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authorSteve Langasek <vorlon@debian.org>2005-01-10 08:53:33 +0000
committerBryan Newbold <bnewbold@robocracy.org>2017-02-20 00:05:30 -0800
commite33f9eb9cf5cc29c36ce2aa7e10cd0f37ae0cc8e (patch)
treeabbf06041619e445f9d0b772b0d58132009d8234 /slib_3.html
parentf559c149c83da84d0b1c285f0298c84aec564af9 (diff)
parent8466d8cfa486fb30d1755c4261b781135083787b (diff)
downloadslib-e33f9eb9cf5cc29c36ce2aa7e10cd0f37ae0cc8e.tar.gz
slib-e33f9eb9cf5cc29c36ce2aa7e10cd0f37ae0cc8e.zip
Import Debian changes 3a1-4.2debian/3a1-4.2
slib (3a1-4.2) unstable; urgency=low * Non-maintainer upload. * Add guile.init.local for use within the build dir, since otherwise we have an (earlier unnoticed) circular build-dep due to a difference between scm and guile. slib (3a1-4.1) unstable; urgency=low * Non-maintainer upload. * Build-depend on guile-1.6 instead of scm, since the new version of scm is wedged in unstable (closes: #281809). slib (3a1-4) unstable; urgency=low * Also check for expected creation on slibcat. (Closes: #240096) slib (3a1-3) unstable; urgency=low * Also check for /usr/share/guile/1.6/slib before installing for guile 1.6. (Closes: #239267) slib (3a1-2) unstable; urgency=low * Add format.scm back into slib until gnucash stops using it. * Call guile-1.6 new-catalog (Closes: #238231) slib (3a1-1) unstable; urgency=low * New upstream release * Remove Info section from doc-base file (Closes: #186950) * Remove period from end of description (linda, lintian) * html gen fixed upstream (Closes: #111778) slib (2d4-2) unstable; urgency=low * Fix url for upstream source (Closes: #144981) * Fix typo in slib.texi (enquque->enqueue) (Closes: #147475) * Add build depends. slib (2d4-1) unstable; urgency=low * New upstream. slib (2d3-1) unstable; urgency=low * New upstream. * Remove texi2html call in debian/rules. Now done upstream. Add make html instead. * Changes to rules and doc-base to conform to upstream html gen * Clean up upstream makefile to make sure it cleans up after itself.
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+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
+ "http://www.w3.org/TR/html40/loose.dtd">
+<HTML>
+<!-- Created on January, 10 2005 by texi2html 1.66 -->
+<!--
+Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author)
+ Karl Berry <karl@freefriends.org>
+ Olaf Bachmann <obachman@mathematik.uni-kl.de>
+ and many others.
+Maintained by: Many creative people <dev@texi2html.cvshome.org>
+Send bugs and suggestions to <users@texi2html.cvshome.org>
+
+-->
+<HEAD>
+<TITLE>SLIB: Scheme Syntax Extension Packages</TITLE>
+
+<META NAME="description" CONTENT="SLIB: Scheme Syntax Extension Packages">
+<META NAME="keywords" CONTENT="SLIB: Scheme Syntax Extension Packages">
+<META NAME="resource-type" CONTENT="document">
+<META NAME="distribution" CONTENT="global">
+<META NAME="Generator" CONTENT="texi2html 1.66">
+
+</HEAD>
+
+<BODY LANG="en" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#800080" ALINK="#FF0000">
+
+<A NAME="SEC21"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_2.html#SEC20"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC22"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_2.html#SEC13"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H1> 3. Scheme Syntax Extension Packages </H1>
+<!--docid::SEC21::-->
+<P>
+
+<TABLE BORDER="0" CELLSPACING="0">
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC22">3.1 Defmacro</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">Supported by all implementations</TD></TR>
+<TR><TH COLSPAN="3" ALIGN="left" VALIGN="TOP">
+</TH></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC24">3.2 R4RS Macros</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">'macro</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC25">3.3 Macro by Example</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">'macro-by-example</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC27">3.4 Macros That Work</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">'macros-that-work</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC30">3.5 Syntactic Closures</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">'syntactic-closures</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC36">3.6 Syntax-Case Macros</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">'syntax-case</TD></TR>
+<TR><TH COLSPAN="3" ALIGN="left" VALIGN="TOP">
+</TH></TR>
+<TR><TH COLSPAN="3" ALIGN="left" VALIGN="TOP">Syntax extensions (macros) included with SLIB.
+</TH></TR>
+<TR><TH COLSPAN="3" ALIGN="left" VALIGN="TOP">
+</TH></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC39">3.7 Fluid-Let</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">'fluid-let</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC40">3.8 Yasos</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">'yasos, 'oop, 'collect</TD></TR>
+</TABLE>
+<P>
+
+<A NAME="Defmacro"></A>
+<HR SIZE="6">
+<A NAME="SEC22"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC23"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.1 Defmacro </H2>
+<!--docid::SEC22::-->
+<P>
+
+Defmacros are supported by all implementations.
+</P>
+<P>
+
+<A NAME="IDX107"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>gentemp</B>
+<DD>Returns a new (interned) symbol each time it is called. The symbol
+names are implementation-dependent
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(gentemp) => scm:G0
+(gentemp) => scm:G1
+</pre></td></tr></table></DL>
+<P>
+
+<A NAME="IDX108"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>defmacro:eval</B> <I>e</I>
+<DD>Returns the <CODE>slib:eval</CODE> of expanding all defmacros in scheme
+expression <VAR>e</VAR>.
+</DL>
+<P>
+
+<A NAME="IDX109"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>defmacro:load</B> <I>filename</I>
+<DD><VAR>filename</VAR> should be a string. If filename names an existing file,
+the <CODE>defmacro:load</CODE> procedure reads Scheme source code expressions
+and definitions from the file and evaluates them sequentially. These
+source code expressions and definitions may contain defmacro
+definitions. The <CODE>macro:load</CODE> procedure does not affect the values
+returned by <CODE>current-input-port</CODE> and
+<CODE>current-output-port</CODE>.
+</DL>
+<P>
+
+<A NAME="IDX110"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>defmacro?</B> <I>sym</I>
+<DD>Returns <CODE>#t</CODE> if <VAR>sym</VAR> has been defined by <CODE>defmacro</CODE>,
+<CODE>#f</CODE> otherwise.
+</DL>
+<P>
+
+<A NAME="IDX111"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macroexpand-1</B> <I>form</I>
+<DD><A NAME="IDX112"></A>
+<DT><U>Function:</U> <B>macroexpand</B> <I>form</I>
+<DD>If <VAR>form</VAR> is a macro call, <CODE>macroexpand-1</CODE> will expand the
+macro call once and return it. A <VAR>form</VAR> is considered to be a macro
+call only if it is a cons whose <CODE>car</CODE> is a symbol for which a
+<CODE>defmacro</CODE> has been defined.
+<P>
+
+<CODE>macroexpand</CODE> is similar to <CODE>macroexpand-1</CODE>, but repeatedly
+expands <VAR>form</VAR> until it is no longer a macro call.
+</P>
+</DL>
+<P>
+
+<A NAME="IDX113"></A>
+</P>
+<DL>
+<DT><U>Macro:</U> <B>defmacro</B> <I>name lambda-list form <small>...</small></I>
+<DD>When encountered by <CODE>defmacro:eval</CODE>, <CODE>defmacro:macroexpand*</CODE>,
+or <CODE>defmacro:load</CODE> defines a new macro which will henceforth be
+expanded when encountered by <CODE>defmacro:eval</CODE>,
+<CODE>defmacro:macroexpand*</CODE>, or <CODE>defmacro:load</CODE>.
+</DL>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC23"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC22"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC24"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.1.1 Defmacroexpand </H3>
+<!--docid::SEC23::-->
+<CODE>(require 'defmacroexpand)</CODE>
+<A NAME="IDX114"></A>
+<P>
+
+<A NAME="IDX115"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>defmacro:expand*</B> <I>e</I>
+<DD>Returns the result of expanding all defmacros in scheme expression
+<VAR>e</VAR>.
