commit 5bdc68d7382a054b62472cc7188e9dc3fa229de4
parent ee83e25307c4925a47700d6ddfe3144b3073a4db
Author: Greg Hendershott <greghendershott@gmail.com>
Date: Thu, 3 Apr 2014 16:52:45 -0400
Fix mismatch in examples. Fixes #7.
Diffstat:
4 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/Transform_.html b/Transform_.html
@@ -62,8 +62,8 @@ transformer can rearrange the syntax – rewrite the code – at compile
time. The pieces of syntax are moved around, but they aren’t actually
evaluated until run time.</p><p>Here is one way to do this:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3elist%29%29" class="RktValLink" data-pltdoc="x">syntax->list</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._datum-~3esyntax%29%29" class="RktValLink" data-pltdoc="x">datum->syntax</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktVal">`</span><span class="RktVal">(</span><span class="RktVal">cond</span><span class="hspace"> </span><span class="RktVal">[</span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadr%29%29" class="RktValLink" data-pltdoc="x">cadr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._caddr%29%29" class="RktValLink" data-pltdoc="x">caddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktVal">[</span><span class="RktVal">else</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadddr%29%29" class="RktValLink" data-pltdoc="x">cadddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span><span class="RktVal">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#t</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktOut">true</span></p></td></tr><tr><td><p><span class="RktRes">"true"</span></p></td></tr><tr><td><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#f</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktOut">false</span></p></td></tr><tr><td><p><span class="RktRes">"false"</span></p></td></tr></table></blockquote><p>That gave the right answer. But how? Let’s pull out the transformer
function itself, and see what it did. We start with an example of some
-input syntax:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#t</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">#<syntax:32:0 (our-if-v2 #t "true" "false")></span></p></td></tr></table></blockquote><p>1. We take the original syntax, and use <span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3edatum%29%29" class="RktValLink" data-pltdoc="x">syntax->datum</a></span> to
-change it into a plain Racket <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._list%29%29" class="RktValLink" data-pltdoc="x">list</a></span>:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3edatum%29%29" class="RktValLink" data-pltdoc="x">syntax->datum</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">(our-if-v2 #t true false)</span></p></td></tr></table></blockquote><p>2. To change this into a Racket <span class="RktSym"><a href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span> form, we need to take
+input syntax:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#t</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">#<syntax:32:0 (our-if-v2 #t "true" "false")></span></p></td></tr></table></blockquote><p>1. We take the original syntax, and use <span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3elist%29%29" class="RktValLink" data-pltdoc="x">syntax->list</a></span> to
+change it into a <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._list%29%29" class="RktValLink" data-pltdoc="x">list</a></span> of syntax objects:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3elist%29%29" class="RktValLink" data-pltdoc="x">syntax->list</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">(#<syntax:32:0 our-if-v2> #<syntax:32:0 #t> #<syntax:32:0 "true"> #<syntax:32:0 "false">)</span></p></td></tr></table></blockquote><p>2. To change this into a Racket <span class="RktSym"><a href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span> form, we need to take
the three interesting pieces—<wbr></wbr>the condition, true-expression, and
false-expression—<wbr></wbr>from the list using <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadr%29%29" class="RktValLink" data-pltdoc="x">cadr</a></span>, <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._caddr%29%29" class="RktValLink" data-pltdoc="x">caddr</a></span>,
and <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadddr%29%29" class="RktValLink" data-pltdoc="x">cadddr</a></span> and arrange them into a <span class="RktSym"><a href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span> form:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="RktVal">`</span><span class="RktVal">(</span><span class="RktVal">cond</span><span class="hspace"> </span><span class="RktVal">[</span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadr%29%29" class="RktValLink" data-pltdoc="x">cadr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._caddr%29%29" class="RktValLink" data-pltdoc="x">caddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">[</span><span class="RktVal">else</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadddr%29%29" class="RktValLink" data-pltdoc="x">cadddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span><span class="RktVal">)</span></td></tr></table></blockquote><p>3. Finally, we change that into <span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._syntax%29%29" class="RktStxLink" data-pltdoc="x">syntax</a></span> using
