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- <div class="section">
- <div class="titlepage"><div><div><h2 class="title" style="clear: both">
- <a name="boost_integer.integer"></a><a class="link" href="integer.html" title="Integer Type Selection">Integer Type Selection</a>
- </h2></div></div></div>
- <div class="toc"><dl class="toc">
- <dt><span class="section"><a href="integer.html#boost_integer.integer.synopsis">Synopsis</a></span></dt>
- <dt><span class="section"><a href="integer.html#boost_integer.integer.easiest">Easiest-to-Manipulate
- Types</a></span></dt>
- <dt><span class="section"><a href="integer.html#boost_integer.integer.sized">Sized Types</a></span></dt>
- <dt><span class="section"><a href="integer.html#boost_integer.integer.example">Example</a></span></dt>
- <dt><span class="section"><a href="integer.html#boost_integer.integer.demonstration_program">Demonstration
- Program</a></span></dt>
- <dt><span class="section"><a href="integer.html#boost_integer.integer.rationale">Rationale</a></span></dt>
- <dt><span class="section"><a href="integer.html#boost_integer.integer.alternative">Alternative</a></span></dt>
- <dt><span class="section"><a href="integer.html#boost_integer.integer.credits">Credits</a></span></dt>
- </dl></div>
- <p>
- The <a href="../../../../../boost/integer.hpp" target="_top"><boost/integer.hpp></a>
- type selection templates allow integer types to be selected based on desired
- characteristics such as number of bits or maximum value. This facility is particularly
- useful for solving generic programming problems.
- </p>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.synopsis"></a><a class="link" href="integer.html#boost_integer.integer.synopsis" title="Synopsis">Synopsis</a>
- </h3></div></div></div>
- <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span>
- <span class="special">{</span>
- <span class="comment">// fast integers from least integers</span>
- <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">LeastInt</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">int_fast_t</span>
- <span class="special">{</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">type</span><span class="special">;</span>
- <span class="special">};</span>
- <span class="comment">// signed</span>
- <span class="keyword">template</span><span class="special"><</span><span class="keyword">int</span> <span class="identifier">Bits</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">int_t</span>
- <span class="special">{</span>
- <span class="comment">/* Member exact may or may not be defined depending upon Bits */</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">exact</span><span class="special">;</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">least</span><span class="special">;</span>
- <span class="keyword">typedef</span> <span class="identifier">int_fast_t</span><span class="special"><</span><span class="identifier">least</span><span class="special">>::</span><span class="identifier">fast</span> <span class="identifier">fast</span><span class="special">;</span>
- <span class="special">};</span>
- <span class="comment">// unsigned</span>
- <span class="keyword">template</span><span class="special"><</span><span class="keyword">int</span> <span class="identifier">Bits</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">uint_t</span>
- <span class="special">{</span>
- <span class="comment">/* Member exact may or may not be defined depending upon Bits */</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">exact</span><span class="special">;</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">least</span><span class="special">;</span>
- <span class="keyword">typedef</span> <span class="identifier">int_fast_t</span><span class="special"><</span><span class="identifier">least</span><span class="special">>::</span><span class="identifier">fast</span> <span class="identifier">fast</span><span class="special">;</span>
- <span class="special">};</span>
- <span class="comment">// signed</span>
- <span class="keyword">template</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">MaxValue</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">int_max_value_t</span>
- <span class="special">{</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">least</span><span class="special">;</span>
- <span class="keyword">typedef</span> <span class="identifier">int_fast_t</span><span class="special"><</span><span class="identifier">least</span><span class="special">>::</span><span class="identifier">fast</span> <span class="identifier">fast</span><span class="special">;</span>
- <span class="special">};</span>
- <span class="keyword">template</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">MinValue</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">int_min_value_t</span>
- <span class="special">{</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">least</span><span class="special">;</span>
- <span class="keyword">typedef</span> <span class="identifier">int_fast_t</span><span class="special"><</span><span class="identifier">least</span><span class="special">>::</span><span class="identifier">fast</span> <span class="identifier">fast</span><span class="special">;</span>
- <span class="special">};</span>
- <span class="comment">// unsigned</span>
- <span class="keyword">template</span><span class="special"><</span><span class="keyword">unsigned</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">Value</span><span class="special">></span>
- <span class="keyword">struct</span> <span class="identifier">uint_value_t</span>
- <span class="special">{</span>
- <span class="keyword">typedef</span> <span class="emphasis"><em>implementation-defined-type</em></span> <span class="identifier">least</span><span class="special">;</span>
- <span class="keyword">typedef</span> <span class="identifier">int_fast_t</span><span class="special"><</span><span class="identifier">least</span><span class="special">>::</span><span class="identifier">fast</span> <span class="identifier">fast</span><span class="special">;</span>
- <span class="special">};</span>
- <span class="special">}</span> <span class="comment">// namespace boost</span>
- </pre>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.easiest"></a><a class="link" href="integer.html#boost_integer.integer.easiest" title="Easiest-to-Manipulate Types">Easiest-to-Manipulate
- Types</a>
- </h3></div></div></div>
- <p>
- The <code class="literal">int_fast_t</code> class template maps its input type to the
- next-largest type that the processor can manipulate the easiest, or to itself
- if the input type is already an easy-to-manipulate type. For instance, processing
- a bunch of <code class="literal">char</code> objects may go faster if they were converted
- to <code class="literal">int</code> objects before processing. The input type, passed
- as the only template parameter, must be a built-in integral type, except
- <code class="literal">bool</code>. Unsigned integral types can be used, as well as
- signed integral types. The output type is given as the nested type <code class="literal">fast</code>.