+</DL>
+<P>
+
+<A NAME="R4RS Macros"></A>
+<HR SIZE="6">
+<A NAME="SEC24"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC23"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC25"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.2 R4RS Macros </H2>
+<!--docid::SEC24::-->
+<P>
+
+<CODE>(require 'macro)</CODE> is the appropriate call if you want R4RS
+<A NAME="IDX116"></A>
+high-level macros but don't care about the low level implementation. If
+an SLIB R4RS macro implementation is already loaded it will be used.
+Otherwise, one of the R4RS macros implemetations is loaded.
+</P>
+<P>
+
+The SLIB R4RS macro implementations support the following uniform
+interface:
+</P>
+<P>
+
+<A NAME="IDX117"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:expand</B> <I>sexpression</I>
+<DD>Takes an R4RS expression, macro-expands it, and returns the result of
+the macro expansion.
+</DL>
+<P>
+
+<A NAME="IDX118"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:eval</B> <I>sexpression</I>
+<DD>Takes an R4RS expression, macro-expands it, evals the result of the
+macro expansion, and returns the result of the evaluation.
+</DL>
+<P>
+
+<A NAME="IDX119"></A>
+</P>
+<DL>
+<DT><U>Procedure:</U> <B>macro:load</B> <I>filename</I>
+<DD><VAR>filename</VAR> should be a string. If filename names an existing file,
+the <CODE>macro:load</CODE> procedure reads Scheme source code expressions and
+definitions from the file and evaluates them sequentially. These source
+code expressions and definitions may contain macro definitions. The
+<CODE>macro:load</CODE> procedure does not affect the values returned by
+<CODE>current-input-port</CODE> and <CODE>current-output-port</CODE>.
+</DL>
+<P>
+
+<A NAME="Macro by Example"></A>
+<HR SIZE="6">
+<A NAME="SEC25"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC24"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC26"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.3 Macro by Example </H2>
+<!--docid::SEC25::-->
+<P>
+
+<CODE>(require 'macro-by-example)</CODE>
+<A NAME="IDX120"></A>
+</P>
+<P>
+
+A vanilla implementation of <CITE>Macro by Example</CITE> (Eugene Kohlbecker,
+R4RS) by Dorai Sitaram, (dorai @ cs.rice.edu) using <CODE>defmacro</CODE>.
+</P>
+<P>
+
+<UL>
+
+<LI>
+generating hygienic global <CODE>define-syntax</CODE> Macro-by-Example macros
+<STRONG>cheaply</STRONG>.
+<P>
+
+</P>
+<LI>
+can define macros which use <CODE>...</CODE>.
+<P>
+
+</P>
+<LI>
+needn't worry about a lexical variable in a macro definition
+clashing with a variable from the macro use context
+<P>
+
+</P>
+<LI>
+don't suffer the overhead of redefining the repl if <CODE>defmacro</CODE>
+natively supported (most implementations)
+<P>
+
+</UL>
+<HR SIZE="6">
+<A NAME="SEC26"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC25"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC27"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.3.1 Caveat </H3>
+<!--docid::SEC26::-->
+These macros are not referentially transparent (see section `Macros' in <CITE>Revised(4) Scheme</CITE>). Lexically scoped macros (i.e., <CODE>let-syntax</CODE>
+and <CODE>letrec-syntax</CODE>) are not supported. In any case, the problem
+of referential transparency gains poignancy only when <CODE>let-syntax</CODE>
+and <CODE>letrec-syntax</CODE> are used. So you will not be courting
+large-scale disaster unless you're using system-function names as local
+variables with unintuitive bindings that the macro can't use. However,
+if you must have the full <CITE>r4rs</CITE> macro functionality, look to the
+more featureful (but also more expensive) versions of syntax-rules
+available in slib <A HREF="slib_3.html#SEC27">3.4 Macros That Work</A>, <A HREF="slib_3.html#SEC30">3.5 Syntactic Closures</A>, and
+<A HREF="slib_3.html#SEC36">3.6 Syntax-Case Macros</A>.
+<P>
+
+<A NAME="IDX121"></A>
+</P>
+<DL>
+<DT><U>Macro:</U> <B>define-syntax</B> <I>keyword transformer-spec</I>
+<DD>The <VAR>keyword</VAR> is an identifier, and the <VAR>transformer-spec</VAR>
+should be an instance of <CODE>syntax-rules</CODE>.
+<P>
+
+The top-level syntactic environment is extended by binding the
+<VAR>keyword</VAR> to the specified transformer.
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax let*
+ (syntax-rules ()
+ ((let* () body1 body2 ...)
+ (let () body1 body2 ...))
+ ((let* ((name1 val1) (name2 val2) ...)
+ body1 body2 ...)
+ (let ((name1 val1))
+ (let* (( name2 val2) ...)
+ body1 body2 ...)))))
+</pre></td></tr></table></DL>
+<P>
+
+<A NAME="IDX122"></A>
+</P>
+<DL>
+<DT><U>Macro:</U> <B>syntax-rules</B> <I>literals syntax-rule <small>...</small></I>
+<DD><VAR>literals</VAR> is a list of identifiers, and each <VAR>syntax-rule</VAR>
+should be of the form
+<P>
+
+<CODE>(<VAR>pattern</VAR> <VAR>template</VAR>)</CODE>
+</P>
+<P>
+
+where the <VAR>pattern</VAR> and <VAR>template</VAR> are as in the grammar above.
+</P>
+<P>
+
+An instance of <CODE>syntax-rules</CODE> produces a new macro transformer by
+specifying a sequence of hygienic rewrite rules. A use of a macro whose
+keyword is associated with a transformer specified by
+<CODE>syntax-rules</CODE> is matched against the patterns contained in the
+<VAR>syntax-rule</VAR>s, beginning with the leftmost <VAR>syntax-rule</VAR>.
+When a match is found, the macro use is trancribed hygienically
+according to the template.
+</P>
+<P>
+
+Each pattern begins with the keyword for the macro. This keyword is not
+involved in the matching and is not considered a pattern variable or
+literal identifier.
+</P>
+</DL>
+<P>
+
+<A NAME="Macros That Work"></A>
+<HR SIZE="6">
+<A NAME="SEC27"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC26"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.4 Macros That Work </H2>
+<!--docid::SEC27::-->
+<P>
+
+<CODE>(require 'macros-that-work)</CODE>
+<A NAME="IDX123"></A>
+</P>
+<P>
+
+<CITE>Macros That Work</CITE> differs from the other R4RS macro
+implementations in that it does not expand derived expression types to
+primitive expression types.
+</P>
+<P>
+
+<A NAME="IDX124"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:expand</B> <I>expression</I>
+<DD><A NAME="IDX125"></A>
+<DT><U>Function:</U> <B>macwork:expand</B> <I>expression</I>
+<DD>Takes an R4RS expression, macro-expands it, and returns the result of
+the macro expansion.
+</DL>
+<P>
+
+<A NAME="IDX126"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:eval</B> <I>expression</I>
+<DD><A NAME="IDX127"></A>
+<DT><U>Function:</U> <B>macwork:eval</B> <I>expression</I>
+<DD><CODE>macro:eval</CODE> returns the value of <VAR>expression</VAR> in the current
+top level environment. <VAR>expression</VAR> can contain macro definitions.
+Side effects of <VAR>expression</VAR> will affect the top level
+environment.
+</DL>
+<P>
+
+<A NAME="IDX128"></A>
+</P>
+<DL>
+<DT><U>Procedure:</U> <B>macro:load</B> <I>filename</I>
+<DD><A NAME="IDX129"></A>
+<DT><U>Procedure:</U> <B>macwork:load</B> <I>filename</I>
+<DD><VAR>filename</VAR> should be a string. If filename names an existing file,
+the <CODE>macro:load</CODE> procedure reads Scheme source code expressions and
+definitions from the file and evaluates them sequentially. These source
+code expressions and definitions may contain macro definitions. The
+<CODE>macro:load</CODE> procedure does not affect the values returned by
+<CODE>current-input-port</CODE> and <CODE>current-output-port</CODE>.
