mirror of
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synced 2025-08-01 21:44:28 +02:00
Remove generated documentation from forward and factory.
Will add to the build. [SVN r84558]
This commit is contained in:
Daniel James
@@ -1,528 +0,0 @@
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/*=============================================================================
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Copyright (c) 2004 Joel de Guzman
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http://spirit.sourceforge.net/
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Use, modification and distribution is subject to the Boost Software
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License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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@@ -1,620 +1,16 @@
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
|
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<title>Chapter 1. Boost.Functional/Factory 1.0</title>
|
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<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
|
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<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
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||||
<link rel="home" href="index.html" title="Chapter 1. Boost.Functional/Factory 1.0">
|
||||
<!-- Copyright (C) 2002 Douglas Gregor <doug.gregor -at- gmail.com>
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||||
Distributed under the Boost Software License, Version 1.0.
|
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(See accompanying file LICENSE_1_0.txt or copy at
|
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http://www.boost.org/LICENSE_1_0.txt) -->
|
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<title>Redirect to generated documentation</title>
|
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<meta http-equiv="refresh" content="0; URL=http://boost-sandbox.sourceforge.net/libs/functional/factory/doc/html/">
|
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</head>
|
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
|
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<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="../../../../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"></div>
|
||||
<div class="chapter">
|
||||
<div class="titlepage"><div>
|
||||
<div><h2 class="title">
|
||||
<a name="boost_functional_factory"></a>Chapter 1. Boost.Functional/Factory 1.0</h2></div>
|
||||
<div><div class="author"><h3 class="author">
|
||||
<span class="firstname">Tobias</span> <span class="surname">Schwinger</span>
|
||||
</h3></div></div>
|
||||
<div><p class="copyright">Copyright © 2007, 2008 Tobias Schwinger</p></div>
|
||||
<div><div class="legalnotice">
|
||||
<a name="id3353252"></a><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></div>
|
||||
</div></div>
|
||||
<div class="toc">
|
||||
<p><b>Table of Contents</b></p>
|
||||
<dl>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_factory.brief_description">Brief Description</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_factory.background">Background</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_factory.reference">Reference</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_factory.acknowledgements">Acknowledgements</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_factory.references">References</a></span></dt>
|
||||
</dl>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_factory.brief_description"></a><a class="link" href="index.html#boost_functional_factory.brief_description" title="Brief Description">Brief Description</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
The template <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">factory</span></code> lets you encapsulate a <code class="computeroutput"><span class="keyword">new</span></code> expression as a function object, <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">value_factory</span></code>
|
||||
encapsulates a constructor invocation without <code class="computeroutput"><span class="keyword">new</span></code>.
|
||||
</p>
|
||||
<pre class="programlisting"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">factory</span></code><span class="special"><</span><span class="identifier">T</span><span class="special">*>()(</span><span class="identifier">arg1</span><span class="special">,</span><span class="identifier">arg2</span><span class="special">,</span><span class="identifier">arg3</span><span class="special">)</span>
|
||||
<span class="comment">// same as new T(arg1,arg2,arg3)
|
||||
</span>
|
||||
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">value_factory</span></code><span class="special"><</span><span class="identifier">T</span><span class="special">>()(</span><span class="identifier">arg1</span><span class="special">,</span><span class="identifier">arg2</span><span class="special">,</span><span class="identifier">arg3</span><span class="special">)</span>
|
||||
<span class="comment">// same as T(arg1,arg2,arg3)
|
||||
</span></pre>
|
||||
<p>
|
||||
For technical reasons the arguments to the function objects have to be LValues.
|
||||
A factory that also accepts RValues can be composed using the <a href="http://www.boost.org/libs/functional/forward/doc/index.html" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_adapter</span></code></a>
|
||||
or <a href="http://www.boost.org/libs/bind/bind.html" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span></code></a>.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_factory.background"></a><a class="link" href="index.html#boost_functional_factory.background" title="Background">Background</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
In traditional Object Oriented Programming a Factory is an object implementing
|
||||
an interface of one or more methods that construct objects conforming to known
|
||||
interfaces.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="comment">// assuming a_concrete_class and another_concrete_class are derived
|
||||
</span><span class="comment">// from an_abstract_class
|
||||
</span>
|
||||
<span class="keyword">class</span> <span class="identifier">a_factory</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">public</span><span class="special">:</span>
|
||||
<span class="keyword">virtual</span> <span class="identifier">an_abstract_class</span><span class="special">*</span> <span class="identifier">create</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
|
||||
<span class="keyword">virtual</span> <span class="special">~</span><span class="identifier">a_factory</span><span class="special">()</span> <span class="special">{</span> <span class="special">}</span>
|
||||
<span class="special">};</span>
|
||||
|
||||
<span class="keyword">class</span> <span class="identifier">a_concrete_factory</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">a_factory</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">public</span><span class="special">:</span>
|
||||
<span class="keyword">virtual</span> <span class="identifier">an_abstract_class</span><span class="special">*</span> <span class="identifier">create</span><span class="special">()</span> <span class="keyword">const</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">return</span> <span class="keyword">new</span> <span class="identifier">a_concrete_class</span><span class="special">();</span>
|
||||
<span class="special">}</span>
|
||||
<span class="special">};</span>
|
||||
|
||||
<span class="keyword">class</span> <span class="identifier">another_concrete_factory</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">a_factory</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">public</span><span class="special">:</span>
|
||||
<span class="keyword">virtual</span> <span class="identifier">an_abstract_class</span><span class="special">*</span> <span class="identifier">create</span><span class="special">()</span> <span class="keyword">const</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">return</span> <span class="keyword">new</span> <span class="identifier">another_concrete_class</span><span class="special">();</span>
|
||||
<span class="special">}</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>
|
||||
<a href="http://www.boost.org/libs/ptr_container/doc/ptr_map.html" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">ptr_map</span></code></a><span class="special"><</span><a href="http://www.sgi.com/tech/stl/string.html" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code></a><span class="special">,</span><span class="identifier">a_factory</span><span class="special">></span> <span class="identifier">factories</span><span class="special">;</span>
|
||||
|
||||
<span class="comment">// [...]
|
||||
</span>
|
||||
<span class="identifier">factories</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="string">"a_name"</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">auto_ptr</span><span class="special"><</span><span class="identifier">a_factory</span><span class="special">>(</span>
|
||||
<span class="keyword">new</span> <span class="identifier">a_concrete_factory</span><span class="special">));</span>
|
||||
<span class="identifier">factories</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="string">"another_name"</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">auto_ptr</span><span class="special"><</span><span class="identifier">a_factory</span><span class="special">>(</span>
|
||||
<span class="keyword">new</span> <span class="identifier">another_concrete_factory</span><span class="special">));</span>
|
||||
|
||||
<span class="comment">// [...]
|
||||
</span>
|
||||
<span class="identifier">std</span><span class="special">::</span><span class="identifier">auto_ptr</span><span class="special"><</span><span class="identifier">an_abstract_class</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="identifier">factories</span><span class="special">.</span><span class="identifier">at</span><span class="special">(</span><span class="identifier">some_name</span><span class="special">).</span><span class="identifier">create</span><span class="special">());</span>
|
||||
|
||||
<span class="comment">// [...]
