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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0.1 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Boost.MultiIndex Documentation - Key extraction reference</title>
<link rel="stylesheet" href="../style.css" type="text/css">
</head>
<body>
<h1><img src="../../../../boost.png" alt="boost.png (6897 bytes)" align=
"middle" width="277" height="86">Boost.MultiIndex Key extraction reference</h1>
<div class="prev_link"><a href="seq_indices.html"><img src="../prev.gif" alt="sequenced indices" border="0"><br>
Sequenced indices
</a></div>
<div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.MultiIndex reference" border="0"><br>
Boost.MultiIndex reference
</a></div>
<div class="next_link"><a href="../compiler_specifics.html"><img src="../next.gif" alt="compiler specifics" border="0"><br>
Compiler specifics
</a></div><br clear="all" style="clear: all;">
<hr>
<h2>Contents</h2>
<ul>
<li><a href="#key_extractors">Key Extractors</a>
<ul>
<li><a href="#chained_pointers">Chained pointers</a></li>
</ul>
</li>
<li><a href="#synopsis">Header
<code>"boost/multi_index/key_extractors.hpp"</code> synopsis</a>
</li>
<li><a href="#identity_synopsis">Header
<code>"boost/multi_index/identity.hpp"</code> synopsis</a>
<ul>
<li><a href="#identity">Template class <code>identity</code></a></li>
</ul>
</li>
<li><a href="#member_synopsis">Header
<code>"boost/multi_index/member.hpp"</code> synopsis</a>
<ul>
<li><a href="#member">Template class <code>member</code></a></li>
<li><a href="#member_offset">Template class <code>member_offset</code></a></li>
<li><a href="#boost_multi_index_member">Macro <code>BOOST_MULTI_INDEX_MEMBER</code></a></li>
</ul>
</li>
<li><a href="#mem_fun_synopsis">Header
<code>"boost/multi_index/mem_fun.hpp"</code> synopsis</a>
<ul>
<li><a href="#const_mem_fun">Template class <code>const_mem_fun</code></a></li>
<li><a href="#mem_fun">Template class <code>mem_fun</code></a></li>
<li><a href="#const_mem_fun_explicit">Template class <code>const_mem_fun_explicit</code></a></li>
<li><a href="#mem_fun_explicit">Template class <code>mem_fun_explicit</code></a></li>
<li><a href="#boost_multi_index_const_mem_fun">Macro <code>BOOST_MULTI_INDEX_CONST_MEM_FUN</code></a></li>
<li><a href="#boost_multi_index_mem_fun">Macro <code>BOOST_MULTI_INDEX_MEM_FUN</code></a></li>
</ul>
</li>
<li><a href="#composite_key_synopsis">Header
<code>"boost/multi_index/composite_key.hpp"</code> synopsis</a>
<ul>
<li><a href="#composite_key">Template class <code>composite_key</code></a></li>
<li><a href="#composite_key_result">Template class <code>composite_key_result</code></a></li>
<li><a href="#composite_key_compare">Template class <code>composite_key_compare</code></a></li>
<li><a href="#composite_key_result_less">Template class <code>composite_key_result_less</code></a></li>
<li><a href="#composite_key_result_greater">Template class <code>composite_key_result_greater</code></a></li>
<li><a href="#less_composite_key_result">Specialization of <code>std::less</code> for <code>composite_key</code> results</a></li>
<li><a href="#greater_composite_key_result">Specialization of <code>std::greater</code> for <code>composite_key</code> results</a></li>
<li><a href="#ordering_semantics">Ordering semantics</a></li>
</ul>
</li>
</ul>
<h2><a name="key_extractors">Key Extractors</a></h2>
<p>
Key extraction classes are used by <a href="ord_indices.html">ordered indices</a> to
obtain the sorting keys from the elements of a <code>multi_index_container</code>.
An <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>
class <code>KeyFromValue</code> is said to be a key extractor from a
type <code>Type</code> if
<ol>
<li>the type <code>KeyFromValue::result_type</code> is defined,</li>
<li><code>k1(ca)</code> is defined and returns a value convertible
to <code>const KeyFromValue::result_type&</code>,</li>
<li>if <code>k2</code> is a copy of <code>k1</code>, <code>k1(ca)</code> is the
same value as <code>k2(ca)</code>,</li>
</ol>
for every <code>k1</code>, <code>k2</code> of type <code>const KeyFromValue</code>,
and <code>ca</code> of type <code>const Type&</code>.