diff --git a/all.html b/all.html
@@ -1,6 +1,6 @@
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>Fear of Macros</title><link rel="stylesheet" type="text/css" href="scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="racket.css" title="default"/><link rel="stylesheet" type="text/css" href="manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="gh.css" title="default"/><script type="text/javascript" src="scribble-common.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--><meta name="keywords" content="Racket,macros,Scheme"><meta name="description" content="Practical Racket macros"><meta name="author" content="Greg Hendershott"><meta name="charset" content="utf-8"><link href='http://fonts.googleapis.com/css?family=Fenix' rel='stylesheet' type='text/css'><script type="text/javascript">var _gaq = _gaq || [];_gaq.push(['_setAccount', 'UA-29709446-1']);_gaq.push(['_setDomainName', 'greghendershott.com']);_gaq.push(['_trackPageview']);(function() {var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);})();</script></head><body id="scribble-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">►</a></td><td></td><td><a href="" class="tocviewselflink" data-pltdoc="x">Fear of Macros</a></td></tr></table></div><div class="tocviewsublistonly" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="#%28part._.Preface%29" class="tocviewlink" data-pltdoc="x">Preface</a></td></tr><tr><td align="right">2 </td><td><a href="#%28part._.Our_plan_of_attack%29" class="tocviewlink" data-pltdoc="x">Our plan of attack</a></td></tr><tr><td align="right">3 </td><td><a href="#%28part._.Transform_%29" class="tocviewlink" data-pltdoc="x">Transform!</a></td></tr><tr><td align="right">4 </td><td><a href="#%28part._pattern-matching%29" class="tocviewlink" data-pltdoc="x">Pattern matching:<span class="mywbr"> </span> syntax-<wbr></wbr>case and syntax-<wbr></wbr>rules</a></td></tr><tr><td align="right">5 </td><td><a href="#%28part._.Syntax_parameters%29" class="tocviewlink" data-pltdoc="x">Syntax parameters</a></td></tr><tr><td align="right">6 </td><td><a href="#%28part._.What_s_the_point_of_splicing-let_%29" class="tocviewlink" data-pltdoc="x">What’s the point of <span class="RktSym"><span class="RktStxLink">splicing-<wbr></wbr>let</span></span>?</a></td></tr><tr><td align="right">7 </td><td><a href="#%28part._.Robust_macros__syntax-parse%29" class="tocviewlink" data-pltdoc="x">Robust macros:<span class="mywbr"> </span> syntax-<wbr></wbr>parse</a></td></tr><tr><td align="right">8 </td><td><a href="#%28part._.References_and_.Acknowledgments%29" class="tocviewlink" data-pltdoc="x">References and Acknowledgments</a></td></tr><tr><td align="right">9 </td><td><a href="#%28part._.Epilogue%29" class="tocviewlink" data-pltdoc="x">Epilogue</a></td></tr></table></div></div></div><div class="tocsub"><table class="tocsublist" cellspacing="0"><tr><td><span class="tocsublinknumber"></span><a href="#%28part._.Fear_of_.Macros%29" class="tocsubseclink" data-pltdoc="x">Fear of Macros</a></td></tr><tr><td><span class="tocsublinknumber">1<tt> </tt></span><a href="#%28part._.Preface%29" class="tocsubseclink" data-pltdoc="x">Preface</a></td></tr><tr><td><span class="tocsublinknumber">2<tt> </tt></span><a href="#%28part._.Our_plan_of_attack%29" class="tocsubseclink" data-pltdoc="x">Our plan of attack</a></td></tr><tr><td><span class="tocsublinknumber">3<tt> </tt></span><a href="#%28part._.Transform_%29" class="tocsubseclink" data-pltdoc="x">Transform!</a></td></tr><tr><td><span class="tocsublinknumber">3.1<tt> </tt></span><a href="#%28part._.What_is_a_syntax_transformer_%29" class="tocsubseclink" data-pltdoc="x">What is a syntax transformer?</a></td></tr><tr><td><span class="tocsublinknumber">3.2<tt> </tt></span><a href="#%28part._.What_s_the_input_%29" class="tocsubseclink" data-pltdoc="x">What’s the input?</a></td></tr><tr><td><span class="tocsublinknumber">3.3<tt> </tt></span><a href="#%28part._.Actually_transforming_the_input%29" class="tocsubseclink" data-pltdoc="x">Actually transforming the input</a></td></tr><tr><td><span class="tocsublinknumber">3.4<tt> </tt></span><a href="#%28part._.Compile_time_vs__run_time%29" class="tocsubseclink" data-pltdoc="x">Compile time vs. run time</a></td></tr><tr><td><span class="tocsublinknumber">3.5<tt> </tt></span><a href="#%28part._begin-for-syntax%29" class="tocsubseclink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">begin-<wbr></wbr>for-<wbr></wbr>syntax</span></span></a></td></tr><tr><td><span class="tocsublinknumber">4<tt> </tt></span><a href="#%28part._pattern-matching%29" class="tocsubseclink" data-pltdoc="x">Pattern matching:<span class="mywbr"> </span> syntax-<wbr></wbr>case and syntax-<wbr></wbr>rules</a></td></tr><tr><td><span class="tocsublinknumber">4.1<tt> </tt></span><a href="#%28part._.Pattern_variable_vs__template---fight_%29" class="tocsubseclink" data-pltdoc="x">Pattern variable vs. template—<wbr></wbr>fight!