|
||||
</span><span class="special">}</span>
|
||||
</pre>
|
||||
<p>
|
||||
This approach has several drawbacks. The most obvious one is that there is
|
||||
lots of boilerplate code. In other words there is too much code to express
|
||||
a rather simple intention. We could use templates to get rid of some of it
|
||||
but the approach remains inflexible:
|
||||
</p>
|
||||
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
|
||||
<li class="listitem">
|
||||
We may want a factory that takes some arguments that are forwarded to the
|
||||
constructor,
|
||||
</li>
|
||||
<li class="listitem">
|
||||
we will probably want to use smart pointers,
|
||||
</li>
|
||||
<li class="listitem">
|
||||
we may want several member functions to create different kinds of objects,
|
||||
</li>
|
||||
<li class="listitem">
|
||||
we might not necessarily need a polymorphic base class for the objects,
|
||||
</li>
|
||||
<li class="listitem">
|
||||
as we will see, we do not need a factory base class at all,
|
||||
</li>
|
||||
<li class="listitem">
|
||||
we might want to just call the constructor - without <code class="computeroutput"><span class="keyword">new</span></code>
|
||||
to create an object on the stack, and
|
||||
</li>
|
||||
<li class="listitem">
|
||||
finally we might want to use customized memory management.
|
||||
</li>
|
||||
</ul></div>
|
||||
<p>
|
||||
Experience has shown that using function objects and generic Boost components
|
||||
for their composition, Design Patterns that describe callback mechasisms (typically
|
||||
requiring a high percentage of boilerplate code with pure Object Oriented methodology)
|
||||
become implementable with just few code lines and without extra classes.
|
||||
</p>
|
||||
<p>
|
||||
Factories are callback mechanisms for constructors, so we provide two class
|
||||
templates, <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">value_factory</span></code> and <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">factory</span></code>,
|
||||
that encasulate object construction via direct application of the constructor
|
||||
and the <code class="computeroutput"><span class="keyword">new</span></code> operator, respectively.
|
||||
</p>
|
||||
<p>
|
||||
We let the function objects forward their arguments to the construction expressions
|
||||
they encapsulate. Overthis <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">factory</span></code>
|
||||
optionally allows the use of smart pointers and <a href="http://www.sgi.com/tech/stl/concepts/allocator.html" target="_top">Allocators</a>.
|
||||
</p>
|
||||
<p>
|
||||
Compile-time polymorphism can be used where appropriate,
|
||||
</p>
|
||||
<pre class="programlisting"><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">void</span> <span class="identifier">do_something</span><span class="special">()</span>
|
||||
<span class="special">{</span>
|
||||
<span class="comment">// [...]
|
||||
</span> <span class="identifier">T</span> <span class="identifier">x</span> <span class="special">=</span> <span class="identifier">T</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span><span class="identifier">b</span><span class="special">);</span>
|
||||
|
||||
<span class="comment">// for conceptually similar objects x we neither need virtual
|
||||
</span> <span class="comment">// functions nor a common base class in this context.
|
||||
</span> <span class="comment">// [...]
|
||||
</span><span class="special">}</span>
|
||||
</pre>
|
||||
<p>
|
||||
Now, to allow inhomogenous signaturs for the constructors of the types passed
|
||||
in for <code class="computeroutput"><span class="identifier">T</span></code> we can use <code class="computeroutput"><span class="identifier">value_factory</span></code> and <a href="http://www.boost.org/libs/bind/bind.html" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span></code></a>
|
||||
to normalize between them.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> <span class="keyword">class</span> <span class="identifier">ValueFactory</span> <span class="special">></span>
|
||||
<span class="keyword">void</span> <span class="identifier">do_something</span><span class="special">(</span><span class="identifier">ValueFactory</span> <span class="identifier">make_obj</span> <span class="special">=</span> <span class="identifier">ValueFactory</span><span class="special">())</span>
|
||||
<span class="special">{</span>
|
||||
<span class="comment">// [...]
|
||||
</span> <span class="keyword">typename</span> <span class="identifier">ValueFactory</span><span class="special">::</span><span class="identifier">result_type</span> <span class="identifier">x</span> <span class="special">=</span> <span class="identifier">make_obj</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span><span class="identifier">b</span><span class="special">);</span>
|
||||
|
||||
<span class="comment">// for conceptually similar objects x we neither need virtual
|
||||
</span> <span class="comment">// functions nor a common base class in this context.
|
||||
</span> <span class="comment">// [...]
|
||||
</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="comment">// [...]
|
||||
</span>
|
||||
<span class="identifier">do_something</span><span class="special">(</span><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">value_factory</span></code><span class="special"><</span><span class="identifier">X</span><span class="special">>());</span>
|
||||
<span class="identifier">do_something</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(</span><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">value_factory</span></code><span class="special"><</span><span class="identifier">Y</span><span class="special">>(),</span><span class="identifier">_1</span><span class="special">,</span><span class="number">5</span><span class="special">,</span><span class="identifier">_2</span><span class="special">));</span>
|
||||
<span class="comment">// construct X(a,b) and Y(a,5,b), respectively.
|
||||
</span>
|
||||
<span class="comment">// [...]
|
||||
</span><span class="special">}</span>
|
||||
</pre>
|
||||
<p>
|
||||
Maybe we want our objects to outlive the function's scope, in this case we
|
||||
have to use dynamic allocation;
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> <span class="keyword">class</span> <span class="identifier">Factory</span> <span class="special">></span>
|
||||
<span class="identifier">whatever</span> <span class="identifier">do_something</span><span class="special">(</span><span class="identifier">Factory</span> <span class="identifier">new_obj</span> <span class="special">=</span> <span class="identifier">Factory</span><span class="special">())</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">typename</span> <span class="identifier">Factory</span><span class="special">::</span><span class="identifier">result_type</span> <span class="identifier">ptr</span> <span class="special">=</span> <span class="identifier">new_obj</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span><span class="identifier">b</span><span class="special">);</span>
|
||||
|
||||
<span class="comment">// again, no common base class or virtual functions needed,
|
||||
</span> <span class="comment">// we could enforce a polymorphic base by writing e.g.
|
||||
</span> <span class="comment">// boost::shared_ptr<base>
|
||||
</span> <span class="comment">// instead of
|
||||
</span> <span class="comment">// typename Factory::result_type
|
||||
</span> <span class="comment">// above.
|
||||
</span> <span class="comment">// Note that we are also free to have the type erasure happen
|
||||
</span> <span class="comment">// somewhere else (e.g. in the constructor of this function's
|
||||
</span> <span class="comment">// result type).
|
||||
</span>
|
||||
<span class="comment">// [...]