+</DL>
+<P>
+
+References:
+</P>
+<P>
+
+The <CITE>Revised^4 Report on the Algorithmic Language Scheme</CITE> Clinger
+and Rees [editors]. To appear in LISP Pointers. Also available as a
+technical report from the University of Oregon, MIT AI Lab, and
+Cornell.
+</P>
+<P>
+
+<center>
+ Macros That Work. Clinger and Rees. POPL '91.
+</center>
+</P>
+<P>
+
+The supported syntax differs from the R4RS in that vectors are allowed
+as patterns and as templates and are not allowed as pattern or template
+data.
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>transformer spec ==> (syntax-rules literals rules)
+
+rules ==> ()
+ | (rule . rules)
+
+rule ==> (pattern template)
+
+pattern ==> pattern_var ; a symbol not in literals
+ | symbol ; a symbol in literals
+ | ()
+ | (pattern . pattern)
+ | (ellipsis_pattern)
+ | #(pattern*) ; extends R4RS
+ | #(pattern* ellipsis_pattern) ; extends R4RS
+ | pattern_datum
+
+template ==> pattern_var
+ | symbol
+ | ()
+ | (template2 . template2)
+ | #(template*) ; extends R4RS
+ | pattern_datum
+
+template2 ==> template
+ | ellipsis_template
+
+pattern_datum ==> string ; no vector
+ | character
+ | boolean
+ | number
+
+ellipsis_pattern ==> pattern ...
+
+ellipsis_template ==> template ...
+
+pattern_var ==> symbol ; not in literals
+
+literals ==> ()
+ | (symbol . literals)
+</pre></td></tr></table><P>
+
+<HR SIZE="6">
+<A NAME="SEC28"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC27"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.4.1 Definitions </H3>
+<!--docid::SEC28::-->
+<P>
+
+</P>
+<DL COMPACT>
+
+<DT>Scope of an ellipsis
+<DD>Within a pattern or template, the scope of an ellipsis (<CODE>...</CODE>) is
+the pattern or template that appears to its left.
+<P>
+
+</P>
+<DT>Rank of a pattern variable
+<DD>The rank of a pattern variable is the number of ellipses within whose
+scope it appears in the pattern.
+<P>
+
+</P>
+<DT>Rank of a subtemplate
+<DD>The rank of a subtemplate is the number of ellipses within whose scope
+it appears in the template.
+<P>
+
+</P>
+<DT>Template rank of an occurrence of a pattern variable
+<DD>The template rank of an occurrence of a pattern variable within a
+template is the rank of that occurrence, viewed as a subtemplate.
+<P>
+
+</P>
+<DT>Variables bound by a pattern
+<DD>The variables bound by a pattern are the pattern variables that appear
+within it.
+<P>
+
+</P>
+<DT>Referenced variables of a subtemplate
+<DD>The referenced variables of a subtemplate are the pattern variables that
+appear within it.
+<P>
+
+</P>
+<DT>Variables opened by an ellipsis template
+<DD>The variables opened by an ellipsis template are the referenced pattern
+variables whose rank is greater than the rank of the ellipsis template.
+<P>
+
+</DL>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC29"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC28"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.4.2 Restrictions </H3>
+<!--docid::SEC29::-->
+<P>
+
+No pattern variable appears more than once within a pattern.
+</P>
+<P>
+
+For every occurrence of a pattern variable within a template, the
+template rank of the occurrence must be greater than or equal to the
+pattern variable's rank.
+</P>
+<P>
+
+Every ellipsis template must open at least one variable.
+</P>
+<P>
+
+For every ellipsis template, the variables opened by an ellipsis
+template must all be bound to sequences of the same length.
+</P>
+<P>
+
+The compiled form of a <VAR>rule</VAR> is
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>rule ==> (pattern template inserted)
+
+pattern ==> pattern_var
+ | symbol
+ | ()
+ | (pattern . pattern)
+ | ellipsis_pattern
+ | #(pattern)
+ | pattern_datum
+
+template ==> pattern_var
+ | symbol
+ | ()
+ | (template2 . template2)
+ | #(pattern)
+ | pattern_datum
+
+template2 ==> template
+ | ellipsis_template
+
+pattern_datum ==> string
+ | character
+ | boolean
+ | number
+
+pattern_var ==> #(V symbol rank)
+
+ellipsis_pattern ==> #(E pattern pattern_vars)
+
+ellipsis_template ==> #(E template pattern_vars)
+
+inserted ==> ()
+ | (symbol . inserted)
+
+pattern_vars ==> ()
+ | (pattern_var . pattern_vars)
+
+rank ==> exact non-negative integer
+</pre></td></tr></table><P>
+
+where V and E are unforgeable values.
+</P>
+<P>
+
+The pattern variables associated with an ellipsis pattern are the
+variables bound by the pattern, and the pattern variables associated
+with an ellipsis template are the variables opened by the ellipsis
+template.
+</P>
+<P>
+
+If the template contains a big chunk that contains no pattern variables
+or inserted identifiers, then the big chunk will be copied
+unnecessarily. That shouldn't matter very often.
+</P>
+<P>
+
+<A NAME="Syntactic Closures"></A>
+<HR SIZE="6">
+<A NAME="SEC30"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.5 Syntactic Closures </H2>
+<!--docid::SEC30::-->
+<P>
+
+<CODE>(require 'syntactic-closures)</CODE>
+<A NAME="IDX130"></A>
+</P>
+<P>
+
+<A NAME="IDX131"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:expand</B> <I>expression</I>
+<DD><A NAME="IDX132"></A>
+<DT><U>Function:</U> <B>synclo:expand</B> <I>expression</I>
+<DD>Returns scheme code with the macros and derived expression types of
+<VAR>expression</VAR> expanded to primitive expression types.
+</DL>
+<P>
+
+<A NAME="IDX133"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:eval</B> <I>expression</I>
+<DD><A NAME="IDX134"></A>
+<DT><U>Function:</U> <B>synclo:eval</B> <I>expression</I>
+<DD><CODE>macro:eval</CODE> returns the value of <VAR>expression</VAR> in the current
+top level environment. <VAR>expression</VAR> can contain macro definitions.
+Side effects of <VAR>expression</VAR> will affect the top level
+environment.
+</DL>
+<P>
+
+<A NAME="IDX135"></A>
+</P>
+<DL>
+<DT><U>Procedure:</U> <B>macro:load</B> <I>filename</I>
+<DD><A NAME="IDX136"></A>
+<DT><U>Procedure:</U> <B>synclo:load</B> <I>filename</I>
+<DD><VAR>filename</VAR> should be a string. If filename names an existing file,
+the <CODE>macro:load</CODE> procedure reads Scheme source code expressions and
+definitions from the file and evaluates them sequentially. These
+source code expressions and definitions may contain macro definitions.
+The <CODE>macro:load</CODE> procedure does not affect the values returned by
+<CODE>current-input-port</CODE> and <CODE>current-output-port</CODE>.
+</DL>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC31"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC30"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.5.1 Syntactic Closure Macro Facility </H3>
+<!--docid::SEC31::-->
+<P>
+
+<center>
+ A Syntactic Closures Macro Facility
+</center>
+<center>
+ by Chris Hanson
+</center>
+<center>
+ 9 November 1991
+</center>
+</P>
+<P>
+
+This document describes <EM>syntactic closures</EM>, a low-level macro
+facility for the Scheme programming language. The facility is an
+alternative to the low-level macro facility described in the
+<CITE>Revised^4 Report on Scheme.</CITE> This document is an addendum to that
+report.