- </p>
- <p>
- <span class="bold"><strong>Implementation Notes:</strong></span> By default, the output
- type is identical to the input type. Eventually, this code's implementation
- should be customized for each platform to give accurate mappings between
- the built-in types and the easiest-to-manipulate built-in types. Also, there
- is no guarantee that the output type actually is easier to manipulate than
- the input type.
- </p>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.sized"></a><a class="link" href="integer.html#boost_integer.integer.sized" title="Sized Types">Sized Types</a>
- </h3></div></div></div>
- <p>
- The <code class="literal">int_t</code>, <code class="literal">uint_t</code>, <code class="literal">int_max_value_t</code>,
- <code class="literal">int_min_value_t</code>, and <code class="literal">uint_value_t</code> class
- templates find the most appropiate built-in integral type for the given template
- parameter. This type is given by the nested type <code class="literal">least</code>.
- The easiest-to-manipulate version of that type is given by the nested type
- <code class="literal">fast</code>. The following table describes each template's criteria.
- </p>
- <div class="table">
- <a name="boost_integer.integer.sized.criteria_for_the_sized_type_class_templates"></a><p class="title"><b>Table 1. Criteria for the Sized Type Class Templates</b></p>
- <div class="table-contents"><table class="table" summary="Criteria for the Sized Type Class Templates">
- <colgroup>
- <col>
- <col>
- </colgroup>
- <thead><tr>
- <th>
- <p>
- Class Template
- </p>
- </th>
- <th>
- <p>
- Template Parameter Mapping
- </p>
- </th>
- </tr></thead>
- <tbody>
- <tr>
- <td>
- <p>
- <code class="literal">boost::int_t<N>::least</code>
- </p>
- </td>
- <td>
- <p>
- The smallest, built-in, signed integral type with at least <span class="emphasis"><em>N</em></span>
- bits, including the sign bit. The parameter should be a positive
- number. A compile-time error results if the parameter is larger
- than the number of bits in the largest integer type.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::int_t<N>::fast</code>
- </p>
- </td>
- <td>
- <p>
- The easiest-to-manipulate, built-in, signed integral type with
- at least <span class="emphasis"><em>N</em></span> bits, including the sign bit. The
- parameter should be a positive number. A compile-time error results
- if the parameter is larger than the number of bits in the largest
- integer type.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::int_t<N>::exact</code>
- </p>
- </td>
- <td>
- <p>
- A built-in, signed integral type with exactly <span class="emphasis"><em>N</em></span>
- bits, including the sign bit. The parameter should be a positive
- number. Note that the member <span class="emphasis"><em>exact</em></span> is defined
- <span class="bold"><strong>only</strong></span> if there exists a type with
- exactly <span class="emphasis"><em>N</em></span> bits.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::uint_t<N>::least</code>
- </p>
- </td>
- <td>
- <p>
- The smallest, built-in, unsigned integral type with at least <span class="emphasis"><em>N</em></span>
- bits. The parameter should be a positive number. A compile-time
- error results if the parameter is larger than the number of bits
- in the largest integer type.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::uint_t<N>::fast</code>
- </p>
- </td>
- <td>
- <p>
- The easiest-to-manipulate, built-in, unsigned integral type with
- at least <span class="emphasis"><em>N</em></span> bits. The parameter should be a
- positive number. A compile-time error results if the parameter
- is larger than the number of bits in the largest integer type.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::uint_t<N>::exact</code>
- </p>
- </td>
- <td>
- <p>
- A built-in, unsigned integral type with exactly <span class="emphasis"><em>N</em></span>
- bits. The parameter should be a positive number. A compile-time
- error results if the parameter is larger than the number of bits
- in the largest integer type. Note that the member <span class="emphasis"><em>exact</em></span>
- is defined <span class="bold"><strong>only</strong></span> if there exists
- a type with exactly N bits.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::int_max_value_t<V>::last</code>
- </p>
- </td>
- <td>
- <p>
- The smallest, built-in, signed integral type that can hold all
- the values in the inclusive range <span class="emphasis"><em>0 - V</em></span>. The
- parameter should be a positive number.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::int_max_value_t<V>::fast</code>
- </p>
- </td>
- <td>
- <p>
- The easiest-to-manipulate, built-in, signed integral type that
- can hold all the values in the inclusive range <span class="emphasis"><em>0 - V</em></span>.
