This file is indexed.

/usr/share/doc/racket/guide/exns.html is in racket-doc 6.1-4.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>10.1&nbsp;Exceptions</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,&quot;tocview_0&quot;);">&#9658;</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x"><span style="font-weight: bold">The Racket Guide</span></a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1&nbsp;</td><td><a href="intro.html" class="tocviewlink" data-pltdoc="x">Welcome to Racket</a></td></tr><tr><td align="right">2&nbsp;</td><td><a href="to-scheme.html" class="tocviewlink" data-pltdoc="x">Racket Essentials</a></td></tr><tr><td align="right">3&nbsp;</td><td><a href="datatypes.html" class="tocviewlink" data-pltdoc="x">Built-<wbr></wbr>In Datatypes</a></td></tr><tr><td align="right">4&nbsp;</td><td><a href="scheme-forms.html" class="tocviewlink" data-pltdoc="x">Expressions and Definitions</a></td></tr><tr><td align="right">5&nbsp;</td><td><a href="define-struct.html" class="tocviewlink" data-pltdoc="x">Programmer-<wbr></wbr>Defined Datatypes</a></td></tr><tr><td align="right">6&nbsp;</td><td><a href="modules.html" class="tocviewlink" data-pltdoc="x">Modules</a></td></tr><tr><td align="right">7&nbsp;</td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">8&nbsp;</td><td><a href="i_o.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">9&nbsp;</td><td><a href="regexp.html" class="tocviewlink" data-pltdoc="x">Regular Expressions</a></td></tr><tr><td align="right">10&nbsp;</td><td><a href="control.html" class="tocviewselflink" data-pltdoc="x">Exceptions and Control</a></td></tr><tr><td align="right">11&nbsp;</td><td><a href="for.html" class="tocviewlink" data-pltdoc="x">Iterations and Comprehensions</a></td></tr><tr><td align="right">12&nbsp;</td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">13&nbsp;</td><td><a href="classes.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">14&nbsp;</td><td><a href="units.html" class="tocviewlink" data-pltdoc="x">Units (Components)</a></td></tr><tr><td align="right">15&nbsp;</td><td><a href="reflection.html" class="tocviewlink" data-pltdoc="x">Reflection and Dynamic Evaluation</a></td></tr><tr><td align="right">16&nbsp;</td><td><a href="macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">17&nbsp;</td><td><a href="languages.html" class="tocviewlink" data-pltdoc="x">Creating Languages</a></td></tr><tr><td align="right">18&nbsp;</td><td><a href="concurrency.html" class="tocviewlink" data-pltdoc="x">Concurrency and Synchronization</a></td></tr><tr><td align="right">19&nbsp;</td><td><a href="performance.html" class="tocviewlink" data-pltdoc="x">Performance</a></td></tr><tr><td align="right">20&nbsp;</td><td><a href="parallelism.html" class="tocviewlink" data-pltdoc="x">Parallelism</a></td></tr><tr><td align="right">21&nbsp;</td><td><a href="running.html" class="tocviewlink" data-pltdoc="x">Running and Creating Executables</a></td></tr><tr><td align="right">22&nbsp;</td><td><a href="More_Libraries.html" class="tocviewlink" data-pltdoc="x">More Libraries</a></td></tr><tr><td align="right">23&nbsp;</td><td><a href="dialects.html" class="tocviewlink" data-pltdoc="x">Dialects of Racket and Scheme</a></td></tr><tr><td align="right">24&nbsp;</td><td><a href="other-editors.html" class="tocviewlink" data-pltdoc="x">Command-<wbr></wbr>Line Tools and Your Editor of Choice</a></td></tr><tr><td align="right"></td><td><a href="doc-bibliography.html" class="tocviewlink" data-pltdoc="x">Bibliography</a></td></tr><tr><td align="right"></td><td><a href="doc-index.html" class="tocviewlink" data-pltdoc="x">Index</a></td></tr></table></div></div><div class="tocviewlist"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,&quot;tocview_1&quot;);">&#9660;</a></td><td>10&nbsp;</td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Exceptions and Control</a></td></tr></table><div class="tocviewsublistbottom" style="display: block;" id="tocview_1"><table cellspacing="0" cellpadding="0"><tr><td align="right">10.1&nbsp;</td><td><a href="" class="tocviewselflink" data-pltdoc="x">Exceptions</a></td></tr><tr><td align="right">10.2&nbsp;</td><td><a href="prompt.html" class="tocviewlink" data-pltdoc="x">Prompts and Aborts</a></td></tr><tr><td align="right">10.3&nbsp;</td><td><a href="conts.html" class="tocviewlink" data-pltdoc="x">Continuations</a></td></tr></table></div></div></div></div><div class="maincolumn"><div class="main"><div class="navsettop"><span class="navleft"><form class="searchform"><input class="searchbox" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, &quot;6.1&quot;, &quot;../&quot;);" onfocus="this.style.color=&quot;black&quot;; this.style.textAlign=&quot;left&quot;; if (this.value == &quot;...search manuals...&quot;) this.value=&quot;&quot;;" onblur="if (this.value.match(/^ *$/)) { this.style.color=&quot;#888&quot;; this.style.textAlign=&quot;center&quot;; this.value=&quot;...search manuals...&quot;; }"/></form>&nbsp;&nbsp;<a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot(&quot;6.1&quot;);">top</a></span><span class="navright">&nbsp;&nbsp;<a href="control.html" title="backward to &quot;10 Exceptions and Control&quot;" data-pltdoc="x">&larr; prev</a>&nbsp;&nbsp;<a href="control.html" title="up to &quot;10 Exceptions and Control&quot;" data-pltdoc="x">up</a>&nbsp;&nbsp;<a href="prompt.html" title="forward to &quot;10.2 Prompts and Aborts&quot;" data-pltdoc="x">next &rarr;</a></span>&nbsp;</div><h4 x-source-module="(lib &quot;scribblings/guide/guide.scrbl&quot;)" x-part-tag="&quot;exns&quot;">10.1<tt>&nbsp;</tt><a name="(part._exns)"></a>Exceptions</h4><p>Whenever a run-time error occurs, an <a name="(tech._exception)"></a><span style="font-style: italic">exception</span> is
raised. Unless the exception is caught, then it is handled by printing
a message associated with the exception, and then escaping from the
