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<html><head><title>bignum (Perl in a Nutshell, 2nd Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Stephen Spainhour" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="0596002416L" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl in a Nutshell, 2nd Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Java and XSLT" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_26.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch08_28.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.27. bignum</h2><p><a name="INDEX-1304" />Supportswhatever big numbers you give it, including large integers andfloats. In addition, bignum lets you specify options for the accuracyand precision of numbers that you'll calculate withit.</p><p>For example:</p><blockquote><pre class="code">#!/usr/local/bin/perl -wuse bignum;my $num1 = 4;my $num2 = 5;my $mult = $num1 * $num2; print sqrt($mult),"\n"; # Yup</pre></blockquote><p>For a number that would be large, you can usebignum's accuracy option, <tt class="literal">a</tt>, toset the number of places after the decimal:</p><blockquote><pre class="code">perl -Mbignum=a,50 -le 'print sqrt(20), "\n";'</pre></blockquote><p>If you wish to use rounding with bignum, you can use the precisionoption, <tt class="literal">p</tt>, with a <tt class="literal">0</tt> or<tt class="literal">1</tt> value to round up a value:</p><blockquote><pre class="code">perl -Mbignum=p,0 -le 'print sqrt(24), "\n";' # Gives 5</pre></blockquote><p>To enable tracing for bignum, use the <tt class="literal">t</tt> or<tt class="literal">trace</tt> options:</p><blockquote><pre class="code">/usr/local/perl5.8-prerc1/bin/perl5.7.3 -Mbignum=p,0,t -le 'print sqrt(24)'MBI import Math::BigInt::Trace :constant upgrade Math::BigFloat::Trace lib CalcMBF import Math::BigFloat::Trace :constant downgrade Math::BigInt::TraceMBI new '24' => '24' (Math::BigInt::Trace)MBF new '24' => '24' (Math::BigFloat)MBF new '4' => '4' (Math::BigFloat)MBF new '1E-4' => '0' (Math::BigFloat)MBI new '2' => '2' (Math::BigInt::Trace)MBF new '2' => '2' (Math::BigInt::Trace)MBI new '38' => '38' (Math::BigInt::Trace)MBI new '38' => '38' (Math::BigInt::Trace)</pre></blockquote><p>The <tt class="literal">l</tt>, or <tt class="literal">lib</tt>, option lets youspecify a different math library:</p><blockquote><pre class="code">perl -Mbignum=l,new_math_lib -e 'print $this ** $that'</pre></blockquote><p>The <tt class="literal">v</tt>, or <tt class="literal">version</tt>, option showsyou the version of all modules used by bignum and then exits.</p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_26.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch08_28.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.26. bigint</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">8.28. bigrat</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"><area shape="rect" coords="1,0,85,94" href="../index.htm"><area shape="rect" coords="86,1,178,103" href="../lwp/index.htm"><area shape="rect" coords="180,0,265,103" href="../lperl/index.htm"><area shape="rect" coords="267,0,353,105" href="../perlnut/index.htm"><area shape="rect" coords="354,1,446,115" href="../prog/index.htm"><area shape="rect" coords="448,0,526,132" href="../tk/index.htm"><area shape="rect" coords="528,1,615,119" href="../cookbook/index.htm"><area shape="rect" coords="617,0,690,135" href="../pxml/index.htm"></map></body></html>⌨️ 快捷键说明
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