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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>15.2 Manipulating Namespaces</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="tocviewselflink" 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" data-pltdoc="x">Concurrency and Synchronization</a></td></tr><tr><td align="right">19 </td><td><a href="performance.html" class="tocviewlink" data-pltdoc="x">Performance</a></td></tr><tr><td align="right">20 </td><td><a href="parallelism.html" class="tocviewlink" data-pltdoc="x">Parallelism</a></td></tr><tr><td align="right">21 </td><td><a href="running.html" class="tocviewlink" data-pltdoc="x">Running and Creating Executables</a></td></tr><tr><td align="right">22 </td><td><a href="More_Libraries.html" class="tocviewlink" data-pltdoc="x">More Libraries</a></td></tr><tr><td align="right">23 </td><td><a href="dialects.html" class="tocviewlink" data-pltdoc="x">Dialects of Racket and Scheme</a></td></tr><tr><td align="right">24 </td><td><a href="other-editors.html" class="tocviewlink" data-pltdoc="x">Command-<wbr></wbr>Line Tools and Your Editor of Choice</a></td></tr><tr><td align="right"></td><td><a href="doc-bibliography.html" class="tocviewlink" data-pltdoc="x">Bibliography</a></td></tr><tr><td align="right"></td><td><a href="doc-index.html" class="tocviewlink" data-pltdoc="x">Index</a></td></tr></table></div></div><div class="tocviewlist"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_1");">▼</a></td><td>15 </td><td><a href="reflection.html" class="tocviewlink" data-pltdoc="x">Reflection and Dynamic Evaluation</a></td></tr></table><div class="tocviewsublist" style="display: block;" id="tocview_1"><table cellspacing="0" cellpadding="0"><tr><td align="right">15.1 </td><td><a href="eval.html" class="tocviewlink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">eval</span></span></a></td></tr><tr><td align="right">15.2 </td><td><a href="mk-namespace.html" class="tocviewselflink" data-pltdoc="x">Manipulating Namespaces</a></td></tr><tr><td align="right">15.3 </td><td><a href="load.html" class="tocviewlink" data-pltdoc="x">Scripting Evaluation and Using <span class="RktSym"><span class="RktValLink">load</span></span></a></td></tr><tr><td align="right">15.4 </td><td><a href="code-inspectors_protect.html" class="tocviewlink" data-pltdoc="x">Code Inspectors for Trusted and Untrusted Code</a></td></tr></table></div></div><div class="tocviewlist"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_2");">►</a></td><td>15.2 </td><td><a href="mk-namespace.html" class="tocviewselflink" data-pltdoc="x">Manipulating Namespaces</a></td></tr></table><div class="tocviewsublistbottom" style="display: none;" id="tocview_2"><table cellspacing="0" cellpadding="0"><tr><td align="right">15.2.1 </td><td><a href="mk-namespace.html#%28part._.Creating_and_.Installing_.Namespaces%29" class="tocviewlink" data-pltdoc="x">Creating and Installing Namespaces</a></td></tr><tr><td align="right">15.2.2 </td><td><a href="mk-namespace.html#%28part._.Sharing_.Data_and_.Code_.Across_.Namespaces%29" class="tocviewlink" data-pltdoc="x">Sharing Data and Code Across Namespaces</a></td></tr></table></div></div></div><div class="tocsub"><div class="tocsubtitle">On this page:</div><table class="tocsublist" cellspacing="0"><tr><td><span class="tocsublinknumber">15.2.1<tt> </tt></span><a href="mk-namespace.html#%28part._.Creating_and_.Installing_.Namespaces%29" class="tocsubseclink" data-pltdoc="x">Creating and Installing Namespaces</a></td></tr><tr><td><span class="tocsublinknumber">15.2.2<tt> </tt></span><a href="mk-namespace.html#%28part._.Sharing_.Data_and_.Code_.Across_.Namespaces%29" class="tocsubseclink" data-pltdoc="x">Sharing Data and Code Across Namespaces</a></td></tr></table></div></div><div class="maincolumn"><div class="main"><div class="navsettop"><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="eval.html" title="backward to "15.1 eval"" data-pltdoc="x">← prev</a> <a href="reflection.html" title="up to "15 Reflection and Dynamic Evaluation"" data-pltdoc="x">up</a> <a href="load.html" title="forward to "15.3 Scripting Evaluation and Using load"" data-pltdoc="x">next →</a></span> </div><h4 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-source-pkg="racket-doc" x-part-tag=""mk-namespace"">15.2<tt> </tt><a name="(part._mk-namespace)"></a>Manipulating Namespaces</h4><p>A <a href="eval.html#%28tech._namespace%29" class="techoutside" data-pltdoc="x"><span class="techinside">namespace</span></a> encapsulates two pieces of information:</p><ul><li><p>A mapping from identifiers to bindings. For example, a
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namespace might map the identifier <span class="RktSym">lambda</span> to the
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<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span> form. An “empty” namespace is one that maps
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every identifier to an uninitialized top-level variable.</p></li><li><p>A mapping from module names to module declarations and
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instances. (The distinction between declaration and instance is
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discussed in <a href="macro-module.html" data-pltdoc="x">Module Instantiations and Visits</a>.)</p></li></ul><p>The first mapping is used for evaluating expressions in a top-level
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context, as in <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=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._eval%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">eval</a></span><span class="stt"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">lambda</span><span class="stt"> </span><span class="RktVal">(</span><span class="RktVal">x</span><span class="RktVal">)</span><span class="stt"> </span><span class="RktVal">(</span><span class="RktVal">+</span><span class="stt"> </span><span class="RktVal">x</span><span class="stt"> </span><span class="RktVal">1</span><span class="RktVal">)</span><span class="RktVal">)</span><span class="RktPn">)</span>. The second
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mapping is used, for example, by <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Module_Names_and_Loading.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._dynamic-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">dynamic-require</a></span> to locate a
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module. The call <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=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._eval%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">eval</a></span><span class="stt"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">require</span><span class="stt"> </span><span class="RktVal">racket/base</span><span class="RktVal">)</span><span class="RktPn">)</span> normally uses
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both pieces: the identifier mapping determines the binding of
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<span class="RktSym">require</span>; if it turns out to mean <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>, then
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the module mapping is used to locate the <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>
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module.</p><p>From the perspective of the core Racket run-time system, all
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evaluation is reflective. Execution starts with an initial namespace
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that contains a few primitive modules, and that is further populated
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by loading files and modules as specified on the command line or as
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supplied in the <a href="intro.html#%28tech._repl%29" class="techoutside" data-pltdoc="x"><span class="techinside">REPL</span></a>. Top-level <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> and
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<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> forms adjusts the identifier mapping, and module
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declarations (typically loaded on demand for a <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)
