listen' can
be polled for connections by `char-ready?' (*note char-ready?:
Files and Ports.). This avoids blocking on connections by
`socket:accept'.
-- Function: socket:accept socket
Accepts a connection on a bound, listening SOCKET. Returns an
input/output port for the connection.
The following example is not too complicated, yet shows the use of
sockets for multiple connections without input blocking.
;;;; Scheme chat server
;;; This program implements a simple `chat' server which accepts
;;; connections from multiple clients, and sends to all clients any
;;; characters received from any client.
;;; To connect to chat `telnet localhost 8001'
(require 'socket)
(require 'i/o-extensions)
(let ((listener-socket (socket:bind (make-stream-socket af_inet) 8001))
(connections '()))
(socket:listen listener-socket 5)
(do () (#f)
(let ((actives (or (apply wait-for-input 5 listener-socket connections)
'())))
(cond ((null? actives))
((memq listener-socket actives)
(set! actives (cdr (memq listener-socket actives)))
(let ((con (socket:accept listener-socket)))
(display "accepting connection from ")
(display (getpeername con))
(newline)
(set! connections (cons con connections))
(display "connected" con)
(newline con))))
(set! connections
(let next ((con-list connections))
(cond ((null? con-list) '())
(else
(let ((con (car con-list)))
(cond ((memq con actives)
(let ((c (read-char con)))
(cond ((eof-object? c)
(display "closing connection from ")
(display (getpeername con))
(newline)
(close-port con)
(next (cdr con-list)))
(else
(for-each (lambda (con)
(file-set-position con 0)
(write-char c con)
(file-set-position con 0))
connections)
(cons con (next (cdr con-list)))))))
(else (cons con (next (cdr con-list)))))))))))))
You can use `telnet localhost 8001' to connect to the chat server, or
you can use a client written in scheme:
;;;; Scheme chat client
;;; this program connects to socket 8001. It then sends all
;;; characters from current-input-port to the socket and sends all
;;; characters from the socket to current-output-port.
(require 'socket)
(require 'i/o-extensions)
(define con (make-stream-socket af_inet))
(set! con (socket:connect con (inet:string->address "localhost") 8001))
(define (go)
(define actives (wait-for-input (* 30 60) con (current-input-port)))
(let ((cs (and actives (memq con actives) (read-char con)))
(ct (and actives (memq (current-input-port) actives) (read-char))))
(cond ((or (eof-object? cs) (eof-object? ct)) (close-port con))
(else (cond (cs (display cs)))
(cond (ct (file-set-position con 0)
(display ct con)
(file-set-position con 0)))
(go)))))
(cond (con (display "Connecting to ")
(display (getpeername con))
(newline)
(go))
(else (display "Server not listening on port 8001")
(newline)))
File: scm.info, Node: SCMDB, Prev: Sockets, Up: Packages
5.14 SCMDB
==========
`(require 'mysql)'
"SCMDB" is an add-on for SCM that ports the MySQL C-library to SCM.
It is available from: `http://www.dedecker.net/jessie/scmdb/'
File: scm.info, Node: The Implementation, Next: Index, Prev: Packages, Up: Top
6 The Implementation
********************
* Menu:
* Data Types::
* Operations::
* Program Self-Knowledge:: What SCM needs to know about itself.
* Improvements To Make::
File: scm.info, Node: Data Types, Next: Operations, Prev: The Implementation, Up: The Implementation
6.1 Data Types
==============
In the descriptions below it is assumed that `long int's are 32 bits in
length. Acutally, SCM is written to work with any `long int' size
larger than 31 bits. With some modification, SCM could work with word
sizes as small as 24 bits.
All SCM objects are represented by type "SCM". Type `SCM' come in 2
basic flavors, Immediates and Cells:
* Menu:
* Immediates::
* Cells:: Non-Immediate types
* Header Cells:: Malloc objects
* Subr Cells:: Built-in and Compiled Procedures
* Ptob Cells:: I/O ports
* Smob Cells:: Miscellaneous datatypes
* Data Type Representations:: How they all fit together
File: scm.info, Node: Immediates, Next: Cells, Prev: Data Types, Up: Data Types
6.1.1 Immediates
----------------
An "immediate" is a data type contained in type `SCM' (`long int').
The type codes distinguishing immediate types from each other vary in
length, but reside in the low order bits.
-- Macro: IMP x
-- Macro: NIMP x
Return non-zero if the `SCM' object X is an immediate or
non-immediate type, respectively.
-- Immediate: inum
immediate 30 bit signed integer. An INUM is flagged by a `1' in
the second to low order bit position. The high order 30 bits are
used for the integer's value.
-- Macro: INUMP x
-- Macro: NINUMP x
Return non-zero if the `SCM' X is an immediate integer or not
an immediate integer, respectively.
-- Macro: INUM x
Returns the C `long integer' corresponding to `SCM' X.
-- Macro: MAKINUM x
Returns the `SCM' inum corresponding to C `long integer' x.
-- Immediate Constant: INUM0
is equivalent to `MAKINUM(0)'.
Computations on INUMs are performed by converting the arguments to
C integers (by a shift), operating on the integers, and converting
the result to an inum. The result is checked for overflow by
converting back to integer and checking the reverse operation.
The shifts used for conversion need to be signed shifts. If the C
implementation does not support signed right shift this fact is
detected in a #if statement in `scmfig.h' and a signed right shift,
`SRS', is constructed in terms of unsigned right shift.
-- Immediate: ichr
characters.
-- Macro: ICHRP x
Return non-zero if the `SCM' object X is a character.
-- Macro: ICHR x
Returns corresponding `unsigned char'.
-- Macro: MAKICHR x
Given `char' X, returns `SCM' character.
-- Immediate: iflags
These are frequently used immediate constants.
-- Immediate Constant: SCM BOOL_T
`#t'
-- Immediate Constant: SCM BOOL_F
`#f'
-- Immediate Constant: SCM EOL
`()'. If `SICP' is `#define'd, `EOL' is `#define'd to be
identical with `BOOL_F'. In this case, both print as `#f'.
-- Immediate Constant: SCM EOF_VAL
end of file token, `#<eof>'.
-- Immediate Constant: SCM UNDEFINED
`#<undefined>' used for variables which have not been defined
and absent optional arguments.
-- Immediate Constant: SCM UNSPECIFIED
`#<unspecified>' is returned for those procedures whose return
values are not specified.
-- Macro: IFLAGP n
Returns non-zero if N is an ispcsym, isym or iflag.
-- Macro: ISYMP n
Returns non-zero if N is an ispcsym or isym.
-- Macro: ISYMNUM n
Given ispcsym, isym, or iflag N, returns its index in the C array
`isymnames[]'.
-- Macro: ISYMCHARS n
Given ispcsym, isym, or iflag N, returns its `char *'
representation (from `isymnames[]').
-- Macro: MAKSPCSYM n
Returns `SCM' ispcsym N.
-- Macro: MAKISYM n
Returns `SCM' iisym N.
-- Macro: MAKIFLAG n
Returns `SCM' iflag N.
-- Variable: isymnames
An array of strings containing the external representations of all
the ispcsym, isym, and iflag immediates. Defined in `repl.c'.
-- Constant: NUM_ISPCSYM
-- Constant: NUM_ISYMS
The number of ispcsyms and ispcsyms+isyms, respectively. Defined
in `scm.h'.
-- Immediate: isym
`and', `begin', `case', `cond', `define', `do', `if', `lambda',
`let', `let*', `letrec', `or', `quote', `set!', `#f', `#t',
`#<undefined>', `#<eof>', `()', and `#<unspecified>'.
-- CAR Immediate: ispcsym
special symbols: syntax-checked versions of first 14 isyms
-- CAR Immediate: iloc
indexes to a variable's location in environment
-- CAR Immediate: gloc
pointer to a symbol's value cell
-- Immediate: CELLPTR
pointer to a cell (not really an immediate type, but here for
completeness). Since cells are always 8 byte aligned, a pointer
to a cell has the low order 3 bits `0'.
There is one exception to this rule, _CAR Immediate_s, described
next.
A "CAR Immediate" is an Immediate point which can only occur in the
`CAR's of evaluated code (as a result of `ceval''s memoization process).
File: scm.info, Node: Cells, Next: Header Cells, Prev: Immediates, Up: Data Types
6.1.2 Cells
-----------
"Cell"s represent all SCM objects other than immediates. A cell has a
`CAR' and a `CDR'. Low-order bits in `CAR' identify the type of
object. The rest of `CAR' and `CDR' hold object data. The number
after `tc' specifies how many bits are in the type code. For instance,
`tc7' indicates that the type code is 7 bits.
-- Macro: NEWCELL x
Allocates a new cell and stores a pointer to it in `SCM' local
variable X.
Care needs to be taken that stores into the new cell pointed to by
X do not create an inconsistent object. *Note Signals::.
All of the C macros decribed in this section assume that their argument
is of type `SCM' and points to a cell (`CELLPTR').
-- Macro: CAR x
-- Macro: CDR x
Returns the `car' and `cdr' of cell X, respectively.
-- Macro: TYP3 x
-- Macro: TYP7 x
-- Macro: TYP16 x
Returns the 3, 7, and 16 bit type code of a cell.
-- Cell: tc3_cons
scheme cons-cell returned by (cons arg1 arg2).
-- Macro: CONSP x
-- Macro: NCONSP x
Returns non-zero if X is a `tc3_cons' or isn't, respectively.
-- Cell: tc3_closure
applicable object returned by (lambda (args) ...). `tc3_closure's
have a pointer to the body of the procedure in the `CAR' and a
pointer to the environment in the `CDR'. Bits 1 and 2
(zero-based) in the `CDR' indicate a lower bound on the number of
required arguments to the closure, which is used to avoid
allocating rest argument lists in the environment cache. This
encoding precludes an immediate value for the `CDR': In the case
of an empty environment all bits above 2 in the `CDR' are zero.
