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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>14.5 Impersonators and Chaperones</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" 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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>14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr></table><div class="tocviewsublist" style="display: block;" id="tocview_1"><table cellspacing="0" cellpadding="0"><tr><td align="right">14.1 </td><td><a href="Namespaces.html" class="tocviewlink" data-pltdoc="x">Namespaces</a></td></tr><tr><td align="right">14.2 </td><td><a href="eval.html" class="tocviewlink" data-pltdoc="x">Evaluation and Compilation</a></td></tr><tr><td align="right">14.3 </td><td><a href="load-lang.html" class="tocviewlink" data-pltdoc="x">The <span class="RktModLink"><span class="RktSym">racket/<span class="mywbr"> </span>load</span></span> Language</a></td></tr><tr><td align="right">14.4 </td><td><a href="Module_Names_and_Loading.html" class="tocviewlink" data-pltdoc="x">Module Names and Loading</a></td></tr><tr><td align="right">14.5 </td><td><a href="" class="tocviewselflink" data-pltdoc="x">Impersonators and Chaperones</a></td></tr><tr><td align="right">14.6 </td><td><a href="securityguards.html" class="tocviewlink" data-pltdoc="x">Security Guards</a></td></tr><tr><td align="right">14.7 </td><td><a href="custodians.html" class="tocviewlink" data-pltdoc="x">Custodians</a></td></tr><tr><td align="right">14.8 </td><td><a href="threadgroups.html" class="tocviewlink" data-pltdoc="x">Thread Groups</a></td></tr><tr><td align="right">14.9 </td><td><a href="inspectors.html" class="tocviewlink" data-pltdoc="x">Structure Inspectors</a></td></tr><tr><td align="right">14.10 </td><td><a href="modprotect.html" class="tocviewlink" data-pltdoc="x">Code Inspectors</a></td></tr><tr><td align="right">14.11 </td><td><a href="plumbers.html" class="tocviewlink" data-pltdoc="x">Plumbers</a></td></tr><tr><td align="right">14.12 </td><td><a href="Sandboxed_Evaluation.html" class="tocviewlink" data-pltdoc="x">Sandboxed Evaluation</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>14.5 </td><td><a href="" class="tocviewselflink" data-pltdoc="x">Impersonators and Chaperones</a></td></tr></table><div class="tocviewsublistbottom" style="display: none;" id="tocview_2"><table cellspacing="0" cellpadding="0"><tr><td align="right">14.5.1 </td><td><a href="#%28part._.Impersonator_.Constructors%29" class="tocviewlink" data-pltdoc="x">Impersonator Constructors</a></td></tr><tr><td align="right">14.5.2 </td><td><a href="#%28part._.Chaperone_.Constructors%29" class="tocviewlink" data-pltdoc="x">Chaperone Constructors</a></td></tr><tr><td align="right">14.5.3 </td><td><a href="#%28part._.Impersonator_.Properties%29" class="tocviewlink" data-pltdoc="x">Impersonator Properties</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._impersonator~3f%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonator?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-of~3f%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonator-<wbr></wbr>of?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-of~3f%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>of?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-ephemeron%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonator-<wbr></wbr>ephemeron</span></span></a></td></tr><tr><td><span class="tocsublinknumber">14.5.1<tt> </tt></span><a href="#%28part._.Impersonator_.Constructors%29" class="tocsubseclink" data-pltdoc="x">Impersonator Constructors</a></td></tr><tr><td><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._impersonate-procedure%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>procedure</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-struct%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>struct</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-vector%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>vector</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-box%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>box</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-hash%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>hash</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-channel%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>channel</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-prompt-tag%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>prompt-<wbr></wbr>tag</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-continuation-mark-key%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonate-<wbr></wbr>continuation-<wbr></wbr>mark-<wbr></wbr>key</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._prop~3aimpersonator-of%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">prop:<span class="mywbr"> </span>impersonator-<wbr></wbr>of</span></span></a></td></tr><tr><td><span class="tocsublinknumber">14.5.2<tt> </tt></span><a href="#%28part._.Chaperone_.Constructors%29" class="tocsubseclink" data-pltdoc="x">Chaperone Constructors</a></td></tr><tr><td><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._chaperone-procedure%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>procedure</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-struct%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>struct</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-vector%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>vector</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-box%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>box</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-hash%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>hash</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-struct-type%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>struct-<wbr></wbr>type</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-evt%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>evt</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-channel%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>channel</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-prompt-tag%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>prompt-<wbr></wbr>tag</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-continuation-mark-key%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">chaperone-<wbr></wbr>continuation-<wbr></wbr>mark-<wbr></wbr>key</span></span></a></td></tr><tr><td><span class="tocsublinknumber">14.5.3<tt> </tt></span><a href="#%28part._.Impersonator_.Properties%29" class="tocsubseclink" data-pltdoc="x">Impersonator Properties</a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._make-impersonator-property%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">make-<wbr></wbr>impersonator-<wbr></wbr>property</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonator-<wbr></wbr>property?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property-accessor-procedure~3f%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonator-<wbr></wbr>property-<wbr></wbr>accessor-<wbr></wbr>procedure?</span></span></a></td></tr><tr><td><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-prop~3aapplication-mark%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">impersonator-<wbr></wbr>prop:<span class="mywbr"> </span>application-<wbr></wbr>mark</span></span></a></td></tr></table></div></div><div class="maincolumn"><div class="main"><div 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</div><h4 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-part-tag=""chaperones"">14.5<tt> </tt><a name="(part._chaperones)"></a>Impersonators and Chaperones</h4><p>An <a name="(tech._impersonator)"></a><span style="font-style: italic">impersonator</span> is a wrapper for a value where the wrapper
redirects some of the value’s operations. Impersonators apply only to procedures,
<a href="structures.html#%28tech._structure%29" class="techoutside" data-pltdoc="x"><span class="techinside">structures</span></a> for which an accessor or mutator is available,
<a href="structures.html#%28tech._structure._type%29" class="techoutside" data-pltdoc="x"><span class="techinside">structure types</span></a>, <a href="hashtables.html#%28tech._hash._table%29" class="techoutside" data-pltdoc="x"><span class="techinside">hash tables</span></a>, <a href="vectors.html#%28tech._vector%29" class="techoutside" data-pltdoc="x"><span class="techinside">vectors</span></a>,
<a href="boxes.html#%28tech._box%29" class="techoutside" data-pltdoc="x"><span class="techinside">box</span></a>es, <a href="channel.html#%28tech._channel%29" class="techoutside" data-pltdoc="x"><span class="techinside">channels</span></a>, and <a href="eval-model.html#%28tech._prompt._tag%29" class="techoutside" data-pltdoc="x"><span class="techinside">prompt tag</span></a>s.
