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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>11.3.2 Parameters</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="icons.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" 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Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewlink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="tocviewselflink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr><tr><td align="right">12 </td><td><a href="Macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">13 </td><td><a href="input-and-output.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr><tr><td align="right">15 </td><td><a href="os.html" class="tocviewlink" data-pltdoc="x">Operating System</a></td></tr><tr><td align="right">16 </td><td><a href="memory.html" class="tocviewlink" data-pltdoc="x">Memory Management</a></td></tr><tr><td align="right">17 </td><td><a href="unsafe.html" class="tocviewlink" data-pltdoc="x">Unsafe Operations</a></td></tr><tr><td align="right">18 </td><td><a href="running.html" class="tocviewlink" data-pltdoc="x">Running Racket</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>11 </td><td><a href="concurrency.html" class="tocviewlink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr></table><div class="tocviewsublist" style="display: none;" id="tocview_1"><table cellspacing="0" cellpadding="0"><tr><td align="right">11.1 </td><td><a href="threads.html" class="tocviewlink" data-pltdoc="x">Threads</a></td></tr><tr><td align="right">11.2 </td><td><a href="all-sync.html" class="tocviewlink" data-pltdoc="x">Synchronization</a></td></tr><tr><td align="right">11.3 </td><td><a href="thread-local-storage.html" class="tocviewselflink" data-pltdoc="x">Thread-<wbr></wbr>Local Storage</a></td></tr><tr><td align="right">11.4 </td><td><a href="futures.html" class="tocviewlink" data-pltdoc="x">Futures</a></td></tr><tr><td align="right">11.5 </td><td><a href="places.html" class="tocviewlink" data-pltdoc="x">Places</a></td></tr><tr><td align="right">11.6 </td><td><a href="engine.html" class="tocviewlink" data-pltdoc="x">Engines</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>11.3 </td><td><a href="thread-local-storage.html" class="tocviewlink" data-pltdoc="x">Thread-<wbr></wbr>Local Storage</a></td></tr></table><div class="tocviewsublistbottom" style="display: block;" id="tocview_2"><table cellspacing="0" cellpadding="0"><tr><td align="right">11.3.1 </td><td><a href="threadcells.html" class="tocviewlink" data-pltdoc="x">Thread Cells</a></td></tr><tr><td align="right">11.3.2 </td><td><a href="" class="tocviewselflink" data-pltdoc="x">Parameters</a></td></tr></table></div></div></div><div class="tocsub"><div class="tocsubtitle">On this page:</div><table class="tocsublist" cellspacing="0"><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._make-parameter%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">make-<wbr></wbr>parameter</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">parameterize</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%2A%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">parameterize*</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._make-derived-parameter%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">make-<wbr></wbr>derived-<wbr></wbr>parameter</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">parameter?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._parameter-procedure~3d~3f%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">parameter-<wbr></wbr>procedure=?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._current-parameterization%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">current-<wbr></wbr>parameterization</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._call-with-parameterization%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">call-<wbr></wbr>with-<wbr></wbr>parameterization</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._parameterization~3f%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">parameterization?</span></span></a></td></tr></table></div></div><div class="maincolumn"><div class="main"><div class="navsettop"><span class="navleft"><form class="searchform"><input class="searchbox" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "6.7", "../");" onfocus="this.style.color="black"; this.style.textAlign="left"; if (this.value == "...search manuals...") this.value="";" onblur="if (this.value.match(/^ *$/)) { this.style.color="#888"; this.style.textAlign="center"; this.value="...search manuals..."; }"/></form> <a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("6.7");">top</a></span><span class="navright"> <a href="threadcells.html" title="backward to "11.3.1 Thread Cells"" data-pltdoc="x">← prev</a> <a href="thread-local-storage.html" title="up to "11.3 Thread-Local Storage"" data-pltdoc="x">up</a> <a href="futures.html" title="forward to "11.4 Futures"" data-pltdoc="x">next →</a></span> </div><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-source-pkg="racket-doc" x-part-tag=""parameters"">11.3.2<tt> </tt><a name="(part._parameters)"></a>Parameters</h5><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p><span class="imageleft"><img src="finger.png" alt="+" width="24" height="24"/></span><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=guide&rel=parameterize.html&version=6.7" class="Sq" data-pltdoc="x">Dynamic Binding: <span class="RktSym"><span class="RktStxLink">parameterize</span></span></a> in <a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=guide&rel=index.html&version=6.7" class="Sq" data-pltdoc="x"><span style="font-weight: bold">The Racket Guide</span></a> introduces parameters.</p></blockquote></blockquote></blockquote><p>See <a href="eval-model.html#%28part._parameter-model%29" data-pltdoc="x">Parameters</a> for basic information on the
parameter model. Parameters correspond to <span style="font-style: italic">preserved thread
fluids</span> in Scsh [<a href="doc-bibliography.html#%28cite._.Gasbichler02%29" data-pltdoc="x">Gasbichler02</a>].</p><p>To parameterize code in a thread- and continuation-friendly manner,
