ceph/src/boost/libs/multiprecision/doc/html/boost_multiprecision/tut/rational/gmp_rational.html

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  25 <div class="section">
  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_multiprecision.tut.rational.gmp_rational"></a><a class="link" href="gmp_rational.html" title="gmp_rational">gmp_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">gmp</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">class</span> <span class="identifier">gmp_rational</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">gmp_rational</span> <span class="special">&gt;</span>         <span class="identifier">mpq_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">gmp_rational</span></code> back-end
  42           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">mpq_rational</span></code>.
  43           It acts as a thin wrapper around the <a href="http://gmplib.org" target="_top">GMP</a>
  44           <code class="computeroutput"><span class="identifier">mpq_t</span></code> to provide a rational
  45           number type that is a drop-in replacement for the native C++ number types,
  46           but with unlimited precision.
  47         </p>
  48 <p>
  49           As well as the usual conversions from arithmetic and string types, instances
  50           of <code class="computeroutput"><span class="identifier">number</span><span class="special">&lt;</span><span class="identifier">gmp_rational</span><span class="special">&gt;</span></code>
  51           are copy constructible and assignable from:
  52         </p>
  53 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  54 <li class="listitem">
  55               The <a href="http://gmplib.org" target="_top">GMP</a> native types: <code class="computeroutput"><span class="identifier">mpz_t</span></code>, <code class="computeroutput"><span class="identifier">mpq_t</span></code>.
  56             </li>
  57 <li class="listitem">
  58               <code class="computeroutput"><span class="identifier">number</span><span class="special">&lt;</span><span class="identifier">gmp_int</span><span class="special">&gt;</span></code>.
  59             </li>
  60 </ul></div>
  61 <p>
  62           There is also a two-argument constructor that accepts a numerator and denominator
  63           (both of type <code class="computeroutput"><span class="identifier">number</span><span class="special">&lt;</span><span class="identifier">gmp_int</span><span class="special">&gt;</span></code>).
  64         </p>
  65 <p>
  66           There are also non-member functions:
  67         </p>
  68 <pre class="programlisting"><span class="identifier">mpz_int</span> <span class="identifier">numerator</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">mpq_rational</span><span class="special">&amp;);</span>
  69 <span class="identifier">mpz_int</span> <span class="identifier">denominator</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">mpq_rational</span><span class="special">&amp;);</span>
  70 </pre>
  71 <p>
  72           which return the numerator and denominator of the number.
  73         </p>
  74 <p>
  75           It's also possible to access the underlying <code class="computeroutput"><span class="identifier">mpq_t</span></code>
  76           via the <code class="computeroutput"><span class="identifier">data</span><span class="special">()</span></code>
  77           member function of <code class="computeroutput"><span class="identifier">mpq_rational</span></code>.
  78         </p>
  79 <p>
  80           Things you should know when using this type:
  81         </p>
  82 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  83 <li class="listitem">
  84               Default constructed <code class="computeroutput"><span class="identifier">mpq_rational</span></code>s
  85               have the value zero (this is the <a href="http://gmplib.org" target="_top">GMP</a>
  86               default behavior).
  87             </li>
  88 <li class="listitem">
  89               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>
  90               being thrown.
  91             </li>
  92 <li class="listitem">
  93               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>
  94               being thrown if the string can not be interpreted as a valid rational
  95               number.
  96             </li>
  97 <li class="listitem">
  98               No changes are made to the <a href="http://gmplib.org" target="_top">GMP</a>
  99               library's global settings, so this type can coexist with existing
 100               <a href="http://gmplib.org" target="_top">GMP</a> code.
 101             </li>
 102 <li class="listitem">
 103               The code can equally be used with <a href="http://mpir.org/" target="_top">MPIR</a>
 104               as the underlying library - indeed that is the preferred option on
 105               Win32.
 106             </li>
 107 </ul></div>
 108 <h6>
 109 <a name="boost_multiprecision.tut.rational.gmp_rational.h0"></a>
 110           <span class="phrase"><a name="boost_multiprecision.tut.rational.gmp_rational.example"></a></span><a class="link" href="gmp_rational.html#boost_multiprecision.tut.rational.gmp_rational.example">Example:</a>
 111         </h6>
 112 <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">gmp</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 113 <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">gmp</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 114 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 115
 116 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
 117 <span class="special">{</span>
 118    <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>
 119
 120    <span class="identifier">mpq_rational</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>
 121
 122    <span class="comment">// Do some arithmetic:</span>
 123    <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>
 124       <span class="identifier">v</span> <span class="special">*=</span> <span class="identifier">i</span><span class="special">;</span>
 125    <span class="identifier">v</span> <span class="special">/=</span> <span class="number">10</span><span class="special">;</span>
 126
 127    <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>
 128    <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>
 129    <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>
 130
 131    <span class="identifier">mpq_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>
 132    <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>
 133
 134    <span class="comment">// Access the underlying data:</span>
 135    <span class="identifier">mpq_t</span> <span class="identifier">q</span><span class="special">;</span>
 136    <span class="identifier">mpq_init</span><span class="special">(</span><span class="identifier">q</span><span class="special">);</span>
 137    <span class="identifier">mpq_set</span><span class="special">(</span><span class="identifier">q</span><span class="special">,</span> <span class="identifier">v</span><span class="special">.</span><span class="identifier">backend</span><span class="special">().</span><span class="identifier">data</span><span class="special">());</span>
 138    <span class="identifier">mpq_clear</span><span class="special">(</span><span class="identifier">q</span><span class="special">);</span>
 139    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 140 <span class="special">}</span>
 141 </pre>
 142 </div>
 143 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 144 <td align="left"></td>
 145 <td align="right"><div class="copyright-footer">Copyright &#169; 2002-2013 John Maddock and Christopher Kormanyos<p>
 146         Distributed under the Boost Software License, Version 1.0. (See accompanying
 147         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>)
 148       </p>
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