+</P>
+<P>
+
+The syntactic closures facility extends the BNF rule for
+<VAR>transformer spec</VAR> to allow a new keyword that introduces a
+low-level macro transformer:
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre><VAR>transformer spec</VAR> := (transformer <VAR>expression</VAR>)
+</pre></td></tr></table><P>
+
+Additionally, the following procedures are added:
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>make-syntactic-closure
+capture-syntactic-environment
+identifier?
+identifier=?
+</pre></td></tr></table><P>
+
+The description of the facility is divided into three parts. The first
+part defines basic terminology. The second part describes how macro
+transformers are defined. The third part describes the use of
+<EM>identifiers</EM>, which extend the syntactic closure mechanism to be
+compatible with <CODE>syntax-rules</CODE>.
+</P>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC32"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC31"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H4> 3.5.1.1 Terminology </H4>
+<!--docid::SEC32::-->
+<P>
+
+This section defines the concepts and data types used by the syntactic
+closures facility.
+</P>
+<P>
+
+<UL>
+
+<LI><EM>Forms</EM> are the syntactic entities out of which programs are
+recursively constructed. A form is any expression, any definition, any
+syntactic keyword, or any syntactic closure. The variable name that
+appears in a <CODE>set!</CODE> special form is also a form. Examples of
+forms:
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>17
+#t
+car
+(+ x 4)
+(lambda (x) x)
+(define pi 3.14159)
+if
+define
+</pre></td></tr></table><P>
+
+</P>
+<LI>An <EM>alias</EM> is an alternate name for a given symbol. It can
+appear anywhere in a form that the symbol could be used, and when quoted
+it is replaced by the symbol; however, it does not satisfy the predicate
+<CODE>symbol?</CODE>. Macro transformers rarely distinguish symbols from
+aliases, referring to both as identifiers.
+<P>
+
+</P>
+<LI>A <EM>syntactic</EM> environment maps identifiers to their
+meanings. More precisely, it determines whether an identifier is a
+syntactic keyword or a variable. If it is a keyword, the meaning is an
+interpretation for the form in which that keyword appears. If it is a
+variable, the meaning identifies which binding of that variable is
+referenced. In short, syntactic environments contain all of the
+contextual information necessary for interpreting the meaning of a
+particular form.
+<P>
+
+</P>
+<LI>A <EM>syntactic closure</EM> consists of a form, a syntactic
+environment, and a list of identifiers. All identifiers in the form
+take their meaning from the syntactic environment, except those in the
+given list. The identifiers in the list are to have their meanings
+determined later. A syntactic closure may be used in any context in
+which its form could have been used. Since a syntactic closure is also
+a form, it may not be used in contexts where a form would be illegal.
+For example, a form may not appear as a clause in the cond special form.
+A syntactic closure appearing in a quoted structure is replaced by its
+form.
+<P>
+
+</UL>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC33"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC32"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H4> 3.5.1.2 Transformer Definition </H4>
+<!--docid::SEC33::-->
+<P>
+
+This section describes the <CODE>transformer</CODE> special form and the
+procedures <CODE>make-syntactic-closure</CODE> and
+<CODE>capture-syntactic-environment</CODE>.
+</P>
+<P>
+
+<A NAME="IDX137"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>transformer</B> <I>expression</I>
+<DD><P>
+
+Syntax: It is an error if this syntax occurs except as a
+<VAR>transformer spec</VAR>.
+</P>
+<P>
+
+Semantics: The <VAR>expression</VAR> is evaluated in the standard transformer
+environment to yield a macro transformer as described below. This macro
+transformer is bound to a macro keyword by the special form in which the
+<CODE>transformer</CODE> expression appears (for example,
+<CODE>let-syntax</CODE>).
+</P>
+<P>
+
+A <EM>macro transformer</EM> is a procedure that takes two arguments, a
+form and a syntactic environment, and returns a new form. The first
+argument, the <EM>input form</EM>, is the form in which the macro keyword
+occurred. The second argument, the <EM>usage environment</EM>, is the
+syntactic environment in which the input form occurred. The result of
+the transformer, the <EM>output form</EM>, is automatically closed in the
+<EM>transformer environment</EM>, which is the syntactic environment in
+which the <CODE>transformer</CODE> expression occurred.
+</P>
+<P>
+
+For example, here is a definition of a push macro using
+<CODE>syntax-rules</CODE>:
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax push
+ (syntax-rules ()
+ ((push item list)
+ (set! list (cons item list)))))
+</pre></td></tr></table><P>
+
+Here is an equivalent definition using <CODE>transformer</CODE>:
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax push
+ (transformer
+ (lambda (exp env)
+ (let ((item
+ (make-syntactic-closure env '() (cadr exp)))
+ (list
+ (make-syntactic-closure env '() (caddr exp))))
+ `(set! ,list (cons ,item ,list))))))
+</pre></td></tr></table><P>
+
+In this example, the identifiers <CODE>set!</CODE> and <CODE>cons</CODE> are closed
+in the transformer environment, and thus will not be affected by the
+meanings of those identifiers in the usage environment
+<CODE>env</CODE>.
+</P>
+<P>
+
+Some macros may be non-hygienic by design. For example, the following
+defines a loop macro that implicitly binds <CODE>exit</CODE> to an escape
+procedure. The binding of <CODE>exit</CODE> is intended to capture free
+references to <CODE>exit</CODE> in the body of the loop, so <CODE>exit</CODE> must
+be left free when the body is closed:
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax loop
+ (transformer
+ (lambda (exp env)
+ (let ((body (cdr exp)))
+ `(call-with-current-continuation
+ (lambda (exit)
+ (let f ()
+ ,@(map (lambda (exp)
+ (make-syntactic-closure env '(exit)
+ exp))
+ body)
+ (f))))))))
+</pre></td></tr></table><P>
+
+To assign meanings to the identifiers in a form, use
+<CODE>make-syntactic-closure</CODE> to close the form in a syntactic
+environment.
+</P>
+</DL>
+<P>
+
+<A NAME="IDX138"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>make-syntactic-closure</B> <I>environment free-names form</I>
+<DD><P>
+
+<VAR>environment</VAR> must be a syntactic environment, <VAR>free-names</VAR> must
+be a list of identifiers, and <VAR>form</VAR> must be a form.
+<CODE>make-syntactic-closure</CODE> constructs and returns a syntactic closure
+of <VAR>form</VAR> in <VAR>environment</VAR>, which can be used anywhere that
+<VAR>form</VAR> could have been used. All the identifiers used in
+<VAR>form</VAR>, except those explicitly excepted by <VAR>free-names</VAR>, obtain
+their meanings from <VAR>environment</VAR>.
+</P>
+<P>
+
+Here is an example where <VAR>free-names</VAR> is something other than the
+empty list. It is instructive to compare the use of <VAR>free-names</VAR> in
+this example with its use in the <CODE>loop</CODE> example above: the examples
+are similar except for the source of the identifier being left
+free.
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax let1
+ (transformer
+ (lambda (exp env)
+ (let ((id (cadr exp))
+ (init (caddr exp))
+ (exp (cadddr exp)))
+ `((lambda (,id)
+ ,(make-syntactic-closure env (list id) exp))
+ ,(make-syntactic-closure env '() init))))))
+</pre></td></tr></table><P>
+
+<CODE>let1</CODE> is a simplified version of <CODE>let</CODE> that only binds a
+single identifier, and whose body consists of a single expression. When
+the body expression is syntactically closed in its original syntactic
+environment, the identifier that is to be bound by <CODE>let1</CODE> must be
+left free, so that it can be properly captured by the <CODE>lambda</CODE> in
+the output form.
+</P>
+<P>
+
+To obtain a syntactic environment other than the usage environment, use
+<CODE>capture-syntactic-environment</CODE>.
+</P>
+</DL>
+<P>
+
+<A NAME="IDX139"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>capture-syntactic-environment</B> <I>procedure</I>
+<DD><P>
+
+<CODE>capture-syntactic-environment</CODE> returns a form that will, when
+transformed, call <VAR>procedure</VAR> on the current syntactic environment.