|
||||
</span><span class="special">}</span>
|
||||
|
||||
<span class="comment">// [... call do_something like above but with __factory__ instead
|
||||
</span><span class="comment">// of __value_factory__]
|
||||
</span></pre>
|
||||
<p>
|
||||
Although we might have created polymorphic objects in the previous example,
|
||||
we have used compile time polymorphism for the factory. If we want to erase
|
||||
the type of the factory and thus allow polymorphism at run time, we can use
|
||||
<a href="http://www.boost.org/doc/html/function.html" target="_top">Boost.Function</a>
|
||||
to do so. The first example can be rewritten as follows.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">function</span><span class="special"><</span> <span class="identifier">an_abstract_class</span><span class="special">*()</span> <span class="special">></span> <span class="identifier">a_factory</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>
|
||||
<a href="http://www.sgi.com/tech/stl/map.html" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span></code></a><span class="special"><</span><a href="http://www.sgi.com/tech/stl/string.html" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code></a><span class="special">,</span><span class="identifier">a_factory</span><span class="special">></span> <span class="identifier">factories</span><span class="special">;</span>
|
||||
|
||||
<span class="comment">// [...]
|
||||
</span>
|
||||
<span class="identifier">factories</span><span class="special">[</span><span class="string">"a_name"</span><span class="special">]</span> <span class="special">=</span> <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">factory</span></code><span class="special"><</span><span class="identifier">a_concrete_class</span><span class="special">*>();</span>
|
||||
<span class="identifier">factories</span><span class="special">[</span><span class="string">"another_name"</span><span class="special">]</span> <span class="special">=</span>
|
||||
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">factory</span></code><span class="special"><</span><span class="identifier">another_concrete_class</span><span class="special">*>();</span>
|
||||
|
||||
<span class="comment">// [...]
|
||||
</span><span class="special">}</span>
|
||||
</pre>
|
||||
<p>
|
||||
Of course we can just as easy create factories that take arguments and/or return
|
||||
<a href="http://www.boost.org/libs/smart_ptr/index.html" target="_top">Smart Pointers</a>.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_factory.reference"></a><a class="link" href="index.html#boost_functional_factory.reference" title="Reference">Reference</a>
|
||||
</h2></div></div></div>
|
||||
<div class="toc"><dl>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_factory.reference.value_factory">value_factory</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_factory.reference.factory">factory</a></span></dt>
|
||||
</dl></div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_functional_factory.reference.value_factory"></a><a class="link" href="index.html#boost_functional_factory.reference.value_factory" title="value_factory">value_factory</a>
|
||||
</h3></div></div></div>
|
||||
<a name="boost_functional_factory.reference.value_factory.description"></a><h5>
|
||||
<a name="boost_functional_factory.reference.value_factory.description-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.value_factory.description">Description</a>
|
||||
</h5>
|
||||
<p>
|
||||
Function object template that invokes the constructor of the type <code class="computeroutput"><span class="identifier">T</span></code>.
|
||||
</p>
|
||||
<a name="boost_functional_factory.reference.value_factory.header"></a><h5>
|
||||
<a name="boost_functional_factory.reference.value_factory.header-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.value_factory.header">Header</a>
|
||||
</h5>
|
||||
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">functional</span><span class="special">/</span><span class="identifier">value_factory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
|
||||
</pre>
|
||||
<a name="boost_functional_factory.reference.value_factory.synopsis"></a><h5>
|
||||
<a name="boost_functional_factory.reference.value_factory.synopsis-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.value_factory.synopsis">Synopsis</a>
|
||||
</h5>
|
||||
<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">typename</span> <span class="identifier">T</span> <span class="special">></span>
|
||||
<span class="keyword">class</span> <span class="identifier">value_factory</span><span class="special">;</span>
|
||||
<span class="special">}</span>
|
||||
</pre>
|
||||
<div class="variablelist">
|
||||
<p class="title"><b>Notation</b></p>
|
||||
<dl>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">T</span></code></span></dt>
|
||||
<dd><p>
|
||||
an arbitrary type with at least one public constructor
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code></span></dt>
|
||||
<dd><p>
|
||||
argument LValues to a constructor of <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">F</span></code></span></dt>
|
||||
<dd><p>
|
||||
the type <code class="computeroutput"><span class="identifier">value_factory</span><span class="special"><</span><span class="identifier">F</span><span class="special">></span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">f</span></code></span></dt>
|
||||
<dd><p>
|
||||
an instance object of <code class="computeroutput"><span class="identifier">F</span></code>
|
||||
</p></dd>
|
||||
</dl>
|
||||
</div>
|
||||
<a name="boost_functional_factory.reference.value_factory.expression_semantics"></a><h5>
|
||||
<a name="boost_functional_factory.reference.value_factory.expression_semantics-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.value_factory.expression_semantics">Expression
|
||||
Semantics</a>
|
||||
</h5>
|
||||
<div class="informaltable"><table class="table">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
Expression
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
Semantics
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">F</span><span class="special">()</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an object of type <code class="computeroutput"><span class="identifier">F</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">F</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an object of type <code class="computeroutput"><span class="identifier">F</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
returns <code class="computeroutput"><span class="identifier">T</span><span class="special">(</span><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span><span class="special">)</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">F</span><span class="special">::</span><span class="identifier">result_type</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
is the type <code class="computeroutput"><span class="identifier">T</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
<a name="boost_functional_factory.reference.value_factory.limits"></a><h5>
|
||||
<a name="boost_functional_factory.reference.value_factory.limits-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.value_factory.limits">Limits</a>
|
||||
</h5>
|
||||
<p>
|
||||
The macro BOOST_FUNCTIONAL_VALUE_FACTORY_MAX_ARITY can be defined to set
|
||||
the maximum arity. It defaults to 10.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_functional_factory.reference.factory"></a><a class="link" href="index.html#boost_functional_factory.reference.factory" title="factory">factory</a>
|
||||
</h3></div></div></div>
|
||||
<a name="boost_functional_factory.reference.factory.description"></a><h5>
|
||||
<a name="boost_functional_factory.reference.factory.description-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.factory.description">Description</a>
|
||||
</h5>
|
||||
<p>
|
||||
Function object template that dynamically constructs a pointee object for
|
||||
the type of pointer given as template argument. Smart pointers may be used
|
||||
for the template argument, given that <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">pointee</span><span class="special"><</span><span class="identifier">Pointer</span><span class="special">>::</span><span class="identifier">type</span></code>
|
||||
yields the pointee type.
|
||||
</p>
|
||||
<p>
|
||||
If an <a href="http://www.sgi.com/tech/stl/concepts/allocator.html" target="_top">Allocator</a>
|
||||
is given, it is used for memory allocation and the placement form of the
|
||||
<code class="computeroutput"><span class="keyword">new</span></code> operator is used to construct
|
||||
the object. A function object that calls the destructor and deallocates the
|
||||
memory with a copy of the Allocator is used for the second constructor argument
|
||||
of <code class="computeroutput"><span class="identifier">Pointer</span></code> (thus it must
|
||||
be a <a href="http://www.boost.org/libs/smart_ptr/index.html" target="_top">Smart Pointer</a>
|
||||
that provides a suitable constructor, such as <a href="http://www.boost.org/libs/smart_ptr/shared_ptr.htm" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_ptr</span></code></a>).