-- Macro: CLOSUREP x
Returns non-zero if X is a `tc3_closure'.
-- Macro: CODE x
-- Macro: ENV x
Returns the code body or environment of closure X,
respectively.
-- Macro: ARGC x
Returns the a lower bound on the number of required arguments
to closure X, it cannot exceed 3.
File: scm.info, Node: Header Cells, Next: Subr Cells, Prev: Cells, Up: Data Types
6.1.3 Header Cells
------------------
"Header"s are Cells whose `CDR's point elsewhere in memory, such as to
memory allocated by `malloc'.
-- Header: spare
spare `tc7' type code
-- Header: tc7_vector
scheme vector.
-- Macro: VECTORP x
-- Macro: NVECTORP x
Returns non-zero if X is a `tc7_vector' or if not,
respectively.
-- Macro: VELTS x
-- Macro: LENGTH x
Returns the C array of `SCM's holding the elements of vector
X or its length, respectively.
-- Header: tc7_ssymbol
static scheme symbol (part of initial system)
-- Header: tc7_msymbol
`malloc'ed scheme symbol (can be GCed)
-- Macro: SYMBOLP x
Returns non-zero if X is a `tc7_ssymbol' or `tc7_msymbol'.
-- Macro: CHARS x
-- Macro: UCHARS x
-- Macro: LENGTH x
Returns the C array of `char's or as `unsigned char's holding
the elements of symbol X or its length, respectively.
-- Header: tc7_string
scheme string
-- Macro: STRINGP x
-- Macro: NSTRINGP x
Returns non-zero if X is a `tc7_string' or isn't,
respectively.
-- Macro: CHARS x
-- Macro: UCHARS x
-- Macro: LENGTH x
Returns the C array of `char's or as `unsigned char's holding
the elements of string X or its length, respectively.
-- Header: tc7_bvect
uniform vector of booleans (bit-vector)
-- Header: tc7_ivect
uniform vector of integers
-- Header: tc7_uvect
uniform vector of non-negative integers
-- Header: tc7_svect
uniform vector of short integers
-- Header: tc7_fvect
uniform vector of short inexact real numbers
-- Header: tc7_dvect
uniform vector of double precision inexact real numbers
-- Header: tc7_cvect
uniform vector of double precision inexact complex numbers
-- Header: tc7_contin
applicable object produced by call-with-current-continuation
-- Header: tc7_specfun
subr that is treated specially within the evaluator
`apply' and `call-with-current-continuation' are denoted by these
objects. Their behavior as functions is built into the evaluator;
they are not directly associated with C functions. This is
necessary in order to make them properly tail recursive.
tc16_cclo is a subtype of tc7_specfun, a cclo is similar to a
vector (and is GCed like one), but can be applied as a function:
1. the cclo itself is consed onto the head of the argument list
2. the first element of the cclo is applied to that list. Cclo
invocation is currently not tail recursive when given 2 or
more arguments.
-- Function: makcclo proc len
makes a closure from the _subr_ PROC with LEN-1 extra
locations for `SCM' data. Elements of a CCLO are referenced
using `VELTS(cclo)[n]' just as for vectors.
-- Macro: CCLO_LENGTH cclo
Expands to the length of CCLO.
File: scm.info, Node: Subr Cells, Next: Ptob Cells, Prev: Header Cells, Up: Data Types
6.1.4 Subr Cells
----------------
A "Subr" is a header whose `CDR' points to a C code procedure. Scheme
primitive procedures are subrs. Except for the arithmetic `tc7_cxr's,
the C code procedures will be passed arguments (and return results) of
type `SCM'.
-- Subr: tc7_asubr
associative C function of 2 arguments. Examples are `+', `-',
`*', `/', `max', and `min'.
-- Subr: tc7_subr_0
C function of no arguments.
-- Subr: tc7_subr_1
C function of one argument.
-- Subr: tc7_cxr
These subrs are handled specially. If inexact numbers are
enabled, the `CDR' should be a function which takes and returns
type `double'. Conversions are handled in the interpreter.
`floor', `ceiling', `truncate', `round', `$sqrt', `$abs', `$exp',
`$log', `$sin', `$cos', `$tan', `$asin', `$acos', `$atan',
`$sinh', `$cosh', `$tanh', `$asinh', `$acosh', `$atanh', and
`exact->inexact' are defined this way.
If the `CDR' is `0' (`NULL'), the name string of the procedure is
used to control traversal of its list structure argument.
`car', `cdr', `caar', `cadr', `cdar', `cddr', `caaar', `caadr',
`cadar', `caddr', `cdaar', `cdadr', `cddar', `cdddr', `caaaar',
`caaadr', `caadar', `caaddr', `cadaar', `cadadr', `caddar',
`cadddr', `cdaaar', `cdaadr', `cdadar', `cdaddr', `cddaar',
`cddadr', `cdddar', and `cddddr' are defined this way.
-- Subr: tc7_subr_3
C function of 3 arguments.
-- Subr: tc7_subr_2
C function of 2 arguments.
-- Subr: tc7_rpsubr
transitive relational predicate C function of 2 arguments. The C
function should return either `BOOL_T' or `BOOL_F'.
-- Subr: tc7_subr_1o
C function of one optional argument. If the optional argument is
not present, `UNDEFINED' is passed in its place.
-- Subr: tc7_subr_2o
C function of 1 required and 1 optional argument. If the optional
argument is not present, `UNDEFINED' is passed in its place.
-- Subr: tc7_lsubr_2
C function of 2 arguments and a list of (rest of) `SCM' arguments.
-- Subr: tc7_lsubr
C function of list of `SCM' arguments.
File: scm.info, Node: Ptob Cells, Next: Smob Cells, Prev: Subr Cells, Up: Data Types
6.1.5 Ptob Cells
----------------
A "ptob" is a port object, capable of delivering or accepting characters.
*Note Ports: (r5rs)Ports. Unlike the types described so far, new
varieties of ptobs can be defined dynamically (*note Defining Ptobs::).
These are the initial ptobs:
-- ptob: tc16_inport
input port.
-- ptob: tc16_outport
output port.
-- ptob: tc16_ioport
input-output port.
-- ptob: tc16_inpipe
input pipe created by `popen()'.
-- ptob: tc16_outpipe
output pipe created by `popen()'.
-- ptob: tc16_strport
String port created by `cwos()' or `cwis()'.
-- ptob: tc16_sfport
Software (virtual) port created by `mksfpt()' (*note Soft Ports::).
-- Macro: PORTP x
-- Macro: OPPORTP x
-- Macro: OPINPORTP x
-- Macro: OPOUTPORTP x
-- Macro: INPORTP x
-- Macro: OUTPORTP x
Returns non-zero if X is a port, open port, open input-port, open
output-port, input-port, or output-port, respectively.
-- Macro: OPENP x
-- Macro: CLOSEDP x
Returns non-zero if port X is open or closed, respectively.
-- Macro: STREAM x
Returns the `FILE *' stream for port X.
Ports which are particularly well behaved are called "fport"s.
Advanced operations like `file-position' and `reopen-file' only work
for fports.
-- Macro: FPORTP x
-- Macro: OPFPORTP x
-- Macro: OPINFPORTP x
-- Macro: OPOUTFPORTP x
Returns non-zero if X is a port, open port, open input-port, or
open output-port, respectively.
File: scm.info, Node: Smob Cells, Next: Data Type Representations, Prev: Ptob Cells, Up: Data Types
6.1.6 Smob Cells
----------------
A "smob" is a miscellaneous datatype. The type code and GCMARK bit occupy
the lower order 16 bits of the `CAR' half of the cell. The rest of the
`CAR' can be used for sub-type or other information. The `CDR'
contains data of size long and is often a pointer to allocated memory.
Like ptobs, new varieties of smobs can be defined dynamically (*note
Defining Smobs::). These are the initial smobs:
-- smob: tc_free_cell
unused cell on the freelist.
-- smob: tc16_flo
single-precision float.
Inexact number data types are subtypes of type `tc16_flo'. If the
sub-type is:
0. a single precision float is contained in the `CDR'.
1. `CDR' is a pointer to a `malloc'ed double.
3. `CDR' is a pointer to a `malloc'ed pair of doubles.
-- smob: tc_dblr
double-precision float.
-- smob: tc_dblc
double-precision complex.
-- smob: tc16_bigpos
-- smob: tc16_bigneg
positive and negative bignums, respectively.
Scm has large precision integers called bignums. They are stored
in sign-magnitude form with the sign occuring in the type code of
the SMOBs bigpos and bigneg. The magnitude is stored as a
`malloc'ed array of type `BIGDIG' which must be an unsigned
integral type with size smaller than `long'. `BIGRAD' is the
radix associated with `BIGDIG'.
`NUMDIGS_MAX' (defined in `scmfig.h') limits the number of digits
of a bignum to 1000. These digits are base `BIGRAD', which is
typically 65536, giving 4816 decimal digits.
Why only 4800 digits? The simple multiplication algorithm SCM
uses is O(n^2); this means the number of processor instructions
required to perform a multiplication is _some multiple_ of the
product of the number of digits of the two multiplicands.
digits * digits ==> operations
5 x
50 100 * x
500 10000 * x
5000 1000000 * x
To calculate numbers larger than this, FFT multiplication
[O(n*log(n))] and other specialized algorithms are required. You
should obtain a package which specializes in number-theoretical
calculations:
`ftp://megrez.math.u-bordeaux.fr/pub/pari/'
-- smob: tc16_promise
made by DELAY. *Note Control features: (r5rs)Control features.
-- smob: tc16_arbiter
synchronization object. *Note Process Synchronization::.
-- smob: tc16_macro
macro expanding function. *Note Macro Primitives::.
-- smob: tc16_array
multi-dimensional array. *Note Arrays::.
This type implements both conventional arrays (those with
arbitrary data as elements *note Conventional Arrays::) and
uniform arrays (those with elements of a uniform type *note
Uniform Array::).
