mirror of
https://github.com/boostorg/integer.git
synced 2025-11-04 02:01:38 +01:00
081eb01f88
So that it doesn't appear in the middle of documentation for things that are in the library.
216 lines
12 KiB
HTML
216 lines
12 KiB
HTML
<html>
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
|
<title>Integer Traits</title>
|
|
<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
|
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
|
|
<link rel="home" href="../index.html" title="Boost.Integer">
|
|
<link rel="up" href="../index.html" title="Boost.Integer">
|
|
<link rel="prev" href="../index.html" title="Boost.Integer">
|
|
<link rel="next" href="integer.html" title="Integer Type Selection">
|
|
</head>
|
|
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
|
<table cellpadding="2" width="100%"><tr>
|
|
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td>
|
|
<td align="center"><a href="../../../../../index.html">Home</a></td>
|
|
<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td>
|
|
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
|
|
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
|
|
<td align="center"><a href="../../../../../more/index.htm">More</a></td>
|
|
</tr></table>
|
|
<hr>
|
|
<div class="spirit-nav">
|
|
<a accesskey="p" href="../index.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="integer.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
|
</div>
|
|
<div class="section">
|
|
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
|
<a name="boost_integer.traits"></a><a class="link" href="traits.html" title="Integer Traits">Integer Traits</a>
|
|
</h2></div></div></div>
|
|
<div class="toc"><dl class="toc">
|
|
<dt><span class="section"><a href="traits.html#boost_integer.traits.motivation">Motivation</a></span></dt>
|
|
<dt><span class="section"><a href="traits.html#boost_integer.traits.synopsis">Synopsis</a></span></dt>
|
|
<dt><span class="section"><a href="traits.html#boost_integer.traits.description">Description</a></span></dt>
|
|
<dt><span class="section"><a href="traits.html#boost_integer.traits.test_program">Test Program</a></span></dt>
|
|
<dt><span class="section"><a href="traits.html#boost_integer.traits.acknowledgements">Acknowledgements</a></span></dt>
|
|
</dl></div>
|
|
<div class="section">
|
|
<div class="titlepage"><div><div><h3 class="title">
|
|
<a name="boost_integer.traits.motivation"></a><a class="link" href="traits.html#boost_integer.traits.motivation" title="Motivation">Motivation</a>
|
|
</h3></div></div></div>
|
|
<p>
|
|
The C++ Standard Library <limits> header supplies a class template
|
|
<code class="computeroutput"><span class="identifier">numeric_limits</span><span class="special"><></span></code>
|
|
with specializations for each fundamental type.
|
|
</p>
|
|
<p>
|
|
For integer types, the interesting members of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><></span></code> are:
|
|
</p>
|
|
<pre class="programlisting"><span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">bool</span> <span class="identifier">is_specialized</span><span class="special">;</span> <span class="comment">// Will be true for integer types.</span>
|
|
<span class="keyword">static</span> <span class="identifier">T</span> <span class="identifier">min</span><span class="special">()</span> <span class="keyword">throw</span><span class="special">();</span> <span class="comment">// Smallest representable value.</span>
|
|
<span class="keyword">static</span> <span class="identifier">T</span> <span class="identifier">max</span><span class="special">()</span> <span class="keyword">throw</span><span class="special">();</span> <span class="comment">// Largest representable value.</span>
|
|
<span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">digits</span><span class="special">;</span> <span class="comment">// For integers, the number of value bits.</span>
|
|
<span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">digits10</span><span class="special">;</span> <span class="comment">// The number of base 10 digits that can be represented.</span>
|
|
<span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">bool</span> <span class="identifier">is_signed</span><span class="special">;</span> <span class="comment">// True if the type is signed.</span>
|
|
<span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">bool</span> <span class="identifier">is_integer</span><span class="special">;</span> <span class="comment">// Will be true for all integer types.</span>
|
|
</pre>
|
|
<p>
|
|
For many uses, these are sufficient. But min() and max() are problematical
|
|
because they are not constant expressions (std::5.19), yet some usages require
|
|
constant expressions.
|
|
</p>
|
|
<p>
|
|
The template class <code class="literal">integer_traits</code> addresses this problem.