An impersonator is <span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._equal~3f%29%29" class="RktValLink" data-pltdoc="x">equal?</a></span> to the original
value, but not <span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._eq~3f%29%29" class="RktValLink" data-pltdoc="x">eq?</a></span> to the original value.</p><p>A <a name="(tech._chaperone)"></a><span style="font-style: italic">chaperone</span> is a kind of impersonator whose refinement of a value’s
operation is restricted to side effects (including, in particular,
raising an exception) or chaperoning values supplied to or produced by
the operation. For example, a vector chaperone can redirect
<span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span> to raise an exception if the accessed vector slot
contains a string, or it can cause the result of <span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span>
to be a chaperoned variant of the value that is in the accessed vector
slot, but it cannot redirect <span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span> to produce a value
that is arbitrarily different from the value in the vector slot.</p><p>A non-<a href="#%28tech._chaperone%29" class="techoutside" data-pltdoc="x"><span class="techinside">chaperone</span></a> <a href="#%28tech._impersonator%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator</span></a>, in contrast, can refine an operation to swap one
value for any other. An impersonator cannot be applied to an immutable value
or refine the access to an immutable field in an instance of a <a href="structures.html#%28tech._structure._type%29" class="techoutside" data-pltdoc="x"><span class="techinside">structure
type</span></a>, since arbitrary redirection of an operation amounts to
mutation of the impersonated value.</p><p>Beware that each of the following operations can be redirected to an
arbitrary procedure through an impersonator on the operation’s
argument—<wbr></wbr>assuming that the operation is available to the creator of
the impersonator:</p><ul class="compact"><li><p>a structure-field accessor</p></li><li><p>a structure-field mutator</p></li><li><p>a structure type property accessor</p></li><li><p>application of a procedure</p></li><li><p><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._unbox%29%29" class="RktValLink" data-pltdoc="x">unbox</a></span></p></li><li><p><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._set-box%21%29%29" class="RktValLink" data-pltdoc="x">set-box!</a></span></p></li><li><p><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span></p></li><li><p><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-set%21%29%29" class="RktValLink" data-pltdoc="x">vector-set!</a></span></p></li><li><p><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29" class="RktValLink" data-pltdoc="x">hash-ref</a></span></p></li><li><p><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%29%29" class="RktValLink" data-pltdoc="x">hash-set</a></span></p></li><li><p><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%21%29%29" class="RktValLink" data-pltdoc="x">hash-set!</a></span></p></li><li><p><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%29%29" class="RktValLink" data-pltdoc="x">hash-remove</a></span></p></li><li><p><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%21%29%29" class="RktValLink" data-pltdoc="x">hash-remove!</a></span></p></li><li><p><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></p></li><li><p><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></p></li><li><p><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._call-with-continuation-prompt%29%29" class="RktValLink" data-pltdoc="x">call-with-continuation-prompt</a></span></p></li><li><p><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span></p></li></ul><p>Derived operations, such as printing a value, can be redirected
through impersonators due to their use of accessor functions. The
<span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._equal~3f%29%29" class="RktValLink" data-pltdoc="x">equal?</a></span>, <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._equal-hash-code%29%29" class="RktValLink" data-pltdoc="x">equal-hash-code</a></span>, and
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._equal-secondary-hash-code%29%29" class="RktValLink" data-pltdoc="x">equal-secondary-hash-code</a></span> operations, in contrast, may bypass
impersonators (but they are not obliged to).</p><p>In addition to redirecting operations that work on a value, a
impersonator can include <a name="(tech._impersonator._property)"></a><span style="font-style: italic">impersonator properties</span> for an impersonated
value. An <a href="#%28tech._impersonator._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator property</span></a> is similar to a <a href="structprops.html#%28tech._structure._type._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">structure
type property</span></a>, but it applies to impersonators instead of structure
types and their instances.</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)._impersonator~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonator?</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 an <a href="#%28tech._impersonator%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator</span></a>, <span class="RktVal">#f</span> otherwise.</div></p><p>Programs and libraries generally should avoid <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span> and
treat impersonators the same as non-impersonator values. In rare cases,
<span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span> may be needed to guard against redirection by an
impersonator of an operation to an arbitrary procedure.</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)._chaperone~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone?</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="#%28tech._chaperone%29" class="techoutside" data-pltdoc="x"><span class="techinside">chaperone</span></a>, <span class="RktVal">#f</span> otherwise.</div></p><p>Programs and libraries generally should avoid <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span> for
the same reason that they should avoid <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span>.</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)._impersonator-of~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-of~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonator-of?</a></span></span><span class="hspace"> </span><span class="RktVar">v1</span><span class="hspace"> </span><span class="RktVar">v2</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">v1</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">v2</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">Indicates whether <span class="RktVar">v1</span> can be considered equivalent modulo
impersonators to <span class="RktVar">v2</span>.</div></p><p>For values that include no impersonators, <span class="RktVar">v1</span> and <span class="RktVar">v2</span> can
be considered impersonators of each other if they are <span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._equal~3f%29%29" class="RktValLink" data-pltdoc="x">equal?</a></span>.</p><p>Otherwise, all impersonators of <span class="RktVar">v2</span> must be intact in <span class="RktVar">v1</span>,
in the sense that parts of <span class="RktVar">v2</span> must be derived from
<span class="RktVar">v1</span> through one of the impersonator constructors (e.g.,
<span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._impersonate-procedure%29%29" class="RktValLink" data-pltdoc="x">impersonate-procedure</a></span> or <span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._chaperone-procedure%29%29" class="RktValLink" data-pltdoc="x">chaperone-procedure</a></span>).</p><p>See also <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._prop~3aimpersonator-of%29%29" class="RktValLink" data-pltdoc="x">prop:impersonator-of</a></span>.</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)._chaperone-of~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-of~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-of?</a></span></span><span class="hspace"> </span><span class="RktVar">v1</span><span class="hspace"> </span><span class="RktVar">v2</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">v1</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">v2</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">Indicates whether <span class="RktVar">v1</span> can be considered equivalent modulo
chaperones to <span class="RktVar">v2</span>.</div></p><p>For values that include no chaperones, <span class="RktVar">v1</span> and <span class="RktVar">v2</span> can
be considered chaperones of each other if they are <span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._equal~3f%29%29" class="RktValLink" data-pltdoc="x">equal?</a></span>,
except that the mutability of vectors and boxes with <span class="RktVar">v1</span> and
<span class="RktVar">v2</span> must be the same.</p><p>Otherwise, all chaperones of <span class="RktVar">v2</span> must be intact in
<span class="RktVar">v1</span>, in the sense that parts of <span class="RktVar">v2</span> must be derived
from <span class="RktVar">v1</span> through one of the chaperone constructors (e.g.,
<span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._chaperone-procedure%29%29" class="RktValLink" data-pltdoc="x">chaperone-procedure</a></span>).</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)._impersonator-ephemeron))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-ephemeron%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonator-ephemeron</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="ephemerons.html#%28def._%28%28quote._~23~25kernel%29._ephemeron~3f%29%29" class="RktValLink" data-pltdoc="x">ephemeron?</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">Produces an <a href="ephemerons.html#%28tech._ephemeron%29" class="techoutside" data-pltdoc="x"><span class="techinside">ephemeron</span></a> that can be used to connect the
reachability of <span class="RktVar">v</span> (in the sense of garbage collection; see
<a href="eval-model.html#%28part._gc-model%29" data-pltdoc="x">Garbage Collection</a>) with the reachability of any value for which
<span class="RktVar">v</span> is an <a href="#%28tech._impersonator%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator</span></a>. That is, the value <span class="RktVar">v</span>
will be considered reachable as long as the result ephemeron is
reachable in addition to any value that <span class="RktVar">v</span> impersonates
(including itself).</div></p><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-part-tag=""Impersonator_Constructors"">14.5.1<tt> </tt><a name="(part._.Impersonator_.Constructors)"></a>Impersonator Constructors</h5><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><span class="RktPn">(</span><a name="(def._((lib._racket/private/base..rkt)._impersonate-procedure))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._impersonate-procedure%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-procedure</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">wrapper-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </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"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">wrapper-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator procedure that has the same arity, name, and
other attributes as <span class="RktVar">proc</span>. When the impersonator procedure is
applied, the arguments are first passed to <span class="RktVar">wrapper-proc</span>, and
then the results from <span class="RktVar">wrapper-proc</span> are passed to
<span class="RktVar">proc</span>. The <span class="RktVar">wrapper-proc</span> can also supply a procedure
that processes the results of <span class="RktVar">proc</span>.</div></p><p>The arity of <span class="RktVar">wrapper-proc</span> must include the arity of
<span class="RktVar">proc</span>. The allowed keyword arguments of <span class="RktVar">wrapper-proc</span>
must be a superset of the allowed keywords of <span class="RktVar">proc</span>. The
required keyword arguments of <span class="RktVar">wrapper-proc</span> must be a subset
of the required keywords of <span class="RktVar">proc</span>.</p><p>For applications without keywords, the result of <span class="RktVar">wrapper-proc</span>
must be either the same number of values as supplied to it or one more
than the number of supplied values, where an extra result is supplied
before the others. The additional result, if any, must be a procedure
that accepts as many results as produced by <span class="RktVar">proc</span>; it must
return the same number of results. If <span class="RktVar">wrapper-proc</span> returns
the same number of values as it is given (i.e., it does not return a
procedure to impersonator <span class="RktVar">proc</span>’s result), then <span class="RktVar">proc</span> is
called in <a href="eval-model.html#%28tech._tail._position%29" class="techoutside" data-pltdoc="x"><span class="techinside">tail position</span></a> with respect to the call to the impersonator.</p><p>For applications that include keyword arguments, <span class="RktVar">wrapper-proc</span>
must return an additional value before any other values but after the
result-impersonating procedure (if any). The additional value must be a
list of replacements for the keyword arguments that were supplied to the
impersonator (i.e., not counting optional arguments that were
not supplied). The arguments must be ordered according to the sorted
order of the supplied arguments’ keywords.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym">procedure-impersonator</span> must be even) add impersonator properties
or override impersonator-property values of <span class="RktVar">proc</span>.</p><p>If any <span class="RktVar">prop</span> is <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-prop~3aapplication-mark%29%29" class="RktValLink" data-pltdoc="x">impersonator-prop:application-mark</a></span> and if the
associated <span class="RktVar">prop-val</span> is a pair, then the call to <span class="RktVar">proc</span>
