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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_multiprecision.tut.rational.cpp_rational"></a><a class="link" href="cpp_rational.html" title="cpp_rational">cpp_rational</a>
  28 </h4></div></div></div>
  29 <p>
  30           <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">multiprecision</span><span class="special">/</span><span class="identifier">cpp_int</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</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_adaptor</span><span class="special">&lt;</span><span class="identifier">cpp_int_backend</span><span class="special">&lt;&gt;</span> <span class="special">&gt;</span>    <span class="identifier">cpp_rational_backend</span><span class="special">;</span>
  35
  36 <span class="keyword">typedef</span> <span class="identifier">number</span><span class="special">&lt;</span><span class="identifier">cpp_rational_backend</span><span class="special">&gt;</span>         <span class="identifier">cpp_rational</span><span class="special">;</span>
  37
  38 <span class="special">}}</span> <span class="comment">// namespaces</span>
  39 </pre>
  40 <p>
  41           The <code class="computeroutput"><span class="identifier">cpp_rational_backend</span></code>
  42           type 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">cpp_rational</span></code>.
  43           It provides a rational number type that is a drop-in replacement for the
  44           native C++ number types, but with unlimited precision.
  45         </p>
  46 <p>
  47           As well as the usual conversions from arithmetic and string types, instances
  48           of <code class="computeroutput"><span class="identifier">cpp_rational</span></code> are copy
  49           constructible and assignable from type <code class="computeroutput"><span class="identifier">cpp_int</span></code>.
  50         </p>
  51 <p>
  52           There is also a two argument constructor that accepts a numerator and denominator:
  53           both of type <code class="computeroutput"><span class="identifier">cpp_int</span></code>.
  54         </p>
  55 <p>
  56           There are also non-member functions:
  57         </p>
  58 <pre class="programlisting"><span class="identifier">cpp_int</span> <span class="identifier">numerator</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">cpp_rational</span><span class="special">&amp;);</span>
  59 <span class="identifier">cpp_int</span> <span class="identifier">denominator</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">cpp_rational</span><span class="special">&amp;);</span>
  60 </pre>
  61 <p>
  62           which return the numerator and denominator of the number.
  63         </p>
  64 <p>
  65           Things you should know when using this type:
  66         </p>
  67 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  68 <li class="listitem">
  69               Default constructed <code class="computeroutput"><span class="identifier">cpp_rational</span></code>s
  70               have the value zero.
  71             </li>
  72 <li class="listitem">
  73               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>
  74               being thrown.
  75             </li>
  76 <li class="listitem">
  77               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>
  78               being thrown if the string can not be interpreted as a valid rational
  79               number.
  80             </li>
  81 </ul></div>
  82 <h6>
  83 <a name="boost_multiprecision.tut.rational.cpp_rational.h0"></a>
  84           <span class="phrase"><a name="boost_multiprecision.tut.rational.cpp_rational.example"></a></span><a class="link" href="cpp_rational.html#boost_multiprecision.tut.rational.cpp_rational.example">Example:</a>
  85         </h6>
  86 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">multiprecision</span><span class="special">/</span><span class="identifier">cpp_int</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  87 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
  88
  89 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
  90 <span class="special">{</span>
  91    <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>
  92
  93    <span class="identifier">cpp_rational</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>
  94
  95    <span class="comment">// Do some arithmetic:</span>
  96    <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">&lt;=</span> <span class="number">1000</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span>
  97       <span class="identifier">v</span> <span class="special">*=</span> <span class="identifier">i</span><span class="special">;</span>
  98    <span class="identifier">v</span> <span class="special">/=</span> <span class="number">10</span><span class="special">;</span>
  99
 100    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">v</span> <span class="special">&lt;&lt;</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>
 101    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">numerator</span><span class="special">(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 102    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">denominator</span><span class="special">(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 103
 104    <span class="identifier">cpp_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>
 105    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">w</span> <span class="special">&lt;&lt;</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>
 106    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 107 <span class="special">}</span>
 108 </pre>
 109 </div>
 110 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 111 <td align="left"></td>
 112 <td align="right"><div class="copyright-footer">Copyright &#169; 2002-2019 John Maddock
 113       and Christopher Kormanyos<p>
 114         Distributed under the Boost Software License, Version 1.0. (See accompanying
 115         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>)
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