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<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>3.14 Definitions: define, define-syntax, ...</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="icons.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 Reference</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="model.html" class="tocviewlink" data-pltdoc="x">Language Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewselflink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="tocviewlink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr><tr><td align="right">12 </td><td><a href="Macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">13 </td><td><a href="input-and-output.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr><tr><td align="right">15 </td><td><a href="os.html" class="tocviewlink" data-pltdoc="x">Operating System</a></td></tr><tr><td align="right">16 </td><td><a href="memory.html" class="tocviewlink" data-pltdoc="x">Memory Management</a></td></tr><tr><td align="right">17 </td><td><a href="unsafe.html" class="tocviewlink" data-pltdoc="x">Unsa
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<span class="RktVar">expr</span>, and the second form <a href="syntax-model.html#%28tech._bind%29" class="techoutside" data-pltdoc="x"><span class="techinside">bind</span></a>s <span class="RktVar">id</span> to a
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procedure. In the second case, the generated procedure is
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<span class="RktPn">(</span><span class="stt">CVT</span><span class="stt"> </span><span class="RktPn">(</span><span class="RktVar">head</span><span class="stt"> </span><span class="RktVar">args</span><span class="RktPn">)</span><span class="stt"> </span><span class="RktVar">body</span><span class="stt"> </span><span class="RktMeta"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=syntax&rel=stxparse-patterns.html%23%2528form._%2528%2528lib._syntax%252Fparse..rkt%2529._......%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">...+</a></span><span class="RktPn">)</span>, using the <span class="stt">CVT</span> meta-function
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defined as follows:</div></p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="stt">CVT</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktVar">id</span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktVar">kw-formals</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktVar">datum</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._~3d%29%29" class="RktValLink" data-pltdoc="x">=</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktVar">kw-formals</span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktVar">datum</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPn">(</span><span class="stt">CVT</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktVar">head</span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktVar">kw-formals</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktVar">datum</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._~3d%29%29" class="RktValLink" data-pltdoc="x">=</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktVar">kw-formals</span><span class="hspace"> </span><span class="RktVar">expr</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span>if<span class="hspace"> </span><span class="RktPn">(</span><span class="stt">CVT</span><span class="hspace"> </span><span class="RktVar">head</span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktVar">datum</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._~3d%29%29" class="RktValLink" data-pltdoc="x">=</a></span><span class="hspace"> </span><span class="RktVar">expr</span></td></tr></table></blockquote><p>In an <a href="syntax-model.html#%28tech._internal._definition._context%29" class="techoutside" data-pltdoc="x"><span class="techinside">internal-definition context</span></a>, a <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span> form
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introduces a local binding; see <a href="syntax-model.html#%28part._intdef-body%29" data-pltdoc="x">Internal Definitions</a>.
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At the top level, the top-level binding for <span class="RktVar">id</span> is created after
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evaluating <span class="RktVar">expr</span>, if it does not exist already, and the
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top-level mapping of <span class="RktVar">id</span> (in the <a href="syntax-model.html#%28tech._namespace%29" data-pltdoc="x">namespace</a> linked
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with the compiled definition) is set to the binding at the same time.</p><p>In a context that allows <a href="stxtrans.html#%28tech._liberal._expansion%29" class="techoutside" data-pltdoc="x"><span class="techinside">liberal expansion</span></a> of <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span>,
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<span class="RktVar">id</span> is bound as syntax if <span class="RktVar">expr</span> is an immediate
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<span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span> form with keyword arguments or <span class="RktVar">args</span> include
