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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>3.6 Locations: #%variable-reference</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
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<a href="eval-model.html#%28tech._location%29" class="techoutside" data-pltdoc="x"><span class="techinside">location</span></a> of <span class="RktVar">id</span>, which must be bound as a variable. If
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no <span class="RktVar">id</span> is supplied, the resulting value refers to an
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“anonymous” variable defined within the enclosing context (i.e.,
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within the enclosing module, or at the top level if the form is not
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inside a module).</div></p><p>When <span class="RktPn">(</span><span class="RktSym"><a href="__top.html#%28form._%28%28quote._~23~25kernel%29._~23~25top%29%29" class="RktStxLink" data-pltdoc="x">#%top</a></span><span class="stt"> </span><span class="RktPn">. </span><span class="RktVar">id</span><span class="RktPn">)</span> is used, then the variable reference refers
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to the same variable as <span class="RktPn">(</span><span class="RktSym"><a href="__top.html#%28form._%28%28quote._~23~25kernel%29._~23~25top%29%29" class="RktStxLink" data-pltdoc="x">#%top</a></span><span class="stt"> </span><span class="RktPn">. </span><span class="RktVar">id</span><span class="RktPn">)</span>. Note that
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<span class="RktPn">(</span><span class="RktSym"><a href="__top.html#%28form._%28%28quote._~23~25kernel%29._~23~25top%29%29" class="RktStxLink" data-pltdoc="x">#%top</a></span><span class="stt"> </span><span class="RktPn">. </span><span class="RktVar">id</span><span class="RktPn">)</span> is not allowed if <span class="RktVar">id</span> is locally bound
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or within a module if <span class="RktVar">id</span> is bound as a transformer.</p><p>A <a href="Locations____variable-reference.html#%28tech._variable._reference%29" class="techoutside" data-pltdoc="x"><span class="techinside">variable reference</span></a> can be used with
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<span class="RktSym"><a href="Namespaces.html#%28def._%28%28quote._~23~25kernel%29._variable-reference-~3eempty-namespace%29%29" class="RktValLink" data-pltdoc="x">variable-reference->empty-namespace</a></span>,
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<span class="RktSym"><a href="Namespaces.html#%28def._%28%28quote._~23~25kernel%29._variable-reference-~3eresolved-module-path%29%29" class="RktValLink" data-pltdoc="x">variable-reference->resolved-module-path</a></span>, and
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<span class="RktSym"><a href="Namespaces.html#%28def._%28%28quote._~23~25kernel%29._variable-reference-~3enamespace%29%29" class="RktValLink" data-pltdoc="x">variable-reference->namespace</a></span>, but facilities like
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<span class="RktSym"><a href="Namespaces.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define-namespace-anchor%29%29" class="RktStxLink" data-pltdoc="x">define-namespace-anchor</a></span> and
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<span class="RktSym"><a href="Namespaces.html#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._namespace-anchor-~3enamespace%29%29" class="RktValLink" data-pltdoc="x">namespace-anchor->namespace</a></span> wrap those to provide a clearer
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interface. A <a href="Locations____variable-reference.html#%28tech._variable._reference%29" class="techoutside" data-pltdoc="x"><span class="techinside">variable reference</span></a> is also useful to low-level
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extensions; see <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=inside&rel=index.html&version=8.6" class="Sq" data-pltdoc="x">Inside: Racket C API</a>.</p><p class="SHistory">Changed in version 8.2.0.7 of package <span class="stt">base</span>: Changed <span class="RktSym"><a href="__top.html#%28form._%28%28quote._~23~25kernel%29._~23~25top%29%29" class="RktStxLink" data-pltdoc="x">#%top</a></span> treatment to be
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consistent with <span class="RktSym"><a href="__top.html#%28form._%28%28quote._~23~25kernel%29._~23~25top%29%29" class="RktStxLink" data-pltdoc="x">#%top</a></span> by itself.</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="__top.html" title="backward to "3.5 Variable References and #%top"" data-pltdoc="x">← prev</a> <a href="syntax.html" title="up to "3 Syntactic Forms"" data-pltdoc="x">up</a> <a href="application.html" title="forward to "3.7 Procedure Applications and #%app"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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