</p>
<p>
Additionally, <code>KeyFromValue</code> is a <i>read/write</i> key extractor
if the following extra conditions are met:
<ol>
<li><code>k1(a)</code> is defined and returns a value convertible
to <code>KeyFromValue::result_type&</code>,</li>
<li><code>const_cast<const KeyFromValue::result_type&>(k1(a))</code>
is the same value as
<code>k1(const_cast<const Type&>(a))</code>,</li>
</ol>
for every <code>k1</code> of type <code>const KeyFromValue</code> and
<code>a</code> of type <code>Type&</code>.
</p>
<p>
Boost.MultiIndex provides five general-purpose key extractors:
<ul>
<li><a href="#identity"><code>identity</code></a>,</li>
<li><a href="#member"><code>member</code></a>,</li>
<li><a href="#const_mem_fun"><code>const_mem_fun</code></a>,</li>
<li><a href="#mem_fun"><code>mem_fun</code></a> and</li>
<li><a href="#composite_key"><code>composite_key</code></a>,</li>
</ul>
plus replacements for some of them:
<ul>
<li><a href="#member_offset"><code>member_offset</code></a>,</li>
<li><a href="#const_mem_fun_explicit"><code>const_mem_fun_explicit</code></a> and</li>
<li><a href="#mem_fun_explicit"><code>mem_fun_explicit</code></a>,</li>
</ul>
that workaround some deficiencies in the support for non-type template parameters
by certain compilers.
</p>
<h3><a name="chained_pointers">Chained pointers</a></h3>
<p>
The key extractors provided by Boost.MultiIndex are templatized according
to the type <code>Type</code> and serve to extract keys not only from objects
of type <code>Type</code>, but also from reference wrappers provided by
<a href="../../../../doc/html/ref.html">Boost.Ref</a> and from <i>chained pointers</i>
to <code>Type</code> (or to reference wrappers of <code>Type</code>): a chained pointer
is any type <code>P</code> such that, for an object <code>p</code> of type
<code>const P</code>
<ul>
<li><code>*p</code> yields an object of type <code>Type&</code> or
<code>boost::reference_wrapper<Type></code>, OR</li>
<li><code>*p</code> yields a chained pointer to <code>Type</code>,</li>
</ul>
that is, chained pointers are arbitrary compositions of pointer-like objects
ultimately dereferencing to values of <code>Type&</code> or
<code>boost::reference_wrapper<Type></code>.
<p>
<h2><a name="synopsis">Header
<a href="../../../../boost/multi_index/key_extractors.hpp">
<code>"boost/multi_index/key_extractors.hpp"</code></a> synopsis</a>
</h2>
<blockquote><pre>
<span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>identity</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>member</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>mem_fun</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
<span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>multi_index</span><span class=special>/</span><span class=identifier>composite_key</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span>
</pre></blockquote>
<p>
This header includes all the key extractors provided by Boost.MultiIndex.
</p>
<h2>
<a name="identity_synopsis">Header
<a href="../../../../boost/multi_index/identity.hpp">
<code>"boost/multi_index/identity.hpp"</code></a> synopsis</a></h2>
<blockquote><pre>
<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
<span class=keyword>namespace</span> <span class=identifier>multi_index</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>struct</span> <span class=identifier>identity</span><span class=special>;</span>
<span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
<span class=special>}</span> <span class=comment>// namespace boost</span>
</pre></blockquote>
<h3><a name="identity">Template class <code>identity</code></a></h3>
<p>
<code>identity</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
that acts as a do-nothing identity functor.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>identity</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Type</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const
// only provided if Type is non-const</span>
<span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=comment>// only provided if Type is const</span>
<span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>remove_const</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
<code>identity<Type></code> is a model of:
<ul>
<li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
from <code>Type</code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<const Type></code>,</li>
<li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<Type></code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a> to
<code>const Type</code>,</li>
<li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>Type</code>.</li>
</ul>
</p>
<h4><code>identity</code> members</h4>
<code>template<typename ChainedPtr> Type& operator()(const ChainedPtr& x)const;</code>
<blockquote>
<b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
type to <code>Type</code>.<br>
<b>Returns:</b> a reference to the object chained-pointed to by <code>x</code>.
</blockquote>
<code>const Type& operator()(const Type&x)const;</code>
<blockquote>
<b>Returns:</b> <code>x</code>.
</blockquote>
<code>Type& operator()(Type &x)const;</code>
<blockquote>
<b>Returns:</b> <code>x</code>.
</blockquote>
<code>const Type& operator()(const reference_wrapper<const Type>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>x.get()</code>.
</blockquote>
<code>Type& operator()(const reference_wrapper<typename remove_const<Type>::type>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>x.get()</code>.
</blockquote>
<code>Type& operator()(const reference_wrapper<Type>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>x.get()</code>.
