commit a2fc5a4dbaeb00764f27b38cbc622c10ad4ffbf9
parent 206ea43f10b54f11add073d346e20854ab3e179d
Author: Greg Hendershott <greghendershott@gmail.com>
Date: Fri, 26 Oct 2012 11:53:30 -0400
Regen index.html for latest changes.
Diffstat:
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/index.html b/index.html
@@ -2,7 +2,7 @@
<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="scribble-style.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]--><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" style="margin-bottom: 1em;"><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" 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="#(part._.Introduction)" class="tocviewlink" pltdoc="x">Introduction</a></td></tr><tr><td align="right">2 </td><td><a href="#(part._.The_plan_of_attack)" class="tocviewlink" pltdoc="x">The plan of attack</a></td></tr><tr><td align="right">3 </td><td><a href="#(part._.Transformers)" class="tocviewlink" pltdoc="x">Transformers</a></td></tr><tr><td align="right">4 </td><td><a href="#(part._.Pattern_matching__syntax-case_and_syntax-rules)" class="tocviewlink" 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="#(part._.Syntax_parameters)" class="tocviewlink" pltdoc="x">Syntax parameters</a></td></tr><tr><td align="right">6 </td><td><a href="#(part._.Robust_macros__syntax-parse)" class="tocviewlink" pltdoc="x">Robust macros:<span class="mywbr"> </span> syntax-<wbr></wbr>parse</a></td></tr><tr><td align="right">7 </td><td><a href="#(part._.Other_questions)" class="tocviewlink" pltdoc="x">Other questions</a></td></tr><tr><td align="right">8 </td><td><a href="#(part._.References_.Acknowledgments)" class="tocviewlink" pltdoc="x">References/<span class="mywbr"> </span>Acknowledgments</a></td></tr><tr><td align="right">9 </td><td><a href="#(part._.Epilogue)" class="tocviewlink" pltdoc="x">Epilogue</a></td></tr></table></div></div></div><div class="tocsub"><table class="tocsublist" cellspacing="0"><tr><td><span class="tocsublinknumber">1<tt> </tt></span><a href="#(part._.Introduction)" class="tocsubseclink" pltdoc="x">Introduction</a></td></tr><tr><td><span class="tocsublinknumber">2<tt> </tt></span><a href="#(part._.The_plan_of_attack)" class="tocsubseclink" pltdoc="x">The plan of attack</a></td></tr><tr><td><span class="tocsublinknumber">3<tt> </tt></span><a href="#(part._.Transformers)" class="tocsubseclink" pltdoc="x">Transformers</a></td></tr><tr><td><span class="tocsublinknumber">3.1<tt> </tt></span><a href="#(part._.What_is_a_syntax_transformer_)" class="tocsubseclink" pltdoc="x">What is a syntax transformer?</a></td></tr><tr><td><span class="tocsublinknumber">3.2<tt> </tt></span><a href="#(part._.What_s_the_input__.Kenneth_)" class="tocsubseclink" pltdoc="x">What’s the input, Kenneth?</a></td></tr><tr><td><span class="tocsublinknumber">3.3<tt> </tt></span><a href="#(part._.Actually_transforming_the_input)" class="tocsubseclink" pltdoc="x">Actually transforming the input</a></td></tr><tr><td><span class="tocsublinknumber">3.4<tt> </tt></span><a href="#(part._.Compile_time_vs__run_time)" class="tocsubseclink" pltdoc="x">Compile time vs. run time</a></td></tr><tr><td><span class="tocsublinknumber">4<tt> </tt></span><a href="#(part._.Pattern_matching__syntax-case_and_syntax-rules)" class="tocsubseclink" 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="#(part._.Patterns_and_templates)" class="tocsubseclink" pltdoc="x">Patterns and templates</a></td></tr><tr><td><span class="tocsublinknumber">4.1.1<tt> </tt></span><a href="#(part.__.A_pattern_variable_can_t_be_used_outside_of_a_template_)" class="tocsubseclink" pltdoc="x">"A pattern variable can’t be used outside of a template"</a></td></tr><tr><td><span class="tocsublinknumber">5<tt> </tt></span><a href="#(part._.Syntax_parameters)" class="tocsubseclink" pltdoc="x">Syntax parameters</a></td></tr><tr><td><span class="tocsublinknumber">6<tt> </tt></span><a href="#(part._.Robust_macros__syntax-parse)" class="tocsubseclink" pltdoc="x">Robust macros:<span class="mywbr"> </span> syntax-<wbr></wbr>parse</a></td></tr><tr><td><span class="tocsublinknumber">7<tt> </tt></span><a href="#(part._.Other_questions)" class="tocsubseclink" pltdoc="x">Other questions</a></td></tr><tr><td><span class="tocsublinknumber">7.1<tt> </tt></span><a href="#(part._.What_s_the_point_of_with-syntax_)" class="tocsubseclink" pltdoc="x">What’s the point of <span class="RktSym"><span class="RktStxLink">with-<wbr></wbr>syntax</span></span>?</a></td></tr><tr><td><span class="tocsublinknumber">7.2<tt> </tt></span><a href="#(part._.What_s_the_point_of_begin-for-syntax_)" class="tocsubseclink" pltdoc="x">What’s the point of <span class="RktSym"><span class="RktStxLink">begin-<wbr></wbr>for-<wbr></wbr>syntax</span></span>?</a></td></tr><tr><td><span class="tocsublinknumber">7.3<tt> </tt></span><a href="#(part._.What_s_the_point_of_racket_splicing_)" class="tocsubseclink" pltdoc="x">What’s the point of <span class="RktSym">racket/<span class="mywbr"> </span>splicing</span>?</a></td></tr><tr><td><span class="tocsublinknumber">8<tt> </tt></span><a href="#(part._.References_.Acknowledgments)" class="tocsubseclink" pltdoc="x">References/<span class="mywbr"> </span>Acknowledgments</a></td></tr><tr><td><span class="tocsublinknumber">9<tt> </tt></span><a href="#(part._.Epilogue)" class="tocsubseclink" 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="https://github.com/greghendershott/fear-of-macros/issues">Greg Hendershott</a></p></span></div><p><div class="SIntrapara"><img src="fear-of-macros.jpg" alt="" />