Conventional Arrays have a pointer to a vector for their `CDR'.
Uniform Arrays have a pointer to a Uniform Vector type (string,
bvect, ivect, uvect, fvect, dvect, or cvect) in their `CDR'.
File: scm.info, Node: Data Type Representations, Prev: Smob Cells, Up: Data Types
6.1.7 Data Type Representations
-------------------------------
IMMEDIATE: B,D,E,F=data bit, C=flag code, P=pointer address bit
................................
inum BBBBBBBBBBBBBBBBBBBBBBBBBBBBBB10
ichr BBBBBBBBBBBBBBBBBBBBBBBB11110100
iflag CCCCCCC101110100
isym CCCCCCC001110100
IMCAR: only in car of evaluated code, cdr has cell's GC bit
ispcsym 000CCCC00CCCC100
iloc 0DDDDDDDDDDDEFFFFFFFFFFF11111100
pointer PPPPPPPPPPPPPPPPPPPPPPPPPPPPP000
gloc PPPPPPPPPPPPPPPPPPPPPPPPPPPPP001
HEAP CELL: G=gc_mark; 1 during mark, 0 other times.
1s and 0s here indicate type. G missing means sys (not GC'd)
SIMPLE
cons ..........SCM car..............0 ...........SCM cdr.............G
closure ..........SCM code...........011 ...........SCM env...........CCG
HEADERs:
ssymbol .........long length....G0000101 ..........char *chars...........
msymbol .........long length....G0000111 ..........char *chars...........
string .........long length....G0001101 ..........char *chars...........
vector .........long length....G0001111 ...........SCM **elts...........
bvect .........long length....G0010101 ..........long *words...........
spare G0010111
ivect .........long length....G0011101 ..........long *words...........
uvect .........long length....G0011111 ......unsigned long *words......
spare G0100101
svect .........long length....G0100111 ........ short *words...........
fvect .........long length....G0101101 .........float *words...........
dvect .........long length....G0101111 ........double *words...........
cvect .........long length....G0110101 ........double *words...........
contin .........long length....G0111101 .............*regs..............
specfun ................xxxxxxxxG1111111 ...........SCM name.............
cclo ..short length..xxxxxx10G1111111 ...........SCM **elts...........
PTOBs
port int portnum.CwroxxxxxxxxG0110111 ..........FILE *stream..........
socket int portnum.C001xxxxxxxxG0110111 ..........FILE *stream..........
inport int portnum.C011xxxxxxxxG0110111 ..........FILE *stream..........
outport int portnum.0101xxxxxxxxG0110111 ..........FILE *stream..........
ioport int portnum.C111xxxxxxxxG0110111 ..........FILE *stream..........
fport int portnum.C 00000000G0110111 ..........FILE *stream..........
pipe int portnum.C 00000001G0110111 ..........FILE *stream..........
strport 00000000000.0 00000010G0110111 ..........FILE *stream..........
sfport int portnum.C 00000011G0110111 ..........FILE *stream..........
SUBRs
spare 010001x1
spare 010011x1
subr_0 ..........int hpoff.....01010101 ...........SCM (*f)()...........
subr_1 ..........int hpoff.....01010111 ...........SCM (*f)()...........
cxr ..........int hpoff.....01011101 .........double (*f)()..........
subr_3 ..........int hpoff.....01011111 ...........SCM (*f)()...........
subr_2 ..........int hpoff.....01100101 ...........SCM (*f)()...........
asubr ..........int hpoff.....01100111 ...........SCM (*f)()...........
subr_1o ..........int hpoff.....01101101 ...........SCM (*f)()...........
subr_2o ..........int hpoff.....01101111 ...........SCM (*f)()...........
lsubr_2 ..........int hpoff.....01110101 ...........SCM (*f)()...........
lsubr ..........int hpoff.....01110111 ...........SCM (*f)()...........
rpsubr ..........int hpoff.....01111101 ...........SCM (*f)()...........
SMOBs
free_cell
000000000000000000000000G1111111 ...........*free_cell........000
flo 000000000000000000000001G1111111 ...........float num............
dblr 000000000000000100000001G1111111 ..........double *real..........
dblc 000000000000001100000001G1111111 .........complex *cmpx..........
bignum ...int length...0000001 G1111111 .........short *digits..........
bigpos ...int length...00000010G1111111 .........short *digits..........
bigneg ...int length...00000011G1111111 .........short *digits..........
xxxxxxxx = code assigned by newsmob();
promise 000000000000000fxxxxxxxxG1111111 ...........SCM val..............
arbiter 000000000000000lxxxxxxxxG1111111 ...........SCM name.............
macro 000000000000000mxxxxxxxxG1111111 ...........SCM name.............
array ...short rank..cxxxxxxxxG1111111 ............*array..............
File: scm.info, Node: Operations, Next: Program Self-Knowledge, Prev: Data Types, Up: The Implementation
6.2 Operations
==============
* Menu:
* Garbage Collection:: Automatically reclaims unused storage
* Memory Management for Environments::
* Signals::
* C Macros::
* Changing Scm::
* Defining Subrs::
* Defining Smobs::
* Defining Ptobs::
* Allocating memory::
* Embedding SCM:: In other programs
* Callbacks::
* Type Conversions:: For use with C code.
* Continuations:: For C and SCM
* Evaluation:: Why SCM is fast
File: scm.info, Node: Garbage Collection, Next: Memory Management for Environments, Prev: Operations, Up: Operations
6.2.1 Garbage Collection
------------------------
The garbage collector is in the latter half of `sys.c'. The primary
goal of "garbage collection" (or "GC") is to recycle those cells no
longer in use. Immediates always appear as parts of other objects, so
they are not subject to explicit garbage collection.
All cells reside in the "heap" (composed of "heap segments"). Note
that this is different from what Computer Science usually defines as a
heap.
* Menu:
* Marking Cells::
* Sweeping the Heap::
File: scm.info, Node: Marking Cells, Next: Sweeping the Heap, Prev: Garbage Collection, Up: Garbage Collection
6.2.1.1 Marking Cells
.....................
The first step in garbage collection is to "mark" all heap objects in
use. Each heap cell has a bit reserved for this purpose. For pairs
(cons cells) the lowest order bit (0) of the CDR is used. For other
types, bit 8 of the CAR is used. The GC bits are never set except
during garbage collection. Special C macros are defined in `scm.h' to
allow easy manipulation when GC bits are possibly set. `CAR', `TYP3',
and `TYP7' can be used on GC marked cells as they are.
-- Macro: GCCDR x
Returns the CDR of a cons cell, even if that cell has been GC
marked.
-- Macro: GCTYP16 x
Returns the 16 bit type code of a cell.
We need to (recursively) mark only a few objects in order to assure that
all accessible objects are marked. Those objects are `sys_protects[]'
(for example, `dynwinds'), the current C-stack and the hash table for
symbols, "symhash".
-- Function: void gc_mark (SCM OBJ)
The function `gc_mark()' is used for marking SCM cells. If OBJ is
marked, `gc_mark()' returns. If OBJ is unmarked, gc_mark sets the
mark bit in OBJ, then calls `gc_mark()' on any SCM components of
OBJ. The last call to `gc_mark()' is tail-called (looped).
-- Function: void mark_locations (STACKITEM X[], sizet LEN))
The function `mark_locations' is used for marking segments of
C-stack or saved segments of C-stack (marked continuations). The
argument LEN is the size of the stack in units of size
`(STACKITEM)'.
Each longword in the stack is tried to see if it is a valid cell
pointer into the heap. If it is, the object itself and any
objects it points to are marked using `gc_mark'. If the stack is
word rather than longword aligned `(#define WORD_ALIGN)', both
alignments are tried. This arrangement will occasionally mark an
object which is no longer used. This has not been a problem in
practice and the advantage of using the c-stack far outweighs it.
File: scm.info, Node: Sweeping the Heap, Prev: Marking Cells, Up: Garbage Collection
6.2.1.2 Sweeping the Heap
.........................
After all found objects have been marked, the heap is swept.
The storage for strings, vectors, continuations, doubles, complexes, and
bignums is managed by malloc. There is only one pointer to each malloc
object from its type-header cell in the heap. This allows malloc
objects to be freed when the associated heap object is garbage
collected.
-- Function: static void gc_sweep ()
The function `gc_sweep' scans through all heap segments. The mark
bit is cleared from marked cells. Unmarked cells are spliced into
FREELIST, where they can again be returned by invocations of
`NEWCELL'.
If a type-header cell pointing to malloc space is unmarked, the
malloc object is freed. If the type header of smob is collected,
the smob's `free' procedure is called to free its storage.
File: scm.info, Node: Memory Management for Environments, Next: Signals, Prev: Garbage Collection, Up: Operations
6.2.2 Memory Management for Environments
----------------------------------------
* "Ecache" was designed and implemented by Radey Shouman.
* This documentation of ecache was written by Tom Lord.
The memory management component of SCM contains special features which
optimize the allocation and garbage collection of environments.
The optimizations are based on certain facts and assumptions:
The SCM evaluator creates many environments with short lifetimes and
these account of a _large portion_ of the total number of objects
allocated.
The general purpose allocator allocates objects from a freelist, and
collects using a mark/sweep algorithm. Research into garbage
collection suggests that such an allocator is sub-optimal for object
populations containing a large portion of short-lived members and that
allocation strategies involving a copying collector are more
appropriate.
It is a property of SCM, reflected throughout the source code, that a
simple copying collector can not be used as the general purpose memory
manager: much code assumes that the run-time stack can be treated as a
garbage collection root set using "conservative garbage collection"
techniques, which are incompatible with objects that change location.
