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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<title>Compile-Time Extrema Templates</title>
</head>
<body bgcolor="white" text="black" link="blue" alink="red" vlink="purple">
<h1><img src="../../../c++boost.gif" alt="c++boost.gif (8819 bytes)"
align="middle" width="277" height="86">Compile-Time Extrema
Templates</h1>
<p>The class templates in <cite><a
href="../../../boost/integer/static_min_max.hpp">&lt;boost/integer/static_min_max.hpp&gt;</a></cite>
provide a compile-time evaluation of the minimum or maximum of
two integers. These facilities are useful for generic programming problems.</p>
<h2><a name="contents">Contents</a></h2>
<ul>
<li><a href="#contents">Contents</a></li>
<li><a href="#synopsis">Synopsis</a></li>
<li><a href="#usage">Usage</a></li>
<li><a href="#example">Example</a></li>
<li><a href="#demo">Demonstration Program</a></li>
<li><a href="#rationale">Rationale</a></li>
<li><a href="#credits">Credits</a></li>
</ul>
<h2><a name="synopsis">Synopsis</a></h2>
<blockquote><pre>
namespace boost
{
template &lt; long Value1, long Value2 &gt;
struct static_signed_min;
template &lt; long Value1, long Value2 &gt;
struct static_signed_max;
template &lt; unsigned long Value1, unsigned long Value2 &gt;
struct static_unsigned_min;
template &lt; unsigned long Value1, unsigned long Value2 &gt;
struct static_unsigned_max;
}
</pre></blockquote>
<h2><a name="usage">Usage</a></h2>
<p>The four class templates provide the combinations for finding the
minimum or maximum of two signed or <code>unsigned</code>
(<code>long</code>) parameters, <var>Value1</var> and <var>Value2</var>,
at compile-time. Each template has a single static data member,
<code>value</code>, which is set to the respective minimum or maximum
of the template's parameters.</p>
<h2><a name="example">Example</a></h2>
<blockquote><pre>
#include &lt;boost/integer/static_min_max.hpp&gt;
template &lt; unsigned long AddendSize1, unsigned long AddendSize2 &gt;
class adder
{
public:
static unsigned long const addend1_size = AddendSize1;
static unsigned long const addend2_size = AddendSize2;
static unsigned long const sum_size = boost::static_unsigned_max&lt;AddendSize1, AddendSize2&gt;::value + 1;
typedef int addend1_type[ addend1_size ];
typedef int addend2_type[ addend2_size ];
typedef int sum_type[ sum_size ];
void operator ()( addend1_type const &amp;a1, addend2_type const &amp;a2, sum_type &amp;s ) const;
};
//...
int main()
{
int const a1[] = { 0, 4, 3 }; // 340
int const a2[] = { 9, 8 }; // 89
int s[ 4 ];
adder&lt;3,2&gt; obj;
obj( a1, a2, s ); // 's' should be 429 or { 9, 2, 4, 0 }
//...
}
</pre></blockquote>
<h2><a name="demo">Demonstration Program</a></h2>
<p>The program <a
href="../test/static_min_max_test.cpp">static_min_max_test.cpp</a> is a
simplistic demonstration of various comparisons using the compile-time
extrema class templates.</p>
<h2><a name="rationale">Rationale</a></h2>
<p>Sometimes the minimum or maximum of several values needs to be found
for later compile-time processing, <i>e.g.</i> for a bound for another
class template.</p>
<h2><a name="credits">Credits</a></h2>
<p>The author of the Boost compile-time extrema class templates is <a
href="../../../../people/daryle_walker.html">Daryle Walker</a>.</p>
<hr>
<p>Revised October 12, 2001</p>
<p>&copy; Copyright Daryle Walker 2001. Permission to copy, use,
modify, sell and distribute this document is granted provided this
copyright notice appears in all copies. This document is provided
&quot;as is&quot; without express or implied warranty, and with no claim
as to its suitability for any purpose.</p>
</body>
</html>