</a></td></tr><tr><td><span class="tocsublinknumber">4.1.1<tt> </tt></span><a href="#%28part._with-syntax%29" class="tocsubseclink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">with-<wbr></wbr>syntax</span></span></a></td></tr><tr><td><span class="tocsublinknumber">4.1.2<tt> </tt></span><a href="#%28part._with-syntax_%29" class="tocsubseclink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">with-<wbr></wbr>syntax*</span></span></a></td></tr><tr><td><span class="tocsublinknumber">4.1.3<tt> </tt></span><a href="#%28part._format-id%29" class="tocsubseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">format-<wbr></wbr>id</span></span></a></td></tr><tr><td><span class="tocsublinknumber">4.1.4<tt> </tt></span><a href="#%28part._.Another_example%29" class="tocsubseclink" data-pltdoc="x">Another example</a></td></tr><tr><td><span class="tocsublinknumber">4.2<tt> </tt></span><a href="#%28part._.Making_our_own_struct%29" class="tocsubseclink" data-pltdoc="x">Making our own <span class="RktSym"><span class="RktStxLink">struct</span></span></a></td></tr><tr><td><span class="tocsublinknumber">4.3<tt> </tt></span><a href="#%28part._hash..refs%29" class="tocsubseclink" data-pltdoc="x">Using dot notation for nested hash lookups</a></td></tr><tr><td><span class="tocsublinknumber">5<tt> </tt></span><a href="#%28part._.Syntax_parameters%29" class="tocsubseclink" data-pltdoc="x">Syntax parameters</a></td></tr><tr><td><span class="tocsublinknumber">6<tt> </tt></span><a href="#%28part._.What_s_the_point_of_splicing-let_%29" class="tocsubseclink" data-pltdoc="x">What’s the point of <span class="RktSym"><span class="RktStxLink">splicing-<wbr></wbr>let</span></span>?</a></td></tr><tr><td><span class="tocsublinknumber">7<tt> </tt></span><a href="#%28part._.Robust_macros__syntax-parse%29" class="tocsubseclink" data-pltdoc="x">Robust macros:<span class="mywbr"> </span> syntax-<wbr></wbr>parse</a></td></tr><tr><td><span class="tocsublinknumber">7.1<tt> </tt></span><a href="#%28part._.Error-handling_strategies_for_functions%29" class="tocsubseclink" data-pltdoc="x">Error-<wbr></wbr>handling strategies for functions</a></td></tr><tr><td><span class="tocsublinknumber">7.2<tt> </tt></span><a href="#%28part._.Error-handling_strategies_for_macros%29" class="tocsubseclink" data-pltdoc="x">Error-<wbr></wbr>handling strategies for macros</a></td></tr><tr><td><span class="tocsublinknumber">7.3<tt> </tt></span><a href="#%28part._.Using_syntax-parse%29" class="tocsubseclink" data-pltdoc="x">Using <span class="RktSym"><span class="RktStxLink">syntax-<wbr></wbr>parse</span></span></a></td></tr><tr><td><span class="tocsublinknumber">8<tt> </tt></span><a href="#%28part._.References_and_.Acknowledgments%29" class="tocsubseclink" data-pltdoc="x">References and Acknowledgments</a></td></tr><tr><td><span class="tocsublinknumber">9<tt> </tt></span><a href="#%28part._.Epilogue%29" class="tocsubseclink" data-pltdoc="x">Epilogue</a></td></tr></table></div></div><div class="maincolumn"><div class="main"><h2><a name="(part._.Fear_of_.Macros)"></a>Fear of Macros</h2><div class="SAuthorListBox"><span class="SAuthorList"><p class="author"><a href="http://www.greghendershott.com">Greg Hendershott</a></p></span></div><p><div class="SIntrapara"></div><div class="SIntrapara"><img src="fear-of-macros.jpg" alt=""/>
-</div><div class="SIntrapara"><span class="Smaller">Copyright (c) 2012-2014 by Greg Hendershott. All rights reserved.</span></div><div class="SIntrapara"><span class="Smaller">Last updated 2014-03-25T08:52:41</span></div><div class="SIntrapara">Feedback and corrections are <a href="https://github.com/greghendershott/fear-of-macros/issues">welcome here</a>.</div></p><p>Contents:</p><table cellspacing="0"><tr><td><p><span class="hspace"> </span><a href="#%28part._.Preface%29" class="toptoclink" data-pltdoc="x">1<span class="hspace"> </span>Preface</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Our_plan_of_attack%29" class="toptoclink" data-pltdoc="x">2<span class="hspace"> </span>Our plan of attack</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Transform_%29" class="toptoclink" data-pltdoc="x">3<span class="hspace"> </span>Transform!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.What_is_a_syntax_transformer_%29" class="toclink" data-pltdoc="x">3.1<span class="hspace"> </span>What is a syntax transformer?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.What_s_the_input_%29" class="toclink" data-pltdoc="x">3.2<span class="hspace"> </span>What’s the input?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Actually_transforming_the_input%29" class="toclink" data-pltdoc="x">3.3<span class="hspace"> </span>Actually transforming the input</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Compile_time_vs__run_time%29" class="toclink" data-pltdoc="x">3.4<span class="hspace"> </span>Compile time vs. run time</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._begin-for-syntax%29" class="toclink" data-pltdoc="x">3.5<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">begin-for-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._pattern-matching%29" class="toptoclink" data-pltdoc="x">4<span class="hspace"> </span>Pattern matching: syntax-case and syntax-rules</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Pattern_variable_vs__template---fight_%29" class="toclink" data-pltdoc="x">4.1<span class="hspace"> </span>Pattern variable vs. template—<wbr></wbr>fight!