is wrapped with <span class="RktSym"><a href="wcm.html#%28form._%28%28quote._~23~25kernel%29._with-continuation-mark%29%29" class="RktStxLink" data-pltdoc="x">with-continuation-mark</a></span> using <span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._car%29%29" class="RktValLink" data-pltdoc="x">car</a></span><span class="stt"> </span><span class="RktVar">prop-val</span><span class="RktPn">)</span> as the mark key and <span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._cdr%29%29" class="RktValLink" data-pltdoc="x">cdr</a></span><span class="stt"> </span><span class="RktVar">prop-val</span><span class="RktPn">)</span> as the mark
value. In addition, if <span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-set-first%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-set-first</a></span> with
<span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._car%29%29" class="RktValLink" data-pltdoc="x">car</a></span><span class="stt"> </span><span class="RktVar">prop-val</span><span class="RktPn">)</span> produces a value for the immediate
continuation frame of the call to the impersonated procedure, the value is
also installed as an immediate value for <span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._car%29%29" class="RktValLink" data-pltdoc="x">car</a></span><span class="stt"> </span><span class="RktVar">prop-val</span><span class="RktPn">)</span> as a
mark during the call to <span class="RktVar">wrapper-proc</span> (which allows tail-calls
of impersonators with respect to wrapping impersonators to be detected within
<span class="RktVar">wrapper-proc</span>).</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._impersonate-struct))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-struct%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-struct</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">v</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">orig-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">redirect-proc</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><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></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><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">orig-proc</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><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="RktSym"><a href="structutils.html#%28def._%28%28quote._~23~25kernel%29._struct-accessor-procedure~3f%29%29" class="RktValLink" data-pltdoc="x">struct-accessor-procedure?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym"><a href="structutils.html#%28def._%28%28quote._~23~25kernel%29._struct-mutator-procedure~3f%29%29" class="RktValLink" data-pltdoc="x">struct-mutator-procedure?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym"><a href="structprops.html#%28def._%28%28quote._~23~25kernel%29._struct-type-property-accessor-procedure~3f%29%29" class="RktValLink" data-pltdoc="x">struct-type-property-accessor-procedure?</a></span><span class="RktPn">)</span></td></tr></table></td></tr></table></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">redirect-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator of <span class="RktVar">v</span>, which redirects certain
operations on the impersonated value. The <span class="RktVar">orig-proc</span>s
indicate the operations to redirect, and the corresponding
<span class="RktVar">redirect-proc</span>s supply the redirections.</div></p><p>The protocol for a <span class="RktVar">redirect-proc</span> depends on the corresponding
<span class="RktVar">orig-proc</span>:</p><ul><li><p>A structure-field accessor: <span class="RktVar">redirect-proc</span>
must accept two arguments, <span class="RktVar">v</span> and the value
<span class="RktVar">field-v</span> that <span class="RktVar">orig-proc</span> produces for
<span class="RktVar">v</span>; it must return a replacement for
<span class="RktVar">field-v</span>. The corresponding field must not be
immutable, and either the field’s structure type must be
accessible via the current <a href="inspectors.html#%28tech._inspector%29" class="techoutside" data-pltdoc="x"><span class="techinside">inspector</span></a> or one of the other
<span class="RktVar">orig-proc</span>s must be a structure-field mutator for the
same field.</p></li><li><p>A structure-field mutator: <span class="RktVar">redirect-proc</span> must accept
two arguments, <span class="RktVar">v</span> and the value <span class="RktVar">field-v</span>
supplied to the mutator; it must return a replacement for
<span class="RktVar">field-v</span> to be propagated to <span class="RktVar">orig-proc</span> and
<span class="RktVar">v</span>.</p></li><li><p>A property accessor: <span class="RktVar">redirect-proc</span> uses the same
protocol as for a structure-field accessor. The accessor’s
property must have been created with <span class="RktVal">'</span><span class="RktVal">can-impersonate</span>
as the second argument to <span class="RktSym"><a href="structprops.html#%28def._%28%28quote._~23~25kernel%29._make-struct-type-property%29%29" class="RktValLink" data-pltdoc="x">make-struct-type-property</a></span>.</p></li></ul><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-struct%29%29" class="RktValLink" data-pltdoc="x">impersonate-struct</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">v</span>.</p><p>Each <span class="RktVar">orig-proc</span> must indicate a distinct operation. If no
<span class="RktVar">orig-proc</span>s are supplied, then no <span class="RktVar">prop</span>s must be
supplied, and <span class="RktVar">v</span> is returned unimpersonated.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._impersonate-vector))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-vector%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-vector</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">vec</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">ref-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">vec</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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</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._not%2Fc%29%29" class="RktValLink" data-pltdoc="x">not/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._immutable~3f%29%29" class="RktValLink" data-pltdoc="x">immutable?</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">ref-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span><span class="hspace"> </span><span class="RktSym"><a href="number-types.html#%28def._%28%28quote._~23~25kernel%29._exact-nonnegative-integer~3f%29%29" class="RktValLink" data-pltdoc="x">exact-nonnegative-integer?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span><span class="hspace"> </span><span class="RktSym"><a href="number-types.html#%28def._%28%28quote._~23~25kernel%29._exact-nonnegative-integer~3f%29%29" class="RktValLink" data-pltdoc="x">exact-nonnegative-integer?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator of <span class="RktVar">vec</span>, which redirects the
<span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span> and <span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-set%21%29%29" class="RktValLink" data-pltdoc="x">vector-set!</a></span> operations.</div></p><p>The <span class="RktVar">ref-proc</span> must accept <span class="RktVar">vec</span>, an index passed to
<span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span>, and the value that <span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span> on
<span class="RktVar">vec</span> produces for the given index; it must produce a
replacement for the value, which is the result of <span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-ref%29%29" class="RktValLink" data-pltdoc="x">vector-ref</a></span>
on the impersonator.</p><p>The <span class="RktVar">set-proc</span> must accept <span class="RktVar">vec</span>, an index passed to
<span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-set%21%29%29" class="RktValLink" data-pltdoc="x">vector-set!</a></span>, and the value passed to <span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-set%21%29%29" class="RktValLink" data-pltdoc="x">vector-set!</a></span>; it
must produce a replacement for the value, which is used
with <span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector-set%21%29%29" class="RktValLink" data-pltdoc="x">vector-set!</a></span> on the original <span class="RktVar">vec</span> to install the
value.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-vector%29%29" class="RktValLink" data-pltdoc="x">impersonate-vector</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">vec</span>.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._impersonate-box))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-box%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-box</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">box</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">unbox-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">box</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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</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._not%2Fc%29%29" class="RktValLink" data-pltdoc="x">not/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._immutable~3f%29%29" class="RktValLink" data-pltdoc="x">immutable?</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">unbox-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator of <span class="RktVar">box</span>, which redirects the
<span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._unbox%29%29" class="RktValLink" data-pltdoc="x">unbox</a></span> and <span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._set-box%21%29%29" class="RktValLink" data-pltdoc="x">set-box!</a></span> operations.</div></p><p>The <span class="RktVar">unbox-proc</span> must accept <span class="RktVar">box</span> and the value that
<span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._unbox%29%29" class="RktValLink" data-pltdoc="x">unbox</a></span> produces on <span class="RktVar">box</span>; it must produce a replacement
value, which is the result of <span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._unbox%29%29" class="RktValLink" data-pltdoc="x">unbox</a></span> on the impersonator.</p><p>The <span class="RktVar">set-proc</span> must accept <span class="RktVar">box</span> and the value passed to
<span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._set-box%21%29%29" class="RktValLink" data-pltdoc="x">set-box!</a></span>; it must produce a replacement
value, which is used with <span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._set-box%21%29%29" class="RktValLink" data-pltdoc="x">set-box!</a></span> on the original
<span class="RktVar">box</span> to install the value.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-box%29%29" class="RktValLink" data-pltdoc="x">impersonate-box</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">box</span>.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._impersonate-hash))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-hash%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-hash</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">hash</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">ref-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">remove-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">key-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span>[</td><td><span class="RktVar">clear-proc</span>]</td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">hash</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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</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._not%2Fc%29%29" class="RktValLink" data-pltdoc="x">not/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._immutable~3f%29%29" class="RktValLink" data-pltdoc="x">immutable?</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">ref-proc</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span></td></tr><tr><td><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="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr></table></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></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="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="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">remove-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">key-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">clear-proc</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="RktVal">#f</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</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="RktPn">)</span><span class="hspace"> </span>=<span class="hspace"> </span><span class="RktVal">#f</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator of <span class="RktVar">hash</span>, which redirects the
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29" class="RktValLink" data-pltdoc="x">hash-ref</a></span>, <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%21%29%29" class="RktValLink" data-pltdoc="x">hash-set!</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%29%29" class="RktValLink" data-pltdoc="x">hash-set</a></span> (as
applicable), <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%29%29" class="RktValLink" data-pltdoc="x">hash-remove</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%21%29%29" class="RktValLink" data-pltdoc="x">hash-remove!</a></span> (as
applicable), <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-clear%29%29" class="RktValLink" data-pltdoc="x">hash-clear</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-clear%21%29%29" class="RktValLink" data-pltdoc="x">hash-clear!</a></span> (as
applicable and if <span class="RktVar">clear-proc</span> is not <span class="RktVal">#f</span>) operations. When
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%29%29" class="RktValLink" data-pltdoc="x">hash-set</a></span>, <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%29%29" class="RktValLink" data-pltdoc="x">hash-remove</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-clear%29%29" class="RktValLink" data-pltdoc="x">hash-clear</a></span> is used on an impersonator of a hash
table, the result is an impersonator with the same redirecting procedures.