computation.</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252F%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">/</a></span><span class="hspace">&nbsp;</span><span class="RktVal">1</span><span class="hspace">&nbsp;</span><span class="RktVal">0</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktErr">/: division by zero</span></p></td></tr><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=pairs.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._car%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">car</a></span><span class="hspace">&nbsp;</span><span class="RktVal">17</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktErr">car: contract violation</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktErr">expected: pair?</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktErr">given: 17</span></p></td></tr></table></blockquote><p>To catch an exception, use the <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span> form:</p><blockquote class="leftindent"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktVar">predicate-expr</span><span class="hspace">&nbsp;</span><span class="RktVar">handler-expr</span><span class="RktPn">]</span><span class="hspace">&nbsp;</span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">body</span><span class="hspace">&nbsp;</span><span class="RktMeta">...+</span><span class="RktPn">)</span></td></tr></table></td></tr></table></blockquote></blockquote><p>Each <span class="RktVar">predicate-expr</span> in a handler determines a kind of
exception that is caught by the <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span> form, and the
value representing the exception is passed to the handler procedure
produced by <span class="RktVar">handler-expr</span>.  The result of the
<span class="RktVar">handler-expr</span> is the result of the <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span>
expression.</p><p>For example, a divide-by-zero error raises an instance of the
<span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%7E3afail%7E3acontract%7E3adivide-by-zero%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail:contract:divide-by-zero</a></span> structure type:</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._exn%7E3afail%7E3acontract%7E3adivide-by-zero%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail:contract:divide-by-zero?</a></span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn</a></span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">+inf.0</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252F%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">/</a></span><span class="hspace">&nbsp;</span><span class="RktVal">1</span><span class="hspace">&nbsp;</span><span class="RktVal">0</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">+inf.0</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._exn%7E3afail%7E3acontract%7E3adivide-by-zero%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail:contract:divide-by-zero?</a></span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn</a></span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">+inf.0</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=pairs.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._car%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">car</a></span><span class="hspace">&nbsp;</span><span class="RktVal">17</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktErr">car: contract violation</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktErr">expected: pair?</span></p></td></tr><tr><td><p><span class="RktErr"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktErr">given: 17</span></p></td></tr></table></blockquote><p>The <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._error%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">error</a></span> function is one way to raise your own exception. It
packages an error message and other information into an
<span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%7E3afail%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail</a></span> structure:</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._error%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">error</a></span><span class="hspace">&nbsp;</span><span class="RktVal">"crash!"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktErr">crash!</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._exn%7E3afail%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn</a></span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">air-bag</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._error%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">error</a></span><span class="hspace">&nbsp;</span><span class="RktVal">"crash!"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'air-bag</span></p></td></tr></table></blockquote><p>The <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%7E3afail%7E3acontract%7E3adivide-by-zero%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail:contract:divide-by-zero</a></span> and <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%7E3afail%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail</a></span>
structure types are sub-types of the <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn</a></span> structure
type. Exceptions raised by core forms and functions always raise an
instance of <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn</a></span> or one of its sub-types, but an exception
does not have to be represented by a structure. The <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._raise%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">raise</a></span>
function lets you raise any value as an exception:</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._raise%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">raise</a></span><span class="hspace">&nbsp;</span><span class="RktVal">2</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktErr">uncaught exception: 2</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=booleans.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._equal%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">equal?</a></span><span class="hspace">&nbsp;</span><span class="RktSym">v</span><span class="hspace">&nbsp;</span><span class="RktVal">2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">two</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._raise%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">raise</a></span><span class="hspace">&nbsp;</span><span class="RktVal">2</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'two</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=booleans.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._equal%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">equal?</a></span><span class="hspace">&nbsp;</span><span class="RktSym">v</span><span class="hspace">&nbsp;</span><span class="RktVal">2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">two</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252F%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">/</a></span><span class="hspace">&nbsp;</span><span class="RktVal">1</span><span class="hspace">&nbsp;</span><span class="RktVal">0</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktErr">/: division by zero</span></p></td></tr></table></blockquote><p>Multiple <span class="RktVar">predicate-expr</span>s in a <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span> form