use <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span>. The <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span> form introduces a
fresh <a href="eval-model.html#%28tech._thread._cell%29" class="techoutside" data-pltdoc="x"><span class="techinside">thread cell</span></a> for the dynamic extent of its body
expressions.</p><p>When a new thread is created, the <a href="eval-model.html#%28tech._parameterization%29" class="techoutside" data-pltdoc="x"><span class="techinside">parameterization</span></a> for the new
thread’s initial continuation is the <a href="eval-model.html#%28tech._parameterization%29" class="techoutside" data-pltdoc="x"><span class="techinside">parameterization</span></a> of the
creator thread. Since each parameter’s <a href="eval-model.html#%28tech._thread._cell%29" class="techoutside" data-pltdoc="x"><span class="techinside">thread cell</span></a> is
<a href="eval-model.html#%28tech._preserved%29" class="techoutside" data-pltdoc="x"><span class="techinside">preserved</span></a>, the new thread “inherits” the parameter values of
its creating thread. When a continuation is moved from one thread to
another, settings introduced with <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span> effectively
move with the continuation.</p><p>In contrast, direct assignment to a parameter (by calling the
parameter procedure with a value) changes the value in a thread cell,
and therefore changes the setting only for the current
thread. Consequently, as far as the memory manager is concerned, the
value originally associated with a parameter through
<span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span> remains reachable as long the continuation is
reachable, even if the parameter is mutated.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._make-parameter))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-parameter%29%29" class="RktValDef RktValLink" data-pltdoc="x">make-parameter</a></span></span><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>[<span class="RktVar">guard</span>]<span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValLink" data-pltdoc="x">parameter?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">guard</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktSym"><a href="function-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._-~3e%29%29" class="RktStxLink" data-pltdoc="x"><span class="nobreak">-></span></a></span><span class="RktPn"> .</span><span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%29%29" class="RktStxLink" data-pltdoc="x">any</a></span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span><span class="hspace"> </span>=<span class="hspace"> </span><span class="RktVal">#f</span></td></tr></table></blockquote></div><div class="SIntrapara">Returns a new parameter procedure. The value of the parameter is
initialized to <span class="RktVar">v</span> in all threads. If <span class="RktVar">guard</span> is
supplied, it is used as the parameter’s guard procedure. A guard
procedure takes one argument. Whenever the parameter procedure is
applied to an argument, the argument is passed on to the guard
procedure. The result returned by the guard procedure is used as the
new parameter value. A guard procedure can raise an exception to
reject a change to the parameter’s value. The <span class="RktVar">guard</span> is not
applied to the initial <span class="RktVar">v</span>.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>syntax</p></div></div><table cellspacing="0" cellpadding="0" class="RktBlk RForeground"><tr><td><span class="RktPn">(</span><a name="(form._((lib._racket/private/more-scheme..rkt)._parameterize))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">parameterize</a></span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktVar">parameter-expr</span><span class="hspace"> </span><span class="RktVar">value-expr</span><span class="RktPn">]</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">body</span><span class="hspace"> </span><span class="RktMeta">...+</span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="stt"> </span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">parameter-expr</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValLink" data-pltdoc="x">parameter?</a></span></td></tr></table></td></tr></table></blockquote></div><div class="SIntrapara"><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p><span class="imageleft"><img src="finger.png" alt="+" width="24" height="24"/></span><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=guide&rel=parameterize.html&version=6.7" class="Sq" data-pltdoc="x">Dynamic Binding: <span class="RktSym"><span class="RktStxLink">parameterize</span></span></a> in <a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=guide&rel=index.html&version=6.7" class="Sq" data-pltdoc="x"><span style="font-weight: bold">The Racket Guide</span></a> introduces <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span>.</p></blockquote></blockquote></blockquote></div></p><p>The result of a <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span> expression is the result of the
last <span class="RktVar">body</span>. The <span class="RktVar">parameter-expr</span>s determine the
parameters to set, and the <span class="RktVar">value-expr</span>s determine the
corresponding values to install while evaluating the
<span class="RktSym">body-expr</span>s. All of the <span class="RktVar">parameter-expr</span>s are evaluated
first (and checked with <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValLink" data-pltdoc="x">parameter?</a></span>), then all
<span class="RktVar">value-expr</span>s are evaluated, and then the parameters are bound
in the continuation to preserved thread cells that contain the values
of the <span class="RktVar">value-expr</span>s. The last <span class="RktSym">body-expr</span> is in tail
position with respect to the entire <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span> form.</p><p>Outside the dynamic extent of a <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span> expression,
parameters remain bound to other thread cells. Effectively, therefore,
old parameters settings are restored as control exits the
