107 lines
85 KiB
HTML
107 lines
85 KiB
HTML
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<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>6.2 Module Syntax</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="tocviewselflink" 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"
|
||
|
|
for a <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> form, much like <span class="RktInBG"><span class="hspace"></span><span class="RktIn">'</span><span class="hspace"></span></span> is a shorthand for a
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=quote.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._quote%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">quote</a></span> form. Unlike <span class="RktInBG"><span class="hspace"></span><span class="RktIn">'</span><span class="hspace"></span></span>, the <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#lang</span><span class="hspace"></span></span>
|
||
|
|
shorthand does not work well in a <a href="intro.html#%28tech._repl%29" class="techoutside" data-pltdoc="x"><span class="techinside">REPL</span></a>, in part because it must be
|
||
|
|
terminated by an end-of-file, but also because the longhand expansion
|
||
|
|
of <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#lang</span><span class="hspace"></span></span> depends on the name of the enclosing file.</p><h5 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-source-pkg="racket-doc" x-part-tag=""module-syntax"">6.2.1<tt> </tt><a name="(part._module-syntax)"></a>The <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> Form</h5><p>The longhand form of a module declaration, which works in a
|
||
|
|
<a href="intro.html#%28tech._repl%29" class="techoutside" data-pltdoc="x"><span class="techinside">REPL</span></a> as well as a file, is</p><blockquote class="leftindent"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span><span class="hspace"> </span><span class="RktVar">name-id</span><span class="hspace"> </span><span class="RktVar">initial-module-path</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">decl</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr></table></td></tr></table></blockquote></blockquote><p>where the <span class="RktVar">name-id</span> is a name for the module,
|
||
|
|
<span class="RktVar">initial-module-path</span> is an initial import, and each
|
||
|
|
<span class="RktVar">decl</span> is an import, export, definition, or expression. In
|
||
|
|
the case of a file, <span class="RktVar">name-id</span> normally matches the name of the
|
||
|
|
containing file, minus its directory path or file extension, but
|
||
|
|
<span class="RktVar">name-id</span> is ignored when the module is <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>d
|
||
|
|
through its file’s path.</p><p>The <span class="RktVar">initial-module-path</span> is needed because even the
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span> form must be imported for further use in the module
|
||
|
|
body. In other words, the <span class="RktVar">initial-module-path</span> import
|
||
|
|
bootstraps the syntax that is available in the body. The most commonly used
|
||
|
|
<span class="RktVar">initial-module-path</span> is <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>, which supplies most
|
||
|
|
of the bindings described in this guide, including <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>,
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span>, and <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._provide%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">provide</a></span>. Another commonly used
|
||
|
|
<span class="RktVar">initial-module-path</span> is <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>, which provides
|
||
|
|
less functionality, but still much of the most commonly needed
|
||
|
|
functions and syntax.</p><p>For example, the <span class="stt">"cake.rkt"</span> example of the
|
||
|
|
<a href="module-basics.html" data-pltdoc="x">previous section</a> could be written as</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span><span class="hspace"> </span><span class="RktSym">cake</span><span class="hspace"> </span><span class="RktSym">racket</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._provide%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">provide</a></span><span class="hspace"> </span><span class="RktSym">print-cake</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">print-cake</span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">"</span><span class="hspace"> </span><span class="RktVal">~a</span><span class="hspace"> </span><span class="RktVal">"</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\.</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">" .-~a-. "</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\|</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">" | ~a | "</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\space</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">"---~a---"</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\-</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktSym">fmt</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td><
|
||
|
|
<a href="intro.html#%28tech._repl%29" class="techoutside" data-pltdoc="x"><span class="techinside">REPL</span></a> to declare a <span class="RktSym">cake</span> module that is not associated
|
||
|
|
with any file. To refer to such an unassociated module, quote the
|
||
|
|
