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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>23.1 More Rackets</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="tocviewlink" 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" dat
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language in the usual sense. Macros can extend a base language (as
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described in <a href="macros.html" data-pltdoc="x">Macros</a>), and alternate parsers can
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construct an entirely new language from the ground up (as described in
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<a href="languages.html" data-pltdoc="x">Creating Languages</a>).</p><p>The <a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a> line that starts a Racket module declares the
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base language of the module. By “Racket,” we usually mean
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<a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a> followed by the base language <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> or
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<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> (of which <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> is an
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extension). The Racket distribution provides additional languages,
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including the following:</p><ul><li><p><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=ts-reference&rel=index.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">typed/racket</span></a> —<wbr></wbr> like
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<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>, but statically typed; see
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<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=ts-guide&rel=index.html&version=8.6" class="Sq" data-pltdoc="x">The Typed Racket Guide</a></p></li><li><p><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?tag=%28mod-path._.%27lazy.%27%29&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">lazy</span></a> —<wbr></wbr> like
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<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>, but avoids evaluating an
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expression until its value is needed; see <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?tag=%28part._%28.%27%28lib._lazy%2Flazy..scrbl%29.%27._.%27top.%27%29%29&version=8.6" class="Sq" data-pltdoc="x">the Lazy Racket
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documentation</a>.</p></li><li><p><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?tag=%28mod-path._.%27frtime.%27%29&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">frtime</span></a> —<wbr></wbr> changes evaluation in an
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even more radical way to support reactive programming; see
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<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?tag=%28part._%28.%27%28lib._frtime%2Fscribblings%2Ffrtime..scrbl%29.%27._.%27top.%27%29%29&version=8.6" class="Sq" data-pltdoc="x">the FrTime documentation</a>.</p></li><li><p><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=scribble&rel=base.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">scribble/base</span></a> —<wbr></wbr> a language, which looks more
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like Latex than Racket, for writing documentation; see
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<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=scribble&rel=index.html&version=8.6" class="Sq" data-pltdoc="x">Scribble: The Racket Documentation Tool</a></p></li></ul><p>Each of these languages is used by starting module with the language
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name after <a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a>. For example, this source of this
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document starts with <a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="stt"> </span><span class="RktSym">scribble/base</span>.</p><p>Furthermore, Racket users can define their own languages, as discussed
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in <a href="languages.html" data-pltdoc="x">Creating Languages</a>. Typically, a language name maps to its
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implementation through a module path by adding
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<span class="RktSym">/lang/reader</span>; for example, the language name
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<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=scribble&rel=base.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">scribble/base</span></a> is expanded to
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<span class="RktSym">scribble/base/lang/reader</span>, which is the module that
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implements the surface-syntax parser. Some language names act as
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language loaders; for example, <a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="stt"> </span><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=planet&rel=hash-lang-planet.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">planet</span></a><span class="stt"> </span><span class="RktVar">planet-path</span> downloads, installs, and uses a
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language via <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=planet&rel=index.html&version=8.6" class="Sq" data-pltdoc="x"><span class="planetName">PLaneT</span></a>.</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="dialects.html" title="backward to "23 Dialects of Racket and Scheme"" data-pltdoc="x">← prev</a> <a href="dialects.html" title="up to "23 Dialects of Racket and Scheme"" data-pltdoc="x">up</a> <a href="standards.html" title="forward to "23.2 Standards"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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