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@@ -0,0 +1,216 @@ +FAQ (Frequently Asked Questions and answers) for SLIB Scheme Library (slib2a6). +Written by Aubrey Jaffer (jaffer@ai.mit.edu). + + INTRODUCTION AND GENERAL INFORMATION + +[] What is SLIB? + +SLIB is a portable scheme library meant to provide compatibiliy and +utility functions for all standard scheme implementations. + +[] What is Scheme? + +Scheme is a programming language in the Lisp family. + +[] Which implementations has SLIB been ported to? + +SLIB is currently supported by Chez, ELK 2.1, GAMBIT, MacScheme, +MITScheme, scheme->C, Scheme48, T3.1, SCM and VSCM + +[] How can I get SLIB? + +SLIB is available via ftp from: + ftp-swiss.ai.mit.edu:pub/scm/slib2a6.tar.gz + prep.ai.mit.edu:pub/gnu/jacal/slib2a6.tar.gz + ftp.maths.tcd.ie:pub/bosullvn/jacal/slib2a6.tar.gz + ftp.cs.indiana.edu:/pub/scheme-repository/imp/slib2a6.tar.gz + +SLIB is also included with SCM floppy disks. + +[] How do I install SLIB? + +Read the INSTALLATION INSTRUCTIONS in "slib/README". + +[] What are slib.texi and slib.info? + +"slib.texi" is the `texinfo' format documentation for SLIB. +"slib.info" is produced from "slib.texi" by either Gnu Emacs or the +program `makeinfo'. "slib.info" can be viewed using either Gnu Emacs +or `info' or a text editor. + +Programs for printing and viewing TexInfo documentation (which SLIB +has) come with GNU Emacs or can be obtained via ftp from: +prep.ai.mit.edu:pub/gnu/texinfo-3.1.tar.gz + +[] How often is SLIB released? + +SLIB was released 9 times in 1993. + +[] What is the latest version? + +The version as of this writing is slib2a6. + +[] What version am I using? + +The Version is in the first line of the files slib/FAQ, slib/ANNOUNCE, +and slib/README. If you have Scheme and SLIB running, type +(slib:report-version) + + SLIB INSTALLATION PROBLEMS + +[] When I load an SLIB initialization file for my Scheme + implementation, I get ERROR: Couldn't find "require.scm" + +Did you remember to set either the environment variable +SCHEME_LIBRARY_PATH or the library-vicinity in your initialization +file to the correct location? Make sure if you set only the +environment variable SCHEME_LIBRARY_PATH that your implementation +supports getenv. + +[] When I load an SLIB initialization file for my Scheme + implementation, I get ERROR: Couldn't find + "/usr/local/lib/slibrequire.scm" + +Notice that it is looking for "slibrequire.scm" rather than +"slib/require.scm". You need to put a trailing slash on either the +environment variable SCHEME_LIBRARY_PATH or in the library-vicinity in +your initialization file. + +[] SLIB used to work, but now I get ERROR: Couldn't find + "slib/require.scm". What happened? + +You changed directories and now the relative pathname +"slib/require.scm" no longer refers to the same directory. The +environment variable SCHEME_LIBRARY_PATH and library-vicinity in your +initialization file should be absolute pathnames. + +[] When I type (require 'macro) I get "ERROR: unbound variable: + require". + +You need to arrange to have your Scheme implementation load the +appropriate SLIB initialization file ("foo.init") before using SLIB. +If your implementation loads an initialization file on startup, you +can have it load the SLIB initialization file automatically. For +example (load "/usr/local/lib/slib/foo.init"). + +[] Why do I get a string-ref (or other) error when I try to load + or use SLIB. + +Check that the version of the Scheme implementation you are using +matches the version for which the SLIB initialization file was +written. There are some notes in the SLIB initialization files about +earlier versions. You may need to get a more recent version of your +Scheme implementation. + + USING SLIB PROCEDURES + +[] I installed SLIB. When I type (random 5) I get "ERROR: + unbound variable: random". Doesn't SLIB have a `random' + function? + +Before you can use most SLIB functions, the associated module needs to +be loaded. You do this by typing the line that appears at the top of +the page in slib.info (or slib.texi) where the function is documented. +In the case of random, the line is (require 'random). + +[] Why doesn't SLIB just load all the functions so I don't have + to type require statements? + +SLIB currently has more than 1 Megabyte of Scheme source code. Many +scheme implementations take unacceptably long to load 1 Megabyte of +source; some implementations cannot allocate enough storage. If you +use a package often, you can put the require statement in your Scheme +initialization file. Consult the manual for your Scheme +implementation to find out the initialization file's name. + +`Autoloads' will work with many Scheme implementations. You could put +the following in your initialization file: + (define (random . args) (require 'random) (apply random args)) + +I find that I only type require statements at top level when +debugging. I put require statements in my Scheme files so that the +appropriate modules are loaded automatically. + +[] Why does SLIB have PRINTF when it already has the more + powerful (CommonLisp) FORMAT? + +CommonLisp FORMAT does not support essential features which PRINTF +does. For instance, how do you format a signed 0 extended number? + + (format t "~8,'0,X~%" -3) ==> 000000-3 + +But printf gets it right: + + (printf "%08x\n" -3) ==> -0000003 + +How can one trunctate a non-numeric field using FORMAT? This feature +is essential for printing reports. The first 20 letters of a name is +sufficient to identify it. But if that name doesn't get trucated to +the desired length it can displace other fields off the page. Once +again, printf gets it right: + + (printf "%.20s\n" "the quick brown fox jumped over the lazy dog") + ==> the quick brown fox + +FORMAT also lacks directives for formatting date and time. printf +does not handle these directly, but a related function strftime does. + +[] Why doesn't SLIB:ERROR call FORMAT? + +Format does not provide a method to truncate fields. When an error +message contains non-terminating or large expressions, the essential +information of the message may be lost in the ensuing deluge. + +FORMAT as currently written in SLIB is not reentrant. Until this is +fixed exception handlers and errors which might occur while using +FORMAT cannot use it. + + MACROS + +[] Why are there so many macro implementations in SLIB? + +The R4RS committee specified only the high level pattern language in +the Revised^4 Report on Scheme and left to the free marketplace of +ideas the details of the low-level facility. Each macro package has a +different low-level facility. The low-level facilities are sometimes +needed because the high level pattern language is insufficiently +powerful to accomplish tasks macros are often written to do. + +[] Why are there both R4RS macros and Common-Lisp style defmacros + in SLIB? + +Most current Scheme implementations predate the adoption of the R4RS +macro specification. It turns out that all of the implementations +can support defmacro natively. + +[] I did (LOAD "slib/yasos.scm"). The error I get is "variable + define-syntax is undefined". + +The way to load the struct macro package is (REQUIRE 'YASOS). + +[] I did (REQUIRE 'YASOS). Now when I type (DEFINE-PREDICATE + CELL?) The error I get is "variable define-predicate is + undefined". + +If like most implementations, your Scheme does not natively support +R4RS macros you will need to install a macro-capable read-eval-print +loop. This is done by: + (require 'macro) ;already done if you did (require 'yasos) + (require 'repl) + (repl:top-level macro:eval) + +This is also true for Schemes which don't support DEFMACRO. The lines +in this case are: + (require 'repl) + (repl:top-level defmacro:eval) + +[] I always use R4RS macros. How can I avoid having to type + require statements every time I start Scheme? + +As is explained in the Repl entry in slib.info (or slib.texi): + + To have your top level loop always use macros, add any interrupt + catching lines and the following lines to your Scheme init file: + (require 'macro) + (require 'repl) + (repl:top-level macro:eval) |