|
||||
</p>
|
||||
<p>
|
||||
If a third template argument is <code class="computeroutput"><span class="identifier">factory_passes_alloc_to_smart_pointer</span></code>,
|
||||
the allocator itself is used for the third constructor argument of <code class="computeroutput"><span class="identifier">Pointer</span></code> (<a href="http://www.boost.org/libs/smart_ptr/shared_ptr.htm" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_ptr</span></code></a> then uses the allocator
|
||||
to manage the memory of its seperately allocated reference counter).
|
||||
</p>
|
||||
<a name="boost_functional_factory.reference.factory.header"></a><h5>
|
||||
<a name="boost_functional_factory.reference.factory.header-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.factory.header">Header</a>
|
||||
</h5>
|
||||
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">functional</span><span class="special">/</span><span class="identifier">factory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
|
||||
</pre>
|
||||
<a name="boost_functional_factory.reference.factory.synopsis"></a><h5>
|
||||
<a name="boost_functional_factory.reference.factory.synopsis-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.factory.synopsis">Synopsis</a>
|
||||
</h5>
|
||||
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span>
|
||||
<span class="special">{</span>
|
||||
<span class="keyword">enum</span> <span class="identifier">factory_alloc_propagation</span>
|
||||
<span class="special">{</span>
|
||||
<span class="identifier">factory_alloc_for_pointee_and_deleter</span><span class="special">,</span>
|
||||
<span class="identifier">factory_passes_alloc_to_smart_pointer</span>
|
||||
<span class="special">};</span>
|
||||
|
||||
<span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">Pointer</span><span class="special">,</span>
|
||||
<span class="keyword">class</span> <span class="identifier">Allocator</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span><span class="special">,</span>
|
||||
<span class="identifier">factory_alloc_propagation</span> <span class="identifier">AllocProp</span> <span class="special">=</span>
|
||||
<span class="identifier">factory_alloc_for_pointee_and_deleter</span> <span class="special">></span>
|
||||
<span class="keyword">class</span> <span class="identifier">factory</span><span class="special">;</span>
|
||||
<span class="special">}</span>
|
||||
</pre>
|
||||
<div class="variablelist">
|
||||
<p class="title"><b>Notation</b></p>
|
||||
<dl>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">T</span></code></span></dt>
|
||||
<dd><p>
|
||||
an arbitrary type with at least one public constructor
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">P</span></code></span></dt>
|
||||
<dd><p>
|
||||
pointer or smart pointer to <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code></span></dt>
|
||||
<dd><p>
|
||||
argument LValues to a constructor of <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">F</span></code></span></dt>
|
||||
<dd><p>
|
||||
the type <code class="computeroutput"><span class="identifier">factory</span><span class="special"><</span><span class="identifier">P</span><span class="special">></span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">f</span></code></span></dt>
|
||||
<dd><p>
|
||||
an instance object of <code class="computeroutput"><span class="identifier">F</span></code>
|
||||
</p></dd>
|
||||
</dl>
|
||||
</div>
|
||||
<a name="boost_functional_factory.reference.factory.expression_semantics"></a><h5>
|
||||
<a name="boost_functional_factory.reference.factory.expression_semantics-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.factory.expression_semantics">Expression
|
||||
Semantics</a>
|
||||
</h5>
|
||||
<div class="informaltable"><table class="table">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
Expression
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
Semantics
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">F</span><span class="special">()</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an object of type <code class="computeroutput"><span class="identifier">F</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">F</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an object of type <code class="computeroutput"><span class="identifier">F</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
dynamically creates an object of type <code class="computeroutput"><span class="identifier">T</span></code>
|
||||
using <code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code> as arguments for the constructor
|
||||
invocation.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">F</span><span class="special">::</span><span class="identifier">result_type</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
is the type <code class="computeroutput"><span class="identifier">P</span></code> with
|
||||
top-level cv-qualifiers removed.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
<a name="boost_functional_factory.reference.factory.limits"></a><h5>
|
||||
<a name="boost_functional_factory.reference.factory.limits-heading"></a>
|
||||
<a class="link" href="index.html#boost_functional_factory.reference.factory.limits">Limits</a>
|
||||
</h5>
|
||||
<p>
|
||||
The macro BOOST_FUNCTIONAL_FACTORY_MAX_ARITY can be defined to set the maximum
|
||||
arity. It defaults to 10.
|
||||
</p>
|
||||
</div>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_factory.acknowledgements"></a><a class="link" href="index.html#boost_functional_factory.acknowledgements" title="Acknowledgements">Acknowledgements</a>
|
||||
</h2></div></div></div>
|
||||
<p>
|
||||
Eric Niebler requested a function to invoke a type's constructor (with the
|
||||
arguments supplied as a Tuple) as a Fusion feature. These Factory utilities
|
||||
are a factored-out generalization of this idea.
|
||||
</p>
|
||||
<p>
|
||||
Dave Abrahams suggested Smart Pointer support for exception safety, providing
|
||||
useful hints for the implementation.
|
||||
</p>
|
||||
<p>
|
||||
Joel de Guzman's documentation style was copied from Fusion.