+<VAR>procedure</VAR> should compute and return a new form to be transformed,
+in that same syntactic environment, in place of the form.
+</P>
+<P>
+
+An example will make this clear. Suppose we wanted to define a simple
+<CODE>loop-until</CODE> keyword equivalent to
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax loop-until
+ (syntax-rules ()
+ ((loop-until id init test return step)
+ (letrec ((loop
+ (lambda (id)
+ (if test return (loop step)))))
+ (loop init)))))
+</pre></td></tr></table><P>
+
+The following attempt at defining <CODE>loop-until</CODE> has a subtle bug:
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax loop-until
+ (transformer
+ (lambda (exp env)
+ (let ((id (cadr exp))
+ (init (caddr exp))
+ (test (cadddr exp))
+ (return (cadddr (cdr exp)))
+ (step (cadddr (cddr exp)))
+ (close
+ (lambda (exp free)
+ (make-syntactic-closure env free exp))))
+ `(letrec ((loop
+ (lambda (,id)
+ (if ,(close test (list id))
+ ,(close return (list id))
+ (loop ,(close step (list id)))))))
+ (loop ,(close init '())))))))
+</pre></td></tr></table><P>
+
+This definition appears to take all of the proper precautions to prevent
+unintended captures. It carefully closes the subexpressions in their
+original syntactic environment and it leaves the <CODE>id</CODE> identifier
+free in the <CODE>test</CODE>, <CODE>return</CODE>, and <CODE>step</CODE> expressions, so
+that it will be captured by the binding introduced by the <CODE>lambda</CODE>
+expression. Unfortunately it uses the identifiers <CODE>if</CODE> and
+<CODE>loop</CODE> within that <CODE>lambda</CODE> expression, so if the user of
+<CODE>loop-until</CODE> just happens to use, say, <CODE>if</CODE> for the
+identifier, it will be inadvertently captured.
+</P>
+<P>
+
+The syntactic environment that <CODE>if</CODE> and <CODE>loop</CODE> want to be
+exposed to is the one just outside the <CODE>lambda</CODE> expression: before
+the user's identifier is added to the syntactic environment, but after
+the identifier loop has been added.
+<CODE>capture-syntactic-environment</CODE> captures exactly that environment
+as follows:
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define-syntax loop-until
+ (transformer
+ (lambda (exp env)
+ (let ((id (cadr exp))
+ (init (caddr exp))
+ (test (cadddr exp))
+ (return (cadddr (cdr exp)))
+ (step (cadddr (cddr exp)))
+ (close
+ (lambda (exp free)
+ (make-syntactic-closure env free exp))))
+ `(letrec ((loop
+ ,(capture-syntactic-environment
+ (lambda (env)
+ `(lambda (,id)
+ (,(make-syntactic-closure env '() `if)
+ ,(close test (list id))
+ ,(close return (list id))
+ (,(make-syntactic-closure env '()
+ `loop)
+ ,(close step (list id)))))))))
+ (loop ,(close init '())))))))
+</pre></td></tr></table><P>
+
+In this case, having captured the desired syntactic environment, it is
+convenient to construct syntactic closures of the identifiers <CODE>if</CODE>
+and the <CODE>loop</CODE> and use them in the body of the
+<CODE>lambda</CODE>.
+</P>
+<P>
+
+A common use of <CODE>capture-syntactic-environment</CODE> is to get the
+transformer environment of a macro transformer:
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(transformer
+ (lambda (exp env)
+ (capture-syntactic-environment
+ (lambda (transformer-env)
+ ...))))
+</pre></td></tr></table></DL>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC34"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC33"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H4> 3.5.1.3 Identifiers </H4>
+<!--docid::SEC34::-->
+<P>
+
+This section describes the procedures that create and manipulate
+identifiers. Previous syntactic closure proposals did not have an
+identifier data type -- they just used symbols. The identifier data
+type extends the syntactic closures facility to be compatible with the
+high-level <CODE>syntax-rules</CODE> facility.
+</P>
+<P>
+
+As discussed earlier, an identifier is either a symbol or an
+<EM>alias</EM>. An alias is implemented as a syntactic closure whose
+<EM>form</EM> is an identifier:
+</P>
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(make-syntactic-closure env '() 'a)
+ => an <EM>alias</EM>
+</pre></td></tr></table><P>
+
+Aliases are implemented as syntactic closures because they behave just
+like syntactic closures most of the time. The difference is that an
+alias may be bound to a new value (for example by <CODE>lambda</CODE> or
+<CODE>let-syntax</CODE>); other syntactic closures may not be used this way.
+If an alias is bound, then within the scope of that binding it is looked
+up in the syntactic environment just like any other identifier.
+</P>
+<P>
+
+Aliases are used in the implementation of the high-level facility
+<CODE>syntax-rules</CODE>. A macro transformer created by <CODE>syntax-rules</CODE>
+uses a template to generate its output form, substituting subforms of
+the input form into the template. In a syntactic closures
+implementation, all of the symbols in the template are replaced by
+aliases closed in the transformer environment, while the output form
+itself is closed in the usage environment. This guarantees that the
+macro transformation is hygienic, without requiring the transformer to
+know the syntactic roles of the substituted input subforms.
+</P>
+<P>
+
+<A NAME="IDX140"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>identifier?</B> <I>object</I>
+<DD>Returns <CODE>#t</CODE> if <VAR>object</VAR> is an identifier, otherwise returns
+<CODE>#f</CODE>. Examples:
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(identifier? 'a)
+ => #t
+(identifier? (make-syntactic-closure env '() 'a))
+ => #t
+(identifier? &quot;a&quot;)
+ => #f
+(identifier? #\a)
+ => #f
+(identifier? 97)
+ => #f
+(identifier? #f)
+ => #f
+(identifier? '(a))
+ => #f
+(identifier? '#(a))
+ => #f
+</pre></td></tr></table><P>
+
+The predicate <CODE>eq?</CODE> is used to determine if two identifers are
+&quot;the same&quot;. Thus <CODE>eq?</CODE> can be used to compare identifiers
+exactly as it would be used to compare symbols. Often, though, it is
+useful to know whether two identifiers &quot;mean the same thing&quot;. For
+example, the <CODE>cond</CODE> macro uses the symbol <CODE>else</CODE> to identify
+the final clause in the conditional. A macro transformer for
+<CODE>cond</CODE> cannot just look for the symbol <CODE>else</CODE>, because the
+<CODE>cond</CODE> form might be the output of another macro transformer that
+replaced the symbol <CODE>else</CODE> with an alias. Instead the transformer
+must look for an identifier that &quot;means the same thing&quot; in the usage
+environment as the symbol <CODE>else</CODE> means in the transformer
+environment.
+</P>
+</DL>
+<P>
+
+<A NAME="IDX141"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>identifier=?</B> <I>environment1 identifier1 environment2 identifier2</I>
+<DD><VAR>environment1</VAR> and <VAR>environment2</VAR> must be syntactic
+environments, and <VAR>identifier1</VAR> and <VAR>identifier2</VAR> must be
+identifiers. <CODE>identifier=?</CODE> returns <CODE>#t</CODE> if the meaning of
+<VAR>identifier1</VAR> in <VAR>environment1</VAR> is the same as that of
+<VAR>identifier2</VAR> in <VAR>environment2</VAR>, otherwise it returns <CODE>#f</CODE>.
+Examples:
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(let-syntax
+ ((foo
+ (transformer
+ (lambda (form env)
+ (capture-syntactic-environment
+ (lambda (transformer-env)
+ (identifier=? transformer-env 'x env 'x)))))))
+ (list (foo)
+ (let ((x 3))
+ (foo))))
+ => (#t #f)
+</pre></td></tr></table><P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(let-syntax ((bar foo))
+ (let-syntax
+ ((foo
+ (transformer
+ (lambda (form env)
+ (capture-syntactic-environment
+ (lambda (transformer-env)
+ (identifier=? transformer-env 'foo
+ env (cadr form))))))))
+ (list (foo foo)
+ (foobar))))
+ => (#f #t)
+</pre></td></tr></table></DL>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC35"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC34"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H4> 3.5.1.4 Acknowledgements </H4>
+<!--docid::SEC35::-->
+<P>
+
+The syntactic closures facility was invented by Alan Bawden and Jonathan
+Rees. The use of aliases to implement <CODE>syntax-rules</CODE> was invented
+by Alan Bawden (who prefers to call them <EM>synthetic names</EM>). Much
+of this proposal is derived from an earlier proposal by Alan
+Bawden.