</blockquote>
<h2>
<a name="member_synopsis">Header
<a href="../../../../boost/multi_index/member.hpp">
<code>"boost/multi_index/member.hpp"</code></a> synopsis</a></h2>
<blockquote><pre>
<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
<span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMember</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>member</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=identifier>OffsetOfMember</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>member_offset</span><span class=special>;</span>
<span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_MEMBER</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)</span> <b>implementation defined</b>
<span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
<span class=special>}</span> <span class=comment>// namespace boost</span>
</pre></blockquote>
<h3><a name="member">Template class <code>member</code></a></h3>
<p>
<code>member</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
aimed at accessing a given member of a class.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMember</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>member</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const</span>
<span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
The <code>PtrToMember</code> template argument specifies the particular
<code>Type Class::*</code> pointer to the member to be extracted.
<code>member<Class,Type,PtrToMember></code> is a model of:
<ul>
<li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
from <code>Class</code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<const Class></code>,</li>
<li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<Class></code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>const Class</code>,</li>
<li>read/write <a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>Class</code>.</li>
</ul>
</p>
<h4><code>member</code> members</h4>
<code>template<typename ChainedPtr> Type& operator()(const ChainedPtr& x)const;</code>
<blockquote>
<b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
type to <code>Type</code>.<br>
<b>Returns:</b> a reference to the object chained-pointed to by <code>x</code>.
</blockquote>
<code>const Type& operator()(const Class&x)const;</code>
<blockquote>
<b>Returns:</b> <code>x.*PtrToMember</code>.
</blockquote>
<code>Type& operator()(const Class&x);</code>
<blockquote>
<b>Returns:</b> <code>x.*PtrToMember</code>.
</blockquote>
<code>const Type& operator()(const reference_wrapper<const Class>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>x.get().*PtrToMember</code>.
</blockquote>
<code>Type& operator()(const reference_wrapper<Class>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>x.get().*PtrToMember</code>.
</blockquote>
<h3><a name="member_offset">Template class <code>member_offset</code></a></h3>
<p>
Some compilers do not properly support pointers to members as non-type
template arguments. The following have been confirmed to have bugs in
this respect:
<ul>
<li>MSVC++ 6.0 (see
<a href="http://support.microsoft.com/default.aspx?scid=kb;EN-US;249045">Microsoft
Knowledge Base article #249045</a>),</li>
<li>MSVC++ 7.0 (not officially confirmed by Microsoft),</li>
<li>Intel C++ 7.0/7.1 for Windows (support issue #207321),</li>
<li>VisualAge 6.0 for AIX (internal defect #288539.)</li>
</ul>
In this situation, <code>member_offset</code> provides an
alternative to <a href="#member"><code>member</code></a> accepting offsets
instead of pointers to members. Please note that the use of
<code>offsetof</code> on non-POD types is forbidden by the standard;
luckily enough, most compilers accept it nevertheless, so
<code>member_offset</code> serves as a workaround for most practical purposes.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>size_t</span> <span class=identifier>OffsetOfMember</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>member_offset</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>Type</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span> <span class=comment>// only provided if Type is non-const</span>
<span class=keyword>const</span> <span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span><span class=special>&</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>As an example of use, given the class</p>
<blockquote><pre>
<span class=keyword>class</span> <span class=identifier>A</span>
<span class=special>{</span>
<span class=keyword>int</span> <span class=identifier>x</span><span class=special>;</span>
<span class=special>}</span>
</pre></blockquote>
<p>
the instantiation <code>member<A,int,&A::x></code> can be simulated then
as <code>member_offset<A,int,offsetof(A,x)></code>.
</p>
<h3><a name="boost_multi_index_member">Macro <code>BOOST_MULTI_INDEX_MEMBER</code></a></h3>
<blockquote><pre>
<span class=identifier>BOOST_MULTI_INDEX_MEMBER</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)</span>
</pre></blockquote>
<p>
This macro is provided as an aid for using <code>member</code> and
<code>member_offset</code> when writing cross-platform code. In the usual cases,
it expands to
</p>
<blockquote><pre>
<span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberName</span><span class=special>></span>
</pre></blockquote>
<p>
but it resolves to
</p>
<blockquote><pre>
<span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member_offset</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>offsetof</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>MemberName</span><span class=special>)></span>
</pre></blockquote>
<p>
if the <a href="../../../../libs/config/config.htm">Boost Configuration Library</a>
defect macro <code>BOOST_NO_POINTER_TO_MEMBER_TEMPLATE_PARAMETERS</code>
is defined.