In addition, operations like
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-iterate-key%29%29" class="RktValLink" data-pltdoc="x">hash-iterate-key</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-map%29%29" class="RktValLink" data-pltdoc="x">hash-map</a></span>, which extract
keys from the table, use <span class="RktVar">key-proc</span> to filter keys extracted
from the table. Operations like <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-iterate-value%29%29" class="RktValLink" data-pltdoc="x">hash-iterate-value</a></span> or
<span class="RktSym">hash-iterate-map</span> implicitly use <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29" class="RktValLink" data-pltdoc="x">hash-ref</a></span> and
therefore redirect through <span class="RktVar">ref-proc</span>.</div></p><p>The <span class="RktVar">ref-proc</span> must accept <span class="RktVar">hash</span> and a key passed
to <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29" class="RktValLink" data-pltdoc="x">hash-ref</a></span>. It must return a replacement key
as well as a procedure. The returned procedure is called only if the
returned key is found in <span class="RktVar">hash</span> via <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29" class="RktValLink" data-pltdoc="x">hash-ref</a></span>, in which
case the procedure is called with <span class="RktVar">hash</span>, the previously
returned key, and the found value. The returned procedure must itself
return a replacement for the found value.</p><p>The <span class="RktVar">set-proc</span> must accept <span class="RktVar">hash</span>, a key passed to
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%21%29%29" class="RktValLink" data-pltdoc="x">hash-set!</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%29%29" class="RktValLink" data-pltdoc="x">hash-set</a></span>, and the value passed to
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%21%29%29" class="RktValLink" data-pltdoc="x">hash-set!</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%29%29" class="RktValLink" data-pltdoc="x">hash-set</a></span>; it must produce two values: a
replacement for the key and a replacement for the value. The returned
key and value are used with <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%21%29%29" class="RktValLink" data-pltdoc="x">hash-set!</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-set%29%29" class="RktValLink" data-pltdoc="x">hash-set</a></span> on
the original <span class="RktVar">hash</span> to install the value.</p><p>The <span class="RktVar">remove-proc</span> must accept <span class="RktVar">hash</span> and a key passed to
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%21%29%29" class="RktValLink" data-pltdoc="x">hash-remove!</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%29%29" class="RktValLink" data-pltdoc="x">hash-remove</a></span>; it must produce the a
replacement for the key, which is used with <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%21%29%29" class="RktValLink" data-pltdoc="x">hash-remove!</a></span> or
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%29%29" class="RktValLink" data-pltdoc="x">hash-remove</a></span> on the original <span class="RktVar">hash</span> to remove any
mapping using the (impersonator-replaced) key.</p><p>The <span class="RktVar">key-proc</span> must accept <span class="RktVar">hash</span> and a key that has
been extracted from <span class="RktVar">hash</span> (by <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-iterate-key%29%29" class="RktValLink" data-pltdoc="x">hash-iterate-key</a></span> or
other operations that use <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-iterate-key%29%29" class="RktValLink" data-pltdoc="x">hash-iterate-key</a></span> internally); it
must produce a replacement for the key, which is then reported as a
key extracted from the table.</p><p>If <span class="RktVar">clear-proc</span> is not <span class="RktVal">#f</span>, it must accept
<span class="RktVar">hash</span> as an argument, and its result is ignored. The fact that
<span class="RktVar">clear-proc</span> returns (as opposed to raising an exception or
otherwise escaping) grants the capability to remove all keys from <span class="RktVar">hash</span>.
If <span class="RktVar">clear-proc</span> is <span class="RktVal">#f</span>, then <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-clear%29%29" class="RktValLink" data-pltdoc="x">hash-clear</a></span> or
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-clear%21%29%29" class="RktValLink" data-pltdoc="x">hash-clear!</a></span> on the impersonator is implemented using
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-iterate-key%29%29" class="RktValLink" data-pltdoc="x">hash-iterate-key</a></span> and <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%29%29" class="RktValLink" data-pltdoc="x">hash-remove</a></span> or <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-remove%21%29%29" class="RktValLink" data-pltdoc="x">hash-remove!</a></span>.</p><p>The <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-iterate-value%29%29" class="RktValLink" data-pltdoc="x">hash-iterate-value</a></span>, <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-map%29%29" class="RktValLink" data-pltdoc="x">hash-map</a></span>, or
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-for-each%29%29" class="RktValLink" data-pltdoc="x">hash-for-each</a></span> functions use a combination of
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-iterate-key%29%29" class="RktValLink" data-pltdoc="x">hash-iterate-key</a></span> and <span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29" class="RktValLink" data-pltdoc="x">hash-ref</a></span>. If a key
produced by <span class="RktVar">key-proc</span> does not yield a value through
<span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29" class="RktValLink" data-pltdoc="x">hash-ref</a></span>, then the <span class="RktSym"><a href="exns.html#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._exn~3afail~3acontract%29%29" class="RktValLink" data-pltdoc="x">exn:fail:contract</a></span> exception is raised.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-hash%29%29" class="RktValLink" data-pltdoc="x">impersonate-hash</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">hash</span>.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._impersonate-channel))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-channel%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-channel</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">channel</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">get-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">put-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">channel</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">get-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</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="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span><span class="hspace"> </span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">put-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator of <span class="RktVar">channel</span>, which redirects the
<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> and <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> operations.</div></p><p>The <span class="RktVar">get-proc</span> generator is called on <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>
or any other operation that fetches results from the channel (such
as a <span class="RktSym"><a href="sync.html#%28def._%28%28quote._~23~25kernel%29._sync%29%29" class="RktValLink" data-pltdoc="x">sync</a></span> on the channel). The <span class="RktVar">get-proc</span> must return
two values: a <a href="channel.html#%28tech._channel%29" class="techoutside" data-pltdoc="x"><span class="techinside">channel</span></a> that is an impersonator of <span class="RktVar">channel</span>, and a
procedure that is used to check the channel’s contents.</p><p>The <span class="RktVar">put-proc</span> must accept <span class="RktVar">channel</span> and the value passed to
<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>; it must produce a replacement
value, which is used with <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> on the original
<span class="RktVar">channel</span> to send the value over the channel.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-channel%29%29" class="RktValLink" data-pltdoc="x">impersonate-channel</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">channel</span>.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._impersonate-prompt-tag))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-prompt-tag%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-prompt-tag</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prompt-tag</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">handle-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">abort-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span>[</td><td><span class="RktVar">cc-guard-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">callcc-impersonate-proc</span>]</td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._continuation-prompt-tag~3f%29%29" class="RktValLink" data-pltdoc="x">continuation-prompt-tag?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prompt-tag</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._continuation-prompt-tag~3f%29%29" class="RktValLink" data-pltdoc="x">continuation-prompt-tag?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">handle-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">abort-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">cc-guard-proc</span><span class="hspace"> </span>:<span class="hspace"> </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="hspace"> </span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">callcc-impersonate-proc</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><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="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="procedures.html#%28def._%28%28quote._~23~25kernel%29._procedure~3f%29%29" class="RktValLink" data-pltdoc="x">procedure?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td>=</td><td><span class="hspace"> </span></td><td><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">p</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">p</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator of <span class="RktVar">prompt-tag</span>, which redirects
the <span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._call-with-continuation-prompt%29%29" class="RktValLink" data-pltdoc="x">call-with-continuation-prompt</a></span> and
<span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span> operations.</div></p><p>The <span class="RktVar">handle-proc</span> must accept the values that the handler
of a continuation prompt would take and it must produce replacement
values, which will be passed to the handler.</p><p>The <span class="RktVar">abort-proc</span> must accept the values passed to
<span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span>; it must produce replacement
values, which are aborted to the appropriate prompt.</p><p>The <span class="RktVar">cc-guard-proc</span> must accept the values produced by
<span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._call-with-continuation-prompt%29%29" class="RktValLink" data-pltdoc="x">call-with-continuation-prompt</a></span> in the case that a
non-composable continuation is applied to replace the continuation
that is delimited by the prompt, but only if
<span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span> is not later used to abort the
continuation delimited by the prompt (in which case
<span class="RktVar">abort-proc</span> is used).</p><p>The <span class="RktVar">callcc-impersonate-proc</span> must accept a procedure that
guards the result of a continuation captured by
<span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._call-with-current-continuation%29%29" class="RktValLink" data-pltdoc="x">call-with-current-continuation</a></span> with the impersonated prompt