Nevertheless, it is possible to use a mostly-separate
copying-collector, just for environments. Roughly speaking, cons pairs
making up environments are initially allocated from a small heap that
is collected by a precise copying collector. These objects must be
handled specially for the collector to work. The (presumably) small
number of these objects that survive one collection of the copying heap
are copied to the general purpose heap, where they will later be
collected by the mark/sweep collector. The remaining pairs are more
rapidly collected than they would otherwise be and all of this
collection is accomplished without having to mark or sweep any other
segment of the heap.
Allocating cons pairs for environments from this special heap is a
heuristic that approximates the (unachievable) goal:
allocate all short-lived objects from the copying-heap, at no
extra cost in allocation time.
Implementation Details
......................
A separate heap (`ecache_v') is maintained for the copying collector.
Pairs are allocated from this heap in a stack-like fashion. Objects in
this heap may be protected from garbage collection by:
1. Pushing a reference to the object on a stack specially maintained
for that purpose. This stack (`scm_estk') is used in place of the
C run-time stack by the SCM evaluator to hold local variables
which refer to the copying heap.
2. Saving a reference to every object in the mark/sweep heap which
directly references the copying heap in a root set that is
specially maintained for that purpose (`scm_egc_roots'). If no
object in the mark/sweep heap directly references an object from
the copying heap, that object can be preserved by storing a direct
reference to it in the copying-collector root set.
3. Keeping no other references to these objects, except references
between the objects themselves, during copying collection.
When the copying heap or root-set becomes full, the copying collector is
invoked. All protected objects are copied to the mark-sweep heap. All
references to those objects are updated. The copying collector root-set
and heap are emptied.
References to pairs allocated specificly for environments are
inaccessible to the Scheme procedures evaluated by SCM. These pairs
are manipulated by only a small number of code fragments in the
interpreter. To support copying collection, those code fragments
(mostly in `eval.c') have been modified to protect environments from
garbage collection using the three rules listed above.
During a mark-sweep collection, the copying collector heap is marked
and swept almost like any ordinary segment of the general purpose heap.
The only difference is that pairs from the copying heap that become
free during a sweep phase are not added to the freelist.
The environment cache is disabled by adding `#define NO_ENV_CACHE' to
`eval.c'; all environment cells are then allocated from the regular
heap.
Relation to Other Work
......................
This work seems to build upon a considerable amount of previous work
into garbage collection techniques about which a considerable amount of
literature is available.
File: scm.info, Node: Signals, Next: C Macros, Prev: Memory Management for Environments, Up: Operations
6.2.3 Signals
-------------
-- Function: init_signals
(in `scm.c') initializes handlers for `SIGINT' and `SIGALRM' if
they are supported by the C implementation. All of the signal
handlers immediately reestablish themselves by a call to
`signal()'.
-- Function: int_signal sig
-- Function: alrm_signal sig
The low level handlers for `SIGINT' and `SIGALRM'.
If an interrupt handler is defined when the interrupt is received, the
code is interpreted. If the code returns, execution resumes from where
the interrupt happened. `Call-with-current-continuation' allows the
stack to be saved and restored.
SCM does not use any signal masking system calls. These are not a
portable feature. However, code can run uninterrupted by use of the C
macros `DEFER_INTS' and `ALLOW_INTS'.
-- Macro: DEFER_INTS
sets the global variable `ints_disabled' to 1. If an interrupt
occurs during a time when `ints_disabled' is 1, then
`deferred_proc' is set to non-zero, one of the global variables
`SIGINT_deferred' or `SIGALRM_deferred' is set to 1, and the
handler returns.
-- Macro: ALLOW_INTS
Checks the deferred variables and if set the appropriate handler is
called.
Calls to `DEFER_INTS' can not be nested. An `ALLOW_INTS' must
happen before another `DEFER_INTS' can be done. In order to check
that this constraint is satisfied `#define CAREFUL_INTS' in
`scmfig.h'.
File: scm.info, Node: C Macros, Next: Changing Scm, Prev: Signals, Up: Operations
6.2.4 C Macros
--------------
-- Macro: ASRTER cond arg pos subr
signals an error if the expression (COND) is 0. ARG is the
offending object, SUBR is the string naming the subr, and POS
indicates the position or type of error. POS can be one of
* `ARGn' (> 5 or unknown ARG number)
* `ARG1'
* `ARG2'
* `ARG3'
* `ARG4'
* `ARG5'
* `WNA' (wrong number of args)
* `OVFLOW'
* `OUTOFRANGE'
* `NALLOC'
* `EXIT'
* `HUP_SIGNAL'
* `INT_SIGNAL'
* `FPE_SIGNAL'
* `BUS_SIGNAL'
* `SEGV_SIGNAL'
* `ALRM_SIGNAL'
* a C string `(char *)'
Error checking is not done by `ASRTER' if the flag `RECKLESS' is
defined. An error condition can still be signaled in this case
with a call to `wta(arg, pos, subr)'.
-- Macro: ASRTGO cond label
`goto' LABEL if the expression (COND) is 0. Like `ASRTER',
`ASRTGO' does is not active if the flag `RECKLESS' is defined.
File: scm.info, Node: Changing Scm, Next: Defining Subrs, Prev: C Macros, Up: Operations
6.2.5 Changing Scm
------------------
When writing C-code for SCM, a precaution is recommended. If your
routine allocates a non-cons cell which will _not_ be incorporated into
a `SCM' object which is returned, you need to make sure that a `SCM'
variable in your routine points to that cell as long as part of it
might be referenced by your code.
In order to make sure this `SCM' variable does not get optimized out
you can put this assignment after its last possible use:
SCM_dummy1 = foo;
or put this assignment somewhere in your routine:
SCM_dummy1 = (SCM) &foo;
`SCM_dummy' variables are not currently defined. Passing the address
of the local `SCM' variable to _any_ procedure also protects it. The
procedure `scm_protect_temp' is provided for this purpose.
-- Function: void scm_protect_temp (SCM *PTR)
Forces the SCM object PTR to be saved on the C-stack, where it
will be traced for GC.
Also, if you maintain a static pointer to some (non-immediate) `SCM'
object, you must either make your pointer be the value cell of a symbol
(see `errobj' for an example) or (permanently) add your pointer to
`sys_protects' using:
-- Function: SCM scm_gc_protect (SCM OBJ)
Permanently adds OBJ to a table of objects protected from garbage
collection. `scm_gc_protect' returns OBJ.
To add a C routine to scm:
1. choose the appropriate subr type from the type list.
2. write the code and put into `scm.c'.
3. add a `make_subr' or `make_gsubr' call to `init_scm'. Or put an
entry into the appropriate `iproc' structure.
To add a package of new procedures to scm (see `crs.c' for example):
1. create a new C file (`foo.c').
2. at the front of `foo.c' put declarations for strings for your
procedure names.
static char s_twiddle_bits[]="twiddle-bits!";
static char s_bitsp[]="bits?";
3. choose the appropriate subr types from the type list in `code.doc'.
4. write the code for the procedures and put into `foo.c'
5. create one `iproc' structure for each subr type used in `foo.c'
static iproc subr3s[]= {
{s_twiddle-bits,twiddle-bits},
{s_bitsp,bitsp},
{0,0} };
6. create an `init_<name of file>' routine at the end of the file
which calls `init_iprocs' with the correct type for each of the
`iproc's created in step 5.
void init_foo()
{
init_iprocs(subr1s, tc7_subr_1);
init_iprocs(subr3s, tc7_subr_3);
}
If your package needs to have a "finalization" routine called to
free up storage, close files, etc, then also have a line in
`init_foo' like:
add_final(final_foo);
`final_foo' should be a (void) procedure of no arguments. The
finals will be called in opposite order from their definition.
The line:
add_feature("foo");
will append a symbol `'foo' to the (list) value of `*features*'.
7. put any scheme code which needs to be run as part of your package
into `Ifoo.scm'.
8. put an `if' into `Init5e2.scm' which loads `Ifoo.scm' if your |
package is included:
(if (defined? twiddle-bits!)
(load (in-vicinity (implementation-vicinity)
"Ifoo"
(scheme-file-suffix))))
or use `(provided? 'foo)' instead of `(defined? twiddle-bits!)'
if you have added the feature.
9. put documentation of the new procedures into `foo.doc'
10. add lines to your `Makefile' to compile and link SCM with your
object file. Add a `init_foo\(\)\;' to the `INITS=...' line at
the beginning of the makefile.
These steps should allow your package to be linked into SCM with a
minimum of difficulty. Your package should also work with dynamic
linking if your SCM has this capability.
Special forms (new syntax) can be added to scm.
1. define a new `MAKISYM' in `scm.h' and increment `NUM_ISYMS'.
2. add a string with the new name in the corresponding place in
`isymnames' in `repl.c'.
3. add `case' clause to `ceval()' near `i_quasiquote' (in `eval.c').
New syntax can now be added without recompiling SCM by the use of the
`procedure->syntax', `procedure->macro', `procedure->memoizing-macro',
and `defmacro'. For details, *Note Syntax::.
File: scm.info, Node: Defining Subrs, Next: Defining Smobs, Prev: Changing Scm, Up: Operations
6.2.6 Defining Subrs
--------------------
If "CCLO" is `#define'd when compiling, the compiled closure feature
will be enabled. It is automatically enabled if dynamic linking is
enabled.
The SCM interpreter directly recognizes subrs taking small numbers of
arguments. In order to create subrs taking larger numbers of arguments
use:
-- Function: make_gsubr name req opt rest fcn
returns a cclo (compiled closure) object of name `char *' NAME
which takes `int' REQ required arguments, `int' OPT optional
arguments, and a list of rest arguments if `int' REST is 1 (0 for
not).
`SCM (*fcn)()' is a pointer to a C function to do the work.
The C function will always be called with REQ + OPT + REST
arguments, optional arguments not supplied will be passed
`UNDEFINED'. An error will be signaled if the subr is called with
too many or too few arguments. Currently a total of 10 arguments
may be specified, but increasing this limit should not be
difficult.