</p>
<h2>
<a name="mem_fun_synopsis">Header
<a href="../../../../boost/multi_index/mem_fun.hpp">
<code>"boost/multi_index/mem_fun.hpp"</code></a> synopsis</a></h2>
<blockquote><pre>
<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
<span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()</span><span class=keyword>const</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>const_mem_fun</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()></span>
<span class=keyword>struct</span> <span class=identifier>mem_fun</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span>
<span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span>
<span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span>
<span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>const_mem_fun_explicit</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span>
<span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span>
<span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span>
<span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>mem_fun_explicit</span><span class=special>;</span>
<span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_CONST_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> <span class=special>\</span>
<b>implementation defined</b>
<span class=preprocessor>#define</span> <span class=identifier>BOOST_MULTI_INDEX_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span> <span class=special>\</span>
<b>implementation defined</b>
<span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
<span class=special>}</span> <span class=comment>// namespace boost</span>
</pre></blockquote>
<h3><a name="const_mem_fun">Template class <code>const_mem_fun</code></a></h3>
<p>
<code>const_mem_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
returning as key the result of invoking a given constant member function of a class.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()</span><span class=keyword>const</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>const_mem_fun</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
The <code>PtrToMemberFunction</code> template argument specifies the particular
<code>Type (Class::*PtrToMemberFunction)()const</code> pointer to the the constant
member function used in the extraction.
<code>const_mem_fun<Class,Type,PtrToMemberFunction></code> is a model of:
<ul>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>Class</code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<const Class></code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<Class></code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>const Class</code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>Class</code>.</li>
</ul>
</p>
<h4><code>const_mem_fun</code> members</h4>
<code>template<typename ChainedPtr> Type operator()(const ChainedPtr& x)const;</code>
<blockquote>
<b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
type to <code>Type</code>.<br>
<b>Returns:</b> <code>(y.*PtrToMemberFunction)()</code>, where <code>y</code> is the
object chained-pointed to by <code>x</code>.
</blockquote>
<code>Type operator()(const Class& x)const;</code>
<blockquote>
<b>Returns:</b> <code>(x.*PtrToMemberFunction)()</code>.
</blockquote>
<code>Type operator()(const reference_wrapper<const Class>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>.
</blockquote>
<code>Type operator()(const reference_wrapper<Class>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>.
</blockquote>
<h3><a name="mem_fun">Template class <code>mem_fun</code></a></h3>
<p>
<code>mem_fun</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
returning as key the result of invoking a given member function of a class.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*</span><span class=identifier>PtrToMemberFunction</span><span class=special>)()></span>
<span class=keyword>struct</span> <span class=identifier>mem_fun</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
The <code>PtrToMemberFunction</code> template argument specifies the particular
<code>Type (Class::*PtrToMemberFunction)()</code> pointer to the the member
function used in the extraction.
<code>mem_fun<Class,Type,PtrToMemberFunction></code> is a model of:
<ul>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<Class></code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>Class</code>.</li>
</ul>
</p>
<h4><code>mem_fun</code> members</h4>
<code>template<typename ChainedPtr> Type operator()(const ChainedPtr& x)const;</code>
<blockquote>
<b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
type to <code>Type</code>.<br>
<b>Returns:</b> <code>(y.*PtrToMemberFunction)()</code>, where <code>y</code> is the
object chained-pointed to by <code>x</code>.
</blockquote>
<code>Type operator()(Class& x)const;</code>
<blockquote>
<b>Returns:</b> <code>(x.*PtrToMemberFunction)()</code>.
</blockquote>
<code>Type operator()(const reference_wrapper<Class>& x)const;</code>
<blockquote>
<b>Returns:</b> <code>(x.get().*PtrToMemberFunction)()</code>.
</blockquote>
<h3><a name="const_mem_fun_explicit">Template class <code>const_mem_fun_explicit</code></a></h3>
<p>
MSVC++ 6.0 do not properly support pointers to constant member functions as non-type
template parameters, thus <a href="#const_mem_fun"><code>const_mem_fun</code></a> cannot be
used in this compiler. A simple workaround consists in specifying the <i>type</i> of
these pointers as an additional template parameter.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span>
<span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span>
<span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span>
<span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>const_mem_fun_explicit</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
<code>const_mem_fun_explicit</code> provides the very same functionality as
its <code>const_mem_fun</code> analogous instantiation. For example, given the type
</p>
<blockquote><pre>
<span class=keyword>struct</span> <span class=identifier>A</span>
<span class=special>{</span>
<span class=keyword>int</span> <span class=identifier>f</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
the extractor <code>const_mem_fun<A,int,&A::f></code> can be replaced by
<code>const_mem_fun_explicit<A,int,int (A::*)()const,&A::f></code>.