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._with-syntax%29" class="toclink" data-pltdoc="x">4.1.1<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._with-syntax_%29" class="toclink" data-pltdoc="x">4.1.2<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax*</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._format-id%29" class="toclink" data-pltdoc="x">4.1.3<span class="hspace"> </span><span class="RktSym"><span class="RktValLink">format-id</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Another_example%29" class="toclink" data-pltdoc="x">4.1.4<span class="hspace"> </span>Another example</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Making_our_own_struct%29" class="toclink" data-pltdoc="x">4.2<span class="hspace"> </span>Making our own <span class="RktSym"><span class="RktStxLink">struct</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._hash..refs%29" class="toclink" data-pltdoc="x">4.3<span class="hspace"> </span>Using dot notation for nested hash lookups</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Syntax_parameters%29" class="toptoclink" data-pltdoc="x">5<span class="hspace"> </span>Syntax parameters</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.What_s_the_point_of_splicing-let_%29" class="toptoclink" data-pltdoc="x">6<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">splicing-let</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Robust_macros__syntax-parse%29" class="toptoclink" data-pltdoc="x">7<span class="hspace"> </span>Robust macros: syntax-parse</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Error-handling_strategies_for_functions%29" class="toclink" data-pltdoc="x">7.1<span class="hspace"> </span>Error-handling strategies for functions</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Error-handling_strategies_for_macros%29" class="toclink" data-pltdoc="x">7.2<span class="hspace"> </span>Error-handling strategies for macros</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Using_syntax-parse%29" class="toclink" data-pltdoc="x">7.3<span class="hspace"> </span>Using <span class="RktSym"><span class="RktStxLink">syntax-parse</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.References_and_.Acknowledgments%29" class="toptoclink" data-pltdoc="x">8<span class="hspace"> </span>References and Acknowledgments</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Epilogue%29" class="toptoclink" data-pltdoc="x">9<span class="hspace"> </span>Epilogue</a></p></td></tr></table><h3>1<tt> </tt><a name="(part._.Preface)"></a>Preface</h3><p>I learned Racket after 25 years of mostly using C and C++.</p><p>Some psychic whiplash resulted.</p><p>"All the parentheses" was actually not a big deal. Instead, the first
+</div><div class="SIntrapara"><span class="Smaller">Copyright (c) 2012-2014 by Greg Hendershott. All rights reserved.</span></div><div class="SIntrapara"><span class="Smaller">Last updated 2014-04-03T16:51:14</span></div><div class="SIntrapara">Feedback and corrections are <a href="https://github.com/greghendershott/fear-of-macros/issues">welcome here</a>.</div></p><p>Contents:</p><table cellspacing="0"><tr><td><p><span class="hspace"> </span><a href="#%28part._.Preface%29" class="toptoclink" data-pltdoc="x">1<span class="hspace"> </span>Preface</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Our_plan_of_attack%29" class="toptoclink" data-pltdoc="x">2<span class="hspace"> </span>Our plan of attack</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Transform_%29" class="toptoclink" data-pltdoc="x">3<span class="hspace"> </span>Transform!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.What_is_a_syntax_transformer_%29" class="toclink" data-pltdoc="x">3.1<span class="hspace"> </span>What is a syntax transformer?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.What_s_the_input_%29" class="toclink" data-pltdoc="x">3.2<span class="hspace"> </span>What’s the input?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Actually_transforming_the_input%29" class="toclink" data-pltdoc="x">3.3<span class="hspace"> </span>Actually transforming the input</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Compile_time_vs__run_time%29" class="toclink" data-pltdoc="x">3.4<span class="hspace"> </span>Compile time vs. run time</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._begin-for-syntax%29" class="toclink" data-pltdoc="x">3.5<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">begin-for-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._pattern-matching%29" class="toptoclink" data-pltdoc="x">4<span class="hspace"> </span>Pattern matching: syntax-case and syntax-rules</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Pattern_variable_vs__template---fight_%29" class="toclink" data-pltdoc="x">4.1<span class="hspace"> </span>Pattern variable vs. template—<wbr></wbr>fight!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._with-syntax%29" class="toclink" data-pltdoc="x">4.1.1<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._with-syntax_%29" class="toclink" data-pltdoc="x">4.1.2<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax*</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._format-id%29" class="toclink" data-pltdoc="x">4.1.3<span class="hspace"> </span><span class="RktSym"><span class="RktValLink">format-id</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Another_example%29" class="toclink" data-pltdoc="x">4.1.4<span class="hspace"> </span>Another example</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Making_our_own_struct%29" class="toclink" data-pltdoc="x">4.2<span class="hspace"> </span>Making our own <span class="RktSym"><span class="RktStxLink">struct</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._hash..refs%29" class="toclink" data-pltdoc="x">4.3<span class="hspace"> </span>Using dot notation for nested hash lookups</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Syntax_parameters%29" class="toptoclink" data-pltdoc="x">5<span