let you handle different kinds of exceptions in different ways. The
predicates are tried in order, and if none of them match, then the
exception is propagated to enclosing contexts.</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">always-fail</span><span class="hspace">&nbsp;</span><span class="RktSym">n</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=number-types.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._even%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">even?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">even</span><span class="RktPn">)</span><span class="RktPn">]</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=number-types.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._positive%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">positive?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">positive</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._raise%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">raise</a></span><span class="hspace">&nbsp;</span><span class="RktSym">n</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><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym">always-fail</span><span class="hspace">&nbsp;</span><span class="RktVal">2</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'even</span></p></td></tr><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym">always-fail</span><span class="hspace">&nbsp;</span><span class="RktVal">3</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'positive</span></p></td></tr><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym">always-fail</span><span class="hspace">&nbsp;</span><span class="RktVal"><span class="nobreak">-3</span></span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktErr">uncaught exception: -3</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=number-types.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._negative%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">negative?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">negative</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">always-fail</span><span class="hspace">&nbsp;</span><span class="RktVal"><span class="nobreak">-3</span></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'negative</span></p></td></tr></table></blockquote><p>Using <span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="stt"> </span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="stt"> </span><span class="RktVal">#t</span><span class="RktPn">)</span> as a predicate captures all exceptions, of course:</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">#t</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">oops</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=pairs.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._car%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">car</a></span><span class="hspace">&nbsp;</span><span class="RktVal">17</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'oops</span></p></td></tr></table></blockquote><p>Capturing all exceptions is usually a bad idea, however. If the user
types Ctl-C in a terminal window or clicks the <span class="ssansserif">Stop</span> button
in DrRacket to interrupt a computation, then normally the
<span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._exn%7E3abreak%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:break</a></span> exception should not be caught. To catch only
exceptions that represent errors, use <span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._exn%7E3afail%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail?</a></span> as the
predicate:</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._exn%7E3afail%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">oops</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=pairs.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._car%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">car</a></span><span class="hspace">&nbsp;</span><span class="RktVal">17</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'oops</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._with-handlers%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">with-handlers</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=exns.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._exn%7E3afail%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">exn:fail?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._lambda%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">lambda</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">oops</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=threads.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._break-thread%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">break-thread</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=threads.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-thread%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">current-thread</a></span><span class="RktPn">)</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktCmt">;</span><span class="RktCmt">&nbsp;</span><span class="RktCmt">simulate Ctl-C</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=pairs.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._car%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">car</a></span><span class="hspace">&nbsp;</span><span class="RktVal">17</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktErr">user break</span></p></td></tr></table></blockquote><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, &quot;6.1&quot;, &quot;../&quot;);" onfocus="this.style.color=&quot;black&quot;; this.style.textAlign=&quot;left&quot;; if (this.value == &quot;...search manuals...&quot;) this.value=&quot;&quot;;" onblur="if (this.value.match(/^ *$/)) { this.style.color=&quot;#888&quot;; this.style.textAlign=&quot;center&quot;; this.value=&quot;...search manuals...&quot;; }"/></form>&nbsp;&nbsp;<a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot(&quot;6.1&quot;);">top</a></span><span class="navright">&nbsp;&nbsp;<a href="control.html" title="backward to &quot;10 Exceptions and Control&quot;" data-pltdoc="x">&larr; prev</a>&nbsp;&nbsp;<a href="control.html" title="up to &quot;10 Exceptions and Control&quot;" data-pltdoc="x">up</a>&nbsp;&nbsp;<a href="prompt.html" title="forward to &quot;10.2 Prompts and Aborts&quot;" data-pltdoc="x">next &rarr;</a></span>&nbsp;</div></div></div><div id="contextindicator">&nbsp;</div></body></html>