</p>
<h3><a name="mem_fun_explicit">Template class <code>mem_fun_explicit</code></a></h3>
<p>
For analogy with <a href="#const_mem_fun_explicit"><code>const_mem_fun_explicit</code></a>,
a variation of <a href="#mem_fun"><code>mem_fun</code></a> is provided accepting
an additional parameter with the type of the pointer to non-constant member function
used for extraction.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span>
<span class=keyword>class</span> <span class=identifier>Class</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Type</span><span class=special>,</span>
<span class=keyword>typename</span> <span class=identifier>PtrToMemberFunctionType</span><span class=special>,</span><span class=identifier>PtrToMemberFunctionType</span> <span class=identifier>PtrToMemberFunction</span>
<span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>mem_fun_explicit</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=keyword>typename</span> <span class=identifier>remove_reference</span><span class=special><</span><span class=identifier>Type</span><span class=special>>::</span><span class=identifier>type</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span> <span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=identifier>Class</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>Type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>Class</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<h3><a name="boost_multi_index_const_mem_fun">Macro
<code>BOOST_MULTI_INDEX_CONST_MEM_FUN</code></a></h3>
<blockquote><pre>
<span class=identifier>BOOST_MULTI_INDEX_CONST_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span>
</pre></blockquote>
<p>
Use this macro when writing cross-platform code selectively using
<code>const_mem_fun_explicit</code> in place of <code>const_mem_fun</code> for
compilers not supporting the latter. In the usual cases, the macro expands to
</p>
<blockquote><pre>
<span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>const_mem_fun</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span><span class=special>></span>
</pre></blockquote>
<p>
but it resolves to
</p>
<blockquote><pre>
<span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>const_mem_fun_explicit</span><span class=special><</span>
<span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*)()</span><span class=keyword>const</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span>
<span class=special>></span>
</pre></blockquote>
<p>
for MSVC++ 6.0 or lower.
</p>
<h3><a name="boost_multi_index_mem_fun">Macro
<code>BOOST_MULTI_INDEX_MEM_FUN</code></a></h3>
<blockquote><pre>
<span class=identifier>BOOST_MULTI_INDEX_MEM_FUN</span><span class=special>(</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>MemberFunName</span><span class=special>)</span>
</pre></blockquote>
<p>
By default, the macro expands to
</p>
<blockquote><pre>
<span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>mem_fun</span><span class=special><</span><span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span><span class=special>></span>
</pre></blockquote>
<p>
but it resolves to
</p>
<blockquote><pre>
<span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>mem_fun_explicit</span><span class=special><</span>
<span class=identifier>Class</span><span class=special>,</span><span class=identifier>Type</span><span class=special>,</span><span class=identifier>Type</span> <span class=special>(</span><span class=identifier>Class</span><span class=special>::*)()</span><span class=special>,&</span><span class=identifier>Class</span><span class=special>::</span><span class=identifier>MemberFunName</span>
<span class=special>></span>
</pre></blockquote>
<p>
for MSVC++ 6.0 or lower.
</p>
<h2>
<a name="composite_key_synopsis">Header
<a href="../../../../boost/multi_index/composite_key.hpp">
<code>"boost/multi_index/composite_key.hpp"</code></a> synopsis</a></h2>
<blockquote><pre>
<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span>
<span class=keyword>namespace</span> <span class=identifier>multi_index</span><span class=special>{</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValuen</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_result</span><span class=special>;</span>
<span class=comment>// comparison for composite_key_result:</span>
<span class=comment>// <b>OP</b> is any of =,<,!=,>,>=,<=</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Compare0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Comparen</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_compare</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_result_less</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_result_greater</span><span class=special>;</span>
<span class=special>}</span> <span class=comment>// namespace boost::multi_index</span>
<span class=special>}</span> <span class=comment>// namespace boost</span>
<span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>less</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>greater</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>>;</span>
<span class=special>}</span> <span class=comment>// namespace std</span>
</pre></blockquote>
<h3><a name="composite_key">Template class <code>composite_key</code></a></h3>
<p>
<code>composite_key</code> is a <a href="#key_extractors"><code>Key Extractor</code></a>
returning the combined value of several key extractors whose type is specified
at compile time. The returned object is of type
<a href="#composite_key_result">