class="hspace"> </span>Syntax parameters</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.What_s_the_point_of_splicing-let_%29" class="toptoclink" data-pltdoc="x">6<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">splicing-let</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Robust_macros__syntax-parse%29" class="toptoclink" data-pltdoc="x">7<span class="hspace"> </span>Robust macros: syntax-parse</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Error-handling_strategies_for_functions%29" class="toclink" data-pltdoc="x">7.1<span class="hspace"> </span>Error-handling strategies for functions</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Error-handling_strategies_for_macros%29" class="toclink" data-pltdoc="x">7.2<span class="hspace"> </span>Error-handling strategies for macros</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Using_syntax-parse%29" class="toclink" data-pltdoc="x">7.3<span class="hspace"> </span>Using <span class="RktSym"><span class="RktStxLink">syntax-parse</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.References_and_.Acknowledgments%29" class="toptoclink" data-pltdoc="x">8<span class="hspace"> </span>References and Acknowledgments</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#%28part._.Epilogue%29" class="toptoclink" data-pltdoc="x">9<span class="hspace"> </span>Epilogue</a></p></td></tr></table><h3>1<tt> </tt><a name="(part._.Preface)"></a>Preface</h3><p>I learned Racket after 25 years of mostly using C and C++.</p><p>Some psychic whiplash resulted.</p><p>"All the parentheses" was actually not a big deal. Instead, the first
mind warp was functional programming. Before long I wrapped my brain
around it, and went on to become comfortable and effective with many
other aspects and features of Racket.</p><p>But two final frontiers remained: Macros and continuations.</p><p>I found that simple macros were easy and understandable, plus there
@@ -105,8 +105,8 @@ transformer can rearrange the syntax – rewrite the code – at compile
time. The pieces of syntax are moved around, but they aren’t actually
evaluated until run time.</p><p>Here is one way to do this:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3elist%29%29" class="RktValLink" data-pltdoc="x">syntax->list</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._datum-~3esyntax%29%29" class="RktValLink" data-pltdoc="x">datum->syntax</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktVal">`</span><span class="RktVal">(</span><span class="RktVal">cond</span><span class="hspace"> </span><span class="RktVal">[</span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadr%29%29" class="RktValLink" data-pltdoc="x">cadr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._caddr%29%29" class="RktValLink" data-pltdoc="x">caddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktVal">[</span><span class="RktVal">else</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadddr%29%29" class="RktValLink" data-pltdoc="x">cadddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span><span class="RktVal">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#t</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktOut">true</span></p></td></tr><tr><td><p><span class="RktRes">"true"</span></p></td></tr><tr><td><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#f</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPlain"><span class="hspace"> </span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">display-and-return</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktOut">false</span></p></td></tr><tr><td><p><span class="RktRes">"false"</span></p></td></tr></table></blockquote><p>That gave the right answer. But how? Let’s pull out the transformer
function itself, and see what it did. We start with an example of some
-input syntax:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#t</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">#<syntax:32:0 (our-if-v2 #t "true" "false")></span></p></td></tr></table></blockquote><p>1. We take the original syntax, and use <span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3edatum%29%29" class="RktValLink" data-pltdoc="x">syntax->datum</a></span> to
-change it into a plain Racket <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._list%29%29" class="RktValLink" data-pltdoc="x">list</a></span>:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3edatum%29%29" class="RktValLink" data-pltdoc="x">syntax->datum</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">(our-if-v2 #t true false)</span></p></td></tr></table></blockquote><p>2. To change this into a Racket <span class="RktSym"><a href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span> form, we need to take
+input syntax:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktPn">(</span><span class="RktSym">our-if-v2</span><span class="hspace"> </span><span class="RktVal">#t</span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="hspace"> </span><span class="RktVal">"false"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">#<syntax:32:0 (our-if-v2 #t "true" "false")></span></p></td></tr></table></blockquote><p>1. We take the original syntax, and use <span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3elist%29%29" class="RktValLink" data-pltdoc="x">syntax->list</a></span> to
