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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN"><!-- This collection of hypertext pages is Copyright 1995-2005 by Steve Summit. --><!-- Content from the book "C Programming FAQs: Frequently Asked Questions" --><!-- (Addison-Wesley, 1995, ISBN 0-201-84519-9) is made available here by --><!-- permission of the author and the publisher as a service to the community. --><!-- It is intended to complement the use of the published text --><!-- and is protected by international copyright laws. --><!-- The on-line content may be accessed freely for personal use --><!-- but may not be published or retransmitted without explicit permission. --><!-- --><!-- this page built Sat Dec 24 21:47:47 2005 by faqproc version 2.7 --><!-- from source file misclang.sgml dated Wed Dec 21 13:02:49 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/misc/multibreak.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:05 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 20.20b</title><link href="nestcomment.html" rev=precedes><link href="funkyasgnop.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="nestcomment.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="funkyasgnop.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../index-2.html"><img src="../images/buttontop.gif" alt="top/contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><hr><p><!-- qbegin --><h1>comp.lang.c FAQ list<font color=blue>·</font><!-- qtag -->Question 20.20b</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>Why isn't there a numbered, multi-level <TT>break</TT> statementto break out of several loops at once?What am I supposed to use instead, a <TT>goto</TT>?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>First, remember why it is that <TT>break</TT> and <TT>continue</TT>exist at all--they are,in effect, ``structured <TT>goto</TT>s''used in preference to <TT>goto</TT>(and accepted as alternatives by most of those who shun <TT>goto</TT>)because they are clean and structured andpretty muchrestricted to a common, idiomatic usages.A hypothetical multi-level <TT>break</TT>, on the other hand,would rapidly lose the inherent cleanliness of the single<TT>break</TT>--programmers and readers of codewould have to carefully count nesting levelsto figure out what a given <TT>break</TT> did,and the insertion of a new intermediately-nested loopcould, er, break things badly.(By this analysis,a numbered <TT>break</TT> statement canbe even more confusing and error-prone than a <TT>goto</TT>/label pair.)</p><p>The right way to break out of several loops at once(which C also does not have)involves a syntax which allows the naming of loops,so that a <TT>break</TT> statement can specifythe name of the loop to be broken out of.</p><p>If you do have to break out of more than one loop at once(or break out of a loop from inside a switch,where <TT>break</TT> would merely end a <TT>case</TT> label)yes, go ahead and use a <TT>goto</TT>.(But when you find the need for a multi-level break,it's often a sign that the loop should be broken out to its own function,at which point you can achieve roughly the same effectas that multi-level breakby using a premature return.)</p><!-- aend --><p><hr><a href="nestcomment.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="funkyasgnop.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../questions.html"><img src="../images/buttontop.gif" alt="contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><br><!-- lastfooter --><a href="../about.html">about this FAQ list</a> <a href="../eskimo.html">about eskimo</a> <a href="../search.html">search</a> <a href="../feedback.html">feedback</a> <a href="copyright.html">copyright</a><p>Hosted by<a href="http://www.eskimo.com/"><img src="../../www.eskimo.com/img/link/eskitiny.gif" alt="Eskimo North"></a></body><!-- Mirrored from c-faq.com/misc/multibreak.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:05 GMT --></html>⌨️ 快捷键说明
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