<code>composite_key_result</code></a><code><composite_key></code>.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>KeyFromValuen</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>KeyFromValue0</span><span class=special>,...,</span><span class=identifier>KeyFromValuen</span><span class=special>></span> <span class=identifier>key_extractor_tuple</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=identifier>Value</span> <span class=identifier>value_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>composite_key</span><span class=special>></span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=identifier>composite_key</span><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>KeyFromValue0</span><span class=special>&</span> <span class=identifier>k0</span><span class=special>=</span><span class=identifier>KeyFromValue0</span><span class=special>(),</span>
<span class=special>...</span>
<span class=keyword>const</span> <span class=identifier>KeyFromValuen</span><span class=special>&</span> <span class=identifier>kn</span><span class=special>=</span><span class=identifier>KeyFromValuen</span><span class=special>());</span>
<span class=identifier>composite_key</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_extractor_tuple</span><span class=special>&</span> <span class=identifier>x</span><span class=special>);</span>
<span class=keyword>const</span> <span class=identifier>key_extractor_tuple</span><span class=special>&</span> <span class=identifier>key_extractors</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>key_extractor_tuple</span><span class=special>&</span> <span class=identifier>key_extractors</span><span class=special>()</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>ChainedPtr</span><span class=special>></span>
<span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>ChainedPtr</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>value_type</span><span class=special>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=keyword>const</span> <span class=identifier>value_type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=identifier>result_type</span> <span class=keyword>operator</span><span class=special>()(</span><span class=keyword>const</span> <span class=identifier>reference_wrapper</span><span class=special><</span><span class=identifier>value_type</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
<code>KeyFromValue0</code>, ... , <code>KeyFromValuen</code> are the types of
the key extractors combined into the composite key. Each of these types
must be a <a href="#key_extractors"><code>Key Extractor</code></a> from
<code>Value</code>. At least a key extractor must be provided. The maximum
number of key extractors of a <code>composite_key</code> instantiation is
implementation defined. <code>composite_key</code> internally stores an
object of every constituent key extractor type.
<code>composite_key<Value,KeyFromValue0,...,KeyFromValuen></code> is a model
of:
<ul>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>Value</code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<const Value></code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from <code>reference_wrapper<Value></code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>const Value</code>,</li>
<li><a href="#key_extractors"><code>Key Extractor</code></a>
from any <a href="#chained_pointers">chained pointer</a>
to <code>Value</code>.</li>
</ul>
</p>
<h4><code>composite_key</code> members</h4>
<code>composite_key(<br>
const KeyFromValue0& k0=KeyFromValue0(),<br>
...<br>
const KeyFromValuen& kn=KeyFromValuen());
</code>
<blockquote>
<b>Effects:</b> Constructs a <code>composite_key</code> that stores
copies of the key extractor objects supplied.
</blockquote>
<code>composite_key(const key_extractor_tuple& x);</code>
<blockquote>
<b>Effects:</b> Constructs a <code>composite_key</code> that stores
copies of the key extractor objects supplied in <code>x</code>.
</blockquote>
<code>const key_extractor_tuple& key_extractors()const;</code>
<blockquote>
<b>Returns:</b> a constant reference to a tuple holding the
key extractors internally stored by the <code>composite_key</code>.
</blockquote>
<code>key_extractor_tuple& key_extractors();</code>
<blockquote>
<b>Returns:</b> a reference to a tuple holding the
key extractors internally stored by the <code>composite_key</code>.
</blockquote>
<code>template<typename ChainedPtr><br>
result_type operator()(const ChainedPtr& x)const;</code>
<blockquote>
<b>Requires:</b> <code>ChainedPtr</code> is a <a href="#chained_pointers">chained pointer</a>
type to <code>result_type</code>.<br>
<b>Returns:</b> a <code>result_type</code> object dependent on
<code>*this</code> and <code>y</code>, where <code>y</code> is the
object chained-pointed to by <code>x</code>.
</blockquote>
<code>result_type operator()(const value_type& x)const;</code>
<blockquote>
<b>Returns:</b> a <code>result_type</code> object dependent on
<code>*this</code> and <code>x</code>.
</blockquote>
<code>result_type operator()(const reference_wrapper<const value_type>& x)const;</code>
<blockquote>
<b>Returns:</b> a <code>result_type</code> object dependent on
<code>*this</code> and <code>x.get()</code>.
</blockquote>
<code>result_type operator()(const reference_wrapper<value_type>& x)const;</code>
<blockquote>
<b>Returns:</b> a <code>result_type</code> object dependent on
<code>*this</code> and <code>x.get()</code>.
</blockquote>
<h3><a name="composite_key_result">Template class
<code>composite_key_result</code></a></h3>
<p>
This is an opaque type returned by <code>composite_key</code>
instantiations as their extracted key.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_result</span>
<span class=special>{</span>
<b>no public interface available</b>
<span class=special>};</span>
<span class=comment>// comparison:</span>
<span class=comment>// <b>OP</b> is any of =,<,!=,>,>=,<=</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span> <b><i>OP</i></b><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>);</span>
</pre></blockquote>
<code>CompositeKey</code> is the <code>composite_key</code> instantiation to
which the <code>composite_key_result</code> type is associated. Objects of type
<code>composite_key_result</code> returned by a composite key must be always treated
as <i>temporary</i>, i.e. they should not be stored or copied.