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keyword arguments.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="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">x</span><span class="hspace"> </span><span class="RktVal">10</span><span class="RktPn">)</span></td></tr><tr><td><p> </p></td></tr><tr><td><span class="stt">> </span><span class="RktSym">x</span></td></tr><tr><td><p><span class="RktRes">10</span></p></td></tr><tr><td><p> </p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="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="RktPn">(</span><span class="RktSym">f</span><span class="hspace"> </span><span class="RktSym">x</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._%2B%29%29" class="RktValLink" data-pltdoc="x">+</a></span><span class="hspace"> </span><span class="RktSym">x</span><span class="hspace"> </span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p> </p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">f</span><span class="hspace"> </span><span class="RktVal">10</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">11</span></p></td></tr><tr><td><p> </p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="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="RktPn">(</span><span class="RktPn">(</span><span class="RktSym">f</span><span class="hspace"> </span><span class="RktSym">x</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktSym">y</span><span class="hspace"> </span><span class="RktVal">20</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._%2B%29%29" class="RktValLink" data-pltdoc="x">+</a></span><span class="hspace"> </span><span class="RktSym">x</span><span class="hspace"> </span><span class="RktSym">y</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p> </p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktSym">f</span><span class="hspace"> </span><span class="RktVal">10</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVal">30</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">40</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktSym">f</span><span class="hspace"> </span><span class="RktVal">10</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">30</span></p></td></tr></table></blockquote></div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>syntax</p></div></div><p class="RForeground"><span class="RktPn">(</spa
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<span class="RktVar">id</span>s, in order, if the number of results matches the number of
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<span class="RktVar">id</span>s; if <span class="RktVar">expr</span> produces a different number of results,
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the <span class="RktSym"><a href="exns.html#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._exn~3afail~3acontract%29%29" class="RktValLink" data-pltdoc="x">exn:fail:contract</a></span> exception is raised.</div></p><p>In an <a href="syntax-model.html#%28tech._internal._definition._context%29" class="techoutside" data-pltdoc="x"><span class="techinside">internal-definition context</span></a> (see <a href="syntax-model.html#%28part._intdef-body%29" data-pltdoc="x">Internal Definitions</a>),
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a <span class="RktSym"><a href="define.html#%28form._%28%28quote._~23~25kernel%29._define-values%29%29" class="RktStxLink" data-pltdoc="x">define-values</a></span> form introduces local bindings.
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At the top level, the top-level binding for each <span class="RktVar">id</span> is
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created after evaluating <span class="RktVar">expr</span>, if it does not exist already,
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and the top-level mapping of each <span class="RktVar">id</span> (in the
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<a href="syntax-model.html#%28tech._namespace%29" data-pltdoc="x">namespace</a> linked with the compiled definition) is set to
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the binding at the same time.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28quote._~23~25kernel%29._define-values%29%29" class="RktStxLink" data-pltdoc="x">define-values</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></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="define.html#%28form._%28%28quote._~23~25kernel%29._define-values%29%29" class="RktStxLink" data-pltdoc="x">define-values</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">x</span><span class="hspace"> </span><span class="RktSym">y</span><span class="hspace"> </span><span class="RktSym">z</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span><span class="hspace"> </span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">2</span><span class="hspace"> </span><span class="RktVal">3</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktSym">z</span></td></tr><tr><td><p><span class="RktRes">3</span></p></td></tr></table></blockquote></div></p><p>If a <span class="RktSym"><a href="define.html#%28form._%28%28quote._~23~25kernel%29._define-values%29%29" class="RktStxLink" data-pltdoc="x">define-values</a></span> form for a function definition in a module
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body has a <a name="(idx._(gentag._109._(lib._scribblings/reference/reference..scrbl)))"></a><span class="RktVal">'</span><span class="RktVal">compiler-hint:cross-module-inline</span>
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<a href="stxprops.html#%28tech._syntax._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">syntax property</span></a> with a true value, then the Racket treats the
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property as a performance hint. See
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<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=guide&rel=performance.html%23%2528part._func-call-performance%2529&version=8.6" class="Sq" data-pltdoc="x">Function-Call Optimizations</a> in <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=guide&rel=index.html&version=8.6" class="Sq" data-pltdoc="x">The Racket Guide</a> for more
