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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="boost_multiprecision.tut.ints.tom_int"></a><a class="link" href="tom_int.html" title="tom_int">tom_int</a>
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</h4></div></div></div>
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<p>
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<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>
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</p>
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<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>
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<span class="keyword">class</span> <span class="identifier">tommath_int</span><span class="special">;</span>
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<span class="keyword">typedef</span> <span class="identifier">number</span><span class="special"><</span><span class="identifier">tommath_int</span> <span class="special">></span> <span class="identifier">tom_int</span><span class="special">;</span>
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<span class="special">}}</span> <span class="comment">// namespaces</span>
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</pre>
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<p>
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The <code class="computeroutput"><span class="identifier">tommath_int</span></code> back-end
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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_int</span></code>.
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It acts as a thin wrapper around the <a href="http://libtom.net" target="_top">libtommath</a>
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<code class="computeroutput"><span class="identifier">tom_int</span></code> to provide an integer
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type that is a drop-in replacement for the native C++ integer types, but
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with unlimited precision.
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</p>
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<p>
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Things you should know when using this type:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
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<li class="listitem">
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Default constructed objects have the value zero (this is <a href="http://libtom.net" target="_top">libtommath</a>'s
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default behavior).
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</li>
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<li class="listitem">
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Although <code class="computeroutput"><span class="identifier">tom_int</span></code> is
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mostly a drop in replacement for the builtin integer types, it should
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be noted that it is a rather strange beast as it's a signed type that
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is not a 2's complement type. As a result the bitwise operations <code class="computeroutput"><span class="special">|</span> <span class="special">&</span> <span class="special">^</span></code> will throw a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">runtime_error</span></code>
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exception if either of the arguments is negative. Similarly the complement
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operator<code class="computeroutput"><span class="special">~</span></code> is deliberately
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not implemented for this type.
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</li>
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<li class="listitem">
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Formatted IO for this type does not support octal or hexadecimal notation
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for negative values, as a result performing formatted output on this
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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>
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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>
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will be thrown.
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</li>
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<li class="listitem">
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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>
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being thrown if the string can not be interpreted as a valid integer.
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</li>
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<li class="listitem">
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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>
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being thrown.
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</li>
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</ul></div>
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<h6>
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<a name="boost_multiprecision.tut.ints.tom_int.h0"></a>
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<span class="phrase"><a name="boost_multiprecision.tut.ints.tom_int.example"></a></span><a class="link" href="tom_int.html#boost_multiprecision.tut.ints.tom_int.example">Example:</a>
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</h6>
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<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>
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<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span>
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<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
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<span class="special">{</span>
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<span class="identifier">boost</span><span class="special">::</span><span class="identifier">multiprecision</span><span class="special">::</span><span class="identifier">tom_int</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>
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<span class="comment">// Do some arithmetic:</span>
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<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>
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<span class="identifier">v</span> <span class="special">*=</span> <span class="identifier">i</span><span class="special">;</span>
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<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!</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">hex</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! in hex format</span>
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<span class="keyword">try</span><span class="special">{</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">hex</span> <span class="special"><<</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">// Ooops! can't print a negative value in hex format!</span>
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<span class="special">}</span>
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<span class="keyword">catch</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">runtime_error</span><span class="special">&</span> <span class="identifier">e</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">what</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>
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<span class="special">}</span>
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<span class="keyword">try</span><span class="special">{</span>
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<span class="comment">// v is not a 2's complement type, bitwise operations are only supported</span>
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<span class="comment">// on positive values:</span>
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<span class="identifier">v</span> <span class="special">=</span> <span class="special">-</span><span class="identifier">v</span> <span class="special">&</span> <span class="number">2</span><span class="special">;</span>
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<span class="special">}</span>
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<span class="keyword">catch</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">runtime_error</span><span class="special">&</span> <span class="identifier">e</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">e</span><span class="special">.</span><span class="identifier">what</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>
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<span class="special">}</span>
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<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
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<span class="special">}</span>
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</pre>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2002-2019 John Maddock
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and Christopher Kormanyos<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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