tag. The <span class="RktVar">callcc-impersonate-proc</span> is applied (under a
<a href="eval-model.html#%28tech._continuation._barrier%29" class="techoutside" data-pltdoc="x"><span class="techinside">continuation barrier</span></a>) when the captured continuation is applied
to refine a guard function (initially <span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span>) that is
specific to the delimiting prompt; this prompt-specific guard is
ultimately composed with any <span class="RktVar">cc-guard-proc</span> that is in effect
at the delimiting prompt, and it is not used in the same case that a
<span class="RktVar">cc-guard-proc</span> is not used (i.e., when
<span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span> is used to abort to the
prompt). In the special case where the delimiting prompt at
application time is a thread’s built-in initial prompt,
<span class="RktVar">callcc-impersonate-proc</span> is ignored (partly on the grounds
that the initial prompt’s result is ignored).</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">impersonate-prompt-tag</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">prompt-tag</span>.</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><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"><a href="creatingunits.html#%28form._%28%28lib._racket%2Funit..rkt%29._tag%29%29" class="RktStxLink" data-pltdoc="x">tag</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">impersonate-prompt-tag</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._make-continuation-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">make-continuation-prompt-tag</a></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="RktSym">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._%2A%29%29" class="RktValLink" data-pltdoc="x">*</a></span><span class="hspace"> </span><span class="RktSym">n</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"><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">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._%2B%29%29" class="RktValLink" data-pltdoc="x">+</a></span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="cont.html#%28def._%28%28quote._~23~25kernel%29._call-with-continuation-prompt%29%29" class="RktValLink" data-pltdoc="x">call-with-continuation-prompt</a></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></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span><span class="hspace"> </span><span class="RktSym"><a href="creatingunits.html#%28form._%28%28lib._racket%2Funit..rkt%29._tag%29%29" class="RktStxLink" data-pltdoc="x">tag</a></span><span class="hspace"> </span><span class="RktVal">5</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym"><a href="creatingunits.html#%28form._%28%28lib._racket%2Funit..rkt%29._tag%29%29" class="RktStxLink" data-pltdoc="x">tag</a></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="RktSym">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">12</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><table cellspacing="0" cellpadding="0" class="prototype RForeground"><tr><td><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._impersonate-continuation-mark-key))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-continuation-mark-key%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonate-continuation-mark-key</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">key</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">get-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym">continuation-mark?</span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">key</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-key~3f%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-key?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">get-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns an impersonator of <span class="RktVar">key</span>, which redirects
<span class="RktSym"><a href="wcm.html#%28form._%28%28quote._~23~25kernel%29._with-continuation-mark%29%29" class="RktStxLink" data-pltdoc="x">with-continuation-mark</a></span> and continuation mark accessors such
as <span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-set-~3elist%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-set->list</a></span>.</div></p><p>The <span class="RktVar">get-proc</span> must accept the value attached to a
continuation mark and it must produce a replacement
value, which will be returned by the continuation mark accessor.</p><p>The <span class="RktVar">set-proc</span> must accept a value passed to
<span class="RktSym"><a href="wcm.html#%28form._%28%28quote._~23~25kernel%29._with-continuation-mark%29%29" class="RktStxLink" data-pltdoc="x">with-continuation-mark</a></span>; it must produce a replacement
value, which is attached to the continuation frame.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">impersonate-prompt-tag</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">key</span>.</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><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">mark-key</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-continuation-mark-key%29%29" class="RktValLink" data-pltdoc="x">impersonate-continuation-mark-key</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._make-continuation-mark-key%29%29" class="RktValLink" data-pltdoc="x">make-continuation-mark-key</a></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="RktSym">l</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28lib._racket%2Fprivate%2Fmap..rkt%29._map%29%29" class="RktValLink" data-pltdoc="x">map</a></span><span class="hspace"> </span><span class="RktSym"><a href="characters.html#%28def._%28%28quote._~23~25kernel%29._char-upcase%29%29" class="RktValLink" data-pltdoc="x">char-upcase</a></span><span class="hspace"> </span><span class="RktSym">l</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="RktSym">s</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="strings.html#%28def._%28%28quote._~23~25kernel%29._string-~3elist%29%29" class="RktValLink" data-pltdoc="x">string->list</a></span><span class="hspace"> </span><span class="RktSym">s</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="wcm.html#%28form._%28%28quote._~23~25kernel%29._with-continuation-mark%29%29" class="RktStxLink" data-pltdoc="x">with-continuation-mark</a></span><span class="hspace"> </span><span class="RktSym">mark-key</span><span class="hspace"> </span><span class="RktVal">"quiche"</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-set-first%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-set-first</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._current-continuation-marks%29%29" class="RktValLink" data-pltdoc="x">current-continuation-marks</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">mark-key</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#\Q #\U #\I #\C #\H #\E)</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>value</p></div></div><p class="RForeground"><a name="(def._((quote._~23~25kernel)._prop~3aimpersonator-of))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._prop~3aimpersonator-of%29%29" class="RktValDef RktValLink" data-pltdoc="x">prop:impersonator-of</a></span></span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="structprops.html#%28def._%28%28quote._~23~25kernel%29._struct-type-property~3f%29%29" class="RktValLink" data-pltdoc="x">struct-type-property?</a></span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara">A <a href="structprops.html#%28tech._structure._type._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">structure type property</span></a> (see <a href="structprops.html" data-pltdoc="x">Structure Type Properties</a>) that
supplies a procedure for extracting an impersonated value from a structure
that represents an impersonator. The property is used for <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-of~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-of?</a></span>
as well as <span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._equal~3f%29%29" class="RktValLink" data-pltdoc="x">equal?</a></span>.</div></p><p>The property value must be a procedure of one argument, which is a
structure whose structure type has the property. The result can be
<span class="RktVal">#f</span> to indicate the structure does not represent an impersonator,
otherwise the result is a value for which the original structure is an
impersonator (so the original structure is an <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-of~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-of?</a></span> and
<span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._equal~3f%29%29" class="RktValLink" data-pltdoc="x">equal?</a></span> to the result value). The result value must have the
same <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._prop~3aimpersonator-of%29%29" class="RktValLink" data-pltdoc="x">prop:impersonator-of</a></span> and <span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._prop~3aequal%2Bhash%29%29" class="RktValLink" data-pltdoc="x">prop:equal+hash</a></span> property
values as the original structure, and the property values must be
inherited from the same structure type (which ensures some consistency
between <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-of~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-of?</a></span> and <span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._equal~3f%29%29" class="RktValLink" data-pltdoc="x">equal?</a></span>).</p><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-part-tag=""Chaperone_Constructors"">14.5.2<tt> </tt><a name="(part._.Chaperone_.Constructors)"></a>Chaperone Constructors</h5><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><span class="RktPn">(</span><a name="(def._((lib._racket/private/base..rkt)._chaperone-procedure))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._chaperone-procedure%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-procedure</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">wrapper-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </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"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">wrapper-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._impersonate-procedure%29%29" class="RktValLink" data-pltdoc="x">impersonate-procedure</a></span>, but for each value supplied to
<span class="RktVar">wrapper-proc</span>, the corresponding result must be the same or a
chaperone of (in the sense of <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-of~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone-of?</a></span>) the supplied
value. The additional result, if any, that precedes the chaperoned
values must be a procedure that accepts as many results as produced by
<span class="RktVar">proc</span>; it must return the same number of results, each of
which is the same or a chaperone of the corresponding original result.</div></p><p>For applications that include keyword arguments, <span class="RktVar">wrapper-proc</span>
must return an additional value before any other values but after the
result-chaperoning procedure (if any). The additional value must be a
list of chaperones of the keyword arguments that were supplied to the
chaperone procedure (i.e., not counting optional arguments that were
not supplied). The arguments must be ordered according to the sorted