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information, and see also <span class="RktSym"><a href="performance-hint.html#%28form._%28%28lib._racket%2Fperformance-hint..rkt%29._begin-encourage-inline%29%29" class="RktStxLink" data-pltdoc="x">begin-encourage-inline</a></span>.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>syntax</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(form._((lib._racket/private/base..rkt)._define-syntax))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">define-syntax</a></span></span><span class="hspace"> </span><span class="RktVar">id</span><span class="hspace"> </span><span class="RktVar">expr</span><span class="RktPn">)</span></p></blockquote></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">define-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktVar">head</span><span class="hspace"> </span><span class="RktVar">args</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVar">body</span><span class="hspace"> </span><span class="RktMeta">...+</span><span class="RktPn">)</span></td></tr></table></blockquote></div><div class="SIntrapara">The first form creates a <a href="syntax-model.html#%28tech._transformer%29" class="techoutside" data-pltdoc="x"><span class="techinside">transformer</span></a> binding (see
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<a href="syntax-model.html#%28part._transformer-model%29" data-pltdoc="x">Transformer Bindings</a>) of <span class="RktVar">id</span> with the value of
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<span class="RktVar">expr</span>, which is an expression at <a href="syntax-model.html#%28tech._phase._level%29" class="techoutside" data-pltdoc="x"><span class="techinside">phase level</span></a> 1 relative
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to the surrounding context. (See <a href="syntax-model.html#%28part._id-model%29" data-pltdoc="x">Identifiers, Binding, and Scopes</a> for information
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on <a href="syntax-model.html#%28tech._phase._level%29" class="techoutside" data-pltdoc="x"><span class="techinside">phase levels</span></a>.) Evaluation of <span class="RktVar">expr</span> side is
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<span class="RktSym"><a href="parameters.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span>d to set <span class="RktSym"><a href="Namespaces.html#%28def._%28%28quote._~23~25kernel%29._current-namespace%29%29" class="RktValLink" data-pltdoc="x">current-namespace</a></span> as in
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<span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let-syntax%29%29" class="RktStxLink" data-pltdoc="x">let-syntax</a></span>.</div></p><p>The second form is a shorthand the same as for <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span>; it
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expands to a definition of the first form where the <span class="RktVar">expr</span> is a
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<span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span> form.</p><p>In an <a href="syntax-model.html#%28tech._internal._definition._context%29" class="techoutside" data-pltdoc="x"><span class="techinside">internal-definition context</span></a> (see <a href="syntax-model.html#%28part._intdef-body%29" data-pltdoc="x">Internal Definitions</a>),
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a <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-syntax</a></span> form introduces a local binding.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="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="RktSym">foo</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._syntax-rules%29%29" class="RktStxLink" data-pltdoc="x">syntax-rules</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29.__%29%29" class="RktStxLink" data-pltdoc="x">_</a></span><span class="hspace"> </span><span class="RktSym">a</span><span class="hspace"> </span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._......%29%29" class="RktStxLink" data-pltdoc="x">...</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._printf%29%29" class="RktValLink" data-pltdoc="x">printf</a></span><span class="hspace"> </span><span class="RktVal">"~a\n"</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._list%29%29" class="RktValLink" data-pltdoc="x">list</a></span><span class="hspace"> </span><span class="RktSym">a</span><span class="hspace"> </span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._......%29%29" class="RktStxLink" data-pltdoc="x">...</a></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">foo</span><span class="hspace"> </span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">2</span><span class="hspace"> </span><span class="RktVal">3</span><span class="hspace"> </span><span class="RktVal">4</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">(1 2 3 4)</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="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">bar</span><span class="hspace"> </span><span class="RktSym">syntax-object</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._syntax-case%29%29" class="RktStxLink" data-pltdoc="x">syntax-case</a></span><span class="hspace"> </span><span class="RktSym">syntax-ob
|
||
|
|
for each <span class="RktVar">id</span>. The <span class="RktVar">expr</span> should produce as many values
|
||
|
|
as <span class="RktVar">id</span>s, and each value is bound to the corresponding
|
||
|
|
<span class="RktVar">id</span>.</div></p><p>When <span class="RktVar">expr</span> produces zero values for a top-level
|
||
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<span class="RktSym"><a href="define.html#%28form._%28%28quote._~23~25kernel%29._define-syntaxes%29%29" class="RktStxLink" data-pltdoc="x">define-syntaxes</a></span> (i.e., not in a module or internal-definition
|
||
|
|
position), then the <span class="RktVar">id</span>s are effectively declared without