|
||||
</p>
|
||||
<p>
|
||||
Further, I want to thank Peter Dimov for sharing his insights on language details
|
||||
and their evolution.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_factory.references"></a><a class="link" href="index.html#boost_functional_factory.references" title="References">References</a>
|
||||
</h2></div></div></div>
|
||||
<div class="orderedlist"><ol class="orderedlist" type="1">
|
||||
<li class="listitem">
|
||||
<a href="http://en.wikipedia.org/wiki/Design_Patterns" target="_top">Design Patterns</a>,
|
||||
Gamma et al. - Addison Wesley Publishing, 1995
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<a href="http://www.sgi.com/tech/stl/" target="_top">Standard Template Library Programmer's
|
||||
Guide</a>, Hewlett-Packard Company, 1994
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<a href="http://www.boost.org/libs/bind/bind.html" target="_top">Boost.Bind</a>,
|
||||
Peter Dimov, 2001-2005
|
||||
</li>
|
||||
<li class="listitem">
|
||||
<a href="http://www.boost.org/doc/html/function.html" target="_top">Boost.Function</a>,
|
||||
Douglas Gregor, 2001-2004
|
||||
</li>
|
||||
</ol></div>
|
||||
</div>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"><p><small>Last revised: November 01, 2008 at 21:44:52 GMT</small></p></td>
|
||||
<td align="right"><div class="copyright-footer"></div></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav"></div>
|
||||
<body>
|
||||
Automatic redirection failed, please go to
|
||||
<a href="http://boost-sandbox.sourceforge.net/libs/functional/factory/doc/html/">http://boost-sandbox.sourceforge.net/libs/functional/factory/doc/html/</a>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,528 +0,0 @@
|
||||
/*=============================================================================
|
||||
Copyright (c) 2004 Joel de Guzman
|
||||
http://spirit.sourceforge.net/
|
||||
|
||||
Use, modification and distribution is subject to 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)
|
||||
=============================================================================*/
|
||||
|
||||
/*=============================================================================
|
||||
Body defaults
|
||||
=============================================================================*/
|
||||
|
||||
body
|
||||
{
|
||||
margin: 1em;
|
||||
font-family: sans-serif;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Paragraphs
|
||||
=============================================================================*/
|
||||
|
||||
p
|
||||
{
|
||||
text-align: left;
|
||||
font-size: 10pt;
|
||||
line-height: 1.15;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Program listings
|
||||
=============================================================================*/
|
||||
|
||||
/* Code on paragraphs */
|
||||
p tt.computeroutput
|
||||
{
|
||||
font-size: 9pt;
|
||||
}
|
||||
|
||||
pre.synopsis
|
||||
{
|
||||
font-size: 90%;
|
||||
margin: 1pc 4% 0pc 4%;
|
||||
padding: 0.5pc 0.5pc 0.5pc 0.5pc;
|
||||
}
|
||||
|
||||
.programlisting,
|
||||
.screen
|
||||
{
|
||||
font-size: 9pt;
|
||||
display: block;
|
||||
margin: 1pc 4% 0pc 4%;
|
||||
padding: 0.5pc 0.5pc 0.5pc 0.5pc;
|
||||
}
|
||||
|
||||
/* Program listings in tables don't get borders */
|
||||
td .programlisting,
|
||||
td .screen
|
||||
{
|
||||
margin: 0pc 0pc 0pc 0pc;
|
||||
padding: 0pc 0pc 0pc 0pc;
|
||||
}
|
||||
|
||||
/*=============================================================================
|
||||
Headings
|
||||
=============================================================================*/
|
||||
|
||||
h1, h2, h3, h4, h5, h6
|
||||
{
|
||||
text-align: left;
|
||||
margin: 1em 0em 0.5em 0em;
|
||||
font-weight: bold;
|
||||
}
|
||||
|
||||
h1 { font: 140% }
|
||||
h2 { font: bold 140% }
|
||||
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||||
@@ -1,564 +1,16 @@
|
||||
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
||||
<title>Chapter<EFBFBD>1.<2E>Boost.Functional/Forward 1.0</title>
|
||||
<link rel="stylesheet" href="boostbook.css" type="text/css">
|
||||
<meta name="generator" content="DocBook XSL Stylesheets V1.68.1">
|
||||
<link rel="start" href="index.html" title="Chapter<65>1.<2E>Boost.Functional/Forward 1.0">
|
||||
<!-- Copyright (C) 2002 Douglas Gregor <doug.gregor -at- gmail.com>
|
||||
|
||||
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) -->
|
||||
<title>Redirect to generated documentation</title>
|
||||
<meta http-equiv="refresh" content="0; URL=http://boost-sandbox.sourceforge.net/libs/functional/forward/doc/html/">
|
||||
</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="../../../../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"></div>
|
||||
<div class="chapter" lang="en">
|
||||
<div class="titlepage"><div>
|
||||
<div><h2 class="title">
|
||||
<a name="boost_functional_forward"></a>Chapter<EFBFBD>1.<2E>Boost.Functional/Forward 1.0</h2></div>
|
||||
<div><div class="author"><h3 class="author">
|
||||
<span class="firstname">Tobias</span> <span class="surname">Schwinger</span>
|
||||
</h3></div></div>
|
||||
<div><p class="copyright">Copyright <20> 2007, 2008 Tobias Schwinger</p></div>
|
||||
<div><div class="legalnotice">
|
||||
<a name="id934161"></a><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></div>
|
||||
</div></div>
|
||||
<div class="toc">
|
||||
<p><b>Table of Contents</b></p>
|
||||
<dl>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_forward.brief_description">Brief Description</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_forward.background">Background</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_forward.reference"> Reference</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_forward.acknowledgements">Acknowledgements</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_forward.references">References</a></span></dt>
|
||||
</dl>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_forward.brief_description"></a><a href="index.html#boost_functional_forward.brief_description" title="Brief Description">Brief Description</a></h2></div></div></div>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_adapter</span></code> provides a reusable adapter
|
||||
template for function objects. It forwards RValues as references to const,
|
||||
while leaving LValues as-is.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">g</span> <span class="comment">// function object that only accept LValues
|
||||
</span><span class="special">{</span>
|
||||
<span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">T0</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T2</span> <span class="special">></span>
|
||||
<span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">T0</span> <span class="special">&</span> <span class="identifier">t0</span><span class="special">,</span> <span class="identifier">T1</span> <span class="special">&</span> <span class="identifier">t1</span><span class="special">,</span> <span class="identifier">T2</span> <span class="special">&</span> <span class="identifier">t2</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
|
||||
|
||||
<span class="keyword">typedef</span> <span class="keyword">void</span> <span class="identifier">result_type</span><span class="special">;</span>
|
||||
<span class="special">};</span>
|
||||
|
||||
<span class="comment">// Adapted version also accepts RValues and forwards
|
||||
</span><span class="comment">// them as references to const, LValues as-is
|
||||
</span><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_adapter</span><span class="special"><</span><span class="identifier">g</span><span class="special">></span> <span class="identifier">f</span><span class="special">;</span>
|
||||
</pre>
|
||||
<p>
|
||||
Another adapter, <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">lighweight_forward_adapter</span></code> allows forwarding
|
||||
with some help from the user accepting and unwrapping reference wrappers (see
|
||||
<a href="http://www.boost.org/doc/html/ref.html" target="_top">Boost.Ref</a>) for
|
||||
reference arguments, const qualifying all other arguments.
|
||||
</p>
|
||||
<p>
|
||||
The target functions must be compatible with <a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top">Boost.ResultOf</a>,
|
||||
and so are the adapters.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_forward.background"></a><a href="index.html#boost_functional_forward.background" title="Background">Background</a></h2></div></div></div>
|
||||
<p>
|
||||
Let's suppose we have some function <code class="computeroutput"><span class="identifier">f</span></code>
|
||||
that we can call like this:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">f</span><span class="special">(</span><span class="number">123</span><span class="special">,</span><span class="identifier">a_variable</span><span class="special">);</span>
|
||||
</pre>
|
||||
<p>
|
||||
Now we want to write another, generic function <code class="computeroutput"><span class="identifier">g</span></code>
|
||||
that can be called the same way and returns some object that calls <code class="computeroutput"><span class="identifier">f</span></code> with the same arguments.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">f</span><span class="special">(</span><span class="number">123</span><span class="special">,</span><span class="identifier">a_variable</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">g</span><span class="special">(</span><span class="identifier">f</span><span class="special">,</span><span class="number">123</span><span class="special">,</span><span class="identifier">a_variable</span><span class="special">).</span><span class="identifier">call_f</span><span class="special">()</span>
|
||||
</pre>
|
||||
<a name="boost_functional_forward.background.why_would_we_want_to_do_it__anyway_"></a><h3>
|
||||
<a name="id934701"></a>
|
||||
<a href="index.html#boost_functional_forward.background.why_would_we_want_to_do_it__anyway_">Why
|
||||
would we want to do it, anyway?</a>
|
||||
</h3>
|
||||
<p>
|
||||
Maybe we want to run <code class="computeroutput"><span class="identifier">f</span></code> several
|
||||
times. Or maybe we want to run it within another thread. Maybe we just want
|
||||
to encapsulate the call expression for now, and then use it with other code
|
||||
that allows to compose more complex expressions in order to decompose it with
|
||||
C++ templates and have the compiler generate some machinery that eventually
|
||||
calls <code class="computeroutput"><span class="identifier">f</span></code> at runtime (in other
|
||||
words; apply a technique that is commonly referred to as Expression Templates).