/* A silly example, taking 2 required args,
1 optional, and a list of rest args */
#include <scm.h>
SCM gsubr_21l(req1,req2,opt,rst)
SCM req1,req2,opt,rst;
{
lputs("gsubr-2-1-l:\n req1: ", cur_outp);
display(req1,cur_outp);
lputs("\n req2: ", cur_outp);
display(req2,cur_outp);
lputs("\n opt: ", cur_outp);
display(opt,cur_outp);
lputs("\n rest: ", cur_outp);
display(rst,cur_outp);
newline(cur_outp);
return UNSPECIFIED;
}
void init_gsubr211()
{
make_gsubr("gsubr-2-1-l", 2, 1, 1, gsubr_21l);
}
File: scm.info, Node: Defining Smobs, Next: Defining Ptobs, Prev: Defining Subrs, Up: Operations
6.2.7 Defining Smobs
--------------------
Here is an example of how to add a new type named `foo' to SCM. The
following lines need to be added to your code:
`long tc16_foo;'
The type code which will be used to identify the new type.
`static smobfuns foosmob = {markfoo,freefoo,printfoo,equalpfoo};'
smobfuns is a structure composed of 4 functions:
typedef struct {
SCM (*mark)P((SCM));
sizet (*free)P((CELLPTR));
int (*print)P((SCM exp, SCM port, int writing));
SCM (*equalp)P((SCM, SCM));
} smobfuns;
`smob.mark'
is a function of one argument of type `SCM' (the cell to
mark) and returns type `SCM' which will then be marked. If
no further objects need to be marked then return an immediate
object such as `BOOL_F'. The smob cell itself will already
have been marked. _Note_ This is different from SCM versions
prior to 5c5. Only additional data specific to a smob type
need be marked by `smob.mark'.
2 functions are provided:
`markcdr(ptr)'
returns `CDR(ptr)'.
`mark0(ptr)'
is a no-op used for smobs containing no additional `SCM'
data. 0 may also be used in this case.
`smob.free'
is a function of one argument of type `CELLPTR' (the cell to
collected) and returns type `sizet' which is the number of
`malloc'ed bytes which were freed. `Smob.free' should free
any `malloc'ed storage associated with this object. The
function free0(ptr) is provided which does not free any
storage and returns 0.
`smob.print'
is 0 or a function of 3 arguments. The first, of type `SCM',
is the smob object. The second, of type `SCM', is the stream
on which to write the result. The third, of type int, is 1
if the object should be `write'n, 0 if it should be
`display'ed, and 2 if it should be `write'n for an error
report. This function should return non-zero if it printed,
and zero otherwise (in which case a hexadecimal number will
be printed).
`smob.equalp'
is 0 or a function of 2 `SCM' arguments. Both of these
arguments will be of type `tc16foo'. This function should
return `BOOL_T' if the smobs are equal, `BOOL_F' if they are
not. If `smob.equalp' is 0, `equal?' will return `BOOL_F' if
they are not `eq?'.
`tc16_foo = newsmob(&foosmob);'
Allocates the new type with the functions from `foosmob'. This
line goes in an `init_' routine.
Promises and macros in `eval.c' and arbiters in `repl.c' provide
examples of SMOBs. There are a maximum of 256 SMOBs. Smobs that must
allocate blocks of memory should use, for example, `must_malloc' rather
than `malloc' *Note Allocating memory::.
File: scm.info, Node: Defining Ptobs, Next: Allocating memory, Prev: Defining Smobs, Up: Operations
6.2.8 Defining Ptobs
--------------------
"ptob"s are similar to smobs but define new types of port to which SCM
procedures can read or write. The following functions are defined in
the `ptobfuns':
typedef struct {
SCM (*mark)P((SCM ptr));
int (*free)P((FILE *p));
int (*print)P((SCM exp, SCM port, int writing));
SCM (*equalp)P((SCM, SCM));
int (*fputc)P((int c, FILE *p));
int (*fputs)P((char *s, FILE *p));
sizet (*fwrite)P((char *s, sizet siz, sizet num, FILE *p));
int (*fflush)P((FILE *stream));
int (*fgetc)P((FILE *p));
int (*fclose)P((FILE *p));
} ptobfuns;
The `.free' component to the structure takes a `FILE *' or other C
construct as its argument, unlike `.free' in a smob, which takes the
whole smob cell. Often, `.free' and `.fclose' can be the same
function. See `fptob' and `pipob' in `sys.c' for examples of how to
define ptobs. Ptobs that must allocate blocks of memory should use,
for example, `must_malloc' rather than `malloc' *Note Allocating
memory::.
File: scm.info, Node: Allocating memory, Next: Embedding SCM, Prev: Defining Ptobs, Up: Operations
6.2.9 Allocating memory
-----------------------
SCM maintains a count of bytes allocated using malloc, and calls the
garbage collector when that number exceeds a dynamically managed limit.
In order for this to work properly, `malloc' and `free' should not be
called directly to manage memory freeable by garbage collection. The
following functions are provided for that purpose:
-- Function: SCM must_malloc_cell (long LEN, SCM C, char *WHAT)
-- Function: char * must_malloc (long LEN, char *WHAT)
LEN is the number of bytes that should be allocated, WHAT is a
string to be used in error or gc messages. `must_malloc' returns
a pointer to newly allocated memory. `must_malloc_cell' returns a
newly allocated cell whose `car' is C and whose `cdr' is a pointer
to newly allocated memory.
-- Function: void must_realloc_cell (SCM Z, long OLEN, long LEN, char
*WHAT)
-- Function: char * must_realloc (char *WHERE, long OLEN, long LEN,
char *WHAT)
`must_realloc_cell' takes as argument Z a cell whose `cdr' should
be a pointer to a block of memory of length OLEN allocated with
`must_malloc_cell' and modifies the `cdr' to point to a block of
memory of length LEN. `must_realloc' takes as argument WHERE the
address of a block of memory of length OLEN allocated by
`must_malloc' and returns the address of a block of length LEN.
The contents of the reallocated block will be unchanged up to the
minimum of the old and new sizes.
WHAT is a pointer to a string used for error and gc messages.
`must_malloc', `must_malloc_cell', `must_realloc', and
`must_realloc_cell' must be called with interrupts deferred *Note
Signals::. `must_realloc' and `must_realloc_cell' must not be called
during initialization (non-zero errjmp_bad) - the initial allocations
must be large enough.
-- Function: void must_free (char *PTR, sizet LEN)
`must_free' is used to free a block of memory allocated by the
above functions and pointed to by PTR. LEN is the length of the
block in bytes, but this value is used only for debugging purposes.
If it is difficult or expensive to calculate then zero may be used
instead.
File: scm.info, Node: Embedding SCM, Next: Callbacks, Prev: Allocating memory, Up: Operations
6.2.10 Embedding SCM
--------------------
The file `scmmain.c' contains the definition of main(). When SCM is
compiled as a library `scmmain.c' is not included in the library; a
copy of `scmmain.c' can be modified to use SCM as an embedded library
module.
-- Function: int main (int ARGC, char **ARGV)
This is the top level C routine. The value of the ARGC argument
is the number of command line arguments. The ARGV argument is a
vector of C strings; its elements are the individual command line
argument strings. A null pointer always follows the last element:
`ARGV[ARGC]' is this null pointer.
-- Variable: char *execpath
This string is the pathname of the executable file being run. This
variable can be examined and set from Scheme (*note Internal
State::). EXECPATH must be set to executable's path in order to
use DUMP (*note Dump::) or DLD.
Rename main() and arrange your code to call it with an ARGV which sets
up SCM as you want it.
If you need more control than is possible through ARGV, here are
descriptions of the functions which main() calls.
-- Function: void init_sbrk (void)
Call this before SCM calls malloc(). Value returned from sbrk()
is used to gauge how much storage SCM uses.
-- Function: char * scm_find_execpath (int ARGC, char **ARGV, char
*SCRIPT_ARG)
ARGC and ARGV are as described in main(). SCRIPT_ARG is the
pathname of the SCSH-style script (*note Scripting::) being
invoked; 0 otherwise. `scm_find_execpath' returns the pathname of
the executable being run; if `scm_find_execpath' cannot determine
the pathname, then it returns 0.
`scm_find_implpath' is defined in `scmmain.c'. Preceeding this are
definitions ofGENERIC_NAME and INIT_GETENV. These, along with IMPLINIT
and DIRSEP control scm_find_implpath()'s operation.
If your application has an easier way to locate initialization code for
SCM, then you can replace `scm_find_implpath'.
-- Function: char * scm_find_implpath (char *EXECPATH)
Returns the full pathname of the Scheme initialization file or 0
if it cannot find it.
The string value of the preprocessor variable INIT_GETENV names an
environment variable (default `"SCM_INIT_PATH"'). If this
environment variable is defined, its value will be returned from
`scm_find_implpath'. Otherwise find_impl_file() is called with the
arguments EXECPATH, GENERIC_NAME (default "scm"), INIT_FILE_NAME
(default "Init5e2_scm"), and the directory separator string |
DIRSEP. If find_impl_file() returns 0 and IMPLINIT is defined,
then a copy of the string IMPLINIT is returned.
-- Function: int init_buf0 (FILE *INPORT)
Tries to determine whether INPORT (usually stdin) is an
interactive input port which should be used in an unbuffered mode.
If so, INPORT is set to unbuffered and non-zero is returned.
Otherwise, 0 is returned.
`init_buf0' should be called before any input is read from INPORT.
Its value can be used as the last argument to
scm_init_from_argv().
-- Function: void scm_init_from_argv (int ARGC, char **ARGV, char
*SCRIPT_ARG, int IVERBOSE, int BUF0STDIN)
Initializes SCM storage and creates a list of the argument strings
PROGRAM-ARGUMENTS from ARGV. ARGC and ARGV must already be
processed to accomodate Scheme Scripts (if desired). The scheme
variable *SCRIPT* is set to the string SCRIPT_ARG, or #f if
SCRIPT_ARG is 0. IVERBOSE is the initial prolixity level. If
BUF0STDIN is non-zero, stdin is treated as an unbuffered port.
