ceph/src/boost/libs/multiprecision/doc/html/boost_multiprecision/tut/ints/gmp_int.html

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  25 <div class="section">
  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_multiprecision.tut.ints.gmp_int"></a><a class="link" href="gmp_int.html" title="gmp_int">gmp_int</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_int</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_int</span> <span class="special">&gt;</span>         <span class="identifier">mpz_int</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_int</span></code> back-end is
  42           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">mpz_int</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">mpz_t</span></code> to provide an integer
  45           type that is a drop-in replacement for the native C++ integer types, but
  46           with unlimited precision.
  47         </p>
  48 <p>
  49           As well as the usual conversions from arithmetic and string types, type
  50           <code class="computeroutput"><span class="identifier">mpz_int</span></code> is copy constructible
  51           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">mpf_t</span></code>, <code class="computeroutput"><span class="identifier">mpz_t</span></code>,
  56               <code class="computeroutput"><span class="identifier">mpq_t</span></code>.
  57             </li>
  58 <li class="listitem">
  59               Instances of <code class="computeroutput"><span class="identifier">number</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> that are wrappers around those
  60               types: <code class="computeroutput"><span class="identifier">number</span><span class="special">&lt;</span><span class="identifier">gmp_float</span><span class="special">&lt;</span><span class="identifier">N</span><span class="special">&gt;</span> <span class="special">&gt;</span></code>, <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>.
  61             </li>
  62 </ul></div>
  63 <p>
  64           It's also possible to access the underlying <code class="computeroutput"><span class="identifier">mpz_t</span></code>
  65           via the <code class="computeroutput"><span class="identifier">data</span><span class="special">()</span></code>
  66           member function of <code class="computeroutput"><span class="identifier">gmp_int</span></code>.
  67         </p>
  68 <p>
  69           Things you should know when using this type:
  70         </p>
  71 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  72 <li class="listitem">
  73               No changes are made to the GMP library's global settings - so you can
  74               safely mix this type with existing code that uses <a href="http://gmplib.org" target="_top">GMP</a>.
  75             </li>
  76 <li class="listitem">
  77               Default constructed <code class="computeroutput"><span class="identifier">gmp_int</span></code>s
  78               have the value zero (this is GMP's default behavior).
  79             </li>
  80 <li class="listitem">
  81               Formatted IO for this type does not support octal or hexadecimal notation
  82               for negative values, as a result performing formatted output on this
  83               type when the argument is negative and either of the flags <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ios_base</span><span class="special">::</span><span class="identifier">oct</span></code> or <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ios_base</span><span class="special">::</span><span class="identifier">hex</span></code>
  84               are set, will result in a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">runtime_error</span></code>
  85               will be thrown.
  86             </li>
  87 <li class="listitem">
  88               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>
  89               being thrown if the string can not be interpreted as a valid integer.
  90             </li>
  91 <li class="listitem">
  92               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>
  93               being thrown.
  94             </li>
  95 <li class="listitem">
  96               Although this type is a wrapper around <a href="http://gmplib.org" target="_top">GMP</a>
  97               it will work equally well with <a href="http://mpir.org/" target="_top">MPIR</a>.
  98               Indeed use of <a href="http://mpir.org/" target="_top">MPIR</a> is recommended
  99               on Win32.
 100             </li>
 101 <li class="listitem">
 102               This backend supports rvalue-references and is move-aware, making instantiations
 103               of <code class="computeroutput"><span class="identifier">number</span></code> on this backend
 104               move aware.
 105             </li>
 106 </ul></div>
 107 <h6>
 108 <a name="boost_multiprecision.tut.ints.gmp_int.h0"></a>
 109           <span class="phrase"><a name="boost_multiprecision.tut.ints.gmp_int.example"></a></span><a class="link" href="gmp_int.html#boost_multiprecision.tut.ints.gmp_int.example">Example:</a>
 110         </h6>
 111 <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>
 112 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 113
 114 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
 115 <span class="special">{</span>
 116    <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>
 117
 118    <span class="identifier">mpz_int</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>
 119
 120    <span class="comment">// Do some arithmetic:</span>
 121    <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>
 122       <span class="identifier">v</span> <span class="special">*=</span> <span class="identifier">i</span><span class="special">;</span>
 123
 124    <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!</span>
 125
 126    <span class="comment">// Access the underlying representation:</span>
 127    <span class="identifier">mpz_t</span> <span class="identifier">z</span><span class="special">;</span>
 128    <span class="identifier">mpz_init</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
 129    <span class="identifier">mpz_set</span><span class="special">(</span><span class="identifier">z</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>
 130    <span class="identifier">mpz_clear</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
 131    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 132 <span class="special">}</span>
 133 </pre>
 134 </div>
 135 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 136 <td align="left"></td>
 137 <td align="right"><div class="copyright-footer">Copyright &#169; 2002-2013 John Maddock and Christopher Kormanyos<p>
 138         Distributed under the Boost Software License, Version 1.0. (See accompanying
 139         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>)
 140       </p>
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