|
||
|
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binding; see <a href="syntax-model.html#%28part._macro-introduced-bindings%29" data-pltdoc="x">Macro-Introduced Bindings</a>.</p><p>In an <a href="syntax-model.html#%28tech._internal._definition._context%29" class="techoutside" data-pltdoc="x"><span class="techinside">internal-definition context</span></a> (see <a href="syntax-model.html#%28part._intdef-body%29" data-pltdoc="x">Internal Definitions</a>),
|
||
|
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a <span class="RktSym"><a href="define.html#%28form._%28%28quote._~23~25kernel%29._define-syntaxes%29%29" class="RktStxLink" data-pltdoc="x">define-syntaxes</a></span> form introduces local bindings.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28quote._~23~25kernel%29._define-syntaxes%29%29" class="RktStxLink" data-pltdoc="x">define-syntaxes</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">foo1</span><span class="hspace"> </span><span class="RktSym">foo2</span><span class="hspace"> </span><span class="RktSym">foo3</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">transformer1</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">syntax-object</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._syntax-case%29%29" class="RktStxLink" data-pltdoc="x">syntax-case</a></span><span class="hspace"> </span><span class="RktSym">syntax-object</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29.__%29%29" class="RktStxLink" data-pltdoc="x">_</a></span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktVal">1</span><span class="RktPn">]</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">]</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktSym">transformer2</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">syntax-object</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._syntax-case%29%29" class="RktStxLink" data-pltdoc="x">syntax-case</a></span><span class="hspace"> </span><span class="RktSym">syntax-object</span><span class="hspace"> </span><span
|
||
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1 instead of <a href="syntax-model.html#%28tech._phase._level%29" class="techoutside" data-pltdoc="x"><span class="techinside">phase level</span></a> 0 relative to its context. The
|
||
|
|
expression for the binding is also at <a href="syntax-model.html#%28tech._phase._level%29" class="techoutside" data-pltdoc="x"><span class="techinside">phase level</span></a> 1. (See
|
||
|
|
<a href="syntax-model.html#%28part._id-model%29" data-pltdoc="x">Identifiers, Binding, and Scopes</a> for information on <a href="syntax-model.html#%28tech._phase._level%29" class="techoutside" data-pltdoc="x"><span class="techinside">phase levels</span></a>.) The form
|
||
|
|
is a shorthand for <span class="RktPn">(</span><span class="RktSym"><a href="begin.html#%28form._%28%28quote._~23~25kernel%29._begin-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">begin-for-syntax</a></span><span class="stt"> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="stt"> </span><span class="RktVar">id</span><span class="stt"> </span><span class="RktVar">expr</span><span class="RktPn">)</span><span class="RktPn">)</span> or
|
||
|
|
<span class="RktPn">(</span><span class="RktSym"><a href="begin.html#%28form._%28%28quote._~23~25kernel%29._begin-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">begin-for-syntax</a></span><span class="stt"> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="stt"> </span><span class="RktPn">(</span><span class="RktVar">head</span><span class="stt"> </span><span class="RktVar">args</span><span class="RktPn">)</span><span class="stt"> </span><span class="RktVar">body</span><span class="stt"> </span><span class="RktMeta"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=syntax&rel=stxparse-patterns.html%23%2528form._%2528%2528lib._syntax%252Fparse..rkt%2529._......%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">...+</a></span><span class="RktPn">)</span><span class="RktPn">)</span>.</div></p><p>Within a module, bindings introduced by <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-for-syntax</a></span>
|
||
|
|
must appear before their uses or in the same
|
||
|
|
<span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-for-syntax</a></span> form (i.e., the <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-for-syntax</a></span>
|
||
|
|
form must be expanded before the use is expanded). In particular,
|
||
|
|
mutually recursive functions bound by <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-for-syntax</a></span> must
|
||
|
|
be defined by the same <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-for-syntax</a></span> form.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-for-syntax</a></span><span class="hspace"> </span><span class="RktSym">helper</span><span class="hspace"> </span><span class="RktVal">2</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="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">make-two</span><span class="hspace"> </span><span class="RktSym">syntax-object</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._printf%29%29" class="RktValLink" data-pltdoc="x">printf</a></span><span class="hspace"> </span><span class="RktVal">"helper is ~a\n"</span><span class="hspace"> </span><span class="RktSym">helper</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktVal">2</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">make-two</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">helper is 2</span></p></td></tr><tr><td><p><span class="RktRes">2</span></p></td></tr><tr><td><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">‘</span><span class="RktCmt">helper</span><span class="RktCmt">'</span><span class="RktCmt"> is not bound in the runtime phase</span></td></tr><tr><td><span class="stt">> </span><span class="RktSym">helper</span></td></tr><tr><td><p><span class="RktErr">helper: undefined;</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">cannot reference an identifier before its definition</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">in module: top-level</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-for-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">filter-ids</span><span class="hspace"> </span><span class="RktSym">ids</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28lib._racket%2Fprivate%2Flist..rkt%29._filter%29%29" class="RktValLink" data-pltdoc="x">filter</a></span><span class="hspace"> </span><span class="RktSym"><a href="stxops.html#%28def._%28%28lib._racket%2Fprivate%2Fstx..rkt%29._identifier~3f%29%29" class="RktValLink" data-pltdoc="x">identifier?