Call `init_signals' and `restore_signals' only if you want SCM to
handle interrupts and signals.
-- Function: void init_signals (void)
Initializes handlers for `SIGINT' and `SIGALRM' if they are
supported by the C implementation. All of the signal handlers
immediately reestablish themselves by a call to `signal()'.
-- Function: void restore_signals (void)
Restores the handlers in effect when `init_signals' was called.
-- Function: SCM scm_top_level (char *INITPATH, SCM (*toplvl_fun)())
This is SCM's top-level. Errors longjmp here. TOPLVL_FUN is a
callback function of zero arguments that is called by
`scm_top_level' to do useful work - if zero, then `repl', which
implements a read-eval-print loop, is called.
If TOPLVL_FUN returns, then `scm_top_level' will return as well.
If the return value of TOPLVL_FUN is an immediate integer then it
will be used as the return value of `scm_top_level'. In the main
function supplied with SCM, this return value is the exit status
of the process.
If the first character of string INITPATH is `;', `(' or
whitespace, then scm_ldstr() is called with INITPATH to initialize
SCM; otherwise INITPATH names a file of Scheme code to be loaded
to initialize SCM.
When a Scheme error is signaled; control will pass into
`scm_top_level' by `longjmp', error messages will be printed to
`current-error-port', and then TOPLVL_FUN will be called again.
TOPLVL_FUN must maintain enough state to prevent errors from being
resignalled. If `toplvl_fun' can not recover from an error
situation it may simply return.
-- Function: void final_scm (int FREEALL)
Calls all finalization routines registered with add_final(). If
FREEALL is non-zero, then all memory which SCM allocated with
malloc() will be freed.
You can call indivdual Scheme procedures from C code in the TOPLVL_FUN
argument passed to scm_top_level(), or from module subrs (registered by
an `init_' function, *note Changing Scm::).
Use `apply' to call Scheme procedures from your C code. For example:
/* If this apply fails, SCM will catch the error */
apply(CDR(intern("srv:startup",sizeof("srv:startup")-1)),
mksproc(srvproc),
listofnull);
func = CDR(intern(rpcname,strlen(rpcname)));
retval = apply(func, cons(mksproc(srvproc), args), EOL);
Functions for loading Scheme files and evaluating Scheme code given as
C strings are described in the next section, (*note Callbacks::).
Here is a minimal embedding program `libtest.c':
/* gcc -o libtest libtest.c libscm.a -ldl -lm -lc */
#include "scm.h"
/* include patchlvl.h for SCM's INIT_FILE_NAME. */
#include "patchlvl.h"
void libtest_init_user_scm()
{
fputs("This is libtest_init_user_scm\n", stderr); fflush(stderr);
sysintern("*the-string*", makfrom0str("hello world\n"));
}
SCM user_main()
{
static int done = 0;
if (done++) return MAKINUM(EXIT_FAILURE);
scm_ldstr("(display *the-string*)");
return MAKINUM(EXIT_SUCCESS);
}
int main(argc, argv)
int argc;
const char **argv; |
{
SCM retval;
char *implpath, *execpath;
init_user_scm = libtest_init_user_scm;
execpath = dld_find_executable(argv[0]);
fprintf(stderr, "dld_find_executable(%s): %s\n", argv[0], execpath);
implpath = find_impl_file(execpath, "scm", INIT_FILE_NAME, dirsep);
fprintf(stderr, "implpath: %s\n", implpath);
scm_init_from_argv(argc, argv, 0L, 0, 0);
retval = scm_top_level(implpath, user_main);
final_scm(!0);
return (int)INUM(retval);
}
-|
dld_find_executable(./libtest): /home/jaffer/scm/libtest
implpath: /home/jaffer/scm/Init5e2.scm |
This is libtest_init_user_scm
hello world
File: scm.info, Node: Callbacks, Next: Type Conversions, Prev: Embedding SCM, Up: Operations
6.2.11 Callbacks
----------------
SCM now has routines to make calling back to Scheme procedures easier.
The source code for these routines are found in `rope.c'.
-- Function: int scm_ldfile (char *FILE)
Loads the Scheme source file FILE. Returns 0 if successful, non-0
if not. This function is used to load SCM's initialization file
`Init5e2.scm'. |
-- Function: int scm_ldprog (char *FILE)
Loads the Scheme source file `(in-vicinity (program-vicinity)
FILE)'. Returns 0 if successful, non-0 if not.
This function is useful for compiled code init_ functions to load
non-compiled Scheme (source) files. `program-vicinity' is the
directory from which the calling code was loaded (*note Vicinity:
(slib)Vicinity.).
-- Function: SCM scm_evstr (char *STR)
Returns the result of reading an expression from STR and
evaluating it.
-- Function: void scm_ldstr (char *STR)
Reads and evaluates all the expressions from STR.
If you wish to catch errors during execution of Scheme code, then you
can use a wrapper like this for your Scheme procedures:
(define (srv:protect proc)
(lambda args
(define result #f) ; put default value here
(call-with-current-continuation
(lambda (cont)
(dynamic-wind (lambda () #t)
(lambda ()
(set! result (apply proc args))
(set! cont #f))
(lambda ()
(if cont (cont #f))))))
result))
Calls to procedures so wrapped will return even if an error occurs.
File: scm.info, Node: Type Conversions, Next: Continuations, Prev: Callbacks, Up: Operations
6.2.12 Type Conversions
-----------------------
These type conversion functions are very useful for connecting SCM and C
code. Most are defined in `rope.c'.
-- Function: SCM long2num (long N)
-- Function: SCM ulong2num (unsigned long N)
Return an object of type `SCM' corresponding to the `long' or
`unsigned long' argument N. If N cannot be converted, `BOOL_F' is
returned. Which numbers can be converted depends on whether SCM
was compiled with the `BIGDIG' or `FLOATS' flags.
To convert integer numbers of smaller types (`short' or `char'),
use the macro `MAKINUM(n)'.
-- Function: long num2long (SCM NUM, char *POS, char *S_CALLER)
-- Function: unsigned long num2ulong (SCM NUM, char *POS, char
*S_CALLER)
-- Function: short num2short (SCM NUM, char *POS, char *S_CALLER)
-- Function: unsigned short num2ushort (SCM NUM, char *POS, char
*S_CALLER)
-- Function: unsigned char num2uchar (SCM NUM, char *POS, char
*S_CALLER)
-- Function: double num2dbl (SCM NUM, char *POS, char *S_CALLER)
These functions are used to check and convert `SCM' arguments to
the named C type. The first argument NUM is checked to see it it
is within the range of the destination type. If so, the converted
number is returned. If not, the `ASRTER' macro calls `wta' with
NUM and strings POS and S_CALLER. For a listing of useful
predefined POS macros, *Note C Macros::.
_Note_ Inexact numbers are accepted only by `num2dbl', `num2long',
and `num2ulong' (for when `SCM' is compiled without bignums). To
convert inexact numbers to exact numbers, *Note inexact->exact:
(r5rs)Numerical operations.
-- Function: unsigned long scm_addr (SCM ARGS, char *S_NAME)
Returns a pointer (cast to an `unsigned long') to the storage
corresponding to the location accessed by
`aref(CAR(args),CDR(args))'. The string S_NAME is used in any
messages from error calls by `scm_addr'.
`scm_addr' is useful for performing C operations on strings or
other uniform arrays (*note Uniform Array::).
-- Function: unsigned long scm_base_addr(SCM RA, char *S_NAME)
Returns a pointer (cast to an `unsigned long') to the beginning of
storage of array RA. Note that if RA is a shared-array, the
strorage accessed this way may be much larger than RA.
_Note_ While you use a pointer returned from `scm_addr' or
`scm_base_addr' you must keep a pointer to the associated `SCM'
object in a stack allocated variable or GC-protected location in
order to assure that SCM does not reuse that storage before you
are done with it. *Note scm_gc_protect: Changing Scm.
-- Function: SCM makfrom0str (char *SRC)
-- Function: SCM makfromstr (char *SRC, sizet LEN)
Return a newly allocated string `SCM' object copy of the
null-terminated string SRC or the string SRC of length LEN,
respectively.
-- Function: SCM makfromstrs (int ARGC, char **ARGV)
Returns a newly allocated `SCM' list of strings corresponding to
the ARGC length array of null-terminated strings ARGV. If ARGV is
less than `0', ARGV is assumed to be `NULL' terminated.
`makfromstrs' is used by `scm_init_from_argv' to convert the
arguments SCM was called with to a `SCM' list which is the value
of SCM procedure calls to `program-arguments' (*note
program-arguments: SCM Session.).
-- Function: char ** makargvfrmstrs (SCM ARGS, char *S_NAME)
Returns a `NULL' terminated list of null-terminated strings copied
from the `SCM' list of strings ARGS. The string S_NAME is used in
messages from error calls by `makargvfrmstrs'.
`makargvfrmstrs' is useful for constructing argument lists suitable
for passing to `main' functions.
-- Function: void must_free_argv (char **ARGV)
Frees the storage allocated to create ARGV by a call to
`makargvfrmstrs'.
File: scm.info, Node: Continuations, Next: Evaluation, Prev: Type Conversions, Up: Operations
6.2.13 Continuations
--------------------
The source files `continue.h' and `continue.c' are designed to function
as an independent resource for programs wishing to use continuations,
but without all the rest of the SCM machinery. The concept of
continuations is explained in *Note call-with-current-continuation:
(r5rs)Control features.
The C constructs `jmp_buf', `setjmp', and `longjmp' implement escape
continuations. On VAX and Cray platforms, the setjmp provided does not
save all the registers. The source files `setjump.mar', `setjump.s',
and `ugsetjump.s' provide implementations which do meet this criteria.
SCM uses the names `jump_buf', `setjump', and `longjump' in lieu of
`jmp_buf', `setjmp', and `longjmp' to prevent name and declaration
conflicts.