order of the supplied arguments’ keywords.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-struct))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-struct%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-struct</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">v</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">orig-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">redirect-proc</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><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></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><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">orig-proc</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><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="RktSym"><a href="structutils.html#%28def._%28%28quote._~23~25kernel%29._struct-accessor-procedure~3f%29%29" class="RktValLink" data-pltdoc="x">struct-accessor-procedure?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym"><a href="structutils.html#%28def._%28%28quote._~23~25kernel%29._struct-mutator-procedure~3f%29%29" class="RktValLink" data-pltdoc="x">struct-mutator-procedure?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym"><a href="structprops.html#%28def._%28%28quote._~23~25kernel%29._struct-type-property-accessor-procedure~3f%29%29" class="RktValLink" data-pltdoc="x">struct-type-property-accessor-procedure?</a></span></td></tr><tr><td><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._one-of%2Fc%29%29" class="RktValLink" data-pltdoc="x">one-of/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-info%29%29" class="RktValLink" data-pltdoc="x">struct-info</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr></table></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">redirect-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-struct%29%29" class="RktValLink" data-pltdoc="x">impersonate-struct</a></span>, but with the following refinements:</div></p><ul><li><p>With a structure-field accessor as <span class="RktVar">orig-proc</span>,
<span class="RktVar">redirect-proc</span> must accept two arguments, <span class="RktVar">v</span> and
the value <span class="RktVar">field-v</span> that <span class="RktVar">orig-proc</span> produces for
<span class="RktVar">v</span>; it must return a chaperone of <span class="RktVar">field-v</span>. The
corresponding field may be immutable.</p></li><li><p>With structure-field mutator as <span class="RktVar">orig-proc</span>,
<span class="RktVar">redirect-proc</span> must accept two arguments, <span class="RktVar">v</span> and
the value <span class="RktVar">field-v</span> supplied to the mutator; it must
return a chaperone of <span class="RktVar">field-v</span> to be propagated to
<span class="RktVar">orig-proc</span> and <span class="RktVar">v</span>.</p></li><li><p>A property accessor can be supplied as <span class="RktVar">orig-proc</span>, and
the property need not have been created with
<span class="RktVal">'</span><span class="RktVal">can-impersonate</span>. The corresponding
<span class="RktVar">redirect-proc</span> uses the same protocol as for a
structure-field accessor.</p></li><li><p>With <span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-info%29%29" class="RktValLink" data-pltdoc="x">struct-info</a></span> as <span class="RktVar">orig-proc</span>, the
corresponding <span class="RktVar">redirect-proc</span> must accept two values,
which are the results of <span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-info%29%29" class="RktValLink" data-pltdoc="x">struct-info</a></span> on <span class="RktVar">v</span>; it
must return each values or a chaperone of each value. The
<span class="RktVar">redirect-proc</span> is not called if <span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-info%29%29" class="RktValLink" data-pltdoc="x">struct-info</a></span>
would return <span class="RktVal">#f</span> as its first argument. An
<span class="RktVar">orig-proc</span> can be <span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-info%29%29" class="RktValLink" data-pltdoc="x">struct-info</a></span> only if some
other <span class="RktVar">orig-proc</span> is supplied.</p></li></ul><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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-vector))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-vector%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-vector</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">vec</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">ref-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">vec</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">ref-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span><span class="hspace"> </span><span class="RktSym"><a href="number-types.html#%28def._%28%28quote._~23~25kernel%29._exact-nonnegative-integer~3f%29%29" class="RktValLink" data-pltdoc="x">exact-nonnegative-integer?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span><span class="hspace"> </span><span class="RktSym"><a href="number-types.html#%28def._%28%28quote._~23~25kernel%29._exact-nonnegative-integer~3f%29%29" class="RktValLink" data-pltdoc="x">exact-nonnegative-integer?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-vector%29%29" class="RktValLink" data-pltdoc="x">impersonate-vector</a></span>, but with support for immutable vectors. The
<span class="RktVar">ref-proc</span> procedure must produce the same value or a chaperone
of the original value, and <span class="RktVar">set-proc</span> must produce the value
that is given or a chaperone of the value. The <span class="RktVar">set-proc</span> will
not be used if <span class="RktVar">vec</span> is immutable.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-box))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-box%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-box</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">box</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">unbox-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">box</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">unbox-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="boxes.html#%28def._%28%28quote._~23~25kernel%29._box~3f%29%29" class="RktValLink" data-pltdoc="x">box?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-box%29%29" class="RktValLink" data-pltdoc="x">impersonate-box</a></span>, but with support for immutable boxes. The
<span class="RktVar">unbox-proc</span> procedure must produce the same value or a
chaperone of the original value, and <span class="RktVar">set-proc</span> must produce
the same value or a chaperone of the value that it is given. The
<span class="RktVar">set-proc</span> will not be used if <span class="RktVar">box</span> is immutable.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-hash))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-hash%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-hash</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">hash</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">ref-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">remove-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">key-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span>[</td><td><span class="RktVar">clear-proc</span>]</td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">hash</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">ref-proc</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span></td></tr><tr><td><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="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr></table></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></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="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="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">remove-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">key-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">clear-proc</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="RktVal">#f</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</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="RktPn">)</span><span class="hspace"> </span>=<span class="hspace"> </span><span class="RktVal">#f</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-hash%29%29" class="RktValLink" data-pltdoc="x">impersonate-hash</a></span>, but with constraints on the given functions
and support for immutable hashes. The <span class="RktVar">ref-proc</span> procedure must
return a found value or a chaperone of the value. The
<span class="RktVar">set-proc</span> procedure must produce two values: the key that it
is given or a chaperone of the key and the value that it is given or a
chaperone of the value. The <span class="RktVar">remove-proc</span> and <span class="RktVar">key-proc</span>
procedures must produce the given key or a chaperone of the key.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-struct-type))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-struct-type%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-struct-type</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">struct-type</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">struct-info-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">make-constructor-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">guard-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="structutils.html#%28def._%28%28quote._~23~25kernel%29._struct-type~3f%29%29" class="RktValLink" data-pltdoc="x">struct-type?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">struct-type</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="structutils.html#%28def._%28%28quote._~23~25kernel%29._struct-type~3f%29%29" class="RktValLink" data-pltdoc="x">struct-type?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">struct-info-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">make-constructor-proc</span><span class="hspace"> </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="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="procedures.html#%28def._%28%28quote._~23~25kernel%29._procedure~3f%29%29" class="RktValLink" data-pltdoc="x">procedure?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">guard-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns a chaperoned value like <span class="RktVar">struct-type</span>, but with
<span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-type-info%29%29" class="RktValLink" data-pltdoc="x">struct-type-info</a></span> and <span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-type-make-constructor%29%29" class="RktValLink" data-pltdoc="x">struct-type-make-constructor</a></span>
operations on the chaperoned structure type redirected. In addition,
when a new structure type is created as a subtype of the chaperoned
structure type, <span class="RktVar">guard-proc</span> is interposed as an extra guard on
creation of instances of the subtype.</div></p><p>The <span class="RktVar">struct-info-proc</span> must accept 8 arguments—<wbr></wbr>the result of
<span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-type-info%29%29" class="RktValLink" data-pltdoc="x">struct-type-info</a></span> on <span class="RktVar">struct-type</span>. It must return 8
values, where each is the same or a chaperone of the corresponding
argument. The 8 values are used as the results of
<span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-type-info%29%29" class="RktValLink" data-pltdoc="x">struct-type-info</a></span> for the chaperoned structure type.</p><p>The <span class="RktVar">make-constructor-proc</span> must accept a single procedure
argument, which is a constructor produced by
<span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-type-make-constructor%29%29" class="RktValLink" data-pltdoc="x">struct-type-make-constructor</a></span> on <span class="RktVar">struct-type</span>. It must
return the same or a chaperone of the procedure, which is used as the
result of <span class="RktSym"><a href="inspectors.html#%28def._%28%28quote._~23~25kernel%29._struct-type-make-constructor%29%29" class="RktValLink" data-pltdoc="x">struct-type-make-constructor</a></span> on the chaperoned
structure type.</p><p>The <span class="RktVar">guard-proc</span> must accept as many argument as a constructor
for <span class="RktVar">struct-type</span>; it must return the same number of arguments,
each the same or a chaperone of the corresponding argument. The
<span class="RktVar">guard-proc</span> is added as a constructor guard when a subtype is
created of the chaperoned structure type.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-struct-type%29%29" class="RktValLink" data-pltdoc="x">chaperone-struct-type</a></span> must be even) add impersonator properties