|
|
</p>
|
|
</div>
|
|
<div class="section">
|
|
<div class="titlepage"><div><div><h3 class="title">
|
|
<a name="boost_integer.traits.synopsis"></a><a class="link" href="traits.html#boost_integer.traits.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="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
|
|
<span class="keyword">class</span> <span class="identifier">integer_traits</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">numeric_limits</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span>
|
|
<span class="special">{</span>
|
|
<span class="keyword">public</span><span class="special">:</span>
|
|
<span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">bool</span> <span class="identifier">is_integral</span> <span class="special">=</span> <span class="keyword">false</span><span class="special">;</span>
|
|
<span class="comment">//</span>
|
|
<span class="comment">// These members are defined only if T is a built-in</span>
|
|
<span class="comment">// integal type:</span>
|
|
<span class="comment">//</span>
|
|
<span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">T</span> <span class="identifier">const_min</span> <span class="special">=</span> <span class="emphasis"><em>implementation-defined</em></span><span class="special">;</span>
|
|
<span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">T</span> <span class="identifier">const_max</span> <span class="special">=</span> <span class="emphasis"><em>implementation-defined</em></span><span class="special">;</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.traits.description"></a><a class="link" href="traits.html#boost_integer.traits.description" title="Description">Description</a>
|
|
</h3></div></div></div>
|
|
<p>
|
|
Template class <code class="literal">integer_traits</code> is derived from <code class="literal">std::numeric_limits</code>.
|
|
The primary specialization adds the single <code class="literal">bool</code> member
|
|
<code class="literal">is_integral</code> with the compile-time constant value <code class="literal">false</code>.
|
|
However, for all integral types <code class="literal">T</code> (std::3.9.1/7 [basic.fundamental]),
|
|
there are specializations provided with the following compile-time constants
|
|
defined:
|
|
</p>
|
|
<div class="informaltable"><table class="table">
|
|
<colgroup>
|
|
<col>
|
|
<col>
|
|
<col>
|
|
</colgroup>
|
|
<thead><tr>
|
|
<th>
|
|
<p>
|
|
member
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
type
|
|
</p>
|
|
</th>
|
|
<th>
|
|
<p>
|
|
value
|
|
</p>
|
|
</th>
|
|
</tr></thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
<code class="literal">is_integral</code>
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
bool
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<code class="literal">true</code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
<code class="literal">const_min</code>
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<code class="literal">T</code>
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
equivalent to <code class="literal">std::numeric_limits<T>::min()</code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td>
|
|
<p>
|
|
<code class="literal">const_max</code>
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
<code class="literal">T</code>
|
|
</p>
|
|
</td>
|
|
<td>
|
|
<p>
|
|
equivalent to <code class="literal">std::numeric_limits<T>::max()</code>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table></div>
|
|
<p>
|
|
Note: The <span class="emphasis"><em>is_integral</em></span> flag is provided, because a user-defined
|
|
integer class should specialize <code class="literal">std::numeric_limits<>::is_integer
|
|
= true</code>, while compile-time constants <code class="literal">const_min</code>
|
|
and <code class="literal">const_max</code> are not provided for that user-defined class,
|
|
unless boost::integer_traits is also specialized.
|
|
</p>
|
|
</div>
|
|
<div class="section">
|
|
<div class="titlepage"><div><div><h3 class="title">
|
|
<a name="boost_integer.traits.test_program"></a><a class="link" href="traits.html#boost_integer.traits.test_program" title="Test Program">Test Program</a>
|
|
</h3></div></div></div>
|
|
<p>
|
|
The program <code class="literal"><a href="../../../test/integer_traits_test.cpp" target="_top">integer_traits_test.cpp</a></code>
|
|
exercises the <code class="literal">integer_traits</code> class.
|
|
</p>
|
|
</div>
|
|
<div class="section">
|
|
<div class="titlepage"><div><div><h3 class="title">
|
|
<a name="boost_integer.traits.acknowledgements"></a><a class="link" href="traits.html#boost_integer.traits.acknowledgements" title="Acknowledgements">Acknowledgements</a>
|
|
</h3></div></div></div>
|
|
<p>
|
|
Beman Dawes, Ed Brey, Steve Cleary, and Nathan Myers discussed the integer
|
|
traits idea on the boost mailing list in August 1999.
|
|
</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="../index.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="integer.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
|
|
</div>
|
|
</body>
|
|
</html>
|