</div><div class="SIntrapara"></div><div class="SIntrapara"><span class="Smaller">Copyright (c) 2012 by Greg Hendershott. All rights reserved.</span>
-</div><div class="SIntrapara"><span class="Smaller">Last updated 2012-10-26 08:58:25</span></div><div class="SIntrapara"><table cellspacing="0"><tr><td><p><span class="hspace"> </span><a href="#(part._.Introduction)" class="toptoclink" pltdoc="x">1<span class="hspace"> </span>Introduction</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.The_plan_of_attack)" class="toptoclink" pltdoc="x">2<span class="hspace"> </span>The 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="#(part._.Transformers)" class="toptoclink" pltdoc="x">3<span class="hspace"> </span>Transformers</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_is_a_syntax_transformer_)" class="toclink" 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="#(part._.What_s_the_input__.Kenneth_)" class="toclink" pltdoc="x">3.2<span class="hspace"> </span>What’s the input, Kenneth?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Actually_transforming_the_input)" class="toclink" 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="#(part._.Compile_time_vs__run_time)" class="toclink" pltdoc="x">3.4<span class="hspace"> </span>Compile time vs. run time</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Pattern_matching__syntax-case_and_syntax-rules)" class="toptoclink" 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="#(part._.Patterns_and_templates)" class="toclink" pltdoc="x">4.1<span class="hspace"> </span>Patterns and templates</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part.__.A_pattern_variable_can_t_be_used_outside_of_a_template_)" class="toclink" pltdoc="x">4.1.1<span class="hspace"> </span>"A pattern variable can’t be used outside of a template"</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Syntax_parameters)" class="toptoclink" 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="#(part._.Robust_macros__syntax-parse)" class="toptoclink" pltdoc="x">6<span class="hspace"> </span>Robust macros: syntax-parse</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Other_questions)" class="toptoclink" pltdoc="x">7<span class="hspace"> </span>Other questions</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_s_the_point_of_with-syntax_)" class="toclink" pltdoc="x">7.1<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">with-syntax</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_s_the_point_of_begin-for-syntax_)" class="toclink" pltdoc="x">7.2<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">begin-for-syntax</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_s_the_point_of_racket_splicing_)" class="toclink" pltdoc="x">7.3<span class="hspace"> </span>What’s the point of <span class="RktSym">racket/splicing</span>?</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.References_.Acknowledgments)" class="toptoclink" pltdoc="x">8<span class="hspace"> </span>References/Acknowledgments</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Epilogue)" class="toptoclink" pltdoc="x">9<span class="hspace"> </span>Epilogue</a></p></td></tr></table></div></p><h3>1<tt> </tt><a name="(part._.Introduction)"></a>Introduction</h3><p>I learned Racket after 25 years of doing C/C++ imperative programming.</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">Last updated 2012-10-26 11:45:11</span></div><div class="SIntrapara"><table cellspacing="0"><tr><td><p><span class="hspace"> </span><a href="#(part._.Introduction)" class="toptoclink" pltdoc="x">1<span class="hspace"> </span>Introduction</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.The_plan_of_attack)" class="toptoclink" pltdoc="x">2<span class="hspace"> </span>The 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="#(part._.Transformers)" class="toptoclink" pltdoc="x">3<span class="hspace"> </span>Transformers</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_is_a_syntax_transformer_)" class="toclink" 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="#(part._.What_s_the_input__.Kenneth_)" class="toclink" pltdoc="x">3.2<span class="hspace"> </span>What’s the input, Kenneth?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Actually_transforming_the_input)" class="toclink" 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="#(part._.Compile_time_vs__run_time)" class="toclink" pltdoc="x">3.4<span class="hspace"> </span>Compile time vs. run time</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Pattern_matching__syntax-case_and_syntax-rules)" class="toptoclink" 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="#(part._.Patterns_and_templates)" class="toclink" pltdoc="x">4.1<span class="hspace"> </span>Patterns and templates</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part.