+change it into a <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._list%29%29" class="RktValLink" data-pltdoc="x">list</a></span> of syntax objects:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax-~3elist%29%29" class="RktValLink" data-pltdoc="x">syntax->list</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Writing.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._displayln%29%29" class="RktValLink" data-pltdoc="x">displayln</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">(#<syntax:32:0 our-if-v2> #<syntax:32:0 #t> #<syntax:32:0 "true"> #<syntax:32:0 "false">)</span></p></td></tr></table></blockquote><p>2. To change this into a Racket <span class="RktSym"><a href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span> form, we need to take
the three interesting pieces—<wbr></wbr>the condition, true-expression, and
false-expression—<wbr></wbr>from the list using <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadr%29%29" class="RktValLink" data-pltdoc="x">cadr</a></span>, <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._caddr%29%29" class="RktValLink" data-pltdoc="x">caddr</a></span>,
and <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadddr%29%29" class="RktValLink" data-pltdoc="x">cadddr</a></span> and arrange them into a <span class="RktSym"><a href="http://docs.racket-lang.org/reference/if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span> form:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="RktVal">`</span><span class="RktVal">(</span><span class="RktVal">cond</span><span class="hspace"> </span><span class="RktVal">[</span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadr%29%29" class="RktValLink" data-pltdoc="x">cadr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._caddr%29%29" class="RktValLink" data-pltdoc="x">caddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">[</span><span class="RktVal">else</span><span class="hspace"> </span><span class="RktRdr">,</span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._cadddr%29%29" class="RktValLink" data-pltdoc="x">cadddr</a></span><span class="hspace"> </span><span class="RktSym">xs</span><span class="RktPn">)</span><span class="RktVal">]</span><span class="RktVal">)</span></td></tr></table></blockquote><p>3. Finally, we change that into <span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._syntax%29%29" class="RktStxLink" data-pltdoc="x">syntax</a></span> using
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>Fear of Macros</title><link rel="stylesheet" type="text/css" href="scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="racket.css" title="default"/><link rel="stylesheet" type="text/css" href="manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="gh.css" title="default"/><script type="text/javascript" src="scribble-common.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--><meta name="keywords" content="Racket,macros,Scheme"><meta name="description" content="Practical Racket macros"><meta name="author" content="Greg Hendershott"><meta name="charset" content="utf-8"><link href='http://fonts.googleapis.com/css?family=Fenix' rel='stylesheet' type='text/css'><script type="text/javascript">var _gaq = _gaq || [];_gaq.push(['_setAccount', 'UA-29709446-1']);_gaq.push(['_setDomainName', 'greghendershott.com']);_gaq.push(['_trackPageview']);(function() {var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);})();</script></head><body id="scribble-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">▼</a></td><td></td><td><a href="" class="tocviewselflink" data-pltdoc="x">Fear of Macros</a></td></tr></table></div><div class="tocviewsublistonly" style="display: block;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="Preface.html" class="tocviewlink" data-pltdoc="x">Preface</a></td></tr><tr><td align="right">2 </td><td><a href="Our_plan_of_attack.html" class="tocviewlink" data-pltdoc="x">Our plan of attack</a></td></tr><tr><td align="right">3 </td><td><a href="Transform_.html" class="tocviewlink" data-pltdoc="x">Transform!</a></td></tr><tr><td align="right">4 </td><td><a href="pattern-matching.html" class="tocviewlink" data-pltdoc="x">Pattern matching:<span class="mywbr"> </span> syntax-<wbr></wbr>case and syntax-<wbr></wbr>rules</a></td></tr><tr><td align="right">5 </td><td><a href="Syntax_parameters.html" class="tocviewlink" data-pltdoc="x">Syntax parameters</a></td></tr><tr><td align="right">6 </td><td><a href="What_s_the_point_of_splicing-let_.html" class="tocviewlink" data-pltdoc="x">What’s the point of <span class="RktSym"><span class="RktStxLink">splicing-<wbr></wbr>let</span></span>?</a></td></tr><tr><td align="right">7 </td><td><a href="Robust_macros__syntax-parse.html" class="tocviewlink" data-pltdoc="x">Robust macros:<span class="mywbr"> </span> syntax-<wbr></wbr>parse</a></td></tr><tr><td align="right">8 </td><td><a href="References_and_Acknowledgments.html" class="tocviewlink" data-pltdoc="x">References and Acknowledgments</a></td></tr><tr><td align="right">9 </td><td><a href="Epilogue.html" class="tocviewlink" data-pltdoc="x">Epilogue</a></td></tr></table></div></div></div><div class="tocsub"><div class="tocsubtitle">On this page:</div><table class="tocsublist" cellspacing="0"><tr><td><span class="tocsublinknumber"></span><a href="#%28part._.Fear_of_.Macros%29" class="tocsubseclink" data-pltdoc="x">Fear of Macros</a></td></tr></table></div></div><div class="maincolumn"><div class="main"><div class="navsettop"><span class="navleft"> </span><span class="navright"> <span class="nonavigation">← prev</span> <span class="nonavigation">up</span> <a href="Preface.html" title="forward to "1 Preface"" data-pltdoc="x">next →</a></span> </div><h2><a name="(part._.Fear_of_.Macros)"></a>Fear of Macros</h2><div class="SAuthorListBox"><span class="SAuthorList"><p class="author"><a href="http://www.greghendershott.com">Greg Hendershott</a></p></span></div><p><div class="SIntrapara"></div><div class="SIntrapara"><img src="fear-of-macros.jpg" alt=""/>