<span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span> expression.</p><p>If a continuation is captured during the evaluation of
<span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span>, invoking the continuation effectively
re-introduces the <a href="eval-model.html#%28tech._parameterization%29" class="techoutside" data-pltdoc="x"><span class="techinside">parameterization</span></a>, since a parameterization is
associated to a continuation via a continuation mark (see
<a href="contmarks.html" data-pltdoc="x">Continuation Marks</a>) using a private key.</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="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="Exiting.html#%28def._%28%28quote._~23~25kernel%29._exit-handler%29%29" class="RktValLink" data-pltdoc="x">exit-handler</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">x</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">no-exit</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="Exiting.html#%28def._%28%28quote._~23~25kernel%29._exit%29%29" class="RktValLink" data-pltdoc="x">exit</a></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">p1</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-parameter%29%29" class="RktValLink" data-pltdoc="x">make-parameter</a></span><span class="hspace"> </span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">p2</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-parameter%29%29" class="RktValLink" data-pltdoc="x">make-parameter</a></span><span class="hspace"> </span><span class="RktVal">2</span><span class="RktPn">)</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"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">p1</span><span class="hspace"> </span><span class="RktVal">3</span><span class="RktPn">]</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktSym">p2</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">p1</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="pairs.html#%28def._%28%28quote._~23~25kernel%29._cons%29%29" class="RktValLink" data-pltdoc="x">cons</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">p1</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">p2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(3 . 1)</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"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">k</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._let%2Fcc%29%29" class="RktStxLink" data-pltdoc="x">let/cc</a></span><span class="hspace"> </span><span class="RktSym">out</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">p1</span><span class="hspace"> </span><span class="RktVal">2</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">p1</span><span class="hspace"> </span><span class="RktVal">3</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="pairs.html#%28def._%28%28quote._~23~25kernel%29._cons%29%29" class="RktValLink" data-pltdoc="x">cons</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._let%2Fcc%29%29" class="RktStxLink" data-pltdoc="x">let/cc</a></span><span class="hspace"> </span><span class="RktSym">k</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">out</span><span class="hspace"> </span><span class="RktSym">k</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">p1</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</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="if.html#%28form._%28%28quote._~23~25kernel%29._if%29%29" class="RktStxLink" data-pltdoc="x">if</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="procedures.html#%28def._%28%28quote._~23~25kernel%29._procedure~3f%29%29" class="RktValLink" data-pltdoc="x">procedure?</a></span><span class="hspace"> </span><span class="RktSym">k</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">k</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">p1</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">k</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(1 . 3)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._make-channel%29%29" class="RktValLink" data-pltdoc="x">make-channel</a></span><span class="RktPn">)</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"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">p1</span><span class="hspace"> </span><span class="RktVal">0</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="threads.html#%28def._%28%28quote._~23~25kernel%29._thread%29%29" class="RktValLink" data-pltdoc="x">thread</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </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="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-put%29%29" class="RktValLink" data-pltdoc="x">channel-put</a></span><span class="hspace"> </span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._cons%29%29" class="RktValLink" data-pltdoc="x">cons</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">p1</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">p2</span><span class="RktPn">)</span><span class="RktPn">)</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">#<thread></span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-get%29%29" class="RktValLink" data-pltdoc="x">channel-get</a></span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(0 . 2)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">k-ch</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._make-channel%29%29" class="RktValLink" data-pltdoc="x">make-channel</a></span><span class="RktPn">)</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"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">send-k</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="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">p1</span><span class="hspace"> </span><span class="RktVal">0</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="threads.html#%28def._%28%28quote._~23~25kernel%29._thread%29%29" class="RktValLink" data-pltdoc="x">thread</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </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="cont.