__.A_pattern_variable_can_t_be_used_outside_of_a_template_)" class="toclink" pltdoc="x">4.1.1<span class="hspace"> </span>"A pattern variable can’t be used outside of a template"</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Syntax_parameters)" class="toptoclink" 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="#(part._.Robust_macros__syntax-parse)" class="toptoclink" pltdoc="x">6<span class="hspace"> </span>Robust macros: syntax-parse</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Other_questions)" class="toptoclink" pltdoc="x">7<span class="hspace"> </span>Other questions</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_s_the_point_of_with-syntax_)" class="toclink" pltdoc="x">7.1<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">with-syntax</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_s_the_point_of_begin-for-syntax_)" class="toclink" pltdoc="x">7.2<span class="hspace"> </span>What’s the point of <span class="RktSym"><span class="RktStxLink">begin-for-syntax</span></span>?</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.What_s_the_point_of_racket_splicing_)" class="toclink" pltdoc="x">7.3<span class="hspace"> </span>What’s the point of <span class="RktSym">racket/splicing</span>?</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.References_.Acknowledgments)" class="toptoclink" pltdoc="x">8<span class="hspace"> </span>References/Acknowledgments</a></p></td></tr><tr><td><p><span class="hspace"></span></p></td></tr><tr><td><p><span class="hspace"> </span><a href="#(part._.Epilogue)" class="toptoclink" pltdoc="x">9<span class="hspace"> </span>Epilogue</a></p></td></tr></table></div></p><h3>1<tt> </tt><a name="(part._.Introduction)"></a>Introduction</h3><p>I learned Racket after 25 years of doing C/C++ imperative programming.</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
@@ -52,7 +52,7 @@ always outputs syntax for a string literal:</p><blockquote class="SCodeFlow"><ta
encounter a chunk of syntax starting with <span class="RktSym">foo</span>, please give it
to my transformer function, and replace it with the syntax I give back
to you." So Racket will give anything that looks like <span class="RktPn">(</span><span class="RktSym">foo</span><span class="stt"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#(form._((lib._racket%2Fprivate%2Fstxcase-scheme..rkt)._......))" class="RktStxLink" pltdoc="x">...</a></span><span class="RktPn">)</span> to our function, and we can change it. Much like a
-search-and-replace.</p><p>Maybe you know that the usual way to define a function in Racket:</p><p><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define))" class="RktStxLink" pltdoc="x">define</a></span><span class="stt"> </span><span class="RktPn">(</span><span class="RktSym">f</span><span class="stt"> </span><span class="RktSym">x</span><span class="RktPn">)</span><span class="stt"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#(form._((lib._racket%2Fprivate%2Fstxcase-scheme..rkt)._......))" class="RktStxLink" pltdoc="x">...</a></span><span class="RktPn">)</span></p><p>is shorthand for:</p><p><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define))" class="RktStxLink" pltdoc="x">define</a></span><span class="stt"> </span><span class="RktSym">f</span><span class="stt"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/lambda.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._lambda))" class="RktStxLink" pltdoc="x">lambda</a></span><span class="stt"> </span><span class="RktPn">(</span><span class="RktSym">x</span><span class="RktPn">)</span><span class="stt"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#(form._((lib._racket%2Fprivate%2Fstxcase-scheme..rkt)._......))" class="RktStxLink" pltdoc="x">...</a></span><span class="RktPn">)</span><span class="RktPn">)</span></p><p>That shorthand lets you avoid typing <span class="RktSym"><a href="http://docs.racket-lang.org/reference/lambda.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._lambda))" class="RktStxLink" pltdoc="x">lambda</a></span> and some parentheses.</p><p>Well there is a similar shorthand for <span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define-syntax))" class="RktStxLink" pltdoc="x">define-syntax</a></span>:</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#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define-syntax))" class="RktStxLink" pltdoc="x">define-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">also-foo</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="RktRdr">#'</span><span class="RktVal">"I am also foo"</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">also-foo</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"I am also foo"</span></p></td></tr></table></blockquote><p>What we want to remember is that this is simply shorthand. We are
