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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>11.3.1 Thread Cells</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">►</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x"><span style="font-weight: bold">The Racket Reference</span></a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="model.html" class="tocviewlink" data-pltdoc="x">Language Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewlink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="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="" class="tocviewselflink" data-pltdoc="x">Thread Cells</a></td></tr><tr><td align="right">11.3.2 </td><td><a href="parameters.html" class="tocviewlink" 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._thread-cell~3f%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">thread-<wbr></wbr>cell?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._make-thread-cell%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">make-<wbr></wbr>thread-<wbr></wbr>cell</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">thread-<wbr></wbr>cell-<wbr></wbr>ref</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-set%21%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">thread-<wbr></wbr>cell-<wbr></wbr>set!</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._current-preserved-thread-cell-values%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">current-<wbr></wbr>preserved-<wbr></wbr>thread-<wbr></wbr>cell-<wbr></wbr>values</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-values~3f%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">thread-<wbr></wbr>cell-<wbr></wbr>values?</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, "6.1", "../");" 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("6.1");">top</a></span><span class="navright"> <a href="thread-local-storage.html" title="backward to "11.3 Thread-Local Storage"" 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="parameters.html" title="forward to "11.3.2 Parameters"" data-pltdoc="x">next →</a></span> </div><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-part-tag=""threadcells"">11.3.1<tt> </tt><a name="(part._threadcells)"></a>Thread Cells</h5><p>A <span style="font-style: italic"><a href="eval-model.html#%28tech._thread._cell%29" class="techoutside" data-pltdoc="x"><span class="techinside">thread cell</span></a></span> contains a thread-specific value; that
is, it contains a specific value for each thread, but it may contain
different values for different threads. A thread cell is created with
a default value that is used for all existing threads. When the cell’s
content is changed with <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-set%21%29%29" class="RktValLink" data-pltdoc="x">thread-cell-set!</a></span>, the cell’s value
changes only for the current thread. Similarly,
<span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span> obtains the value of the cell that is
specific to the current thread.</p><p>A thread cell’s value can be <span style="font-style: italic"><a href="eval-model.html#%28tech._preserved%29" class="techoutside" data-pltdoc="x"><span class="techinside">preserved</span></a></span>, which means
that when a new thread is created, the cell’s initial value for the
new thread is the same as the creating thread’s current value. If a
thread cell is non-preserved, then the cell’s initial value for a
newly created thread is the default value (which was supplied when the
cell was created).</p><p>Within the current thread, the current values of all preserved threads
cells can be captured through
<span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._current-preserved-thread-cell-values%29%29" class="RktValLink" data-pltdoc="x">current-preserved-thread-cell-values</a></span>. The captured set of
values can be imperatively installed into the current thread through
another call to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._current-preserved-thread-cell-values%29%29" class="RktValLink" data-pltdoc="x">current-preserved-thread-cell-values</a></span>. The
capturing and restoring threads can be different.</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)._thread-cell~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">thread-cell?</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._thread._cell%29" class="techoutside" data-pltdoc="x"><span class="techinside">thread cell</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._((quote._~23~25kernel)._make-thread-cell))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-thread-cell%29%29" class="RktValDef RktValLink" data-pltdoc="x">make-thread-cell</a></span></span><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>[<span class="RktVar">preserved?</span>]<span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell~3f%29%29" class="RktValLink" data-pltdoc="x">thread-cell?</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">preserved?</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><span class="hspace"> </span>=<span class="hspace"> </span><span class="RktVal">#f</span></td></tr></table></blockquote></div><div class="SIntrapara">Creates and returns a new thread cell. Initially, <span class="RktVar">v</span> is the
cell’s value for all threads. If <span class="RktVar">preserved?</span> is true, then the
cell’s initial value for a newly created threads is the creating
thread’s value for the cell, otherwise the cell’s value is initially
<span class="RktVar">v</span> in all future threads.</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)._thread-cell-ref))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValDef RktValLink" data-pltdoc="x">thread-cell-ref</a></span></span><span class="hspace"> </span><span class="RktVar">cell</span><span class="RktPn">)</span><span class="hspace"> </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></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">cell</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell~3f%29%29" class="RktValLink" data-pltdoc="x">thread-cell?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns the
current value of <span class="RktVar">cell</span> for the current thread.</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)._thread-cell-set!))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-set%21%29%29" class="RktValDef RktValLink" data-pltdoc="x">thread-cell-set!</a></span></span><span class="hspace"> </span><span class="RktVar">cell</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="data-structure-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%29%29" class="RktStxLink" data-pltdoc="x">any</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">cell</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell~3f%29%29" class="RktValLink" data-pltdoc="x">thread-cell?</a></span></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">Sets the