|
||||
</p>
|
||||
<a name="boost_functional_forward.background.now__how_do_we_do_it_"></a><h3>
|
||||
<a name="id934755"></a>
|
||||
<a href="index.html#boost_functional_forward.background.now__how_do_we_do_it_">Now,
|
||||
how do we do it?</a>
|
||||
</h3>
|
||||
<p>
|
||||
The bad news is: It's impossible.
|
||||
</p>
|
||||
<p>
|
||||
That is so because there is a slight difference between a variable and an expression
|
||||
that evaluates to its value: Given
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">y</span><span class="special">;</span>
|
||||
<span class="keyword">int</span> <span class="keyword">const</span> <span class="identifier">z</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
|
||||
</pre>
|
||||
<p>
|
||||
and
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">T</span> <span class="special">></span> <span class="keyword">void</span> <span class="identifier">func1</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&</span> <span class="identifier">x</span><span class="special">);</span>
|
||||
</pre>
|
||||
<p>
|
||||
we can call
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">func1</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span> <span class="comment">// x is a reference to a non-const object
|
||||
</span><span class="identifier">func1</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span> <span class="comment">// x is a reference to a const object
|
||||
</span></pre>
|
||||
<p>
|
||||
where
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">func1</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// fails to compile.
|
||||
</span></pre>
|
||||
<p>
|
||||
This way we can safely have <code class="computeroutput"><span class="identifier">func1</span></code>
|
||||
store its reference argument and the compiler keeps us from storing a reference
|
||||
to an object with temporary lifetime.
|
||||
</p>
|
||||
<p>
|
||||
It is important to realize that non-constness and whether an object binds to
|
||||
a non-const reference parameter are two different properties. The latter is
|
||||
the distinction between LValues and RValues. The names stem from the left hand
|
||||
side and the right hand side of assignment expressions, thus LValues are typically
|
||||
the ones you can assign to, and RValues the temporary results from the right
|
||||
hand side expression.
|
||||
</p>
|
||||
<pre class="programlisting"><span class="identifier">y</span> <span class="special">=</span> <span class="number">1</span><span class="special">+</span><span class="number">2</span><span class="special">;</span> <span class="comment">// a is LValue, 1+2 is the expression producing the RValue,
|
||||
</span><span class="comment">// 1+2 = a; // usually makes no sense.
|
||||
</span>
|
||||
<span class="identifier">func1</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span> <span class="comment">// works, because y is an LValue
|
||||
</span><span class="comment">// func1(1+2); // fails to compile, because we only got an RValue.
|
||||
</span></pre>
|
||||
<p>
|
||||
If we add const qualification on the parameter, our function also accepts RValues:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">T</span> <span class="special">></span> <span class="keyword">void</span> <span class="identifier">func2</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&</span> <span class="identifier">x</span><span class="special">);</span>
|
||||
|
||||
<span class="comment">// [...] function scope:
|
||||
</span><span class="identifier">func2</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// x is a reference to a const temporary, object,
|
||||
</span><span class="identifier">func2</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span> <span class="comment">// x is a reference to a const object, while y is not const, and
|
||||
</span><span class="identifier">func2</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span> <span class="comment">// x is a reference to a const object, just like z.
|
||||
</span></pre>
|
||||
<p>
|
||||
In all cases, the argument <code class="computeroutput"><span class="identifier">x</span></code>
|
||||
in <code class="computeroutput"><span class="identifier">func2</span></code> is a const-qualified
|
||||
LValue. We can use function overloading to identify non-const LValues:
|
||||
</p>
|
||||
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">T</span> <span class="special">></span> <span class="keyword">void</span> <span class="identifier">func3</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&</span> <span class="identifier">x</span><span class="special">);</span> <span class="comment">// #1
|
||||
</span><span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">T</span> <span class="special">></span> <span class="keyword">void</span> <span class="identifier">func3</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&</span> <span class="identifier">x</span><span class="special">);</span> <span class="comment">// #2
|
||||
</span>
|
||||
<span class="comment">// [...] function scope:
|
||||
</span><span class="identifier">func3</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// x is a reference to a const, temporary object in #1,
|
||||
</span><span class="identifier">func3</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span> <span class="comment">// x is a reference to a non-const object in #2, and
|
||||
</span><span class="identifier">func3</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span> <span class="comment">// x is a reference to a const object in #1.
|
||||
</span></pre>
|
||||
<p>
|
||||
Note that all arguments <code class="computeroutput"><span class="identifier">x</span></code> in
|
||||
the overloaded function <code class="computeroutput"><span class="identifier">func3</span></code>
|
||||
are LValues. In fact, there is no way to transport RValues into a function
|
||||
as-is in C++98. Also note that we can't distinguish between what used to be
|
||||
a const qualified LValue and an RValue.
|
||||
</p>
|
||||
<p>
|
||||
That's as close as we can get to a generic forwarding function <code class="computeroutput"><span class="identifier">g</span></code> as described above by the means of C++
|
||||
98. See <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n1385.htm" target="_top">The
|
||||
Forwarding Problem</a> for a very detailed discussion including solutions
|
||||
that require language changes.
|
||||
</p>
|
||||
<p>
|
||||
Now, for actually implementing it, we need 2^N overloads for N parameters (each
|
||||
with and without const qualifier) for each number of arguments (that is 2^(Nmax+1)
|
||||
- 2^Nmin). Right, that means the compile-time complexity is O(2^N), however
|
||||
the factor is low so it works quite well for a reasonable number (< 10)
|
||||
of arguments.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_forward.reference"></a><a href="index.html#boost_functional_forward.reference" title=" Reference"> Reference</a></h2></div></div></div>
|
||||
<div class="toc"><dl>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_forward.reference.forward_adapter">forward_adapter</a></span></dt>
|
||||
<dt><span class="section"><a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter">lightweight_forward_adapter</a></span></dt>
|
||||
</dl></div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_functional_forward.reference.forward_adapter"></a><a href="index.html#boost_functional_forward.reference.forward_adapter" title="forward_adapter">forward_adapter</a></h3></div></div></div>
|
||||
<a name="boost_functional_forward.reference.forward_adapter.description"></a><h4>
|
||||
<a name="id935594"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.forward_adapter.description">Description</a>
|
||||
</h4>
|
||||
<p>
|
||||
Function object adapter template whose instances are callable with LValue
|
||||
and RValue arguments. RValue arguments are forwarded as reference-to-const
|
||||
typed LValues.