-</div><div class="SIntrapara"><span class="Smaller">Copyright (c) 2012-2014 by Greg Hendershott. All rights reserved.</span></div><div class="SIntrapara"><span class="Smaller">Last updated 2014-03-25T08:52:33</span></div><div class="SIntrapara">Feedback and corrections are <a href="https://github.com/greghendershott/fear-of-macros/issues">welcome here</a>.</div></p><p>Contents:</p><table cellspacing="0"><tr><td><p><span class="hspace"> </span><a href="Preface.html" class="toptoclink" data-pltdoc="x">1<span class="hspace"> </span>Preface</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Our_plan_of_attack.html" class="toptoclink" data-pltdoc="x">2<span class="hspace"> </span>Our plan of attack</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html" class="toptoclink" data-pltdoc="x">3<span class="hspace"> </span>Transform!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.What_is_a_syntax_transformer_%29" class="toclink" data-pltdoc="x">3.1<span class="hspace"> </span>What is a syntax transformer?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.What_s_the_input_%29" class="toclink" data-pltdoc="x">3.2<span class="hspace"> </span>What’s the input?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.Actually_transforming_the_input%29" class="toclink" data-pltdoc="x">3.3<span class="hspace"> </span>Actually transforming the input</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.Compile_time_vs__run_time%29" class="toclink" data-pltdoc="x">3.4<span class="hspace"> </span>Compile time vs. run time</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._begin-for-syntax%29" class="toclink" data-pltdoc="x">3.5<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">begin-for-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html" class="toptoclink" data-pltdoc="x">4<span class="hspace"> </span>Pattern matching: syntax-case and syntax-rules</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._.Pattern_variable_vs__template---fight_%29" class="toclink" data-pltdoc="x">4.1<span class="hspace"> </span>Pattern variable vs. template—<wbr></wbr>fight!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._with-syntax%29" class="toclink" data-pltdoc="x">4.1.1<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._with-syntax_%29" class="toclink" data-pltdoc="x">4.1.2<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax*</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._format-id%29" class="toclink" data-pltdoc="x">4.1.3<span class="hspace"> </span><span class="RktSym"><span class="RktValLink">format-id</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._.Another_example%29" class="toclink" data-pltdoc="x">4.1.4<span class="hspace"> </span>Another example</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._.Making_our_own_struct%29" class="toclink" data-pltdoc="x">4.2<span class="hspace"> </span>Making our own <span class="RktSym"><span class="RktStxLink">struct</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._hash..refs%29" class="toclink" data-pltdoc="x">4.3<span class="hspace"> </span>Using dot notation for nested hash lookups</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Syntax_parameters.html" class="toptoclink" data-pltdoc="x">5<span class="hspace"> </span>Syntax parameters</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="What_s_the_point_of_splicing-let_.html" class="toptoclink" data-pltdoc="x">6<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">splicing-let</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html" class="toptoclink" data-pltdoc="x">7<span class="hspace"> </span>Robust macros: syntax-parse</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html#%28part._.Error-handling_strategies_for_functions%29" class="toclink" data-pltdoc="x">7.1<span class="hspace"> </span>Error-handling strategies for functions</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html#%28part._.Error-handling_strategies_for_macros%29" class="toclink" data-pltdoc="x">7.2<span class="hspace"> </span>Error-handling strategies for macros</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html#%28part._.Using_syntax-parse%29" class="toclink" data-pltdoc="x">7.3<span class="hspace"> </span>Using <span class="RktSym"><span class="RktStxLink">syntax-parse</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="References_and_Acknowledgments.html" class="toptoclink" data-pltdoc="x">8<span class="hspace"> </span>References and Acknowledgments</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Epilogue.html" class="toptoclink" data-pltdoc="x">9<span class="hspace"> </span>Epilogue</a></p></td></tr></table><div class="navsetbottom"><span class="navleft"> </span><span class="navright"> <span class="nonavigation">← prev</span> <span class="nonavigation">up</span> <a href="Preface.html" title="forward to "1 Preface"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
-\ No newline at end of file
