45 lines
4.2 KiB
HTML
45 lines
4.2 KiB
HTML
<?xml version="1.0" encoding="utf-8" ?>
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
|
|
<!-- Copyright Aleksey Gurtovoy 2006. Distributed under the Boost -->
|
|
<!-- Software License, Version 1.0. (See accompanying -->
|
|
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="generator" content="Docutils 0.3.6: http://docutils.sourceforge.net/" />
|
|
<title>THE BOOST MPL LIBRARY: Partial Metafunction Application</title>
|
|
<link rel="stylesheet" href="../style.css" type="text/css" />
|
|
</head>
|
|
<body class="docframe">
|
|
<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./more-lambda-capabilities.html" class="navigation-link">Prev</a> <a href="./metafunction-composition.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group">Back <a href="./metafunction-composition.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./more-lambda-capabilities.html" class="navigation-link">Up</a> <a href="../index.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./tutorial_toc.html" class="navigation-link">Full TOC</a></span></td>
|
|
<td class="header-group page-location"><a href="../index.html" class="navigation-link">Front Page</a> / <a href="./tutorial-metafunctions.html" class="navigation-link">Tutorial: Metafunctions and Higher-Order Metaprogramming</a> / <a href="./more-lambda-capabilities.html" class="navigation-link">More Lambda Capabilities</a> / <a href="./partial-metafunction.html" class="navigation-link">Partial Metafunction Application</a></td>
|
|
</tr></table><div class="header-separator"></div>
|
|
<div class="section" id="partial-metafunction">
|
|
<h1><a class="toc-backref" href="./more-lambda-capabilities.html#id52" name="partial-metafunction">Partial Metafunction Application</a></h1>
|
|
<p>Consider the lambda expression <tt class="literal"><span class="pre">mpl::plus<_1,_1></span></tt>. A single
|
|
argument is directed to both of <tt class="literal"><span class="pre">plus</span></tt>'s parameters, thereby
|
|
adding a number to itself. Thus, a <em>binary</em> metafunction,
|
|
<tt class="literal"><span class="pre">plus</span></tt>, is used to build a <em>unary</em> lambda expression. In other
|
|
words, we've created a whole new computation! We're not done yet,
|
|
though: By supplying a non-placeholder as one of the arguments, we
|
|
can build a unary lambda expression that adds a fixed value, say
|
|
42, to its argument:</p>
|
|
<pre class="literal-block">
|
|
mpl::plus<_1, mpl::int_<42> >
|
|
</pre>
|
|
<!-- @ apply_test = 'enum { value = mpl::apply<', ''' >::type::value };
|
|
BOOST_STATIC_ASSERT(value == %d);'''
|
|
|
|
example.wrap(apply_test[0],
|
|
', mpl::int_<3>' + apply_test[1] % 45)
|
|
compile() -->
|
|
<p>The process of binding argument values to a subset of a function's
|
|
parameters is known in the world of functional programming as
|
|
<strong>partial function application</strong>.</p>
|
|
</div>
|
|
|
|
<div class="footer-separator"></div>
|
|
<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./more-lambda-capabilities.html" class="navigation-link">Prev</a> <a href="./metafunction-composition.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group">Back <a href="./metafunction-composition.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./more-lambda-capabilities.html" class="navigation-link">Up</a> <a href="../index.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./tutorial_toc.html" class="navigation-link">Full TOC</a></span></td>
|
|
</tr></table></body>
|
|
</html>
|