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adjust the module mapping.</p><h5 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-source-pkg="racket-doc" x-part-tag=""Creating_and_Installing_Namespaces"">15.2.1<tt> </tt><a name="(part._.Creating_and_.Installing_.Namespaces)"></a>Creating and Installing Namespaces</h5><p>The function <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._make-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-empty-namespace</a></span> creates a new, empty
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<a href="eval.html#%28tech._namespace%29" class="techoutside" data-pltdoc="x"><span class="techinside">namespace</span></a>. Since the namespace is truly empty, it cannot at
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first be used to evaluate any top-level expression—<wbr></wbr>not even
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<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="RktSym">racket</span><span class="RktPn">)</span>. In particular,</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=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-namespace</a></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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._make-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-empty-namespace</a></span><span class="RktPn">)</span><span class="RktPn">]</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">racket</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></blockquote><p>fails, because the namespace does not include the primitive modules on
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which <span class="RktSym">racket</span> is built.</p><p>To make a namespace useful, some modules must be <a name="(tech._attached)"></a><span style="font-style: italic">attached</span>
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from an existing namespace. Attaching a module adjusts the mapping of
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module names to instances by transitively copying entries (the module
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and all its imports) from an existing namespace’s mapping. Normally,
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instead of just attaching the primitive modules—<wbr></wbr>whose names and
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organization are subject to change—<wbr></wbr>a higher-level module is
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attached, such as <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>.</p><p>The <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._make-base-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-base-empty-namespace</a></span> function provides a namespace
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that is empty, except that <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> is
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attached. The resulting namespace is still “empty” in the sense that
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the identifiers-to-bindings part of the namespace has no mappings;
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only the module mapping has been populated. Nevertheless, with an
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initial module mapping, further modules can be loaded.</p><p>A namespace created with <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._make-base-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-base-empty-namespace</a></span> is
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suitable for many basic dynamic tasks. For example, suppose that a
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<span class="RktMod">my-dsl</span> library implements a domain-specific language
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in which you want to execute commands from a user-specified file. A
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namespace created with <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._make-base-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-base-empty-namespace</a></span> is enough to
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get started:</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=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">run-dsl</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=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._file%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">file</a></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=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-namespace</a></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=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._make-base-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-base-empty-namespace</a></span><span class="RktPn">)</span><span class="RktPn">]</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">my-dsl</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=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._load%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">load</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=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._file%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">file</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></blockquote><p>Note that the <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span> of <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-namespace</a></span> does
|
|
not affect the meaning of identifiers like <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span>
|
|
within the <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span> body. Those identifiers obtain their
|
|
meaning from the enclosing context (probably a module). Only
|
|
expressions that are dynamic with respect to this code, such as the
|
|
content of <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._load%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">load</a></span>ed files, are affected by the
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span>.</p><p>Another subtle point in the above example is the use of
|
|
<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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span><span class="stt"> </span><span class="RktVal">'</span><span class="RktVal">my-dsl</span><span class="RktPn">)</span> instead of <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=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._eval%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">eval</a></span><span class="stt"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">require</span><span class="stt"> </span><span class="RktVal">my-dsl</span><span class="RktVal">)</span><span class="RktPn">)</span>. The latter would not work, because <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._eval%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">eval</a></span>
|
|
needs to obtain a meaning for <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> in the namespace, and
|
|
the namespace’s identifier mapping is initially empty. The
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span> function, in contrast, directly imports the
|
|
given module into the current namespace. Starting with
|
|
<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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span><span class="stt"> </span><span class="RktVal">'</span><span class="RktVal">racket/base</span><span class="RktPn">)</span> would introduce a binding
|
|
for <span class="RktSym">require</span> and make a subsequent <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=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._eval%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">eval</a></span><span class="stt"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">require</span><span class="stt"> </span><span class="RktVal">my-dsl</span><span class="RktVal">)</span><span class="RktPn">)</span> work. The above is better, not only because it is
|
|
more compact, but also because it avoids introducing bindings that are
|
|
not part of the domain-specific languages.</p><h5 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-source-pkg="racket-doc" x-part-tag=""Sharing_Data_and_Code_Across_Namespaces"">15.2.2<tt> </tt><a name="(part._.Sharing_.Data_and_.Code_.Across_.Namespaces)"></a>Sharing Data and Code Across Namespaces</h5><p>Modules not attached to a new namespace will be loaded and
|
|
instantiated afresh if they are demanded by evaluation. For example,
|
|
<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> does not include
|
|