</a></span><span class="hspace"> </span><span class="RktSym">ids</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><table cellspacing="0" cellpadding="
|
||
|
|
many values as supplied <span class="RktVar">id</span>s, and all of the <span class="RktVar">id</span>s are
|
||
|
|
bound (at <a href="syntax-model.html#%28tech._phase._level%29" class="techoutside" data-pltdoc="x"><span class="techinside">phase level</span></a> 1).</div></p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fdefine..rkt%29._define-values-for-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-values-for-syntax</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">foo1</span><span class="hspace"> </span><span class="RktSym">foo2</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span><span class="hspace"> </span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">2</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="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">bar</span><span class="hspace"> </span><span class="RktSym">syntax-object</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._printf%29%29" class="RktValLink" data-pltdoc="x">printf</a></span><span class="hspace"> </span><span class="RktVal">"foo1 is ~a foo2 is ~a\n"</span><span class="hspace"> </span><span class="RktSym">foo1</span><span class="hspace"> </span><span class="RktSym">foo2</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktRdr">#'</span><span class="RktVal">2</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">bar</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">foo1 is 1 foo2 is 2</span></p></td></tr><tr><td><p><span class="RktRes">2</span></p></td></tr></table></blockquote></div></p><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-source-pkg="racket-doc" x-part-tag=""require-syntax"">3.14.1<tt> </tt><a name="(part._require-syntax)"></a><a name="(mod-path._racket/require-syntax)"></a><span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span> Macros</h5><p><div class="SIntrapara"><table cellspacing="0" cellpadding="0" class="defmodule"><tr><td align="left"><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span><span class="stt"> </span><a href="define.html#%28mod-path._racket%2Frequire-syntax%29" class="RktModLink" data-pltdoc="x"><span class="RktSym">racket/require-syntax</span></a><span class="RktPn">)</span></td><td align="right"><span class="RpackageSpec"><span class="Smaller"> package:</span> <a href="https://pkgs.racket-lang.org/package/base" title="Install this package using `raco pkg install base`"><span class="stt">base</span></a></span></td></tr></table></div><div class="SIntrapara">The bindings documented in this section are provided by the <a href="define.html#%28mod-path._racket%2Frequire-syntax%29" class="RktModLink" data-pltdoc="
|
||
|
|
<span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span> sub-form. The <span class="RktVar">proc-expr</span> must produce a
|
||
|
|
procedure that accepts and returns a syntax object representing a
|
||
|
|
<span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span> sub-form.</div></p><p>This form expands to <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-syntax</a></span> with a use of
|
||
|
|
<span class="RktSym"><a href="stxtrans.html#%28def._%28%28lib._racket%2Frequire-transform..rkt%29._make-require-transformer%29%29" class="RktValLink" data-pltdoc="x">make-require-transformer</a></span> (see <a href="stxtrans.html#%28part._require-trans%29" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">require</span></span> Transformers</a> for
|
||
|
|
more information).</p><p>The second form is a shorthand the same as for <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-syntax</a></span>; it
|
||
|
|
expands to a definition of the first form where the <span class="RktVar">proc-expr</span> is a
|
||
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<span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span> form.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/require-syntax..rkt)._syntax-local-require-introduce))"></a><span title="Provided from: racket/require-syntax | Package: base"><span class="RktSym"><a href="define.html#%28def._%28%28lib._racket%2Frequire-syntax..rkt%29._syntax-local-require-introduce%29%29" class="RktValDef RktValLink" data-pltdoc="x">syntax-local-require-introduce</a></span></span><span class="hspace"> </span><span class="RktVar">stx</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax~3f%29%29" class="RktValLink" data-pltdoc="x">syntax?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">stx</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax~3f%29%29" class="RktValLink" data-pltdoc="x">syntax?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">For backward compatibility only; equivalent to <span class="RktSym"><a href="stxtrans.html#%28def._%28%28quote._~23~25kernel%29._syntax-local-introduce%29%29" class="RktValLink" data-pltdoc="x">syntax-local-introduce</a></span>.