-- Data type: CONTINUATION jmpbuf length stkbse other parent
is a `typedef'ed structure holding all the information needed to
represent a continuation. The OTHER slot can be used to hold any
data the user wishes to put there by defining the macro
`CONTINUATION_OTHER'.
-- Macro: SHORT_ALIGN
If `SHORT_ALIGN' is `#define'd (in `scmfig.h'), then the it is
assumed that pointers in the stack can be aligned on `short int'
boundaries.
-- Data type: STACKITEM
is a pointer to objects of the size specified by `SHORT_ALIGN'
being `#define'd or not.
-- Macro: CHEAP_CONTINUATIONS
If `CHEAP_CONTINUATIONS' is `#define'd (in `scmfig.h') each
`CONTINUATION' has size `sizeof CONTINUATION'. Otherwise, all but
"root" `CONTINUATION's have additional storage (immediately
following) to contain a copy of part of the stack.
_Note_ On systems with nonlinear stack disciplines (multiple
stacks or non-contiguous stack frames) copying the stack will not
work properly. These systems need to #define
`CHEAP_CONTINUATIONS' in `scmfig.h'.
-- Macro: STACK_GROWS_UP
Expresses which way the stack grows by its being `#define'd or not.
-- Variable: long thrown_value
Gets set to the VALUE passed to `throw_to_continuation'.
-- Function: long stack_size (STACKITEM *START)
Returns the number of units of size `STACKITEM' which fit between
START and the current top of stack. No check is done in this
routine to ensure that START is actually in the current stack
segment.
-- Function: CONTINUATION * make_root_continuation (STACKITEM
*STACK_BASE)
Allocates (`malloc') storage for a `CONTINUATION' of the current
extent of stack. This newly allocated `CONTINUATION' is returned
if successful, `0' if not. After `make_root_continuation'
returns, the calling routine still needs to
`setjump(NEW_CONTINUATION->jmpbuf)' in order to complete the
capture of this continuation.
-- Function: CONTINUATION * make_continuation (CONTINUATION
*PARENT_CONT)
Allocates storage for the current `CONTINUATION', copying (or
encapsulating) the stack state from `PARENT_CONT->stkbse' to the
current top of stack. The newly allocated `CONTINUATION' is
returned if successful, `0'q if not. After `make_continuation'
returns, the calling routine still needs to
`setjump(NEW_CONTINUATION->jmpbuf)' in order to complete the
capture of this continuation.
-- Function: void free_continuation (CONTINUATION *CONT)
Frees the storage pointed to by CONT. Remember to free storage
pointed to by `CONT->other'.
-- Function: void throw_to_continuation (CONTINUATION *CONT, long
VALUE, CONTINUATION *ROOT_CONT)
Sets `thrown_value' to VALUE and returns from the continuation
CONT.
If `CHEAP_CONTINUATIONS' is `#define'd, then
`throw_to_continuation' does `longjump(CONT->jmpbuf, val)'.
If `CHEAP_CONTINUATIONS' is not `#define'd, the CONTINUATION CONT
contains a copy of a portion of the C stack (whose bound must be
`CONT(ROOT_CONT)->stkbse'). Then:
* the stack is grown larger than the saved stack, if neccessary.
* the saved stack is copied back into it's original position.
* `longjump(CONT->jmpbuf, val)';
File: scm.info, Node: Evaluation, Prev: Continuations, Up: Operations
6.2.14 Evaluation
-----------------
SCM uses its type representations to speed evaluation. All of the
`subr' types (*note Subr Cells::) are `tc7' types. Since the `tc7'
field is in the low order bit position of the `CAR' it can be retrieved
and dispatched on quickly by dereferencing the SCM pointer pointing to
it and masking the result.
All the SCM "Special Forms" get translated to immediate symbols
(`isym') the first time they are encountered by the interpreter
(`ceval'). The representation of these immediate symbols is engineered
to occupy the same bits as `tc7'. All the `isym's occur only in the
`CAR' of lists.
If the `CAR' of a expression to evaluate is not immediate, then it may
be a symbol. If so, the first time it is encountered it will be
converted to an immediate type `ILOC' or `GLOC' (*note Immediates::).
The codes for `ILOC' and `GLOC' lower 7 bits distinguish them from all
the other types we have discussed.
Once it has determined that the expression to evaluate is not immediate,
`ceval' need only retrieve and dispatch on the low order 7 bits of the
`CAR' of that cell, regardless of whether that cell is a closure,
header, or subr, or a cons containing `ILOC' or `GLOC'.
In order to be able to convert a SCM symbol pointer to an immediate
`ILOC' or `GLOC', the evaluator must be holding the pointer to the list
in which that symbol pointer occurs. Turning this requirement to an
advantage, `ceval' does not recursively call itself to evaluate symbols
in lists; It instead calls the macro "EVALCAR". `EVALCAR' does symbol
lookup and memoization for symbols, retrieval of values for `ILOC's and
`GLOC's, returns other immediates, and otherwise recursively calls
itself with the `CAR' of the list.
`ceval' inlines evaluation (using `EVALCAR') of almost all procedure
call arguments. When `ceval' needs to evaluate a list of more than
length 3, the procedure `eval_args' is called. So `ceval' can be said
to have one level lookahead. The avoidance of recursive invocations of
`ceval' for the most common cases (special forms and procedure calls)
results in faster execution. The speed of the interpreter is currently
limited on most machines by interpreter size, probably having to do
with its cache footprint. In order to keep the size down, certain
`EVALCAR' calls which don't need to be fast (because they rarely occur
or because they are part of expensive operations) are instead calls to
the C function `evalcar'.
-- Variable: symhash
Top level symbol values are stored in the `symhash' table.
`symhash' is an array of lists of `ISYM's and pairs of symbols and
values.
-- Immediate: ILOC
Whenever a symbol's value is found in the local environment the
pointer to the symbol in the code is replaced with an immediate
object (`ILOC') which specifies how many environment frames down
and how far in to go for the value. When this immediate object is
subsequently encountered, the value can be retrieved quickly.
`ILOC's work up to a maximum depth of 4096 frames or 4096 identifiers
in a frame. Radey Shouman added "FARLOC" to handle cases exceeding
these limits. A `FARLOC' consists of a pair whose CAR is the immediate
type `IM_FARLOC_CAR' or `IM_FARLOC_CDR', and whose CDR is a pair of
INUMs specifying the frame and distance with a larger range than
`ILOC's span.
Adding `#define TEST_FARLOC' to `eval.c' causes `FARLOC's to be
generated for all local identifiers; this is useful only for testing
memoization.
-- Immediate: GLOC
Pointers to symbols not defined in local environments are changed
to one plus the value cell address in symhash. This incremented
pointer is called a `GLOC'. The low order bit is normally
reserved for GCmark; But, since references to variables in the
code always occur in the `CAR' position and the GCmark is in the
`CDR', there is no conflict.
If the compile FLAG `CAUTIOUS' is #defined then the number of arguments
is always checked for application of closures. If the compile FLAG
`RECKLESS' is #defined then they are not checked. Otherwise, number of
argument checks for closures are made only when the function position
(whose value is the closure) of a combination is not an `ILOC' or
`GLOC'. When the function position of a combination is a symbol it
will be checked only the first time it is evaluated because it will
then be replaced with an `ILOC' or `GLOC'.
-- Macro: EVAL expression env
-- Macro: SIDEVAL expression env
`EVAL' Returns the result of evaluating EXPRESSION in ENV.
`SIDEVAL' evaluates EXPRESSION in ENV when the value of the
expression is not used.
Both of these macros alter the list structure of EXPRESSION as it
is memoized and hence should be used only when it is known that
EXPRESSION will not be referenced again. The C function `eval' is
safe from this problem.
-- Function: SCM eval (SCM EXPRESSION)
Returns the result of evaluating EXPRESSION in the top-level
environment. `eval' copies `expression' so that memoization does
not modify `expression'.
File: scm.info, Node: Program Self-Knowledge, Next: Improvements To Make, Prev: Operations, Up: The Implementation
6.3 Program Self-Knowledge
==========================
* Menu:
* File-System Habitat::
* Executable Pathname::
* Script Support::
File: scm.info, Node: File-System Habitat, Next: Executable Pathname, Prev: Program Self-Knowledge, Up: Program Self-Knowledge
6.3.1 File-System Habitat
-------------------------
Where should software reside? Although individually a minor annoyance,
cumulatively this question represents many thousands of frustrated user
hours spent trying to find support files or guessing where packages need
to be installed. Even simple programs require proper habitat; games
need to find their score files.
Aren't there standards for this? Some Operating Systems have devised
regimes of software habitats - only to have them violated by large
software packages and imports from other OS varieties.
In some programs, the expected locations of support files are fixed at
time of compilation. This means that the program may not run on
configurations unanticipated by the authors. Compiling locations into a
program also can make it immovable - necessitating recompilation to
install it.
Programs of the world unite! You have nothing to lose but loss
itself.
The function `find_impl_file' in `scm.c' is an attempt to create a
utility (for inclusion in programs) which will hide the details of
platform-dependent file habitat conventions. It takes as input the
pathname of the executable file which is running. If there are systems
for which this information is either not available or unrelated to the
locations of support files, then a higher level interface will be
needed.
-- Function: char * find_impl_file (char *EXEC_PATH, char
*GENERIC_NAME, char *INITNAME, char *SEP)
Given the pathname of this executable (EXEC_PATH), test for the
existence of INITNAME in the implementation-vicinity of this
program. Return a newly allocated string of the path if
successful, 0 if not. The SEP argument is a _null-terminated
string_ of the character used to separate directory components.
* One convention is to install the support files for an executable
program in the same directory as the program. This possibility is
tried first, which satisfies not only programs using this
convention, but also uninstalled builds when testing new releases,
etc.