<code>composite_key_result</code> is <i>not</i> guaranteed to be a model of
<a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
<code>Default Constructible</code></a> or
<a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>.
Every object of type <code>composite_key_result<CompositeKey></code> is
internally asociated to the <code>CompositeKey</code> from which it is returned
and the object of type <code>CompositeKey::result_type</code> to which the
composite key was applied.
</p>
<h4><a name="ckey_result_notation">Notation</a></h4>
<p>
Given an <code>x</code> of type <code>composite_key_result<CompositeKey></code>,
we use the following notation:
<ul>
<li><code>ck(x)</code> is the <code>CompositeKey</code> object associated to
<code>x</code>,</li>
<li><code>v(x)</code> is the object of type <code>CompositeKey::value_type</code>
associated to <code>x</code>,</li>
<li><code>k<sub>i</sub>(x) = ck(x).key_extractors().get<i>()</code>,
that is, is the <code>i</code>-th key extractor of <code>ck(x)</code>,</li>
<li><code>x<sub>i</sub> = k<sub>i</sub>(x)(v(x))</code>, that is, the
key extracted from <code>v(x)</code> by the <code>i</code>-th key extractor,</li>
<li><code>length(x)</code> is the number of key extractors of <code>ck(x)</code>.</li>
</ul>
Also, if <code>y</code> is a tuple of values, we define:
<ul>
<li><code>y<sub>i</sub>=y.get<i>()</code>,</li>
<li><code>length(y)</code> is the number of elements of <code>y</code>.</li>
</ul>
</p>
<h4>Comparison operators</h4>
<code>template<typename CompositeKey1,typename CompositeKey2><br>
bool operator==(<br>
const composite_key_result<CompositeKey1>& x,<br>
const composite_key_result<CompositeKey2>& y);<br>
template<typename CompositeKey,typename Value0,...,typename Valuen><br>
bool operator==(<br>
const composite_key_result<CompositeKey>& x,<br>
const tuple<Value0,...,Valuen>& y);<br>
template<typename Value0,...,typename Valuen,typename CompositeKey><br>
bool operator==(<br>
const tuple<Value0,...,Valuen>& x,<br>
const composite_key_result<CompositeKey>& y);
</code>
<blockquote>
<b>Requires:</b> <code>length(x)==length(y)</code>. The expression
<code>x<sub>i</sub>==y<sub>i</sub></code> is valid for all <code>i</code>
in <code>[0,length(x))</code>.</br>
<b>Returns:</b> <code>true</code> if and only if
<blockquote>
<code>x<sub>i</sub>==y<sub>i</sub></code> for all <code>i</code>
in <code>[0,length(x))</code>.
</blockquote>
<b>Complexity:</b> No more key extraction operations and comparisons
are performed than those necessary for the evaluation of the expression above,
starting at <code>i==0</code>. The evaluation is short-circuited as soon as
the result is determined to be <code>false</code>.
</blockquote>
<code>template<typename CompositeKey1,typename CompositeKey2><br>
bool operator<(<br>
const composite_key_result<CompositeKey1>& x,<br>
const composite_key_result<CompositeKey2>& y);<br>
template<typename CompositeKey,typename Value0,...,typename Valuen><br>
bool operator<(<br>
const composite_key_result<CompositeKey>& x,<br>
const tuple<Value0,...,Valuen>& y);<br>
template<typename Value0,...,typename Valuen,typename CompositeKey><br>
bool operator<(<br>
const tuple<Value0,...,Valuen>& x,<br>
const composite_key_result<CompositeKey>& y);
</code>
<blockquote>
<b>Requires:</b> The expressions
<code>x<sub>i</sub><y<sub>i</sub></code> and
<code>y<sub>i</sub><x<sub>i</sub></code> are valid for all <code>i</code>
in <code>[0,min(length(x),length(y)))</code>.</br>
<b>Returns:</b> <code>true</code> if and only if there exists some
<code>j</code> in the range <code>[0,min(length(x),length(y)))</code>
such that
<blockquote>
<code>!(x<sub>i</sub><y<sub>i</sub>) && !(y<sub>i</sub><x<sub>i</sub>)</code>
for all <code>i</code> in <code>[0,j)</code>,<br>
<code> x<sub>j</sub><y<sub>j</sub></code>.
</blockquote>
<b>Complexity:</b> No more key extraction operations and comparisons
are performed than those necessary for the evaluation of the expression above,
starting at <code>i==0</code>. The evaluation is short-circuited as soon as
the result is determined to be <code>false</code>.
