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| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_multiprecision.tut.rational.gmp_rational"></a><a class="link" href="gmp_rational.html" title="gmp_rational">gmp_rational</a> |
| </h4></div></div></div> |
| <p> |
| <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">gmp</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> |
| </p> |
| <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> |
| |
| <span class="keyword">class</span> <span class="identifier">gmp_rational</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">number</span><span class="special"><</span><span class="identifier">gmp_rational</span> <span class="special">></span> <span class="identifier">mpq_rational</span><span class="special">;</span> |
| |
| <span class="special">}}</span> <span class="comment">// namespaces</span> |
| </pre> |
| <p> |
| The <code class="computeroutput"><span class="identifier">gmp_rational</span></code> back-end |
| 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>. |
| It acts as a thin wrapper around the <a href="http://gmplib.org" target="_top">GMP</a> |
| <code class="computeroutput"><span class="identifier">mpq_t</span></code> to provide a rational |
| number type that is a drop-in replacement for the native C++ number types, |
| but with unlimited precision. |
| </p> |
| <p> |
| As well as the usual conversions from arithmetic and string types, instances |
| of <code class="computeroutput"><span class="identifier">number</span><span class="special"><</span><span class="identifier">gmp_rational</span><span class="special">></span></code> |
| are copy constructible and assignable from: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| 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>. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">number</span><span class="special"><</span><span class="identifier">gmp_int</span><span class="special">></span></code>. |
| </li> |
| </ul></div> |
| <p> |
| There is also a two-argument constructor that accepts a numerator and denominator |
| (both of type <code class="computeroutput"><span class="identifier">number</span><span class="special"><</span><span class="identifier">gmp_int</span><span class="special">></span></code>). |
| </p> |
| <p> |
| There are also non-member functions: |
| </p> |
| <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">&);</span> |
| <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">&);</span> |
| </pre> |
| <p> |
| which return the numerator and denominator of the number. |
| </p> |
| <p> |
| It's also possible to access the underlying <code class="computeroutput"><span class="identifier">mpq_t</span></code> |
| via the <code class="computeroutput"><span class="identifier">data</span><span class="special">()</span></code> |
| member function of <code class="computeroutput"><span class="identifier">mpq_rational</span></code>. |
| </p> |
| <p> |
| Things you should know when using this type: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| Default constructed <code class="computeroutput"><span class="identifier">mpq_rational</span></code>s |
| have the value zero (this is the <a href="http://gmplib.org" target="_top">GMP</a> |
| default behavior). |
| </li> |
| <li class="listitem"> |
| 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> |
| being thrown. |
| </li> |
| <li class="listitem"> |
| 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> |
| being thrown if the string can not be interpreted as a valid rational |
| number. |
| </li> |
| <li class="listitem"> |
| No changes are made to the <a href="http://gmplib.org" target="_top">GMP</a> |
| library's global settings, so this type can coexist with existing |
| <a href="http://gmplib.org" target="_top">GMP</a> code. |
| </li> |
| <li class="listitem"> |
| The code can equally be used with <a href="http://mpir.org/" target="_top">MPIR</a> |
| as the underlying library - indeed that is the preferred option on |
| Win32. |
| </li> |
| </ul></div> |
| <h6> |
| <a name="boost_multiprecision.tut.rational.gmp_rational.h0"></a> |
| <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> |
| </h6> |
| <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">gmp</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <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">gmp</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <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> |
| |
| <span class="identifier">mpq_rational</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> |
| |
| <span class="comment">// Do some arithmetic:</span> |
| <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> |
| <span class="identifier">v</span> <span class="special">*=</span> <span class="identifier">i</span><span class="special">;</span> |
| <span class="identifier">v</span> <span class="special">/=</span> <span class="number">10</span><span class="special">;</span> |
| |
| <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> |
| <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> |
| <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> |
| |
| <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> |
| <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> |
| |
| <span class="comment">// Access the underlying data:</span> |
| <span class="identifier">mpq_t</span> <span class="identifier">q</span><span class="special">;</span> |
| <span class="identifier">mpq_init</span><span class="special">(</span><span class="identifier">q</span><span class="special">);</span> |
| <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> |
| <span class="identifier">mpq_clear</span><span class="special">(</span><span class="identifier">q</span><span class="special">);</span> |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| </div> |
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| <td align="right"><div class="copyright-footer">Copyright © 2002-2013 John Maddock and Christopher Kormanyos<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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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