19 lines
16 KiB
HTML
19 lines
16 KiB
HTML
|
<!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"/><meta name="viewport" content="width=device-width, initial-scale=0.8"/><title>16 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="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-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="index.html" class="tocviewlink" data-pltdoc="x">The Racket Guide</a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="intro.html" class="tocviewlink" data-pltdoc="x">Welcome to Racket</a></td></tr><tr><td align="right">2 </td><td><a href="to-scheme.html" class="tocviewlink" data-pltdoc="x">Racket Essentials</a></td></tr><tr><td align="right">3 </td><td><a href="datatypes.html" class="tocviewlink" data-pltdoc="x">Built-<wbr></wbr>In Datatypes</a></td></tr><tr><td align="right">4 </td><td><a href="scheme-forms.html" class="tocviewlink" data-pltdoc="x">Expressions and Definitions</a></td></tr><tr><td align="right">5 </td><td><a href="define-struct.html" class="tocviewlink" data-pltdoc="x">Programmer-<wbr></wbr>Defined Datatypes</a></td></tr><tr><td align="right">6 </td><td><a href="modules.html" class="tocviewlink" data-pltdoc="x">Modules</a></td></tr><tr><td align="right">7 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">8 </td><td><a href="i_o.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">9 </td><td><a href="regexp.html" class="tocviewlink" data-pltdoc="x">Regular Expressions</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Exceptions and Control</a></td></tr><tr><td align="right">11 </td><td><a href="for.html" class="tocviewlink" data-pltdoc="x">Iterations and Comprehensions</a></td></tr><tr><td align="right">12 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">13 </td><td><a href="classes.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">14 </td><td><a href="units.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">15 </td><td><a href="reflection.html" class="tocviewlink" data-pltdoc="x">Reflection and Dynamic Evaluation</a></td></tr><tr><td align="right">16 </td><td><a href="macros.html" class="tocviewselflink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">17 </td><td><a href="languages.html" class="tocviewlink" data-pltdoc="x">Creating Languages</a></td></tr><tr><td align="right">18 </td><td><a href="concurrency.html" class="tocviewlink" data-pl
|
||
|
|
<a name="(tech._transformer)"></a><span style="font-style: italic">transformer</span> that <a name="(tech._expand)"></a><span style="font-style: italic">expands</span> the original form
|
||
|
|
into existing forms. To put it another way, a macro is an
|
||
|
|
extension to the Racket compiler. Most of the syntactic forms of
|
||
|
|
<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=index.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">racket/base</span></a> and <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=index.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">racket</span></a> are
|
||
|
|
actually macros that expand into a small set of core constructs.</p><p>Like many languages, Racket provides pattern-based macros that
|
||
|
|
make simple transformations easy to implement and reliable to
|
||
|
|
use. Racket also supports arbitrary macro transformers that are
|
||
|
|
implemented in Racket—<wbr></wbr>or in a macro-extended variant of Racket.</p><p>This chapter provides an introduction to Racket macros, but see
|
||
|
|
<a href="https://www.greghendershott.com/fear-of-macros/"><span style="font-style: italic">Fear of
|
||
|
|
Macros</span></a> for an introduction from a different perspective.</p><p>Racket includes additional support for macro development:
|
||
|
|
A <a href="https://docs.racket-lang.org/macro-debugger/index.html"><span style="font-style: italic">macro
|
||
|
|
debugger</span></a> to make it easier for experienced programmers
|
||
|
|
to debug their macros and for novices to study their behavior,
|
||
|
|
and of macros. And the <a href="https://docs.racket-lang.org/syntax/index.html"><span style="font-style: italic">syntax/parse
|
||
|
|
library</span></a> for writing macros and specifying syntax that
|
||
|
|
automatically validates macro uses and reports syntax
|
||
|
|
errors.</p><table cellspacing="0" cellpadding="0"><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html" class="toclink" data-pltdoc="x">16.1<span class="hspace"> </span>Pattern-Based Macros</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._define-syntax-rule%29" class="toclink" data-pltdoc="x">16.1.1<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">define-syntax-rule</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._.Lexical_.Scope%29" class="toclink" data-pltdoc="x">16.1.2<span class="hspace"> </span>Lexical Scope</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._define-syntax_and_syntax-rules%29" class="toclink" data-pltdoc="x">16.1.3<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">define-syntax</span></span> and <span class="RktSym"><span class="RktStxLink">syntax-rules</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._.Matching_.Sequences%29" class="toclink" data-pltdoc="x">16.1.4<span class="hspace"> </span>Matching Sequences</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._.Identifier_.Macros%29" class="toclink" data-pltdoc="x">16.1.5<span class="hspace"> </span>Identifier Macros</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._set__.Transformers%29" class="toclink" data-pltdoc="x">16.1.6<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">set!</span></span> Transformers</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._.Macro-.Generating_.Macros%29" class="toclink" data-pltdoc="x">16.1.7<span class="hspace"> </span>Macro-Generating Macros</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="pattern-macros.html#%28part._pattern-macro-example%29" class="toclink" data-pltdoc="x">16.1.8<span class="hspace"> </span>Extended Example: Call-by-Reference Functions</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="proc-macros.html" class="toclink" data-pltdoc="x">16.2<span class="hspace"> </span>General Macro Transformers</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="stx-obj.html" class="toclink" data-pltdoc="x">16.2.1<span class="hspace"> </span>Syntax Objects</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="macro-transformers.html" class="toclink" data-pltdoc="x">16.2.2<span class="hspace"> </span>Macro Transformer Procedures</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="syntax-case.html" class="toclink" data-pltdoc="x">16.2.3<span class="hspace"> </span>Mixing Patterns and Expressions: <span class="RktSym"><span class="RktStxLink">syntax-case</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="with-syntax.html" class="toclink" data-pltdoc="x">16.2.4<span class="hspace"> </span><span class="RktSym"><span class="RktStxLink">with-syntax</span></span> and <span class="RktSym"><span class="RktValLink">generate-temporaries</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="stx-phases.html" class="toclink" data-pltdoc="x">16.2.5<span class="hspace"> </span>Compile and Run-Time Phases</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="phases.html"
|