or override impersonator-property values of <span class="RktVar">struct-type</span>.</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)._chaperone-evt))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-evt%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-evt</a></span></span><span class="hspace"> </span><span class="RktVar">evt</span><span class="hspace"> </span><span class="RktVar">proc</span><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></p></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="sync.html#%28def._%28%28quote._~23~25kernel%29._evt~3f%29%29" class="RktValLink" data-pltdoc="x">evt?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">evt</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="sync.html#%28def._%28%28quote._~23~25kernel%29._evt~3f%29%29" class="RktValLink" data-pltdoc="x">evt?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="sync.html#%28def._%28%28quote._~23~25kernel%29._evt~3f%29%29" class="RktValLink" data-pltdoc="x">evt?</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="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span><span class="hspace"> </span><span class="RktSym"><a href="sync.html#%28def._%28%28quote._~23~25kernel%29._evt~3f%29%29" class="RktValLink" data-pltdoc="x">evt?</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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Returns a chaperoned value like <span class="RktVar">evt</span>, but with <span class="RktVar">proc</span>
as an event generator when the result is synchronized with functions
like <span class="RktSym"><a href="sync.html#%28def._%28%28quote._~23~25kernel%29._sync%29%29" class="RktValLink" data-pltdoc="x">sync</a></span>.</div></p><p>The <span class="RktVar">proc</span> generator is called on synchronization, much like
the procedure passed to <span class="RktSym"><a href="sync.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._guard-evt%29%29" class="RktValLink" data-pltdoc="x">guard-evt</a></span>, except that <span class="RktVar">proc</span>
is given <span class="RktVar">evt</span>. The <span class="RktVar">proc</span> must return two values: a
<a href="sync.html#%28tech._synchronizable._event%29" class="techoutside" data-pltdoc="x"><span class="techinside">synchronizable event</span></a> that is a chaperone of <span class="RktVar">evt</span>, and a
procedure that is used to check the event’s result if it is chosen in
a selection. The latter procedure accepts the result of <span class="RktVar">evt</span>,
and it must return a chaperone of that value.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-evt%29%29" class="RktValLink" data-pltdoc="x">chaperone-evt</a></span> must be even) add impersonator properties
or override impersonator-property values of <span class="RktVar">evt</span>.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-channel))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-channel%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-channel</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">channel</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">get-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">put-proc</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">channel</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">get-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</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="RktPn">(</span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span><span class="hspace"> </span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">put-proc</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="channel.html#%28def._%28%28quote._~23~25kernel%29._channel~3f%29%29" class="RktValLink" data-pltdoc="x">channel?</a></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="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#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-channel%29%29" class="RktValLink" data-pltdoc="x">impersonate-channel</a></span>, but with restrictions on the
<span class="RktVar">get-proc</span> and <span class="RktVar">put-proc</span> procedures.</div></p><p>The <span class="RktVar">get-proc</span> must return two values: a <a href="channel.html#%28tech._channel%29" class="techoutside" data-pltdoc="x"><span class="techinside">channel</span></a>
that is a chaperone of <span class="RktVar">channel</span>, and a procedure that
is used to check the channel’s contents. The latter procedure
must return the original value or a chaperone of that value.</p><p>The <span class="RktVar">put-proc</span> must produce a replacement value that is
either the original value communicated on the channel or a
chaperone of that value.</p><p>Pairs of <span class="RktVar">prop</span> and <span class="RktVar">prop-val</span> (the number of arguments
to <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-channel%29%29" class="RktValLink" data-pltdoc="x">chaperone-channel</a></span> must be odd) add impersonator properties
or override impersonator-property values of <span class="RktVar">channel</span>.</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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-prompt-tag))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-prompt-tag%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-prompt-tag</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prompt-tag</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">handle-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">abort-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span>[</td><td><span class="RktVar">cc-guard-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">callcc-chaperone-proc</span>]</td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._continuation-prompt-tag~3f%29%29" class="RktValLink" data-pltdoc="x">continuation-prompt-tag?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prompt-tag</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._continuation-prompt-tag~3f%29%29" class="RktValLink" data-pltdoc="x">continuation-prompt-tag?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">handle-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">abort-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">cc-guard-proc</span><span class="hspace"> </span>:<span class="hspace"> </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="hspace"> </span><span class="RktSym"><a href="values.html#%28def._%28%28quote._~23~25kernel%29._values%29%29" class="RktValLink" data-pltdoc="x">values</a></span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace"> </span></td><td><span class="RktVar">callcc-chaperone-proc</span></td><td><span class="hspace"> </span></td><td>:</td><td><span class="hspace"> </span></td><td><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="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="procedures.html#%28def._%28%28quote._~23~25kernel%29._procedure~3f%29%29" class="RktValLink" data-pltdoc="x">procedure?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td>=</td><td><span class="hspace"> </span></td><td><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">p</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">p</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">impersonate-prompt-tag</a></span>, but produces a chaperoned value.
The <span class="RktVar">handle-proc</span> procedure must produce the same values or
chaperones of the original values, <span class="RktVar">abort-proc</span> must produce
the same values or chaperones of the values that it is given, and
<span class="RktVar">cc-guard-proc</span> must produce the same values or chaperones of
the original result values, and <span class="RktVar">callcc-chaperone-proc</span> must
produce a procedure that is a chaperone or the same as the given
procedure.</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><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">bad-chaperone</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">chaperone-prompt-tag</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._make-continuation-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">make-continuation-prompt-tag</a></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="RktSym">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._%2A%29%29" class="RktValLink" data-pltdoc="x">*</a></span><span class="hspace"> </span><span class="RktSym">n</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"><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">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._%2B%29%29" class="RktValLink" data-pltdoc="x">+</a></span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="cont.html#%28def._%28%28quote._~23~25kernel%29._call-with-continuation-prompt%29%29" class="RktValLink" data-pltdoc="x">call-with-continuation-prompt</a></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></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span><span class="hspace"> </span><span class="RktSym">bad-chaperone</span><span class="hspace"> </span><span class="RktVal">5</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">bad-chaperone</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="RktSym">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktErr">abort-current-continuation: non-chaperone result;</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">received a value that is not a chaperone of the original</span></p></td></tr><tr><td><p><span class="RktErr">value</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">original: 5</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">received: 6</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="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">good-chaperone</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">chaperone-prompt-tag</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._make-continuation-prompt-tag%29%29" class="RktValLink" data-pltdoc="x">make-continuation-prompt-tag</a></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="RktSym">n</span><span class="RktPn">)</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="number-types.html#%28def._%28%28quote._~23~25kernel%29._even~3f%29%29" class="RktValLink" data-pltdoc="x">even?</a></span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="exns.html#%28def._%28%28quote._~23~25kernel%29._error%29%29" class="RktValLink" data-pltdoc="x">error</a></span><span class="hspace"> </span><span class="RktVal">"not even"</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="RktSym">n</span><span class="RktPn">)</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="number-types.html#%28def._%28%28quote._~23~25kernel%29._even~3f%29%29" class="RktValLink" data-pltdoc="x">even?</a></span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">n</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="exns.html#%28def._%28%28quote._~23~25kernel%29._error%29%29" class="RktValLink" data-pltdoc="x">error</a></span><span class="hspace"> </span><span class="RktVal">"not even"</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><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="cont.html#%28def._%28%28quote._~23~25kernel%29._call-with-continuation-prompt%29%29" class="RktValLink" data-pltdoc="x">call-with-continuation-prompt</a></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></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="cont.html#%28def._%28%28quote._~23~25kernel%29._abort-current-continuation%29%29" class="RktValLink" data-pltdoc="x">abort-current-continuation</a></span><span class="hspace"> </span><span class="RktSym">good-chaperone</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="RktSym">good-chaperone</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="RktSym">n</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">n</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">2</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><table cellspacing="0" cellpadding="0" class="prototype RForeground"><tr><td><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._chaperone-continuation-mark-key))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-continuation-mark-key%29%29" class="RktValDef RktValLink" data-pltdoc="x">chaperone-continuation-mark-key</a></span></span></td><td><span class="hspace"> </span></td><td><span class="RktVar">key</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">get-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">set-proc</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktVar">prop-val</span><span class="hspace"> </span><span class="RktMeta">...</span></td><td><span class="hspace"> </span></td></tr><tr><td><span class="hspace"> </span></td><td><span class="hspace"> </span></td><td><span class="RktMeta">...</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td></tr></table></blockquote></td></tr><tr><td><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._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-key~3f%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-key?</a></span><span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone~3f%29%29" class="RktValLink" data-pltdoc="x">chaperone?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">key</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-key~3f%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-key?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">get-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">set-proc</span><span class="hspace"> </span>:<span class="hspace"> </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></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">prop-val</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></td></tr></table></blockquote></div><div class="SIntrapara">Like <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonate-continuation-mark-key%29%29" class="RktValLink" data-pltdoc="x">impersonate-continuation-mark-key</a></span>, but produces a
