1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>tommath_rational</title> 5<link rel="stylesheet" href="../../../multiprecision.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../index.html" title="Chapter 1. Boost.Multiprecision"> 8<link rel="up" href="../rational.html" title="Rational Number Types"> 9<link rel="prev" href="gmp_rational.html" title="gmp_rational"> 10<link rel="next" href="br.html" title="Use With Boost.Rational"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="gmp_rational.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../rational.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="br.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="boost_multiprecision.tut.rational.tommath_rational"></a><a class="link" href="tommath_rational.html" title="tommath_rational">tommath_rational</a> 28</h4></div></div></div> 29<p> 30 <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">multiprecision</span><span class="special">/</span><span class="identifier">tommath</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> 31 </p> 32<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">multiprecision</span><span class="special">{</span> 33 34<span class="keyword">typedef</span> <span class="identifier">rational_adpater</span><span class="special"><</span><span class="identifier">tommath_int</span><span class="special">></span> <span class="identifier">tommath_rational</span><span class="special">;</span> 35<span class="keyword">typedef</span> <span class="identifier">number</span><span class="special"><</span><span class="identifier">tommath_rational</span> <span class="special">></span> <span class="identifier">tom_rational</span><span class="special">;</span> 36 37<span class="special">}}</span> <span class="comment">// namespaces</span> 38</pre> 39<p> 40 The <code class="computeroutput"><span class="identifier">tommath_rational</span></code> back-end 41 is used via the typedef <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">multiprecision</span><span class="special">::</span><span class="identifier">tom_rational</span></code>. 42 It acts as a thin wrapper around <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">rational</span><span class="special"><</span><span class="identifier">tom_int</span><span class="special">></span></code> to provide a rational number type that 43 is a drop-in replacement for the native C++ number types, but with unlimited 44 precision. 45 </p> 46<p> 47 The advantage of using this type rather than <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">rational</span><span class="special"><</span><span class="identifier">tom_int</span><span class="special">></span></code> directly, is that it is expression-template 48 enabled, greatly reducing the number of temporaries created in complex 49 expressions. 50 </p> 51<p> 52 There are also non-member functions: 53 </p> 54<pre class="programlisting"><span class="identifier">tom_int</span> <span class="identifier">numerator</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">tom_rational</span><span class="special">&);</span> 55<span class="identifier">tom_int</span> <span class="identifier">denominator</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">tom_rational</span><span class="special">&);</span> 56</pre> 57<p> 58 which return the numerator and denominator of the number. 59 </p> 60<p> 61 Things you should know when using this type: 62 </p> 63<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 64<li class="listitem"> 65 Default constructed <code class="computeroutput"><span class="identifier">tom_rational</span></code>s 66 have the value zero (this the inherited Boost.Rational behavior). 67 </li> 68<li class="listitem"> 69 Division by zero results in a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">overflow_error</span></code> 70 being thrown. 71 </li> 72<li class="listitem"> 73 Conversion from a string results in a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">runtime_error</span></code> 74 being thrown if the string can not be interpreted as a valid rational 75 number. 76 </li> 77<li class="listitem"> 78 No changes are made to <a href="http://libtom.net" target="_top">libtommath</a>'s 79 global state, so this type can safely coexist with other <a href="http://libtom.net" target="_top">libtommath</a> 80 code. 81 </li> 82<li class="listitem"> 83 Performance of this type has been found to be pretty poor - this need 84 further investigation - but it appears that Boost.Rational needs some 85 improvement in this area. 86 </li> 87</ul></div> 88<h6> 89<a name="boost_multiprecision.tut.rational.tommath_rational.h0"></a> 90 <span class="phrase"><a name="boost_multiprecision.tut.rational.tommath_rational.example"></a></span><a class="link" href="tommath_rational.html#boost_multiprecision.tut.rational.tommath_rational.example">Example:</a> 91 </h6> 92<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">multiprecision</span><span class="special">/</span><span class="identifier">tommath</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 93<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 94 95<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> 96<span class="special">{</span> 97 <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">multiprecision</span><span class="special">;</span> 98 99 <span class="identifier">tom_rational</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> 100 101 <span class="comment">// Do some arithmetic:</span> 102 <span class="keyword">for</span><span class="special">(</span><span class="keyword">unsigned</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><=</span> <span class="number">1000</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> 103 <span class="identifier">v</span> <span class="special">*=</span> <span class="identifier">i</span><span class="special">;</span> 104 <span class="identifier">v</span> <span class="special">/=</span> <span class="number">10</span><span class="special">;</span> 105 106 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">v</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="comment">// prints 1000! / 10</span> 107 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">numerator</span><span class="special">(</span><span class="identifier">v</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 108 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">denominator</span><span class="special">(</span><span class="identifier">v</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 109 110 <span class="identifier">tom_rational</span> <span class="identifier">w</span><span class="special">(</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">);</span> <span class="comment">// Component wise constructor</span> 111 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">w</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="comment">// prints 2/3</span> 112 113 <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 114<span class="special">}</span> 115</pre> 116</div> 117<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 118<td align="left"></td> 119<td align="right"><div class="copyright-footer">Copyright © 2002-2020 John 120 Maddock and Christopher Kormanyos<p> 121 Distributed under the Boost Software License, Version 1.0. (See accompanying 122 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 123 </p> 124</div></td> 125</tr></table> 126<hr> 127<div class="spirit-nav"> 128<a accesskey="p" href="gmp_rational.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../rational.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="br.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 129</div> 130</body> 131</html> 132