- The parameter should be a positive number.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::int_min_value_t<V>::least</code>
- </p>
- </td>
- <td>
- <p>
- The smallest, built-in, signed integral type that can hold all
- the values in the inclusive range <span class="emphasis"><em>V - 0</em></span>. The
- parameter should be a negative number.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::int_min_value_t<V>::fast</code>
- </p>
- </td>
- <td>
- <p>
- The easiest-to-manipulate, built-in, signed integral type that
- can hold all the values in the inclusive range <span class="emphasis"><em>V - 0</em></span>.
- The parameter should be a negative number.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::uint_value_t<V>::least</code>
- </p>
- </td>
- <td>
- <p>
- The smallest, built-in, unsigned integral type that can hold all
- positive values up to and including <span class="emphasis"><em>V</em></span>. The
- parameter should be a positive number.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="literal">boost::uint_value_t<V>::fast</code>
- </p>
- </td>
- <td>
- <p>
- The easiest-to-manipulate, built-in, unsigned integral type that
- can hold all positive values up to and including <span class="emphasis"><em>V</em></span>.
- The parameter should be a positive number.
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- </div>
- <br class="table-break">
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.example"></a><a class="link" href="integer.html#boost_integer.integer.example" title="Example">Example</a>
- </h3></div></div></div>
- <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">integer</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- <span class="comment">//...</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">int_t</span><span class="special"><</span><span class="number">24</span><span class="special">>::</span><span class="identifier">least</span> <span class="identifier">my_var</span><span class="special">;</span> <span class="comment">// my_var has at least 24-bits</span>
- <span class="comment">//...</span>
- <span class="comment">// This one is guaranteed not to be truncated:</span>
- <span class="identifier">boost</span><span class="special">::</span><span class="identifier">int_max_value_t</span><span class="special"><</span><span class="number">1000</span><span class="special">>::</span><span class="identifier">least</span> <span class="identifier">my1000</span> <span class="special">=</span> <span class="number">1000</span><span class="special">;</span>
- <span class="comment">//...</span>
- <span class="comment">// This one is guaranteed not to be truncated, and as fast</span>
- <span class="comment">// to manipulate as possible, its size may be greater than</span>
- <span class="comment">// that of my1000:</span>
- <span class="identifier">boost</span><span class="special">::</span><span class="identifier">int_max_value_t</span><span class="special"><</span><span class="number">1000</span><span class="special">>::</span><span class="identifier">fast</span> <span class="identifier">my_fast1000</span> <span class="special">=</span> <span class="number">1000</span><span class="special">;</span>
- <span class="special">}</span>
- </pre>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.demonstration_program"></a><a class="link" href="integer.html#boost_integer.integer.demonstration_program" title="Demonstration Program">Demonstration
- Program</a>
- </h3></div></div></div>
- <p>
- The program <a href="../../../test/integer_test.cpp" target="_top">integer_test.cpp</a>
- is a simplistic demonstration of the results from instantiating various examples
- of the sized type class templates.
- </p>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.rationale"></a><a class="link" href="integer.html#boost_integer.integer.rationale" title="Rationale">Rationale</a>
- </h3></div></div></div>
- <p>
- The rationale for the design of the templates in this header includes:
- </p>
- <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
- <li class="listitem">
- Avoid recursion because of concern about C++'s limited guaranteed recursion
- depth (17).
- </li>
- <li class="listitem">
- Avoid macros on general principles.
- </li>
- <li class="listitem">
- Try to keep the design as simple as possible.
- </li>
- </ul></div>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.alternative"></a><a class="link" href="integer.html#boost_integer.integer.alternative" title="Alternative">Alternative</a>
- </h3></div></div></div>
- <p>
- If the number of bits required is known beforehand, it may be more appropriate
- to use the types supplied in <a href="../../../../../boost/cstdint.hpp" target="_top"><boost/cstdint.hpp></a>.
- </p>
- </div>
- <div class="section">
- <div class="titlepage"><div><div><h3 class="title">
- <a name="boost_integer.integer.credits"></a><a class="link" href="integer.html#boost_integer.integer.credits" title="Credits">Credits</a>
- </h3></div></div></div>
- <p>
- The author of most of the Boost integer type choosing templates is <a href="http://www.boost.org/people/beman_dawes.html" target="_top">Beman Dawes</a>. He
- gives thanks to Valentin Bonnard and <a href="http://www.boost.org/people/kevlin_henney.htm" target="_top">Kevlin
- Henney</a> for sharing their designs for similar templates. <a href="http://www.boost.org/people/daryle_walker.html" target="_top">Daryle
- Walker</a> designed the value-based sized templates.
- </p>
- </div>
- </div>
- <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
- <td align="left"></td>
- <td align="right"><div class="copyright-footer">Copyright © 2001-2009 Beman
- Dawes, Daryle Walker, Gennaro Prota, John Maddock<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>)
- </p>
- </div></td>
- </tr></table>
- <hr>
- <div class="spirit-nav">
- <a accesskey="p" href="traits.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gcd_lcm.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
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