chaperoned value. The <span class="RktVar">get-proc</span> procedure must produce the
same value or a chaperone of the original value, and <span class="RktVar">set-proc</span>
must produce the same value or a chaperone of the value that it is
given.</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><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">bad-chaperone</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-continuation-mark-key%29%29" class="RktValLink" data-pltdoc="x">chaperone-continuation-mark-key</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._make-continuation-mark-key%29%29" class="RktValLink" data-pltdoc="x">make-continuation-mark-key</a></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="RktSym">l</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28lib._racket%2Fprivate%2Fmap..rkt%29._map%29%29" class="RktValLink" data-pltdoc="x">map</a></span><span class="hspace"> </span><span class="RktSym"><a href="characters.html#%28def._%28%28quote._~23~25kernel%29._char-upcase%29%29" class="RktValLink" data-pltdoc="x">char-upcase</a></span><span class="hspace"> </span><span class="RktSym">l</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym"><a href="strings.html#%28def._%28%28quote._~23~25kernel%29._string-~3elist%29%29" class="RktValLink" data-pltdoc="x">string->list</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="wcm.html#%28form._%28%28quote._~23~25kernel%29._with-continuation-mark%29%29" class="RktStxLink" data-pltdoc="x">with-continuation-mark</a></span><span class="hspace"> </span><span class="RktSym">bad-chaperone</span><span class="hspace"> </span><span class="RktVal">"timballo"</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-set-first%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-set-first</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._current-continuation-marks%29%29" class="RktValLink" data-pltdoc="x">current-continuation-marks</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">bad-chaperone</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktErr">with-continuation-mark: non-chaperone result;</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">received a value that is not a chaperone of the original</span></p></td></tr><tr><td><p><span class="RktErr">value</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">original: "timballo"</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace"> </span><span class="RktErr">received: '(#\t #\i #\m #\b #\a #\l #\l #\o)</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="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">checker</span><span class="hspace"> </span><span class="RktSym">s</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="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._~3e%29%29" class="RktValLink" data-pltdoc="x">></a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="strings.html#%28def._%28%28quote._~23~25kernel%29._string-length%29%29" class="RktValLink" data-pltdoc="x">string-length</a></span><span class="hspace"> </span><span class="RktSym">s</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVal">5</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">s</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="exns.html#%28def._%28%28quote._~23~25kernel%29._error%29%29" class="RktValLink" data-pltdoc="x">error</a></span><span class="hspace"> </span><span class="RktVal">"expected string of length at least 5"</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="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">good-chaperone</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._chaperone-continuation-mark-key%29%29" class="RktValLink" data-pltdoc="x">chaperone-continuation-mark-key</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._make-continuation-mark-key%29%29" class="RktValLink" data-pltdoc="x">make-continuation-mark-key</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">checker</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">checker</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="wcm.html#%28form._%28%28quote._~23~25kernel%29._with-continuation-mark%29%29" class="RktStxLink" data-pltdoc="x">with-continuation-mark</a></span><span class="hspace"> </span><span class="RktSym">good-chaperone</span><span class="hspace"> </span><span class="RktVal">"zabaione"</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._continuation-mark-set-first%29%29" class="RktValLink" data-pltdoc="x">continuation-mark-set-first</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="contmarks.html#%28def._%28%28quote._~23~25kernel%29._current-continuation-marks%29%29" class="RktValLink" data-pltdoc="x">current-continuation-marks</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">good-chaperone</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">"zabaione"</span></p></td></tr></table></blockquote></td></tr></table></p><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-part-tag=""Impersonator_Properties"">14.5.3<tt> </tt><a name="(part._.Impersonator_.Properties)"></a>Impersonator Properties</h5><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><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._make-impersonator-property))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-impersonator-property%29%29" class="RktValDef RktValLink" data-pltdoc="x">make-impersonator-property</a></span></span><span class="hspace"> </span><span class="RktVar">name</span><span class="RktPn">)</span></td><td><span class="hspace"> </span></td><td>→</td><td><span class="hspace"> </span></td><td><table cellspacing="0" cellpadding="0"><tr><td><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></td></tr><tr><td><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#%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="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._boolean~3f%29%29" class="RktValLink" data-pltdoc="x">boolean?</a></span><span class="RktPn">)</span></td></tr><tr><td><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="#%28def._%28%28quote._~23~25kernel%29._impersonator~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator?</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></td></tr></table></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">name</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="symbols.html#%28def._%28%28quote._~23~25kernel%29._symbol~3f%29%29" class="RktValLink" data-pltdoc="x">symbol?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Creates a new <a href="#%28tech._impersonator._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator property</span></a> and returns three values:</div></p><ul><li><p>an <a name="(tech._impersonator._property._descriptor)"></a><span style="font-style: italic">impersonator property descriptor</span>, for use with
<span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._impersonate-procedure%29%29" class="RktValLink" data-pltdoc="x">impersonate-procedure</a></span>, <span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._chaperone-procedure%29%29" class="RktValLink" data-pltdoc="x">chaperone-procedure</a></span>,
and other impersonator constructors;</p></li><li><p>an <a name="(tech._impersonator._property._predicate)"></a><span style="font-style: italic">impersonator property predicate</span> procedure, which takes
an arbitrary value and returns <span class="RktVal">#t</span> if the value is an
impersonator with a value for the property, <span class="RktVal">#f</span>
otherwise;</p></li><li><p>an <a name="(tech._impersonator._property._accessor)"></a><span style="font-style: italic">impersonator property accessor</span> procedure, which
returns the value associated with an impersonator for the property;
if a value given to the accessor is not an impersonator or does not
have a value for the property (i.e. if the corresponding impersonator
property predicate returns <span class="RktVal">#f</span>), the <span class="RktSym"><a href="exns.html#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._exn~3afail~3acontract%29%29" class="RktValLink" data-pltdoc="x">exn:fail:contract</a></span> exception is raised.</p></li></ul><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)._impersonator-property~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonator-property?</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="#%28tech._impersonator._property._descriptor%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator property
descriptor</span></a> value, <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)._impersonator-property-accessor-procedure~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property-accessor-procedure~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonator-property-accessor-procedure?</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 an accessor procedure produced
by <span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._make-impersonator-property%29%29" class="RktValLink" data-pltdoc="x">make-impersonator-property</a></span>, <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>value</p></div></div><p class="RForeground"><a name="(def._((quote._~23~25kernel)._impersonator-prop~3aapplication-mark))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-prop~3aapplication-mark%29%29" class="RktValDef RktValLink" data-pltdoc="x">impersonator-prop:application-mark</a></span></span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="#%28def._%28%28quote._~23~25kernel%29._impersonator-property~3f%29%29" class="RktValLink" data-pltdoc="x">impersonator-property?</a></span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara">An <a href="#%28tech._impersonator._property%29" class="techoutside" data-pltdoc="x"><span class="techinside">impersonator property</span></a> that is recognized by <span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._impersonate-procedure%29%29" class="RktValLink" data-pltdoc="x">impersonate-procedure</a></span>
and <span class="RktSym"><a href="#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._chaperone-procedure%29%29" class="RktValLink" data-pltdoc="x">chaperone-procedure</a></span>.</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="Module_Names_and_Loading.html" title="backward to "14.4 Module Names and Loading"" data-pltdoc="x">← prev</a> <a href="security.html" title="up to "14 Reflection and Security"" data-pltdoc="x">up</a> <a href="securityguards.html" title="forward to "14.6 Security Guards"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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