module name:</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="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">cake</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">print-cake</span><span class="hspace"> </span><span class="RktVal">3</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td><p><span class="RktOut"></span><span class="hspace"> </span><span class="RktOut"></span><span class="hspace"> </span><span class="RktOut">... </span><span class="hspace"> </span><span class="RktOut"></span></p></td></tr><tr><td><p><span class="RktOut"></span><span class="hspace"> </span><span class="RktOut">.-|||-. </span></p></td></tr><tr><td><p><span class="RktOut"></span><span class="hspace"> </span><span class="RktOut">| </span><span class="hspace"> </span><span class="RktOut"></span><span class="hspace"> </span><span class="RktOut">| </span></p></td></tr><tr><td><p><span class="RktOut">---------</span></p></td></tr></table></td></tr></table></blockquote></div></p><p>Declaring a module does not immediately evaluate the body definitions
|
||
|
|
and expressions of the module. The module must be explicitly
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>d at the top level to trigger evaluation. After
|
||
|
|
evaluation is triggered once, later <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>s do not
|
||
|
|
re-evaluate the module body.</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="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span><span class="hspace"> </span><span class="RktSym">hi</span><span class="hspace"> </span><span class="RktSym">racket</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Writing.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._printf%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">printf</a></span><span class="hspace"> </span><span class="RktVal">"Hello\n"</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"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">hi</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">Hello</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">hi</span><span class="RktPn">)</span></td></tr></table></blockquote></div></p><h5 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-source-pkg="racket-doc" x-part-tag=""hash-lang"">6.2.2<tt> </tt><a name="(part._hash-lang)"></a>The <span class="RktMod">#lang</span> Shorthand</h5><p>The body of a <span class="RktMod">#lang</span> shorthand has no specific syntax,
|
||
|
|
because the syntax is determined by the language name that follows
|
||
|
|
<span class="RktMod">#lang</span>.</p><p>In the case of <span class="RktMod">#lang</span> <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>, the syntax
|
||
|
|
is</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="hspace"> </span><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></td></tr><tr><td><span class="RktVar">decl</span><span class="hspace"> </span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=stx-patterns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fstxcase-scheme..rkt%2529._......%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">...</a></span></td></tr></table></blockquote><p>which reads the same as</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span><span class="hspace"> </span><span class="RktVar">name</span><span class="hspace"> </span><span class="RktSym">racket</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">decl</span><span class="hspace"> </span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=stx-patterns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fstxcase-scheme..rkt%2529._......%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">...</a></span><span class="RktPn">)</span></td></tr></table></blockquote><p>where <span class="RktVar">name</span> is derived from the name of the file that
|
||
|
|
contains the <span class="RktMod">#lang</span> form.</p><p>The <span class="RktMod">#lang</span> <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> form has the same
|
||
|
|
syntax as <span class="RktMod">#lang</span> <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>, except that
|
||
|
|
the longhand expansion uses <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> instead of
|
||
|
|
<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>. The <span class="RktMod">#lang</span> <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=scribble&rel=manual.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">scribble/manual</span></a> form, in
|
||
|
|
contrast, has a completely different syntax that doesn’t even look
|
||
|
|
like Racket, and which we do not attempt to describe in this guide.</p><p>Unless otherwise specified, a module that is documented as a
|
||
|
|
“language” using the <span class="RktMod">#lang</span> notation will expand to
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> in the same way as <span class="RktMod">#lang</span>
|
||
|
|
<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>. The documented language name can be used
|
||
|
|
directly with <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> or <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>, too.</p><h5 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-source-pkg="racket-doc" x-part-tag=""submodules"">6.2.3<tt> </tt><a name="(part._submodules)"></a>Submodules</h5><p>A <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> form can be nested within a module, in which case
|
||
|
|
the nested <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> form declares a
|
||
|
|