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%2Fec%29%29" class="RktStxLink" data-pltdoc="x">let/ec</a></span><span class="hspace"> </span><span class="RktSym">esc</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-put%29%29" class="RktValLink" data-pltdoc="x">channel-put</a></span><span class="hspace"> </span><span class="RktSym">ch</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._let%2Fcc%29%29" class="RktStxLink" data-pltdoc="x">let/cc</a></span><span class="hspace"> </span><span class="RktSym">k</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-put%29%29" class="RktValLink" data-pltdoc="x">channel-put</a></span><span class="hspace"> </span><span class="RktSym">k-ch</span><span class="hspace"> </span><span class="RktSym">k</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">esc</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</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">send-k</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#<thread></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"><a href="threads.html#%28def._%28%28quote._~23~25kernel%29._thread%29%29" class="RktValLink" data-pltdoc="x">thread</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-get%29%29" class="RktValLink" data-pltdoc="x">channel-get</a></span><span class="hspace"> </span><span class="RktSym">k-ch</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="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">v</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">p1</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="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">v</span><span class="RktPn">)</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">#<thread></span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-get%29%29" class="RktValLink" data-pltdoc="x">channel-get</a></span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">1</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym">send-k</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#<thread></span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="threads.html#%28def._%28%28quote._~23~25kernel%29._thread%29%29" class="RktValLink" data-pltdoc="x">thread</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-get%29%29" class="RktValLink" data-pltdoc="x">channel-get</a></span><span class="hspace"> </span><span class="RktSym">k-ch</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">p1</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#<thread></span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._channel-get%29%29" class="RktValLink" data-pltdoc="x">channel-get</a></span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">0</span></p></td></tr></table></blockquote></div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>syntax</p></div></div><table cellspacing="0" cellpadding="0" class="RktBlk RForeground"><tr><td><span class="RktPn">(</span><a name="(form._((lib._racket/private/more-scheme..rkt)._parameterize*))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%2A%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">parameterize*</a></span></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktVar">parameter-expr</span><span class="hspace"> </span><span class="RktVar">value-expr</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">body</span><span class="hspace"> </span><span class="RktMeta">...+</span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr></table></blockquote></div><div class="SIntrapara">Analogous to <span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%2A%29%29" class="RktStxLink" data-pltdoc="x">let*</a></span> compared to <span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span>, <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%2A%29%29" class="RktStxLink" data-pltdoc="x">parameterize*</a></span>
is the same as a nested series of single-parameter <span class="RktSym"><a href="#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span>
forms.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><table cellspacing="0" cellpadding="0" class="prototype RForeground"><tr><td valign="top"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._make-derived-parameter))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-derived-parameter%29%29" class="RktValDef RktValLink" data-pltdoc="x">make-derived-parameter</a></span></span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">parameter</span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">guard</span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">wrap</span><span class="RktPn">)</span></td><td valign="top"><span class="hspace"> </span></td><td valign="top">→</td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValLink" data-pltdoc="x">parameter?</a></span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">parameter</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValLink" data-pltdoc="x">parameter?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">guard</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktSym"><a href="function-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._-~3e%29%29" class="RktStxLink" data-pltdoc="x"><span class="nobreak">-></span></a></span><span class="RktPn"> .</span><span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%29%29" class="RktStxLink" data-pltdoc="x">any</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">wrap</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="hspace"> </span><span class="RktPn">. </span><span class="RktSym"><a href="function-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._-~3e%29%29" class="RktStxLink" data-pltdoc="x"><span class="nobreak">-></span></a></span><span class="RktPn"> .</span><span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%29%29" class="RktStxLink" data-pltdoc="x">any</a></span><span class="RktPn">)</span></td></tr></table></blockquote></div><div class="SIntrapara">Returns a parameter procedure that sets or retrieves the same value as
<span class="RktVar">parameter</span>, but with:</div></p><ul><li><p><span class="RktVar">guard</span> applied when setting the parameter (before any
guard associated with <span class="RktVar">parameter</span>), and</p></li><li><p><span class="RktVar">wrap</span> applied when obtaining the parameter’s value.</p></li></ul><p>See also <span class="RktSym"><a href="chaperones.html#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._chaperone-procedure%29%29" class="RktValLink" data-pltdoc="x">chaperone-procedure</a></span>, which can also be used to guard
