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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_multiprecision.tut.ints.tom_int"></a><a class="link" href="tom_int.html" title="tom_int">tom_int</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">tommath</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">tommath_int</span><span class="special">;</span>
<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>
<span class="special">}}</span> <span class="comment">// namespaces</span>
</pre>
<p>
The <code class="computeroutput"><span class="identifier">tommath_int</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">tom_int</span></code>.
It acts as a thin wrapper around the <a href="http://libtom.org/?page=features&newsitems=5&whatfile=ltm" target="_top">libtommath</a>
<code class="computeroutput"><span class="identifier">tom_int</span></code> to provide an integer
type that is a drop-in replacement for the native C++ integer types, but
with unlimited precision.
</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 objects have the value zero (this is <a href="http://libtom.org/?page=features&newsitems=5&whatfile=ltm" target="_top">libtommath</a>'s
default behavior).
</li>
<li class="listitem">
Although <code class="computeroutput"><span class="identifier">tom_int</span></code> is
mostly a drop in replacement for the builtin integer types, it should
be noted that it is a rather strange beast as it's a signed type that
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>
exception if either of the arguments is negative. Similarly the complement
operator<code class="computeroutput"><span class="special">~</span></code> is deliberately
not implemented for this type.
</li>
<li class="listitem">
Formatted IO for this type does not support octal or hexadecimal notation
for negative values, as a result performing formatted output on this
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>
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>
will be 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 integer.
</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>
</ul></div>
<h6>
<a name="boost_multiprecision.tut.ints.tom_int.h0"></a>
<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>
</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">tommath</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="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>
<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">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>
<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>
<span class="keyword">try</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">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>
<span class="special">}</span>
<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>
<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">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>
<span class="special">}</span>
<span class="keyword">try</span><span class="special">{</span>
<span class="comment">// v is not a 2's complement type, bitwise operations are only supported</span>
<span class="comment">// on positive values:</span>
<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>
<span class="special">}</span>
<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>
<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">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>
<span class="special">}</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
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