<a name="(tech._submodule)"></a><span style="font-style: italic">submodule</span>. Submodules can be referenced directly by the
|
||
|
|
enclosing module using a quoted name. The following example prints
|
||
|
|
<span class="RktVal">"Tony"</span> by importing <span class="RktSym">tiger</span> from the <span class="RktSym">zoo</span>
|
||
|
|
submodule:</p><blockquote class="SCodeFlow"><blockquote class="Rfilebox"><p class="Rfiletitle"><span class="Rfilename"><span class="stt">"park.rkt"</span></span></p><blockquote class="Rfilecontent"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="hspace"> </span><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></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span><span class="hspace"> </span><span class="RktSym">zoo</span><span class="hspace"> </span><span class="RktSym">racket</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._provide%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">provide</a></span><span class="hspace"> </span><span class="RktSym">tiger</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">tiger</span><span class="hspace"> </span><span class="RktVal">"Tony"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">zoo</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktSym">tiger</span></td></tr></table></blockquote></blockquote></blockquote><p>Running a module does not necessarily run its submodules. In the above
|
||
|
|
example, running <span class="stt">"park.rkt"</span> runs its submodule <span class="RktSym">zoo</span>
|
||
|
|
only because the <span class="stt">"park.rkt"</span> module <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>s the
|
||
|
|
<span class="RktSym">zoo</span> submodule. Otherwise, a module and each of its submodules can be run
|
||
|
|
independently. Furthermore, if <span class="stt">"park.rkt"</span> is compiled to a
|
||
|
|
bytecode file (via <span class="stt">raco make</span>), then the code for
|
||
|
|
<span class="stt">"park.rkt"</span> or the code for <span class="RktSym">zoo</span> can be loaded independently.</p><p>Submodules can be nested within submodules, and a submodule can be
|
||
|
|
referenced directly by a module other than its enclosing module by
|
||
|
|
using a <a href="module-paths.html#%28elem._submod%29" data-pltdoc="x">submodule path</a>.</p><p>A <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span> form is similar to a nested <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> form:</p><blockquote class="leftindent"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span><span class="hspace"> </span><span class="RktVar">name-id</span><span class="hspace"> </span><span class="RktVar">initial-module-path-or-#f</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">decl</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr></table></td></tr></table></blockquote></blockquote><p>The <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span> form differs from <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> in that it
|
||
|
|
inverts the possibilities for reference between the submodule and
|
||
|
|
enclosing module:</p><ul><li><p>A submodule declared with <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span> can be
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>d by its enclosing module, but the submodule
|
||
|
|
cannot <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span> the enclosing module or lexically
|
||
|
|
reference the enclosing module’s bindings.</p></li><li><p>A submodule declared with <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span> can <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>
|
||
|
|
its enclosing module, but the enclosing module cannot
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span> the submodule.</p></li></ul><p>In addition, a <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span> form can specify <span class="RktVal">#f</span> in place of an
|
||
|
|
<span class="RktVar">initial-module-path</span>, in which case the submodule sees all of
|
||
|
|
the enclosing module’s bindings—<wbr></wbr>including bindings that are not
|
||
|
|
exported via <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._provide%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">provide</a></span>.</p><p>One use of submodules declared with <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span> and <span class="RktVal">#f</span> is
|
||
|
|
to export additional bindings through a submodule that are not
|
||
|
|
normally exported from the module:</p><blockquote class="SCodeFlow"><blockquote class="Rfilebox"><p class="Rfiletitle"><span class="Rfilename"><span class="stt">"cake.rkt"</span></span></p><blockquote class="Rfilecontent"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="hspace"> </span><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></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._provide%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">provide</a></span><span class="hspace"> </span><span class="RktSym">print-cake</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">print-cake</span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">"</span><span class="hspace"> </span><span class="RktVal">~a</span><span class="hspace"> </span><span class="RktVal">"</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\.</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">" .-~a-. "</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\|</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">" | ~a | "</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\space</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">"---~a---"</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\-</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktSym">fmt</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span cla