+</div><div class="SIntrapara"><span class="Smaller">Copyright (c) 2012-2014 by Greg Hendershott. All rights reserved.</span></div><div class="SIntrapara"><span class="Smaller">Last updated 2014-04-03T16:51:05</span></div><div class="SIntrapara">Feedback and corrections are <a href="https://github.com/greghendershott/fear-of-macros/issues">welcome here</a>.</div></p><p>Contents:</p><table cellspacing="0"><tr><td><p><span class="hspace"> </span><a href="Preface.html" class="toptoclink" data-pltdoc="x">1<span class="hspace"> </span>Preface</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Our_plan_of_attack.html" class="toptoclink" data-pltdoc="x">2<span class="hspace"> </span>Our plan of attack</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html" class="toptoclink" data-pltdoc="x">3<span class="hspace"> </span>Transform!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.What_is_a_syntax_transformer_%29" class="toclink" data-pltdoc="x">3.1<span class="hspace"> </span>What is a syntax transformer?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.What_s_the_input_%29" class="toclink" data-pltdoc="x">3.2<span class="hspace"> </span>What’s the input?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.Actually_transforming_the_input%29" class="toclink" data-pltdoc="x">3.3<span class="hspace"> </span>Actually transforming the input</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._.Compile_time_vs__run_time%29" class="toclink" data-pltdoc="x">3.4<span class="hspace"> </span>Compile time vs. run time</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Transform_.html#%28part._begin-for-syntax%29" class="toclink" data-pltdoc="x">3.5<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">begin-for-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html" class="toptoclink" data-pltdoc="x">4<span class="hspace"> </span>Pattern matching: syntax-case and syntax-rules</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._.Pattern_variable_vs__template---fight_%29" class="toclink" data-pltdoc="x">4.1<span class="hspace"> </span>Pattern variable vs. template—<wbr></wbr>fight!</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._with-syntax%29" class="toclink" data-pltdoc="x">4.1.1<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._with-syntax_%29" class="toclink" data-pltdoc="x">4.1.2<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax*</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._format-id%29" class="toclink" data-pltdoc="x">4.1.3<span class="hspace"> </span><span class="RktSym"><span class="RktValLink">format-id</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._.Another_example%29" class="toclink" data-pltdoc="x">4.1.4<span class="hspace"> </span>Another example</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._.Making_our_own_struct%29" class="toclink" data-pltdoc="x">4.2<span class="hspace"> </span>Making our own <span class="RktSym"><span class="RktStxLink">struct</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-matching.html#%28part._hash..refs%29" class="toclink" data-pltdoc="x">4.3<span class="hspace"> </span>Using dot notation for nested hash lookups</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Syntax_parameters.html" class="toptoclink" data-pltdoc="x">5<span class="hspace"> </span>Syntax parameters</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="What_s_the_point_of_splicing-let_.html" class="toptoclink" data-pltdoc="x">6<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">splicing-let</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html" class="toptoclink" data-pltdoc="x">7<span class="hspace"> </span>Robust macros: syntax-parse</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html#%28part._.Error-handling_strategies_for_functions%29" class="toclink" data-pltdoc="x">7.1<span class="hspace"> </span>Error-handling strategies for functions</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html#%28part._.Error-handling_strategies_for_macros%29" class="toclink" data-pltdoc="x">7.2<span class="hspace"> </span>Error-handling strategies for macros</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Robust_macros__syntax-parse.html#%28part._.Using_syntax-parse%29" class="toclink" data-pltdoc="x">7.3<span class="hspace"> </span>Using <span class="RktSym"><span class="RktStxLink">syntax-parse</span></span></a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="References_and_Acknowledgments.html" class="toptoclink" data-pltdoc="x">8<span class="hspace"> </span>References and Acknowledgments</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Epilogue.html" class="toptoclink" data-pltdoc="x">9<span class="hspace"> </span>Epilogue</a></p></td></tr></table><div class="navsetbottom"><span class="navleft"> </span><span class="navright"> <span class="nonavigation">← prev</span> <span class="nonavigation">up</span> <a href="Preface.html" title="forward to "1 Preface"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
+\ No newline at end of file
diff --git a/index.rkt b/index.rkt
@@ -447,11 +447,11 @@ input syntax:
(displayln stx)
]
-1. We take the original syntax, and use @racket[syntax->datum] to
-change it into a plain Racket @racket[list]:
+1. We take the original syntax, and use @racket[syntax->list] to
+change it into a @racket[list] of syntax objects:
@i[
-(define xs (syntax->datum stx))
+(define xs (syntax->list stx))
(displayln xs)
]