|
||||
</p>
|
||||
<p>
|
||||
An arity can be given as second, numeric non-type template argument to restrict
|
||||
forwarding to a specific arity. If a third, numeric non-type template argument
|
||||
is present, the second and third template argument are treated as minimum
|
||||
and maximum arity, respectively. Specifying an arity can be helpful to improve
|
||||
the readability of diagnostic messages and compile time performance.
|
||||
</p>
|
||||
<p>
|
||||
<a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top">Boost.ResultOf</a>
|
||||
can be used to determine the result types of specific call expressions.
|
||||
</p>
|
||||
<a name="boost_functional_forward.reference.forward_adapter.header"></a><h4>
|
||||
<a name="id935646"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.forward_adapter.header">Header</a>
|
||||
</h4>
|
||||
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">functional</span><span class="special">/</span><span class="identifier">forward_adapter</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
|
||||
</pre>
|
||||
<a name="boost_functional_forward.reference.forward_adapter.synopsis"></a><h4>
|
||||
<a name="id935721"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.forward_adapter.synopsis">Synopsis</a>
|
||||
</h4>
|
||||
<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">Function</span><span class="special">,</span>
|
||||
<span class="keyword">int</span> <span class="identifier">Arity_Or_MinArity</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">MaxArity</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span> <span class="special">></span>
|
||||
<span class="keyword">class</span> <span class="identifier">forward_adapter</span><span class="special">;</span>
|
||||
<span class="special">}</span>
|
||||
</pre>
|
||||
<div class="variablelist">
|
||||
<p class="title"><b>Notation</b></p>
|
||||
<dl>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">F</span></code></span></dt>
|
||||
<dd><p>
|
||||
a possibly const qualified function object type or reference type thereof
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">f</span></code></span></dt>
|
||||
<dd><p>
|
||||
an object convertible to <code class="computeroutput"><span class="identifier">F</span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">FA</span></code></span></dt>
|
||||
<dd><p>
|
||||
the type <code class="computeroutput"><span class="identifier">forward_adapter</span><span class="special"><</span><span class="identifier">F</span><span class="special">></span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">fa</span></code></span></dt>
|
||||
<dd><p>
|
||||
an instance object of <code class="computeroutput"><span class="identifier">FA</span></code>,
|
||||
initialized with <code class="computeroutput"><span class="identifier">f</span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code></span></dt>
|
||||
<dd><p>
|
||||
arguments to <code class="computeroutput"><span class="identifier">fa</span></code>
|
||||
</p></dd>
|
||||
</dl>
|
||||
</div>
|
||||
<p>
|
||||
The result type of a target function invocation must be
|
||||
</p>
|
||||
<pre class="programlisting"><a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span></code></a><span class="special"><</span><span class="identifier">F</span><span class="special">*(</span><span class="identifier">TA0</span> <span class="special">[</span><span class="keyword">const</span><span class="special">]&...</span><span class="identifier">TAN</span> <span class="special">[</span><span class="keyword">const</span><span class="special">]&])>::</span><span class="identifier">type</span>
|
||||
</pre>
|
||||
<p>
|
||||
where <code class="computeroutput"><span class="identifier">TA0</span></code>...<code class="computeroutput"><span class="identifier">TAN</span></code> denote the argument types of <code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code>.
|
||||
</p>
|
||||
<a name="boost_functional_forward.reference.forward_adapter.expression_semantics"></a><h4>
|
||||
<a name="id936177"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.forward_adapter.expression_semantics">Expression
|
||||
Semantics</a>
|
||||
</h4>
|
||||
<div class="informaltable"><table class="table">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
Expression
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
Semantics
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">FA</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an adapter, initializes the target function with <code class="computeroutput"><span class="identifier">f</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">FA</span><span class="special">()</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an adapter, attempts to use <code class="computeroutput"><span class="identifier">F</span></code>'s
|
||||
default constructor.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">fa</span><span class="special">(</span><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
calls <code class="computeroutput"><span class="identifier">f</span></code> with with
|
||||
arguments <code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
<a name="boost_functional_forward.reference.forward_adapter.limits"></a><h4>
|
||||
<a name="id936405"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.forward_adapter.limits">Limits</a>
|
||||
</h4>
|
||||
<p>
|
||||
The macro BOOST_FUNCTIONAL_FORWARD_ADAPTER_MAX_ARITY can be defined to set
|
||||
the maximum call arity. It defaults to 6.
|
||||
</p>
|
||||
<a name="boost_functional_forward.reference.forward_adapter.complexity"></a><h4>
|
||||
<a name="id936434"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.forward_adapter.complexity">Complexity</a>
|
||||
</h4>
|
||||
<p>
|
||||
Preprocessing time: O(2^N), where N is the arity limit. Compile time: O(2^N),
|
||||
where N depends on the arity range. Run time: O(0) if the compiler inlines,
|
||||
O(1) otherwise.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h3 class="title">
|
||||
<a name="boost_functional_forward.reference.lightweight_forward_adapter"></a><a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter" title="lightweight_forward_adapter">lightweight_forward_adapter</a></h3></div></div></div>
|
||||
<a name="boost_functional_forward.reference.lightweight_forward_adapter.description"></a><h4>
|
||||
<a name="id936485"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter.description">Description</a>
|
||||
</h4>
|
||||
<p>
|
||||
Function object adapter template whose instances are callable with LValue
|
||||
and RValue arguments. All arguments are forwarded as reference-to-const typed
|
||||
LValues, except for reference wrappers which are unwrapped and may yield
|
||||
non-const LValues.
|
||||
</p>
|
||||
<p>
|
||||
An arity can be given as second, numeric non-type template argument to restrict
|
||||
forwarding to a specific arity. If a third, numeric non-type template argument
|
||||
is present, the second and third template argument are treated as minimum
|
||||
and maximum arity, respectively. Specifying an arity can be helpful to improve
|
||||
the readability of diagnostic messages and compile time performance.
|
||||
</p>
|
||||
<p>
|
||||
<a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top">Boost.ResultOf</a>
|
||||
can be used to determine the result types of specific call expressions.