|
||
|
|
imported by a module that uses <span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="stt"> </span><span class="RktVal">"cake.rkt"</span><span class="RktPn">)</span>, since
|
||
|
|
most clients of <span class="stt">"cake.rkt"</span> will not want the extra function. A
|
||
|
|
module can require the <span class="RktSym">extra</span> <a href="Module_Syntax.html#%28tech._submodule%29" class="techoutside" data-pltdoc="x"><span class="techinside">submodule</span></a> using
|
||
|
|
<span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="stt"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._submod%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">submod</a></span><span class="stt"> </span><span class="RktVal">"cake.rkt"</span><span class="stt"> </span><span class="RktSym">extras</span><span class="RktPn">)</span><span class="RktPn">)</span> to access the otherwise
|
||
|
|
hidden <span class="RktSym">show</span> function.<span class="refelem"><span class="refcolumn"><span class="refcontent">See <a href="module-paths.html#%28elem._submod%29" data-pltdoc="x">submodule paths</a>
|
||
|
|
for more information on <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._submod%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">submod</a></span>.</span></span></span></p><h5 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-source-pkg="racket-doc" x-part-tag=""main-and-test"">6.2.4<tt> </tt><a name="(part._main-and-test)"></a>Main and Test Submodules</h5><p>The following variant of <span class="stt">"cake.rkt"</span> includes a <span class="RktSym">main</span>
|
||
|
|
submodule that calls <span class="RktSym">print-cake</span>:</p><blockquote class="SCodeFlow"><blockquote class="Rfilebox"><p class="Rfiletitle"><span class="Rfilename"><span class="stt">"cake.rkt"</span></span></p><blockquote class="Rfilecontent"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="hspace"> </span><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></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">print-cake</span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">"</span><span class="hspace"> </span><span class="RktVal">~a</span><span class="hspace"> </span><span class="RktVal">"</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\.</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">" .-~a-. "</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\|</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">" | ~a | "</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\space</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktVal">"---~a---"</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">#\-</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">show</span><span class="hspace"> </span><span class="RktSym">fmt</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Writing.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._printf%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">printf</a></span><span class="hspace"> </span><span class="RktSym">fmt</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases
|
||
|
|
submodules. Nevertheless, running the above module via <span class="stt">racket</span>
|
||
|
|
or DrRacket prints a cake with 10 candles, because the <span class="RktSym">main</span>
|
||
|
|
<a href="Module_Syntax.html#%28tech._submodule%29" class="techoutside" data-pltdoc="x"><span class="techinside">submodule</span></a> is a special case.</p><p>When a module is provided as a program name to the <span class="stt">racket</span>
|
||
|
|
executable or run directly within DrRacket, if the module has a
|
||
|
|
<a name="(idx._(gentag._1._(lib._scribblings/guide/guide..scrbl)))"></a><span class="RktSym">main</span> submodule, the <span class="RktSym">main</span> submodule is run
|
||
|
|
after its enclosing module. Declaring a <span class="RktSym">main</span> submodule
|
||
|
|
thus specifies extra actions to be performed when a module is run directly,
|
||
|
|
instead of <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span>d as a library within a larger program.</p><p>A <span class="RktSym">main</span> submodule does not have to be declared with
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span>. If the <span class="RktSym">main</span> module does not need to use
|
||
|
|
bindings from its enclosing module, it can be declared with
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module</a></span>. More commonly, <span class="RktSym">main</span> is declared using
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span>:</p><blockquote class="leftindent"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span><span class="hspace"> </span><span class="RktVar">name-id</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">decl</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr></table></td></tr></table></blockquote></blockquote><p>A submodule declared with <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span> is like one declared with
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span> using <span class="RktVal">#f</span> as its
|
||
|
|
<span class="RktVar">initial-module-path</span>. In addition,
|
||
|
|
multiple <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span> forms can specify the same submodule name,
|
||
|
|
