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<html><head><title>Relational Operators (Programming Perl)</title><!-- STYLESHEET --><link rel="stylesheet" type="text/css" href="../style/style1.css"><!-- METADATA --><!--Dublin Core Metadata--><meta name="DC.Creator" content=""><meta name="DC.Date" content=""><meta name="DC.Format" content="text/xml" scheme="MIME"><meta name="DC.Generator" content="XSLT stylesheet, xt by James Clark"><meta name="DC.Identifier" content=""><meta name="DC.Language" content="en-US"><meta name="DC.Publisher" content="O'Reilly & Associates, Inc."><meta name="DC.Source" content="" scheme="ISBN"><meta name="DC.Subject.Keyword" content=""><meta name="DC.Title" content="Relational Operators"><meta name="DC.Type" content="Text.Monograph"></head><body><!-- START OF BODY --><!-- TOP BANNER --><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home"><map name="banner-map"><AREA SHAPE="RECT" COORDS="0,0,466,71" HREF="index.htm" ALT="Programming Perl"><AREA SHAPE="RECT" COORDS="467,0,514,18" HREF="jobjects/fsearch.htm" ALT="Search this book"></map><!-- TOP NAV BAR --><div class="navbar"><table width="515" border="0"><tr><td align="left" valign="top" width="172"><a href="ch03_10.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0"></a></td><td align="center" valign="top" width="171"><a href="ch03_01.htm">Chapter 3: Unary and Binary Operators</a></td><td align="right" valign="top" width="172"><a href="ch03_12.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr></table></div><hr width="515" align="left"><!-- SECTION BODY --><h2 class="sect1">3.11. Relational Operators</h2><p><a name="INDEX-928"></a><a name="INDEX-929"></a><a name="INDEX-930"></a><a name="INDEX-931"></a><a name="INDEX-932"></a><a name="INDEX-933"></a><a name="INDEX-934"></a><a name="INDEX-935"></a><a name="INDEX-936"></a>Perl has two classes of relational operators. One class operates onnumeric values, the other on string values, as shown in<a href="ch03_11.htm#perl3-tab-relational">Table 3-5</a>.</p><a name="perl3-tab-relational"></a><h4 class="objtitle">Table 3.5. Relational Operators</h4><table border="1"><tr><th>Numeric</th><th>String</th><th>Meaning</th></tr><tr><td><tt class="literal"> ></tt></td><td><tt class="literal">gt</tt></td><td>Greater than</td></tr><tr><td><tt class="literal"> >=</tt></td><td><tt class="literal">ge</tt></td><td>Greater than or equal to</td></tr><tr><td><tt class="literal"> <</tt></td><td><tt class="literal">lt</tt></td><td>Less than</td></tr><tr><td><tt class="literal"> <=</tt></td><td><tt class="literal">le</tt></td><td>Less than or equal to</td></tr></table><p><a name="INDEX-937"></a><a name="INDEX-938"></a>These operators return <tt class="literal">1</tt> for true and<tt class="literal">""</tt> for false. Note that relational operators arenonassociating, which means that <tt class="literal">$a < $b < $c</tt> is a syntax error.</p><p><a name="INDEX-939"></a><a name="INDEX-940"></a><a name="INDEX-941"></a><a name="INDEX-942"></a>In the absence of locale declarations, string comparisons are based onthe ASCII/Unicode collating sequences, and, unlike in some computerlanguages,trailing spaces count in the comparison. With a localedeclaration, the collation order specified by the locale is used.(Locale-based collation mechanisms may or may not interact well withthe Unicode collation mechanisms currently indevelopment.)</p><!-- BOTTOM NAV BAR --><hr width="515" align="left"><div class="navbar"><table width="515" border="0"><tr><td align="left" valign="top" width="172"><a href="ch03_10.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0"></a></td><td align="center" valign="top" width="171"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0"></a></td><td align="right" valign="top" width="172"><a href="ch03_12.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr><tr><td align="left" valign="top" width="172">3.10. Named Unary and File Test Operators</td><td align="center" valign="top" width="171"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0"></a></td><td align="right" valign="top" width="172">3.12. Equality Operators</td></tr></table></div><hr width="515" align="left"><!-- LIBRARY NAV BAR --><img src="../gifs/smnavbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links"><p><font size="-1"><a href="copyrght.htm">Copyright © 2001</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"> <area shape="rect" coords="2,-1,79,99" href="../index.htm"><area shape="rect" coords="84,1,157,108" href="../perlnut/index.htm"><area shape="rect" coords="162,2,248,125" href="../prog/index.htm"><area shape="rect" coords="253,2,326,130" href="../advprog/index.htm"><area shape="rect" coords="332,1,407,112" href="../cookbook/index.htm"><area shape="rect" coords="414,2,523,103" href="../sysadmin/index.htm"></map><!-- END OF BODY --></body></html>⌨️ 快捷键说明
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