</div></p><p class="SHistory">Changed in version 6.90.0.29 of package <span class="stt">base</span>: Made equivalent to <span class="RktSym"><a href="stxtrans.html#%28def._%28%28quote._~23~25kernel%29._syntax-local-introduce%29%29" class="RktValLink" data-pltdoc="x">syntax-local-introduce</a></span>.</p><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-source-pkg="racket-doc" x-part-tag=""provide-syntax"">3.14.2<tt> </tt><a name="(part._provide-syntax)"></a><a name="(mod-path._racket/provide-syntax)"></a><span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._provide%29%29" class="RktStxLink" data-pltdoc="x">provide</a></span> Macros</h5><p><div class="SIntrapara"><table cellspacing="0" cellpadding="0" class="defmodule"><tr><td align="left"><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span><span class="stt"> </span><a href="define.html#%28mod-path._racket%2Fprovide-syntax%29" class="RktModLink" data-pltdoc="x"><span class="RktSym">racket/provide-syntax</span></a><span class="RktPn">)</span></td><td align="right"><span class="RpackageSpec"><span class="Smaller"> package:</span> <a href="https://pkgs.racket-lang.org/package/base" title="Install this package using `raco pkg install base`"><span class="stt">base</span></a></span></td></tr></table></div><div class="SIntrapara">The bindings documented in this section are provided by the <a href="define.html#%28mod-path._racket%2Fprovide-syntax%29" class="RktModLink" data-pltdoc="x"><span class="RktSym">racket/provide-syntax</span></a> library, not <a href="index.html" class="RktModLink" data-pltdoc="x"><span class="RktSym">racket/base</span></a> or <a href="index.html" class="RktModLink" data-pltdoc="x"><span class="RktSym">racket</span></a>.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>syntax</p></div></div><p class="RForeground"><span class="RktPn">(</span><a nam
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<span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._provide%29%29" class="RktStxLink" data-pltdoc="x">provide</a></span> sub-form. The <span class="RktVar">proc-expr</span> must produce a
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procedure that accepts and returns a syntax object representing a
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<span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._provide%29%29" class="RktStxLink" data-pltdoc="x">provide</a></span> sub-form.</div></p><p>This form expands to <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-syntax</a></span> with a use of
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<span class="RktSym"><a href="stxtrans.html#%28def._%28%28lib._racket%2Fprovide-transform..rkt%29._make-provide-transformer%29%29" class="RktValLink" data-pltdoc="x">make-provide-transformer</a></span> (see <a href="stxtrans.html#%28part._provide-trans%29" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">provide</span></span> Transformers</a> for
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more information).</p><p>The second form is a shorthand the same as for <span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-syntax%29%29" class="RktStxLink" data-pltdoc="x">define-syntax</a></span>; it
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expands to a definition of the first form where the <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=syntax&rel=Library_Syntax_Classes_and_Literal_Sets.html%23%2528form._%2528%2528lib._syntax%252Fparse..rkt%2529._expr%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">expr</a></span> is a
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<span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span> form.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/provide-syntax..rkt)._syntax-local-provide-introduce))"></a><span title="Provided from: racket/provide-syntax | Package: base"><span class="RktSym"><a href="define.html#%28def._%28%28lib._racket%2Fprovide-syntax..rkt%29._syntax-local-provide-introduce%29%29" class="RktValDef RktValLink" data-pltdoc="x">syntax-local-provide-introduce</a></span></span><span class="hspace"> </span><span class="RktVar">stx</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax~3f%29%29" class="RktValLink" data-pltdoc="x">syntax?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">stx</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="stxops.html#%28def._%28%28quote._~23~25kernel%29._syntax~3f%29%29" class="RktValLink" data-pltdoc="x">syntax?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">For backward compatibility only; equivalent to <span class="RktSym"><a href="stxtrans.html#%28def._%28%28quote._~23~25kernel%29._syntax-local-introduce%29%29" class="RktValLink" data-pltdoc="x">syntax-local-introduce</a></span>.</div></p><p class="SHistory">Changed in version 6.90.0.29 of package <span class="stt">base</span>: Made equivalent to <span class="RktSym"><a href="stxtrans.html#%28def._%28%28quote._~23~25kernel%29._syntax-local-introduce%29%29" class="RktValLink" data-pltdoc="x">syntax-local-introduce</a></span>.</p><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" id="searchbox" type="text" tabindex="1" placeholder="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "8.6", "../");"/></form> <a href="https://docs.racket-lang.org/index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("8.6");">top</a><span class="tocsettoggle"> <a href="javascript:void(0);" title="show/hide table of contents" onclick="TocsetToggle();">contents</a></span></span><span class="navright"> <a href="case.html" title="backward to "3.13 Dispatch: case"" data-pltdoc="x">← prev</a> <a href="syntax.html" title="up to "3 Syntactic Forms"" data-pltdoc="x">up</a> <a href="begin.html" title="forward to "3.15 Sequencing: begin, begin0, and begin-for-syntax"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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