19 lines
2.9 KiB
HTML
19 lines
2.9 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>snap</title><link rel="stylesheet" href="../../jargon.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.61.0"/><link rel="home" href="../index.html" title="The Jargon File"/><link rel="up" href="../S.html" title="S"/><link rel="previous" href="snail-mail.html" title="snail-mail"/><link rel="next" href="snarf.html" title="snarf"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">snap</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="snail-mail.html">Prev</a> </td><th width="60%" align="center">S</th><td width="20%" align="right"> <a accesskey="n" href="snarf.html">Next</a></td></tr></table><hr/></div><dt><a id="snap"/><dt xmlns="" id="snap"><b>snap</b>: <span xmlns="http://www.w3.org/1999/xhtml" class="grammar">v.</span></dt></dt><dd><p> To replace a pointer to a pointer with a direct pointer; to replace
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an old address with the forwarding address found there. If you telephone
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the main number for an institution and ask for a particular person by name,
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the operator may tell you that person's extension before connecting you, in
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the hopes that you will <span class="firstterm">snap your
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pointer</span> and dial direct next time. The underlying metaphor may
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be that of a rubber band stretched through a number of intermediate points;
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if you remove all the thumbtacks in the middle, it snaps into a straight
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line from first to last. See <a href="../C/chase-pointers.html"><i class="glossterm">chase pointers</i></a>.</p><p>Often, the behavior of a <a href="../T/trampoline.html"><i class="glossterm">trampoline</i></a> is to
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perform an error check once and then snap the pointer that invoked it so as
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henceforth to bypass the trampoline (and its one-shot error check). In
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this context one also speaks of <span class="firstterm">snapping
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links</span>. For example, in a LISP implementation, a function
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interface trampoline might check to make sure that the caller is passing
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the correct number of arguments; if it is, and if the caller and the callee
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are both compiled, then snapping the link allows that particular path to
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use a direct procedure-call instruction with no further overhead.</p></dd><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="snail-mail.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="../S.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="snarf.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">snail-mail </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> snarf</td></tr></table></div></body></html>
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