<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=mzlib_class.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">racket/class</span></a>, and loading <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=mzlib_class.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">racket/class</span></a>
|
|
again will create a distinct class datatype:</p><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="RktSym">racket/class</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">class?</span><span class="hspace"> </span><span class="RktSym">object%</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#t</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">class?</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=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-namespace</a></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=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._make-base-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-base-empty-namespace</a></span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">racket/class</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">loads again</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=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._eval%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">eval</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">object%</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">#f</span></p></td></tr></table></blockquote><p>For cases when dynamically loaded code needs to share more code and
|
|
data with its context, use the <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-attach-module%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-attach-module</a></span>
|
|
function. The first argument to <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-attach-module%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-attach-module</a></span> is a
|
|
source namespace from which to draw a module instance; in some cases,
|
|
the current namespace is known to include the module that needs to be
|
|
shared:</p><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="RktSym">racket/class</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">class?</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=let.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fletstx-scheme..rkt%2529._let%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">ns</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=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._make-base-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-base-empty-namespace</a></span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-attach-module%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-attach-module</a></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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-namespace</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">racket/class</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">ns</span><span class="RktPn">)</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=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-namespace</a></span><span class="hspace"> </span><span class="RktSym">ns</span><span class="RktPn">]</span><span class="RktPn">)</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-require</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">racket/class</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">uses attached</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=eval.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._eval%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">eval</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">object%</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">#t</span></p></td></tr></table></blockquote><p>Within a module, however, the combination of
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define-namespace-anchor%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define-namespace-anchor</a></span> and
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._namespace-anchor-%7E3eempty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-anchor->empty-namespace</a></span> offers a more reliable
|
|
method for obtaining a source namespace:</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/base</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._require%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktSym">racket/class</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=Namespaces.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define-namespace-anchor%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define-namespace-anchor</a></span><span class="hspace"> </span><span class="RktSym">a</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">load-plug-in</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=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._file%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">file</a></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=let.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fletstx-scheme..rkt%2529._let%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">ns</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=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._make-base-empty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-base-empty-namespace</a></span><span class="RktPn">)</span><span class="RktPn">]</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-attach-module%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-attach-module</a></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=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._namespace-anchor-%7E3eempty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-anchor->empty-namespace</a></span><span class="hspace"> </span><span class="RktSym">a</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">racket/class</span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym">ns</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=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</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=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-namespace</a></span><span class="hspace"> </span><span class="RktSym">ns</span><span class="RktPn">]</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=Module_Names_and_Loading.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._dynamic-require%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">dynamic-require</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=reference&rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._file%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">file</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">plug-in%</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></blockquote><p>The anchor bound by <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._namespace-attach-module%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-attach-module</a></span> connects the
|
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run time of a module with the namespace in which a module is loaded
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(which might differ from the current namespace). In the above
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example, since the enclosing module requires
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<a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=mzlib_class.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">racket/class</span></a>, the namespace produced by
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<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Namespaces.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._namespace-anchor-%7E3eempty-namespace%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">namespace-anchor->empty-namespace</a></span> certainly contains an
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instance of <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=mzlib_class.html&version=8.6" class="RktModLink Sq" data-pltdoc="x"><span class="RktSym">racket/class</span></a>. Moreover, that instance is
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the same as the one imported into the module, so the class datatype is
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shared.</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="eval.html" title="backward to "15.1 eval"" data-pltdoc="x">← prev</a> <a href="reflection.html" title="up to "15 Reflection and Dynamic Evaluation"" data-pltdoc="x">up</a> <a href="load.html" title="forward to "15.3 Scripting Evaluation and Using load"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html> |