+</P>
+<P>
+
+<A NAME="Syntax-Case Macros"></A>
+<HR SIZE="6">
+<A NAME="SEC36"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC35"> &lt; </A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.6 Syntax-Case Macros </H2>
+<!--docid::SEC36::-->
+<P>
+
+<CODE>(require 'syntax-case)</CODE>
+<A NAME="IDX142"></A>
+</P>
+<P>
+
+<A NAME="IDX143"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:expand</B> <I>expression</I>
+<DD><A NAME="IDX144"></A>
+<DT><U>Function:</U> <B>syncase:expand</B> <I>expression</I>
+<DD>Returns scheme code with the macros and derived expression types of
+<VAR>expression</VAR> expanded to primitive expression types.
+</DL>
+<P>
+
+<A NAME="IDX145"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>macro:eval</B> <I>expression</I>
+<DD><A NAME="IDX146"></A>
+<DT><U>Function:</U> <B>syncase:eval</B> <I>expression</I>
+<DD><CODE>macro:eval</CODE> returns the value of <VAR>expression</VAR> in the current
+top level environment. <VAR>expression</VAR> can contain macro definitions.
+Side effects of <VAR>expression</VAR> will affect the top level
+environment.
+</DL>
+<P>
+
+<A NAME="IDX147"></A>
+</P>
+<DL>
+<DT><U>Procedure:</U> <B>macro:load</B> <I>filename</I>
+<DD><A NAME="IDX148"></A>
+<DT><U>Procedure:</U> <B>syncase:load</B> <I>filename</I>
+<DD><VAR>filename</VAR> should be a string. If filename names an existing file,
+the <CODE>macro:load</CODE> procedure reads Scheme source code expressions and
+definitions from the file and evaluates them sequentially. These
+source code expressions and definitions may contain macro definitions.
+The <CODE>macro:load</CODE> procedure does not affect the values returned by
+<CODE>current-input-port</CODE> and <CODE>current-output-port</CODE>.
+</DL>
+<P>
+
+This is version 2.1 of <CODE>syntax-case</CODE>, the low-level macro facility
+proposed and implemented by Robert Hieb and R. Kent Dybvig.
+</P>
+<P>
+
+This version is further adapted by Harald Hanche-Olsen
+&lt;hanche @ imf.unit.no&gt; to make it compatible with, and easily usable
+with, SLIB. Mainly, these adaptations consisted of:
+</P>
+<P>
+
+<UL>
+<LI>
+Removing white space from `<TT>expand.pp</TT>' to save space in the
+distribution. This file is not meant for human readers anyway<small>...</small>
+<P>
+
+</P>
+<LI>
+Removed a couple of Chez scheme dependencies.
+<P>
+
+</P>
+<LI>
+Renamed global variables used to minimize the possibility of name
+conflicts.
+<P>
+
+</P>
+<LI>
+Adding an SLIB-specific initialization file.
+<P>
+
+</P>
+<LI>
+Removing a couple extra files, most notably the documentation (but see
+below).
+</UL>
+<P>
+
+If you wish, you can see exactly what changes were done by reading the
+shell script in the file `<TT>syncase.sh</TT>'.
+</P>
+<P>
+
+The two PostScript files were omitted in order to not burden the SLIB
+distribution with them. If you do intend to use <CODE>syntax-case</CODE>,
+however, you should get these files and print them out on a PostScript
+printer. They are available with the original <CODE>syntax-case</CODE>
+distribution by anonymous FTP in
+`<TT>cs.indiana.edu:/pub/scheme/syntax-case</TT>'.
+</P>
+<P>
+
+In order to use syntax-case from an interactive top level, execute:
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(require 'syntax-case)
+<A NAME="IDX149"></A>(require 'repl)
+<A NAME="IDX150"></A>(repl:top-level macro:eval)
+</pre></td></tr></table>See the section Repl (see section <A HREF="slib_7.html#SEC264">7.5.1 Repl</A>) for more information.
+<P>
+
+To check operation of syntax-case get
+`<TT>cs.indiana.edu:/pub/scheme/syntax-case</TT>', and type
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(require 'syntax-case)
+<A NAME="IDX151"></A><A NAME="IDX152"></A>(syncase:sanity-check)
+</pre></td></tr></table><P>
+
+Beware that <CODE>syntax-case</CODE> takes a long time to load -- about 20s on
+a SPARCstation SLC (with SCM) and about 90s on a Macintosh SE/30 (with
+Gambit).
+</P>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC37"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.6.1 Notes </H3>
+<!--docid::SEC37::-->
+<P>
+
+All R4RS syntactic forms are defined, including <CODE>delay</CODE>. Along
+with <CODE>delay</CODE> are simple definitions for <CODE>make-promise</CODE> (into
+which <CODE>delay</CODE> expressions expand) and <CODE>force</CODE>.
+</P>
+<P>
+
+<CODE>syntax-rules</CODE> and <CODE>with-syntax</CODE> (described in <CITE>TR356</CITE>)
+are defined.
+</P>
+<P>
+
+<CODE>syntax-case</CODE> is actually defined as a macro that expands into
+calls to the procedure <CODE>syntax-dispatch</CODE> and the core form
+<CODE>syntax-lambda</CODE>; do not redefine these names.
+</P>
+<P>
+
+Several other top-level bindings not documented in TR356 are created:
+<UL>
+<LI>the &quot;hooks&quot; in `<TT>hooks.ss</TT>'
+<LI>the <CODE>build-</CODE> procedures in `<TT>output.ss</TT>'
+<LI><CODE>expand-syntax</CODE> (the expander)
+</UL>
+<P>
+
+The syntax of define has been extended to allow <CODE>(define <VAR>id</VAR>)</CODE>,
+which assigns <VAR>id</VAR> to some unspecified value.
+</P>
+<P>
+
+We have attempted to maintain R4RS compatibility where possible. The
+incompatibilities should be confined to `<TT>hooks.ss</TT>'. Please let us
+know if there is some incompatibility that is not flagged as such.
+</P>
+<P>
+
+Send bug reports, comments, suggestions, and questions to Kent Dybvig
+(dyb @ iuvax.cs.indiana.edu).
+</P>
+<P>
+
+<HR SIZE="6">
+<A NAME="SEC38"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC37"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC39"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.6.2 Note from SLIB maintainer </H3>
+<!--docid::SEC38::-->
+<P>
+
+<CODE>(require 'structure)</CODE>
+</P>
+<P>
+
+<A NAME="IDX153"></A>
+Included with the <CODE>syntax-case</CODE> files was `<TT>structure.scm</TT>'
+which defines a macro <CODE>define-structure</CODE>. I have no
+documentation for this macro; it is not used by any other code in
+SLIB.
+</P>
+<P>
+
+<A NAME="Fluid-Let"></A>
+<HR SIZE="6">
+<A NAME="SEC39"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC38"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC40"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.7 Fluid-Let </H2>
+<!--docid::SEC39::-->
+<P>
+
+<CODE>(require 'fluid-let)</CODE>
+<A NAME="IDX154"></A>
+</P>
+<P>
+
+<A NAME="IDX155"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>fluid-let</B> <I><CODE>(<VAR>bindings</VAR> <small>...</small>)</CODE> <VAR>forms</VAR><small>...</small></I>
+<DD></DL>
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(fluid-let ((<VAR>variable</VAR> <VAR>init</VAR>) <small>...</small>)
+ <VAR>expression</VAR> <VAR>expression</VAR> <small>...</small>)
+</pre></td></tr></table><P>
+
+The <VAR>init</VAR>s are evaluated in the current environment (in some
+unspecified order), the current values of the <VAR>variable</VAR>s are saved,
+the results are assigned to the <VAR>variable</VAR>s, the <VAR>expression</VAR>s
+are evaluated sequentially in the current environment, the
+<VAR>variable</VAR>s are restored to their original values, and the value of
+the last <VAR>expression</VAR> is returned.
