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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>18.3 Interactive Help</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="tocviewlink" 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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browser (using the user’s selected browser) to display the results.</p><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p>See <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=net&rel=sendurl.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">net/sendurl</span></a> for information on how
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the user’s browser is launched to display help information.</p></blockquote></blockquote></blockquote><p>A simple <span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span> or <span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="RktPn">)</span> form opens the main
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documentation page.</p><p>The <span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="stt"> </span><span class="RktVar">string</span><span class="stt"> </span><span class="RktMeta"><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> form—<wbr></wbr>using literal strings, as
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opposed to expressions that produce strings—<wbr></wbr>performs a
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string-matching search. For example,</p><blockquote class="SCodeFlow"><p><span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="hspace"> </span><span class="RktVal">"web browser"</span><span class="hspace"> </span><span class="RktVal">"firefox"</span><span class="RktPn">)</span></p></blockquote><p>searches the documentation index for references that include the
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phrase “web browser” or “firefox.”</p><p>A <span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="stt"> </span><span class="RktVar">id</span><span class="RktPn">)</span> form looks for documentation specific to the
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current binding of <span class="RktVar">id</span>. For example,</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><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="hspace"> </span><span class="RktSym">net/url</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="hspace"> </span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=net&rel=url.html%23%2528def._%2528%2528lib._net%252Furl..rkt%2529._url-%7E3estring%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">url->string</a></span><span class="RktPn">)</span></td></tr></table></blockquote><p>opens a web browser to show the documentation for <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=net&rel=url.html%23%2528def._%2528%2528lib._net%252Furl..rkt%2529._url-%7E3estring%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">url->string</a></span>
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from the <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=net&rel=url.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">net/url</span></a> library.</p><p>For the purposes of <span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span>, a <span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._for-label%29%29" class="RktStxLink" data-pltdoc="x">for-label</a></span> require
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introduces a binding without actually executing the
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<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=net&rel=url.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">net/url</span></a> library—<wbr></wbr>for cases when you want to check
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documentation, but cannot or do not want to run the providing module.</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><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="hspace"> </span><span class="RktSym">racket/gui</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">does not work in </span><span class="stt">racket</span></td></tr><tr><td><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="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._for-label%29%29" class="RktStxLink" data-pltdoc="x">for-label</a></span><span class="hspace"> </span><span class="RktSym">racket/gui</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">ok in </span><span class="stt">racket</span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="hspace"> </span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=gui&rel=frame_.html&version=8.6" class="RktValLink Sq" data-pltdoc="x">frame%</a></span><span class="RktPn">)</span></td></tr></table></blockquote><p>If <span class="RktVar">id</span> has no for-label and normal binding, then <span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span>
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lists all libraries that are known to export a binding for
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<span class="RktVar">id</span>.</p><p>The <span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="stt"> </span><span class="RktVar">id</span><span class="stt"> </span><span class="RktPn">#:from</span><span class="stt"> </span><span class="RktVar">module-path</span><span class="RktPn">)</span> variant is similar to
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<span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="stt"> </span><span class="RktVar">id</span><span class="RktPn">)</span>, but using only the exports of
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<span class="RktVar">module-path</span>. (The <span class="RktVar">module-path</span> module is required
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<span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._for-label%29%29" class="RktStxLink" data-pltdoc="x">for-label</a></span> in a temporary namespace.)</p><blockquote class="SCodeFlow"><p><span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="hspace"> </span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=gui&rel=frame_.html&version=8.6" class="RktValLink Sq" data-pltdoc="x">frame%</a></span><span class="hspace"> </span><span class="RktPn">#:from</span><span class="hspace"> </span><span class="RktSym">racket/gui</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">equivalent to the above</span></p></blockquote><p>The <span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="stt"> </span><span class="RktPn">#:search</span><span class="stt"> </span><span class="RktVar">datum</span><span class="stt"> </span><span class="RktMeta"><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> form is similar to
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<span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="stt"> </span><span class="RktVar">string</span><span class="stt"> </span><span class="RktMeta"><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>, where any non-string form of
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<span class="RktVar">datum</span> is converted to a string using <span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._display%29%29" class="RktValLink" data-pltdoc="x">display</a></span>. No
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<span class="RktVar">datum</span> is evaluated as an expression.</p><p>For example,</p><blockquote class="SCodeFlow"><p><span class="RktPn">(</span><span class="RktSym"><a href="Interactive_Help.html#%28form._%28%28lib._racket%2Fhelp..rkt%29._help%29%29" class="RktStxLink" data-pltdoc="x">help</a></span><span class="hspace"> </span><span class="RktPn">#:search</span><span class="hspace"> </span><span class="RktVal">"web browser"</span><span class="hspace"> </span><span class="RktSym">firefox</span><span class="RktPn">)</span></p></blockquote><p>also searches the documentation index for references that include the
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phrase “web browser” or “firefox.”</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="collects.html" title="backward to "18.2 Libraries and Collections"" data-pltdoc="x">← prev</a> <a href="running.html" title="up to "18 Running Racket"" data-pltdoc="x">up</a> <a href="interaction-info.html" title="forward to "18.4 Interaction Configuration"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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