+search-and-replace.</p><p>Maybe you know that the usual way to define a function in Racket:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define))" class="RktStxLink" pltdoc="x">define</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym">f</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">x</span><span class="RktPn">)</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#(form._((lib._racket%2Fprivate%2Fstxcase-scheme..rkt)._......))" class="RktStxLink" pltdoc="x">...</a></span><span class="RktPn">)</span><span class="RktMeta"></span></td></tr></table></blockquote><p>is shorthand for:</p><blockquote class="SCodeFlow"><table cellspacing="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define))" class="RktStxLink" pltdoc="x">define</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym">f</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/lambda.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._lambda))" class="RktStxLink" pltdoc="x">lambda</a></span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktPn">(</span><span class="RktSym">x</span><span class="RktPn">)</span><span class="RktMeta"></span><span class="hspace"> </span><span class="RktMeta"></span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#(form._((lib._racket%2Fprivate%2Fstxcase-scheme..rkt)._......))" class="RktStxLink" pltdoc="x">...</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktMeta"></span></td></tr></table></blockquote><p>That shorthand lets you avoid typing <span class="RktSym"><a href="http://docs.racket-lang.org/reference/lambda.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._lambda))" class="RktStxLink" pltdoc="x">lambda</a></span> and some parentheses.</p><p>Well there is a similar shorthand for <span class="RktSym"><a href="http://docs.racket-lang.org/reference/define.html#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define-syntax))" class="RktStxLink" pltdoc="x">define-syntax</a></span>:</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#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define-syntax))" class="RktStxLink" pltdoc="x">define-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">also-foo</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="RktRdr">#'</span><span class="RktVal">"I am also foo"</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">also-foo</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"I am also foo"</span></p></td></tr></table></blockquote><p>What we want to remember is that this is simply shorthand. We are
still defining a transformer function, which takes syntax and returns
syntax. Everything we do with macros, will be built on top of this
basic idea. It’s not magic.</p><p>Speaking of shorthand, there is also a shorthand for <span class="RktSym"><a href="http://docs.racket-lang.org/reference/stx-patterns.html#(form._((lib._racket%2Fprivate%2Fstxcase-scheme..rkt)._syntax))" class="RktStxLink" pltdoc="x">syntax</a></span>,
@@ -71,7 +71,7 @@ information about lexical scoping (which you don’t need to worry about
now, but will turn out to be important later.)</p><p>There are a variety of functions available to access a syntax object:</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#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define))" class="RktStxLink" 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"><a href="http://docs.racket-lang.org/reference/if.html#(form._((quote._~23~25kernel)._if))" class="RktStxLink" pltdoc="x">if</a></span><span class="hspace"> </span><span class="RktSym">x</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#(def._((quote._~23~25kernel)._list))" class="RktValLink" pltdoc="x">list</a></span><span class="hspace"> </span><span class="RktVal">"true"</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVal">#f</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/stxops.html#(def._((quote._~23~25kernel)._syntax-~3edatum))" class="RktValLink" pltdoc="x">syntax->datum</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(if<span class="stt"> </span>x<span class="stt"> </span>(list<span class="stt"> </span>"true")<span class="stt"> </span>#f)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-e))" class="RktValLink" pltdoc="x">syntax-e</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(#<syntax:11:0 if><span class="stt"> </span>#<syntax:11:0 x><span class="stt"> </span>#<syntax:11:0 (list "true")><span class="stt"> </span>#<syntax:11:0 #f>)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-~3elist))" class="RktValLink" pltdoc="x">syntax->list</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(#<syntax:11:0 if><span class="stt"> </span>#<syntax:11:0 x><span class="stt"> </span>#<syntax:11:0 (list "true")><span class="stt"> </span>#<syntax:11:0 #f>)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-source))" class="RktValLink" pltdoc="x">syntax-source</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'eval</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-line))" class="RktValLink" pltdoc="x">syntax-line</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">11</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-column))" class="RktValLink" pltdoc="x">syntax-column</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">0</span></p></td></tr></table></blockquote><p>When we want to transform syntax, we’ll generally take the pieces we