+</P>
+<P>
+
+The syntax of this special form is similar to that of <CODE>let</CODE>, but
+<CODE>fluid-let</CODE> temporarily rebinds existing <VAR>variable</VAR>s. Unlike
+<CODE>let</CODE>, <CODE>fluid-let</CODE> creates no new bindings; instead it
+<EM>assigns</EM> the values of each <VAR>init</VAR> to the binding (determined
+by the rules of lexical scoping) of its corresponding
+<VAR>variable</VAR>.
+</P>
+<P>
+
+<A NAME="Yasos"></A>
+<HR SIZE="6">
+<A NAME="SEC40"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC39"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC41"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H2> 3.8 Yasos </H2>
+<!--docid::SEC40::-->
+<P>
+
+<CODE>(require 'oop)</CODE> or <CODE>(require 'yasos)</CODE>
+<A NAME="IDX156"></A>
+<A NAME="IDX157"></A>
+</P>
+<P>
+
+`Yet Another Scheme Object System' is a simple object system for Scheme
+based on the paper by Norman Adams and Jonathan Rees: <CITE>Object
+Oriented Programming in Scheme</CITE>, Proceedings of the 1988 ACM Conference
+on LISP and Functional Programming, July 1988 [ACM #552880].
+</P>
+<P>
+
+Another reference is:
+</P>
+<P>
+
+Ken Dickey.
+&lt;A HREF=&quot;ftp://ftp.cs.indiana.edu/pub/scheme-repository/doc/pubs/swob.txt&quot;&gt;
+Scheming with Objects
+&lt;/A&gt;
+<CITE>AI Expert</CITE> Volume 7, Number 10 (October 1992), pp. 24-33.
+</P>
+<P>
+
+<TABLE BORDER="0" CELLSPACING="0">
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC41">3.8.1 Terms</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">Definitions and disclaimer.</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC42">3.8.2 Interface</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">The Yasos macros and procedures.</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC43">3.8.3 Setters</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">Dylan-like setters in Yasos.</TD></TR>
+<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="slib_3.html#SEC44">3.8.4 Examples</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP">Usage of Yasos and setters.</TD></TR>
+</TABLE>
+<P>
+
+<A NAME="Yasos terms"></A>
+<HR SIZE="6">
+<A NAME="SEC41"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC40"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC42"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC40"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.8.1 Terms </H3>
+<!--docid::SEC41::-->
+<P>
+
+</P>
+<DL COMPACT>
+<DT><EM>Object</EM>
+<DD>Any Scheme data object.
+<P>
+
+</P>
+<DT><EM>Instance</EM>
+<DD>An instance of the OO system; an <EM>object</EM>.
+<P>
+
+</P>
+<DT><EM>Operation</EM>
+<DD>A <VAR>method</VAR>.
+</DL>
+<P>
+
+</P>
+<DL COMPACT>
+<DT><EM>Notes:</EM>
+<DD>The object system supports multiple inheritance. An instance can
+inherit from 0 or more ancestors. In the case of multiple inherited
+operations with the same identity, the operation used is that from the
+first ancestor which contains it (in the ancestor <CODE>let</CODE>). An
+operation may be applied to any Scheme data object--not just instances.
+As code which creates instances is just code, there are no <EM>classes</EM>
+and no meta-<VAR>anything</VAR>. Method dispatch is by a procedure call a la
+CLOS rather than by <CODE>send</CODE> syntax a la Smalltalk.
+<P>
+
+</P>
+<DT><EM>Disclaimer:</EM>
+<DD>There are a number of optimizations which can be made. This
+implementation is expository (although performance should be quite
+reasonable). See the L&amp;FP paper for some suggestions.
+</DL>
+<P>
+
+<A NAME="Yasos interface"></A>
+<HR SIZE="6">
+<A NAME="SEC42"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC41"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC43"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC40"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.8.2 Interface </H3>
+<!--docid::SEC42::-->
+<P>
+
+<A NAME="IDX158"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>define-operation</B> <I><CODE>(</CODE>opname self arg <small>...</small><CODE>)</CODE> <VAR>default-body</VAR></I>
+<DD>Defines a default behavior for data objects which don't handle the
+operation <VAR>opname</VAR>. The default behavior (for an empty
+<VAR>default-body</VAR>) is to generate an error.
+</DL>
+<P>
+
+<A NAME="IDX159"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>define-predicate</B> <I>opname?</I>
+<DD>Defines a predicate <VAR>opname?</VAR>, usually used for determining the
+<EM>type</EM> of an object, such that <CODE>(<VAR>opname?</VAR> <VAR>object</VAR>)</CODE>
+returns <CODE>#t</CODE> if <VAR>object</VAR> has an operation <VAR>opname?</VAR> and
+<CODE>#f</CODE> otherwise.
+</DL>
+<P>
+
+<A NAME="IDX160"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>object</B> <I><CODE>((<VAR>name</VAR> <VAR>self</VAR> <VAR>arg</VAR> <small>...</small>) <VAR>body</VAR>)</CODE> <small>...</small></I>
+<DD>Returns an object (an instance of the object system) with operations.
+Invoking <CODE>(<VAR>name</VAR> <VAR>object</VAR> <VAR>arg</VAR> <small>...</small></CODE> executes the
+<VAR>body</VAR> of the <VAR>object</VAR> with <VAR>self</VAR> bound to <VAR>object</VAR> and
+with argument(s) <VAR>arg</VAR><small>...</small>.
+</DL>
+<P>
+
+<A NAME="IDX161"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>object-with-ancestors</B> <I><CODE>((</CODE>ancestor1 init1<CODE>)</CODE> <small>...</small><CODE>)</CODE> operation <small>...</small></I>
+<DD>A <CODE>let</CODE>-like form of <CODE>object</CODE> for multiple inheritance. It
+returns an object inheriting the behaviour of <VAR>ancestor1</VAR> etc. An
+operation will be invoked in an ancestor if the object itself does not
+provide such a method. In the case of multiple inherited operations
+with the same identity, the operation used is the one found in the first
+ancestor in the ancestor list.
+</DL>
+<P>
+
+<A NAME="IDX162"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>operate-as</B> <I>component operation self arg <small>...</small></I>
+<DD>Used in an operation definition (of <VAR>self</VAR>) to invoke the
+<VAR>operation</VAR> in an ancestor <VAR>component</VAR> but maintain the object's
+identity. Also known as &quot;send-to-super&quot;.
+</DL>
+<P>
+
+<A NAME="IDX163"></A>
+</P>
+<DL>
+<DT><U>Procedure:</U> <B>print</B> <I>obj port</I>
+<DD>A default <CODE>print</CODE> operation is provided which is just <CODE>(format
+<VAR>port</VAR> <VAR>obj</VAR>)</CODE> (see section <A HREF="slib_4.html#SEC53">4.2 Format (version 3.0)</A>) for non-instances and prints
+<VAR>obj</VAR> preceded by `<SAMP>#&lt;INSTANCE&gt;</SAMP>' for instances.
+</DL>
+<P>
+
+<A NAME="IDX164"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>size</B> <I>obj</I>
+<DD>The default method returns the number of elements in <VAR>obj</VAR> if it is
+a vector, string or list, <CODE>2</CODE> for a pair, <CODE>1</CODE> for a character
+and by default id an error otherwise. Objects such as collections
+(see section <A HREF="slib_7.html#SEC194">7.1.9 Collections</A>) may override the default in an obvious way.
+</DL>
+<P>
+
+<A NAME="Setters"></A>
+<HR SIZE="6">
+<A NAME="SEC43"></A>
+<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
+<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC42"> &lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC44"> &gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC21"> &lt;&lt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_3.html#SEC40"> Up </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_4.html#SEC45"> &gt;&gt; </A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib.html#SEC_Top">Top</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[Index]</TD>
+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<H3> 3.8.3 Setters </H3>
+<!--docid::SEC43::-->
+<P>
+
+<EM>Setters</EM> implement <EM>generalized locations</EM> for objects
+associated with some sort of mutable state. A <EM>getter</EM> operation
+retrieves a value from a generalized location and the corresponding
+setter operation stores a value into the location. Only the getter is
+named -- the setter is specified by a procedure call as below. (Dylan
+uses special syntax.) Typically, but not necessarily, getters are
+access operations to extract values from Yasos objects (see section <A HREF="slib_3.html#SEC40">3.8 Yasos</A>).
+Several setters are predefined, corresponding to getters <CODE>car</CODE>,
+<CODE>cdr</CODE>, <CODE>string-ref</CODE> and <CODE>vector-ref</CODE> e.g., <CODE>(setter
+car)</CODE> is equivalent to <CODE>set-car!</CODE>.
+</P>
+<P>
+
+This implementation of setters is similar to that in Dylan(TM)
+(<CITE>Dylan: An object-oriented dynamic language</CITE>, Apple Computer
+Eastern Research and Technology). Common LISP provides similar
+facilities through <CODE>setf</CODE>.
+</P>
+<P>
+
+<A NAME="IDX165"></A>
+</P>
+<DL>
+<DT><U>Function:</U> <B>setter</B> <I>getter</I>
+<DD>Returns the setter for the procedure <VAR>getter</VAR>. E.g., since
+<CODE>string-ref</CODE> is the getter corresponding to a setter which is
+actually <CODE>string-set!</CODE>:
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(define foo &quot;foo&quot;)
+((setter string-ref) foo 0 #\F) ; set element 0 of foo
+foo => &quot;Foo&quot;
+</pre></td></tr></table></DL>
+<P>
+
+<A NAME="IDX166"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>set</B> <I>place new-value</I>
+<DD>If <VAR>place</VAR> is a variable name, <CODE>set</CODE> is equivalent to
+<CODE>set!</CODE>. Otherwise, <VAR>place</VAR> must have the form of a procedure
+call, where the procedure name refers to a getter and the call indicates
+an accessible generalized location, i.e., the call would return a value.
+The return value of <CODE>set</CODE> is usually unspecified unless used with a
+setter whose definition guarantees to return a useful value.
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>(set (string-ref foo 2) #\O) ; generalized location with getter
+foo => &quot;FoO&quot;
+(set foo &quot;foo&quot;) ; like set!
+foo => &quot;foo&quot;
+</pre></td></tr></table></DL>
+<P>
+
+<A NAME="IDX167"></A>
+</P>
+<DL>
+<DT><U>Procedure:</U> <B>add-setter</B> <I>getter setter</I>
+<DD>Add procedures <VAR>getter</VAR> and <VAR>setter</VAR> to the (inaccessible) list
+of valid setter/getter pairs. <VAR>setter</VAR> implements the store
+operation corresponding to the <VAR>getter</VAR> access operation for the
+relevant state. The return value is unspecified.
+</DL>
+<P>
+
+<A NAME="IDX168"></A>
+</P>
+<DL>
+<DT><U>Procedure:</U> <B>remove-setter-for</B> <I>getter</I>
+<DD>Removes the setter corresponding to the specified <VAR>getter</VAR> from the
+list of valid setters. The return value is unspecified.
+</DL>
+<P>
+
+<A NAME="IDX169"></A>
+</P>
+<DL>
+<DT><U>Syntax:</U> <B>define-access-operation</B> <I>getter-name</I>
+<DD>Shorthand for a Yasos <CODE>define-operation</CODE> defining an operation
+<VAR>getter-name</VAR> that objects may support to return the value of some
+mutable state. The default operation is to signal an error. The return
+value is unspecified.
+</DL>
+<P>
+
+<A NAME="Yasos examples"></A>
+<HR SIZE="6">
+<A NAME="SEC44"></A>
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+</TR></TABLE>
+<H3> 3.8.4 Examples </H3>
+<!--docid::SEC44::-->
+<P>
+
+<TABLE><tr><td>&nbsp;</td><td class=example><pre>;;; These definitions for PRINT and SIZE are
+;;; already supplied by
+(require 'yasos)
+
+(define-operation (print obj port)
+ (format port
+ (if (instance? obj) &quot;#&lt;instance&gt;&quot; &quot;~s&quot;)
+ obj))
+
+(define-operation (size obj)
+ (cond
+ ((vector? obj) (vector-length obj))
+ ((list? obj) (length obj))
+ ((pair? obj) 2)
+ ((string? obj) (string-length obj))
+ ((char? obj) 1)
+ (else
+ (slib:error &quot;Operation not supported: size&quot; obj))))
+
+(define-predicate cell?)
+(define-operation (fetch obj))
+(define-operation (store! obj newValue))
+
+(define (make-cell value)
+ (object
+ ((cell? self) #t)
+ ((fetch self) value)
+ ((store! self newValue)
+ (set! value newValue)
+ newValue)
+ ((size self) 1)
+ ((print self port)
+ (format port &quot;#&lt;Cell: ~s&gt;&quot; (fetch self)))))
+
+(define-operation (discard obj value)
+ (format #t &quot;Discarding ~s~%&quot; value))
+
+(define (make-filtered-cell value filter)
+ (object-with-ancestors
+ ((cell (make-cell value)))
+ ((store! self newValue)
+ (if (filter newValue)
+ (store! cell newValue)
+ (discard self newValue)))))
+
+(define-predicate array?)
+(define-operation (array-ref array index))
+(define-operation (array-set! array index value))
+
+(define (make-array num-slots)
+ (let ((anArray (make-vector num-slots)))
+ (object
+ ((array? self) #t)
+ ((size self) num-slots)
+ ((array-ref self index)
+ (vector-ref anArray index))
+ ((array-set! self index newValue)
+ (vector-set! anArray index newValue))
+ ((print self port)
+ (format port &quot;#&lt;Array ~s&gt;&quot; (size self))))))
+
+(define-operation (position obj))
+(define-operation (discarded-value obj))
+
+(define (make-cell-with-history value filter size)
+ (let ((pos 0) (most-recent-discard #f))
+ (object-with-ancestors
+ ((cell (make-filtered-call value filter))
+ (sequence (make-array size)))
+ ((array? self) #f)
+ ((position self) pos)
+ ((store! self newValue)
+ (operate-as cell store! self newValue)
+ (array-set! self pos newValue)
+ (set! pos (+ pos 1)))
+ ((discard self value)
+ (set! most-recent-discard value))
+ ((discarded-value self) most-recent-discard)
+ ((print self port)
+ (format port &quot;#&lt;Cell-with-history ~s&gt;&quot;
+ (fetch self))))))
+
+(define-access-operation fetch)
+(add-setter fetch store!)
+(define foo (make-cell 1))
+(print foo #f)
+=> &quot;#&lt;Cell: 1&gt;&quot;
+(set (fetch foo) 2)
+=>
+(print foo #f)
+=> &quot;#&lt;Cell: 2&gt;&quot;
+(fetch foo)
+=> 2
+</pre></td></tr></table><P>
+
+<A NAME="Textual Conversion Packages"></A>
+<HR SIZE="6">
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_toc.html#SEC_Contents">Contents</A>]</TD>
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+<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="slib_abt.html#SEC_About"> ? </A>]</TD>
+</TR></TABLE>
+<BR>
+<FONT SIZE="-1">
+This document was generated
+by <I>Steve Langasek</I> on <I>January, 10 2005</I>
+using <A HREF="http://texi2html.cvshome.org"><I>texi2html</I></A>
+</FONT>
+
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