* Another convention is to install the executables in a directory
named `bin', `BIN', `exe', or `EXE' and support files in a
directroy named `lib', which is a peer the executable directory.
This arrangement allows multiple executables can be stored in a
single directory. For example, the executable might be in
`/usr/local/bin/' and initialization file in `/usr/local/lib/'.
If the executable directory name matches, the peer directroy `lib'
is tested for INITNAME.
* Sometimes `lib' directories become too crowded. So we look in any
subdirectories of `lib' or `src' having the name (sans type suffix
such as `.EXE') of the program we are running. For example, the
executable might be `/usr/local/bin/foo' and initialization file
in `/usr/local/lib/foo/'.
* But the executable name may not be the usual program name; So also
look in any GENERIC_NAME subdirectories of `lib' or `src' peers.
* Finally, if the name of the executable file being run has a (system
dependent) suffix which is not needed to invoke the program, then
look in a subdirectory (of the one containing the executable file)
named for the executable (without the suffix); And look in a
GENERIC_NAME subdirectory. For example, the executable might be
`C:\foo\bar.exe' and the initialization file in `C:\foo\bar\'.
File: scm.info, Node: Executable Pathname, Next: Script Support, Prev: File-System Habitat, Up: Program Self-Knowledge
6.3.2 Executable Pathname
-------------------------
For purposes of finding `Init5e2.scm', dumping an executable, and |
dynamic linking, a SCM session needs the pathname of its executable
image.
When a program is executed by MS-DOS, the full pathname of that
executable is available in `argv[0]'. This value can be passed
directly to `find_impl_file' (*note File-System Habitat::).
In order to find the habitat for a unix program, we first need to know
the full pathname for the associated executable file.
-- Function: char * dld_find_executable (const char *COMMAND)
`dld_find_executable' returns the absolute path name of the file
that would be executed if COMMAND were given as a command. It
looks up the environment variable PATH, searches in each of the
directory listed for COMMAND, and returns the absolute path name
for the first occurrence. Thus, it is advisable to invoke
`dld_init' as:
main (int argc, const char **argv) |
{
...
if (dld_init (dld_find_executable (argv[0]))) {
...
}
...
}
*Note@:* If the current process is executed using the
`execve' call without passing the correct path name as
argument 0, `dld_find_executable (argv[0]) ' will also fail
to locate the executable file.
`dld_find_executable' returns zero if `command' is not found in
any of the directories listed in `PATH'.
File: scm.info, Node: Script Support, Prev: Executable Pathname, Up: Program Self-Knowledge
6.3.3 Script Support
--------------------
Source code for these C functions is in the file `script.c'. *Note
Scripting:: for a description of script argument processing.
`script_find_executable' is only defined on unix systems.
-- Function: char * script_find_executable (const char *NAME)
`script_find_executable' returns the path name of the executable
which is invoked by the script file NAME; NAME if it is a binary
executable (not a script); or 0 if NAME does not exist or is not
executable.
-- Function: char ** script_process_argv (int ARGC; char **ARGV)
Given an "main" style argument vector ARGV and the number of
arguments, ARGC, `script_process_argv' returns a newly allocated
argument vector in which the second line of the script being
invoked is substituted for the corresponding meta-argument.
If the script does not have a meta-argument, or if the file named
by the argument following a meta-argument cannot be opened for
reading, then 0 is returned.
`script_process_argv' correctly processes argument vectors of
nested script invocations.
-- Function: int script_count_argv (char **ARGV)
Returns the number of argument strings in ARGV.
File: scm.info, Node: Improvements To Make, Prev: Program Self-Knowledge, Up: The Implementation
6.4 Improvements To Make
========================
* Allow users to set limits for `malloc()' storage.
* Prefix and make more uniform all C function, variable, and constant
names. Provide a file full of #define's to provide backward
compatability.
* `lgcd()' _needs_ to generate at most one bignum, but currently
generates more.
* `divide()' could use shifts instead of multiply and divide when
scaling.
* Currently, `dump'ing an executable does not preserve ports. When
loading a `dump'ed executable, disk files could be reopened to the
same file and position as they had when the executable was dumped.
* Copying all of the stack is wasteful of storage. Any time a
call-with-current-continuation is called the stack could be
re-rooted with a frame which calls the contin just created. This
in combination with checking stack depth could also be used to
allow stacks deeper than 64K on the IBM PC.
* In the quest for speed, there has been some discussion about a
"Forth" style Scheme interpreter.
Provided there is still type code space available in SCM, if
we devote some of the IMCAR codes to "inlined" operations, we
should get a significant performance boost. What is
eliminated is the having to look up a `GLOC' or `ILOC' and
then dispatch on the subr type. The IMCAR operation would be
dispatched to directly. Another way to view this is that we
make available special form versions of `CAR', `CDR', etc.
Since the actual operation code is localized in the
interpreter, it is much easier than uncompilation and then
recompilation to handle `(trace car)'; For instance a switch
gets set which tells the interpreter to instead always look
up the values of the associated symbols.
* Scott Schwartz <schwartz@galapagos.cse.psu.edu> suggests: One way
to tidy up the dynamic loading stuff would be to grab the code
from perl5.
* Menu:
* VMS Dynamic Linking:: Finishing the job.
File: scm.info, Node: VMS Dynamic Linking, Prev: Improvements To Make, Up: Improvements To Make
6.4.1 VMS Dynamic Linking
-------------------------
George Carrette (gjc@mitech.com) outlines how to dynamically link on
VMS. There is already some code in `dynl.c' to do this, but someone
with a VMS system needs to finish and debug it.
1. Say you have this `main.c' program:
main()
{init_lisp();
lisp_repl();}
2. and you have your lisp in files `repl.c', `gc.c', `eval.c' and
there are some toplevel non-static variables in use called
`the_heap', `the_environment', and some read-only toplevel
structures, such as `the_subr_table'.
$ LINK/SHARE=LISPRTL.EXE/DEBUG REPL.OBJ,GC.OBJ,EVAL.OBJ,LISPRTL.OPT/OPT
3. where `LISPRTL.OPT' must contain at least this:
SYS$LIBRARY:VAXCRTL/SHARE
UNIVERSAL=init_lisp
UNIVERSAL=lisp_repl
PSECT_ATTR=the_subr_table,SHR,NOWRT,LCL
PSECT_ATTR=the_heap,NOSHR,LCL
PSECT_ATTR=the_environment,NOSHR,LCL
_Notice_ The "psect" (Program Section) attributes.
`LCL'
means to keep the name local to the shared library. You
almost always want to do that for a good clean library.
`SHR,NOWRT'
means shared-read-only. Which is the default for code, and
is also good for efficiency of some data structures.
`NOSHR,LCL'
is what you want for everything else.
Note: If you do not have a handy list of all these toplevel
variables, do not dispair. Just do your link with the
/MAP=LISPRTL.MAP/FULL and then search the map file,
$SEARCH/OUT=LISPRTL.LOSERS LISPRTL.MAP ", SHR,NOEXE, RD, WRT"
And use an emacs keyboard macro to muck the result into the proper
form. Of course only the programmer can tell if things can be
made read-only. I have a DCL command procedure to do this if you
want it.
4. Now MAIN.EXE would be linked thusly:
$ DEFINE LISPRTL USER$DISK:[JAFFER]LISPRTL.EXE
$LINK MAIN.OBJ,SYS$INPUT:/OPT
SYS$LIBRARY:VAXCRTL/SHARE
LISPRTL/SHARE
Note the definition of the `LISPRTL' logical name. Without such a
definition you will need to copy `LISPRTL.EXE' over to `SYS$SHARE'
(aka `SYS$LIBRARY') in order to invoke the main program once it is
linked.
5. Now say you have a file of optional subrs, `MYSUBRS.C'. And there
is a routine `INIT_MYSUBRS' that must be called before using it.
$ CC MYSUBRS.C
$ LINK/SHARE=MYSUBRS.EXE MYSUBRS.OBJ,SYS$INPUT:/OPT
SYS$LIBRARY:VAXCRTL/SHARE
LISPRTL/SHARE
UNIVERSAL=INIT_MYSUBRS
Ok. Another hint is that you can avoid having to add the `PSECT'
declaration of `NOSHR,LCL' by declaring variables `status' in the
C language source. That works great for most things.
6. Then the dynamic loader would have to do this:
{void (*init_fcn)();
long retval;
retval = lib$find_image_symbol("MYSUBRS","INIT_MYSUBRS",&init_fcn,
"SYS$DISK:[].EXE");
if (retval != SS$_NORMAL) error(...);
(*init_fcn)();}
But of course all string arguments must be `(struct dsc$descriptor
*)' and the last argument is optional if `MYSUBRS' is defined as a
logical name or if `MYSUBRS.EXE' has been copied over to
`SYS$SHARE'. The other consideration is that you will want to turn
off <C-c> or other interrupt handling while you are inside most
`lib$' calls.
As far as the generation of all the `UNIVERSAL=...' declarations.
Well, you could do well to have that automatically generated from
the public `LISPRTL.H' file, of course.
VMS has a good manual called the `Guide to Writing Modular
Procedures' or something like that, which covers this whole area
rather well, and also talks about advanced techniques, such as a
way to declare a program section with a pointer to a procedure
that will be automatically invoked whenever any shared image is
dynamically activated. Also, how to set up a handler for normal
or abnormal program exit so that you can clean up side effects
(such as opening a database). But for use with `LISPRTL' you
probably don't need that hair.
One fancier option that is useful under VMS for `LISPLIB.EXE' is to
define all your exported procedures through an "call vector"
instead of having them just be pointers into random places in the
image, which is what you get by using `UNIVERSAL'.
If you set up the call vector thing correctly it will allow you to
modify and relink `LISPLIB.EXE' without having to relink programs
that have been linked against it.
File: scm.info, Node: Index, Prev: The Implementation, Up: Top
Procedure and Macro Index
*************************
This is an alphabetical list of all the procedures and macros in SCM.
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