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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 Syntactic Forms</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="../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">Unsafe Operations</a></td></tr><tr><td align="right">18 </td><td><a href="running.html" class="tocv
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expanded expression, plus many closely related non-core forms.
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See <a href="syntax-model.html#%28part._fully-expanded%29" data-pltdoc="x">Fully Expanded Programs</a> for the core grammar.</p><table cellspacing="0" cellpadding="0"><tr><td><p><span class="hspace"> </span><a href="module.html" class="toclink" data-pltdoc="x">3.1<span class="hspace"> </span>Modules: <span class="RktSym"><span class="RktStxLink">module</span></span>, <span class="RktSym"><span class="RktStxLink">module*</span></span>, ...</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="require.html" class="toclink" data-pltdoc="x">3.2<span class="hspace"> </span>Importing and Exporting: <span class="RktSym"><span class="RktStxLink">require</span></span> and <span class="RktSym"><span class="RktStxLink">provide</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="require.html#%28part._.Additional_require_.Forms%29" class="toclink" data-pltdoc="x">3.2.1<span class="hspace"> </span>Additional <span class="RktSym"><span class="RktStxLink">require</span></span> Forms</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="require.html#%28part._.Additional_provide_.Forms%29" class="toclink" data-pltdoc="x">3.2.2<span class="hspace"> </span>Additional <span class="RktSym"><span class="RktStxLink">provide</span></span> Forms</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="quote.html" class="toclink" data-pltdoc="x">3.3<span class="hspace"> </span>Literals: <span class="RktSym"><span class="RktStxLink">quote</span></span> and <span class="RktSym"><span class="RktStxLink">#%datum</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="__expression.html" class="toclink" data-pltdoc="x">3.4<span class="hspace"> </span>Expression Wrapper: <span class="RktSym"><span class="RktStxLink">#%expression</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="__top.html" class="toclink" data-pltdoc="x">3.5<span class="hspace"> </span>Variable References and <span class="RktSym"><span class="RktStxLink">#%top</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="Locations____variable-reference.html" class="toclink" data-pltdoc="x">3.6<span class="hspace"> </span>Locations: <span class="RktSym"><span class="RktStxLink">#%variable-reference</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="application.html" class="toclink" data-pltdoc="x">3.7<span class="hspace"> </span>Procedure Applications and <span class="RktSym"><span class="RktStxLink">#%app</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="lambda.html" class="toclink" data-pltdoc="x">3.8<span class="hspace"> </span>Procedure Expressions: <span class="RktSym"><span class="RktStxLink">lambda</span></span> and <span class="RktSym"><span class="RktStxLink">case-lambda</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="let.html" class="toclink" data-pltdoc="x">3.9<span class="hspace"> </span>Local Binding: <span class="RktSym"><span class="RktStxLink">let</span></span>, <span class="RktSym"><span class="RktStxLink">let*</span></span>, <span class="RktSym"><span class="RktStxLink">letrec</span></span>, ...</a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="local.html" class="toclink" data-pltdoc="x">3.10<span class="hspace"> </span>Local Definitions: <span class="RktSym"><span class="RktStxLink">local</span></span></a></p></td></tr><tr><td><p><span class="hspace"> </span><a href="shared.html" class="toclink" data-pltdoc="x">3.11<span class="hspace"> </span>Constructing Graphs: <span class="RktSym"><span class="RktStxLink">shared</span></span></a></p></td></tr><tr><t
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a combination of (syntax-wrapped) pairs, symbols, and other data (not
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a sequence of characters). These grammatical specifications are shown
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as in the following specification of a <span class="RktKw">something</span>
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form:</p><blockquote class="leftindent"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><span class="RktPn">(</span><span class="RktKw">something</span><span class="hspace"> </span><span class="RktVar">id</span><span class="hspace"> </span><span class="RktVar">thing-expr</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt"> </span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">thing-expr</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><span class="RktSym"><a href="number-types.html#%28def._%28%28quote._~23~25kernel%29._number~3f%29%29" class="RktValLink" data-pltdoc="x">number?</a></span></td></tr></table></td></tr></table></blockquote></blockquote><p>Within such specifications,</p><ul><li><p><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> indicates zero or more repetitions of the
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preceding datum; more generally, <span style="font-style: italic">N</span> consecutive
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<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>s a row indicate a consecutive repetition of the
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preceding <span style="font-style: italic">N</span> datums.</p></li><li><p><span class="RktSym"><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> indicates one or more repetitions of the
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preceding datum.</p></li><li><p>Italic meta-identifiers play the role of non-terminals. Some
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meta-identifier names imply syntactic constraints:</p><ul><li><p>A meta-identifier that ends in <span class="RktVar">id</span> stands for an
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identifier.</p></li><li><p>A meta-identifier that ends in <span class="RktVar">keyword</span> stands
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for a keyword.</p></li><li><p>A meta-identifier that ends with <span class="RktVar">expr</span> (such as
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<span class="RktVar">thing-expr</span>) stands for a sub-form that is
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expanded as an expression.</p></li><li><p>A meta-identifier that ends with <span class="RktVar">body</span> stands
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for a sub-form that is expanded in an
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internal-definition context (see
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<a href="syntax-model.html#%28part._intdef-body%29" data-pltdoc="x">Internal Definitions</a>).</p></li></ul></li><li><p>Contracts indicate constraints on sub-expression results. For
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example, <span class="RktVar">thing-expr</span><span class="stt"> </span>:<span class="stt"> </span><span class="RktSym"><a href="number-types.html#%28def._%28%28quote._~23~25kernel%29._number~3f%29%29" class="RktValLink" data-pltdoc="x">number?</a></span> indicates that
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the expression <span class="RktVar">thing-expr</span> must produce a number.</p></li></ul><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="notation.html" title="backward to "2 Notation for Documentation"" data-pltdoc="x">← prev</a> <a href="index.html" title="up to "The Racket Reference"" data-pltdoc="x">up</a> <a href="module.html" title="forward to "3.1 Modules: module, module*, ..."" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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