|
||||
</p>
|
||||
<a name="boost_functional_forward.reference.lightweight_forward_adapter.header"></a><h4>
|
||||
<a name="id936540"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter.header">Header</a>
|
||||
</h4>
|
||||
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">functional</span><span class="special">/</span><span class="identifier">lightweight_forward_adapter</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
|
||||
</pre>
|
||||
<a name="boost_functional_forward.reference.lightweight_forward_adapter.synopsis"></a><h4>
|
||||
<a name="id936616"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter.synopsis">Synopsis</a>
|
||||
</h4>
|
||||
<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">Function</span><span class="special">,</span>
|
||||
<span class="keyword">int</span> <span class="identifier">Arity_Or_MinArity</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">MaxArity</span> <span class="special">=</span> <span class="emphasis"><em>unspecified</em></span> <span class="special">></span>
|
||||
<span class="keyword">struct</span> <span class="identifier">lightweight_forward_adapter</span><span class="special">;</span>
|
||||
<span class="special">}</span>
|
||||
</pre>
|
||||
<div class="variablelist">
|
||||
<p class="title"><b>Notation</b></p>
|
||||
<dl>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">F</span></code></span></dt>
|
||||
<dd><p>
|
||||
a possibly const qualified function object type or reference type thereof
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">f</span></code></span></dt>
|
||||
<dd><p>
|
||||
an object convertible to <code class="computeroutput"><span class="identifier">F</span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">FA</span></code></span></dt>
|
||||
<dd><p>
|
||||
the type <code class="computeroutput"><span class="identifier">lightweight_forward_adapter</span><span class="special"><</span><span class="identifier">F</span><span class="special">></span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">fa</span></code></span></dt>
|
||||
<dd><p>
|
||||
an instance of <code class="computeroutput"><span class="identifier">FA</span></code>, initialized
|
||||
with <code class="computeroutput"><span class="identifier">f</span></code>
|
||||
</p></dd>
|
||||
<dt><span class="term"><code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code></span></dt>
|
||||
<dd><p>
|
||||
arguments to <code class="computeroutput"><span class="identifier">fa</span></code>
|
||||
</p></dd>
|
||||
</dl>
|
||||
</div>
|
||||
<p>
|
||||
The result type of a target function invocation must be
|
||||
</p>
|
||||
<pre class="programlisting"><a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span></code></a><span class="special"><</span><span class="identifier">F</span><span class="special">*(</span><span class="identifier">TA0</span> <span class="special">[</span><span class="keyword">const</span><span class="special">]&...</span><span class="identifier">TAN</span> <span class="special">[</span><span class="keyword">const</span><span class="special">]&])>::</span><span class="identifier">type</span>
|
||||
</pre>
|
||||
<p>
|
||||
where <code class="computeroutput"><span class="identifier">TA0</span></code>...<code class="computeroutput"><span class="identifier">TAN</span></code> denote the argument types of <code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code>.
|
||||
</p>
|
||||
<a name="boost_functional_forward.reference.lightweight_forward_adapter.expression_semantics"></a><h4>
|
||||
<a name="id937073"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter.expression_semantics">Expression
|
||||
Semantics</a>
|
||||
</h4>
|
||||
<div class="informaltable"><table class="table">
|
||||
<colgroup>
|
||||
<col>
|
||||
<col>
|
||||
</colgroup>
|
||||
<thead><tr>
|
||||
<th>
|
||||
<p>
|
||||
Expression
|
||||
</p>
|
||||
</th>
|
||||
<th>
|
||||
<p>
|
||||
Semantics
|
||||
</p>
|
||||
</th>
|
||||
</tr></thead>
|
||||
<tbody>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">FA</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an adapter, initializes the target function with <code class="computeroutput"><span class="identifier">f</span></code>.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">FA</span><span class="special">()</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
creates an adapter, attempts to use <code class="computeroutput"><span class="identifier">F</span></code>'s
|
||||
default constructor.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>
|
||||
<p>
|
||||
<code class="computeroutput"><span class="identifier">fa</span><span class="special">(</span><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span><span class="special">)</span></code>
|
||||
</p>
|
||||
</td>
|
||||
<td>
|
||||
<p>
|
||||
calls <code class="computeroutput"><span class="identifier">f</span></code> with with
|
||||
const arguments <code class="computeroutput"><span class="identifier">a0</span></code>...<code class="computeroutput"><span class="identifier">aN</span></code>. If <code class="computeroutput"><span class="identifier">aI</span></code>
|
||||
is a reference wrapper it is unwrapped.
|
||||
</p>
|
||||
</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table></div>
|
||||
<a name="boost_functional_forward.reference.lightweight_forward_adapter.limits"></a><h4>
|
||||
<a name="id937311"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter.limits">Limits</a>
|
||||
</h4>
|
||||
<p>
|
||||
The macro BOOST_FUNCTIONAL_LIGHTWEIGHT_FORWARD_ADAPTER_MAX_ARITY can be defined
|
||||
to set the maximum call arity. It defaults to 10.
|
||||
</p>
|
||||
<a name="boost_functional_forward.reference.lightweight_forward_adapter.complexity"></a><h4>
|
||||
<a name="id937342"></a>
|
||||
<a href="index.html#boost_functional_forward.reference.lightweight_forward_adapter.complexity">Complexity</a>
|
||||
</h4>
|
||||
<p>
|
||||
Preprocessing time: O(N), where N is the arity limit. Compile time: O(N),
|
||||
where N is the effective arity of a call. Run time: O(0) if the compiler
|
||||
inlines, O(1) otherwise.
|
||||
</p>
|
||||
</div>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_forward.acknowledgements"></a><a href="index.html#boost_functional_forward.acknowledgements" title="Acknowledgements">Acknowledgements</a></h2></div></div></div>
|
||||
<p>
|
||||
As these utilities are factored out of the <a href="http://www.boost.org/libs/fusion/doc/html/index.html" target="_top">Boost.Fusion</a>
|
||||
functional module, I want to thank Dan Marsden and Joel de Guzman for letting
|
||||
me participate in the development of that great library in the first place.
|
||||
</p>
|
||||
<p>
|
||||
Further, I want to credit the authors of the references below, for their in-depth
|
||||
investigation of the problem and the solution implemented here.
|
||||
</p>
|
||||
<p>
|
||||
Last but not least I want to thank Vesa Karnoven and Paul Mensonides for the
|
||||
Boost Preprocessor library. Without it, I would have ended up with an external
|
||||
code generator for this one.
|
||||
</p>
|
||||
</div>
|
||||
<div class="section" lang="en">
|
||||
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
|
||||
<a name="boost_functional_forward.references"></a><a href="index.html#boost_functional_forward.references" title="References">References</a></h2></div></div></div>
|
||||
<div class="orderedlist"><ol type="1">
|
||||
<li>
|
||||
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n1385.htm" target="_top">The
|
||||
Forwarding Problem</a>, Peter Dimov, Howard E. Hinnant, David Abrahams,
|
||||
2002
|
||||
</li>
|
||||
<li>
|
||||
<a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top">Boost.ResultOf</a>,
|
||||
Douglas Gregor, 2004
|
||||
</li>
|
||||
<li>
|
||||
<a href="http://www.boost.org/doc/html/ref.html" target="_top">Boost.Ref</a>, Jaakko
|
||||
Jarvi, Peter Dimov, Douglas Gregor, David Abrahams, 1999-2002
|
||||
</li>
|
||||
</ol></div>
|
||||
</div>
|
||||
</div>
|
||||
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
|
||||
<td align="left"><p><small>Last revised: November 01, 2008 at 19:58:50 GMT</small></p></td>
|
||||
<td align="right"><div class="copyright-footer"></div></td>
|
||||
</tr></table>
|
||||
<hr>
|
||||
<div class="spirit-nav"></div>
|
||||
<body>
|
||||
Automatic redirection failed, please go to
|
||||
<a href="http://boost-sandbox.sourceforge.net/libs/functional/forward/doc/html/">http://boost-sandbox.sourceforge.net/libs/functional/forward/doc/html/</a>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
Reference in New Issue
Block a user