value in <span class="RktVar">cell</span> to <span class="RktVar">v</span> for the current thread.</div></p><p><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><p>Examples:</p></td></tr><tr><td><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="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">cnp</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-thread-cell%29%29" class="RktValLink" data-pltdoc="x">make-thread-cell</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">nerve</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td></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">cp</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-thread-cell%29%29" class="RktValLink" data-pltdoc="x">make-thread-cell</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">cancer</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktVal">#t</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cnp</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(nerve)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cp</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(cancer)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-set%21%29%29" class="RktValLink" data-pltdoc="x">thread-cell-set!</a></span><span class="hspace"> </span><span class="RktSym">cnp</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">nerve</span><span class="hspace"> </span><span class="RktVal">nerve</span><span class="RktVal">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-set%21%29%29" class="RktValLink" data-pltdoc="x">thread-cell-set!</a></span><span class="hspace"> </span><span class="RktSym">cp</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">cancer</span><span class="hspace"> </span><span class="RktVal">cancer</span><span class="RktVal">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cnp</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(nerve nerve)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cp</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(cancer cancer)</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"><tr><td></td></tr></table></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></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="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cnp</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="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cp</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-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><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="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cp</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">'(nerve)</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">'(cancer cancer)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-set%21%29%29" class="RktValLink" data-pltdoc="x">thread-cell-set!</a></span><span class="hspace"> </span><span class="RktSym">cp</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">cancer</span><span class="hspace"> </span><span class="RktVal">cancer</span><span class="hspace"> </span><span class="RktVal">cancer</span><span class="RktVal">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-ref%29%29" class="RktValLink" data-pltdoc="x">thread-cell-ref</a></span><span class="hspace"> </span><span class="RktSym">cp</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(cancer cancer cancer)</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-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="RktVal">'</span><span class="RktVal">ok</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td></td></tr></table></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">'(cancer cancer)</span></p></td></tr></table></blockquote></td></tr></table></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)._current-preserved-thread-cell-values))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._current-preserved-thread-cell-values%29%29" class="RktValDef RktValLink" data-pltdoc="x">current-preserved-thread-cell-values</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._thread-cell-values~3f%29%29" class="RktValLink" data-pltdoc="x">thread-cell-values?</a></span></p></blockquote></td></tr><tr><td><span class="RktPn">(</span><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._current-preserved-thread-cell-values%29%29" class="RktValDef RktValLink" data-pltdoc="x">current-preserved-thread-cell-values</a></span></span><span class="hspace"> </span><span class="RktVar">thread-cell-vals</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="void.html#%28def._%28%28quote._~23~25kernel%29._void~3f%29%29" class="RktValLink" data-pltdoc="x">void?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">thread-cell-vals</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-values~3f%29%29" class="RktValLink" data-pltdoc="x">thread-cell-values?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">When called with no arguments, this procedure produces a
<span class="RktVar">thread-cell-vals</span> that represents the current values (in the
current thread) for all preserved thread cells.</div></p><p>When called with a <span class="RktVar">thread-cell-vals</span> generated by a previous
call to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._current-preserved-thread-cell-values%29%29" class="RktValLink" data-pltdoc="x">current-preserved-thread-cell-values</a></span>, the values of
all preserved thread cells (in the current thread) are set to the
values captured in <span class="RktVar">thread-cell-vals</span>; if a preserved thread
cell was created after <span class="RktVar">thread-cell-vals</span> was generated, then
the thread cell’s value for the current thread reverts to its initial
value.</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)._thread-cell-values~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._thread-cell-values~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">thread-cell-values?</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 set of thread cell values
produced by <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._current-preserved-thread-cell-values%29%29" class="RktValLink" data-pltdoc="x">current-preserved-thread-cell-values</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, "6.1", "../");" 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("6.1");">top</a></span><span class="navright"> <a href="thread-local-storage.html" title="backward to "11.3 Thread-Local Storage"" 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="parameters.html" title="forward to "11.3.2 Parameters"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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