parameter procedures.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._parameter~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">parameter?</a></span></span><span class="hspace"> </span><span class="RktVar">v</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._boolean~3f%29%29" class="RktValLink" data-pltdoc="x">boolean?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns <span class="RktVal">#t</span> if <span class="RktVar">v</span> is a parameter procedure,
<span class="RktVal">#f</span> otherwise.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._parameter-procedure~3d~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter-procedure~3d~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">parameter-procedure=?</a></span></span><span class="hspace"> </span><span class="RktVar">a</span><span class="hspace"> </span><span class="RktVar">b</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._boolean~3f%29%29" class="RktValLink" data-pltdoc="x">boolean?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">a</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValLink" data-pltdoc="x">parameter?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">b</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameter~3f%29%29" class="RktValLink" data-pltdoc="x">parameter?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns <span class="RktVal">#t</span> if the parameter procedures <span class="RktVar">a</span> and
<span class="RktVar">b</span> always modify the same parameter with the same guards
(although possibly with different <a href="chaperones.html#%28tech._chaperone%29" class="techoutside" data-pltdoc="x"><span class="techinside">chaperones</span></a>), <span class="RktVal">#f</span>
otherwise.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._racket/private/more-scheme..rkt)._current-parameterization))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._current-parameterization%29%29" class="RktValDef RktValLink" data-pltdoc="x">current-parameterization</a></span></span><span class="RktPn"></span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameterization~3f%29%29" class="RktValLink" data-pltdoc="x">parameterization?</a></span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara">Returns the
current continuation’s <a href="eval-model.html#%28tech._parameterization%29" class="techoutside" data-pltdoc="x"><span class="techinside">parameterization</span></a>.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><table cellspacing="0" cellpadding="0" class="prototype RForeground"><tr><td valign="top"><span class="RktPn">(</span><a name="(def._((lib._racket/private/more-scheme..rkt)._call-with-parameterization))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._call-with-parameterization%29%29" class="RktValDef RktValLink" data-pltdoc="x">call-with-parameterization</a></span></span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">parameterization</span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td></tr><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">thunk</span><span class="RktPn">)</span></td><td valign="top"><span class="hspace"> </span></td><td valign="top">→</td><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktSym"><a href="data-structure-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%29%29" class="RktStxLink" data-pltdoc="x">any</a></span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">parameterization</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameterization~3f%29%29" class="RktValLink" data-pltdoc="x">parameterization?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">thunk</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="function-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._-~3e%29%29" class="RktStxLink" data-pltdoc="x"><span class="nobreak">-></span></a></span><span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%29%29" class="RktStxLink" data-pltdoc="x">any</a></span><span class="RktPn">)</span></td></tr></table></blockquote></div><div class="SIntrapara">Calls <span class="RktVar">thunk</span> (via a tail call) with <span class="RktVar">parameterization</span>
as the current <a href="eval-model.html#%28tech._parameterization%29" class="techoutside" data-pltdoc="x"><span class="techinside">parameterization</span></a>.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._parameterization~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._parameterization~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">parameterization?</a></span></span><span class="hspace"> </span><span class="RktVar">v</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._boolean~3f%29%29" class="RktValLink" data-pltdoc="x">boolean?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns <span class="RktVal">#t</span> if <span class="RktVar">v</span> is a <a href="eval-model.html#%28tech._parameterization%29" class="techoutside" data-pltdoc="x"><span class="techinside">parameterization</span></a>
returned by <span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._current-parameterization%29%29" class="RktValLink" data-pltdoc="x">current-parameterization</a></span>, <span class="RktVal">#f</span> otherwise.</div></p><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "6.7", "../");" onfocus="this.style.color="black"; this.style.textAlign="left"; if (this.value == "...search manuals...") this.value="";" onblur="if (this.value.match(/^ *$/)) { this.style.color="#888"; this.style.textAlign="center"; this.value="...search manuals..."; }"/></form> <a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("6.7");">top</a></span><span class="navright"> <a href="threadcells.html" title="backward to "11.3.1 Thread Cells"" data-pltdoc="x">← prev</a> <a href="thread-local-storage.html" title="up to "11.3 Thread-Local Storage"" data-pltdoc="x">up</a> <a href="futures.html" title="forward to "11.4 Futures"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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