in which case the bodies of the <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span> forms are combined to
|
||
|
|
create a single submodule.</p><p>The combining behavior of <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span> is particularly useful for
|
||
|
|
defining a <span class="RktSym">test</span> submodule, which can be conveniently run
|
||
|
|
using <span class="stt">raco test</span> in much the same way that <span class="RktSym">main</span> is
|
||
|
|
conveniently run with <span class="stt">racket</span>. For example, the following
|
||
|
|
<span class="stt">"physics.rkt"</span> module exports <span class="RktSym">drop</span> and
|
||
|
|
<span class="RktSym">to-energy</span> functions, and it defines a <span class="RktSym">test</span> module to
|
||
|
|
hold unit tests:</p><blockquote class="SCodeFlow"><blockquote class="Rfilebox"><p class="Rfiletitle"><span class="Rfilename"><span class="stt">"physics.rkt"</span></span></p><blockquote class="Rfilecontent"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="hspace"> </span><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></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span><span class="hspace"> </span><span class="RktSym">test</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktSym">rackunit</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">ε</span><span class="hspace"> </span><span class="RktVal">1e-10</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._provide%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">provide</a></span><span class="hspace"> </span><span class="RktSym">drop</span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym">to-energy</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">drop</span><span class="hspace"> </span><span class="RktSym">t</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252A%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">*</a></span><span class="hspace"> </span><span class="RktVal">1/2</span><span class="hspace"> </span><span class="RktVal">9.8</span><span class="hspace"> </span><span class="RktSym">t</span><span class="hspace"> </span><span class="RktSym">t</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><
|
||
|
|
the <span class="RktSym">drop</span> and <span class="RktSym">to-energy</span> tests—<wbr></wbr>or even trigger the
|
||
|
|
loading of the test code, if the module is compiled—<wbr></wbr>but running
|
||
|
|
<span class="stt">raco test physics.rkt</span> at a command line runs the tests.</p><p>The above <span class="stt">"physics.rkt"</span> module is equivalent to using
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span>:</p><blockquote class="SCodeFlow"><blockquote class="Rfilebox"><p class="Rfiletitle"><span class="Rfilename"><span class="stt">"physics.rkt"</span></span></p><blockquote class="Rfilecontent"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><a href="Module_Syntax.html#%28part._hash-lang%29" class="RktModLink" data-pltdoc="x"><span class="RktMod">#lang</span></a><span class="hspace"> </span><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></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._provide%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">provide</a></span><span class="hspace"> </span><span class="RktSym">drop</span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym">to-energy</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">drop</span><span class="hspace"> </span><span class="RktSym">t</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252A%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">*</a></span><span class="hspace"> </span><span class="RktVal">1/2</span><span class="hspace"> </span><span class="RktVal">49/5</span><span class="hspace"> </span><span class="RktSym">t</span><span class="hspace"> </span><span class="RktSym">t</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">to-energy</span><span class="hspace"> </span><span class="RktSym">m</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252A%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">*</a></span><span class="hspace"> </span><span class="RktSym">m</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._expt%2529%2529&
|
||
|
|
interleaved with function definitions.</p><p>The combining behavior of <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span> is also sometimes helpful
|
||
|
|
for a <span class="RktSym">main</span> module. Even when combining is not needed,
|
||
|
|
<span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._module%252B%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module+</a></span><span class="stt"> </span><span class="RktSym">main</span><span class="stt"> </span><span class="RktSym">....</span><span class="RktPn">)</span> is preferred as it is more readable than
|
||
|
|
<span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=module.html%23%2528form._%2528%2528quote._%7E23%7E25kernel%2529._module%252A%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">module*</a></span><span class="stt"> </span><span class="RktSym">main</span><span class="stt"> </span><span class="RktVal">#f</span><span class="stt"> </span><span class="RktSym">....</span><span class="RktPn">)</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="module-basics.html" title="backward to "6.1 Module Basics"" data-pltdoc="x">← prev</a> <a href="modules.html" title="up to "6 Modules"" data-pltdoc="x">up</a> <a href="module-paths.html" title="forward to "6.3 Module Paths"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
|