were given, maybe rearrange their order, perhaps change some of the
pieces, and often introduce brand-new pieces.</p><h4>3.3<tt> </tt><a name="(part._.Actually_transforming_the_input)"></a>Actually transforming the input</h4><p>Let’s write a transformer function that reverses the syntax it was
-given:</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#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define-syntax))" class="RktStxLink" pltdoc="x">define-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">reverse-me</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/stxops.html#(def._((quote._~23~25kernel)._datum-~3esyntax))" class="RktValLink" pltdoc="x">datum->syntax</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#(def._((lib._racket%2Fprivate%2Flist..rkt)._reverse))" class="RktValLink" pltdoc="x">reverse</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#(def._((quote._~23~25kernel)._cdr))" class="RktValLink" pltdoc="x">cdr</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-~3edatum))" class="RktValLink" pltdoc="x">syntax->datum</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">reverse-me</span><span class="hspace"> </span><span class="RktVal">"backwards"</span><span class="hspace"> </span><span class="RktVal">"am"</span><span class="hspace"> </span><span class="RktVal">"i"</span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/values.html#(def._((quote._~23~25kernel)._values))" class="RktValLink" pltdoc="x">values</a></span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"i"</span></p></td></tr><tr><td><p><span class="RktRes">"am"</span></p></td></tr><tr><td><p><span class="RktRes">"backwards"</span></p></td></tr></table></blockquote><p>Understand Yoda, can we. Great, but how does this work?</p><p>First we take the input syntax, and give it to
+given:</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#(form._((lib._racket%2Fprivate%2Fbase..rkt)._define-syntax))" class="RktStxLink" pltdoc="x">define-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">reverse-me</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="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._datum-~3esyntax))" class="RktValLink" pltdoc="x">datum->syntax</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#(def._((lib._racket%2Fprivate%2Flist..rkt)._reverse))" class="RktValLink" pltdoc="x">reverse</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#(def._((quote._~23~25kernel)._cdr))" class="RktValLink" pltdoc="x">cdr</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-~3edatum))" class="RktValLink" pltdoc="x">syntax->datum</a></span><span class="hspace"> </span><span class="RktSym">stx</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">reverse-me</span><span class="hspace"> </span><span class="RktVal">"backwards"</span><span class="hspace"> </span><span class="RktVal">"am"</span><span class="hspace"> </span><span class="RktVal">"i"</span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/values.html#(def._((quote._~23~25kernel)._values))" class="RktValLink" pltdoc="x">values</a></span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"i"</span></p></td></tr><tr><td><p><span class="RktRes">"am"</span></p></td></tr><tr><td><p><span class="RktRes">"backwards"</span></p></td></tr></table></blockquote><p>Understand Yoda, can we. Great, but how does this work?</p><p>First we take the input syntax, and give it to
<span class="RktSym"><a href="http://docs.racket-lang.org/reference/stxops.html#(def._((quote._~23~25kernel)._syntax-~3edatum))" class="RktValLink" pltdoc="x">syntax->datum</a></span>. This converts the syntax into a plain old
list:</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/stxops.html#(def._((quote._~23~25kernel)._syntax-~3edatum))" class="RktValLink" pltdoc="x">syntax->datum</a></span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktPn">(</span><span class="RktSym">reverse-me</span><span class="hspace"> </span><span class="RktVal">"backwards"</span><span class="hspace"> </span><span class="RktVal">"am"</span><span class="hspace"> </span><span class="RktVal">"i"</span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/values.html#(def._((quote._~23~25kernel)._values))" class="RktValLink" pltdoc="x">values</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(reverse-me<span class="stt"> </span>"backwards"<span class="stt"> </span>"am"<span class="stt"> </span>"i"<span class="stt"> </span>values)</span></p></td></tr></table></blockquote><p>Using <span class="RktSym"><a href="http://docs.racket-lang.org/reference/pairs.html#(def._((quote._~23~25kernel)._cdr))" class="RktValLink" pltdoc="x">cdr</a></span> slices off the first item of the list,
<span class="RktSym">reverse-me</span>, leaving the remainder:
