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<html><head><title>Equality 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="Equality 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_11.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_13.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">3.12. Equality Operators</h2><p><a name="INDEX-943"></a><a name="INDEX-944"></a><a name="INDEX-945"></a><a name="INDEX-946"></a><a name="INDEX-947"></a><a name="INDEX-948"></a><a name="INDEX-949"></a><a name="INDEX-950"></a><a name="INDEX-951"></a> The equality operators listed in<a href="ch03_12.htm#perl3-tab-equality">Table 3-6</a> are much like the relationaloperators.</p><a name="perl3-tab-equality"></a><h4 class="objtitle">Table 3.6. Equality 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">eq</tt></td><td>Equal to</td></tr><tr><td><tt class="literal">!=</tt></td><td><tt class="literal">ne</tt></td><td>Not equal to</td></tr><tr><td><tt class="literal"><=></tt></td><td><tt class="literal">cmp</tt></td><td>Comparison, with signed result</td></tr></table><p>The equal and not-equal operators return <tt class="literal">1</tt> for true and <tt class="literal">""</tt> forfalse (just as the relational operators do). The <tt class="literal"><=></tt> and <tt class="literal">cmp</tt>operators return <tt class="literal">-1</tt> if the left operand is less than the right operand,<tt class="literal">0</tt> if they are equal, and <tt class="literal">+1</tt> if the left operand is greater than theright. Although the equality operators appear to be similar tothe relational operators, they do have a lower precedence level, so<tt class="literal">$a < $b <=> $c < $d</tt> is syntactically valid.</p><p><a name="INDEX-952"></a>For reasons that are apparent to anyone who has seen <em class="citetitle">Star Wars</em>, the <tt class="literal"><=></tt> operator is known as the "spaceship"operator.</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_11.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_13.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr><tr><td align="left" valign="top" width="172">3.11. Relational 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">3.13. Bitwise 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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