</blockquote>
<code>template<typename CompositeKey1,typename CompositeKey2><br>
bool operator <b><i>OP</i></b>(<br>
const composite_key_result<CompositeKey1>& x,<br>
const composite_key_result<CompositeKey2>& y);<br>
template<typename CompositeKey,typename Value0,...,typename Valuen><br>
bool operator <b><i>OP</i></b>(<br>
const composite_key_result<CompositeKey>& x,<br>
const tuple<Value0,...,Valuen>& y);<br>
template<typename Value0,...,typename Valuen,typename CompositeKey><br>
bool operator <b><i>OP</i></b>(<br>
const tuple<Value0,...,Valuen>& x,<br>
const composite_key_result<CompositeKey>& y);
</code>
<p>
(<code><b><i>OP</i></b></code> is any of <code>!=</code>, <code>></code>,
<code>>=</code>, <code><=</code>.)
</p>
<blockquote>
<b>Requires:</b> The expressions given below are valid (for the particular
<code><b><i>OP</i></b></code> considered.)</br>
<b>Returns:</b> <code>true</code> if and only if
<blockquote>
<code>!(x==y)</code> (<code><b><i>OP</i></b></code> is <code>!=</code>),<br>
<code> y< x </code> (<code><b><i>OP</i></b></code> is <code>> </code>),<br>
<code>!(x< y)</code> (<code><b><i>OP</i></b></code> is <code>>=</code>),<br>
<code>!(y< x)</code> (<code><b><i>OP</i></b></code> is <code><=</code>).
</blockquote>
</blockquote>
<h3><a name="composite_key_compare">Template class
<code>composite_key_compare</code></a></h3>
<p>
<code>composite_key_compare</code> compares <code>composite_key_result</code>
instantiations between them and with tuples of values using an internally stored
collection of elementary comparison predicates.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Compare0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Comparen</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_compare</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Compare0</span><span class=special>,...,</span><span class=identifier>Comparen</span><span class=special>></span> <span class=identifier>key_comp_tuple</span><span class=special>;</span>
<span class=identifier>composite_key_compare</span><span class=special>(</span>
<span class=keyword>const</span> <span class=identifier>Compare0</span><span class=special>&</span> <span class=identifier>co</span><span class=special>=</span><span class=identifier>Compare0</span><span class=special>(),</span>
<span class=special>...</span>
<span class=keyword>const</span> <span class=identifier>Comparen</span><span class=special>&</span> <span class=identifier>cn</span><span class=special>=</span><span class=identifier>Comparen</span><span class=special>());</span>
<span class=identifier>composite_key_compare</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>key_comp_tuple</span><span class=special>&</span> <span class=identifier>x</span><span class=special>);</span>
<span class=keyword>const</span> <span class=identifier>key_comp_tuple</span><span class=special>&</span> <span class=identifier>key_comps</span><span class=special>()</span><span class=keyword>const</span><span class=special>{</span><span class=keyword>return</span> <span class=special>*</span><span class=keyword>this</span><span class=special>;}</span>
<span class=identifier>key_comp_tuple</span><span class=special>&</span> <span class=identifier>key_comps</span><span class=special>(){</span><span class=keyword>return</span> <span class=special>*</span><span class=keyword>this</span><span class=special>;}</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
<code>Compare0</code>, ... , <code>Compare0</code> are the types of the comparison
predicates stored by <code>composite_key_compare</code>. Each of these types
must be a <a href="http://www.sgi.com/tech/stl/BinaryPredicate.html">
<code>Binary Predicate</code></a>. At least a
comparison predicate must be provided. The maximum number of comparison predicates of
a <code>composite_key_compare</code> instantiation is implementation defined.
<code>composite_key_compare</code> is
<a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>.
It is also
<a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
<code>Default Constructible</code></a>
if each <code>Comparei</code> is
<a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
<code>Default Constructible</code></a>.
</p>
<p>
Note that formally it is not required that the <code>Comparei</code> types
behave as comparison predicates in any definite way. However, the
semantics of <code>composite_key_compare</code> are well defined if this
is the case, as explained in the <a href="#ordering_semantics">ordering
semantics</a> section.
</p>
<h4>Notation</h4>
<p>
In what follows we use the same <a href="#ckey_result_notation">notation</a>
introduced for <code>composite_key_result</code>.
<h4><code>composite_key_compare</code> members</h4>
<code>composite_key_compare(<br>
const Compare0& c0=Compare0(),<br>
...<br>
const Comparen& kn=Comparen());
</code>
<blockquote>
<b>Effects:</b> Constructs a <code>composite_key_compare</code> that stores
copies of the comparison predicates supplied.
</blockquote>
<code>composite_key_compare(const key_comp_tuple& x);</code>
<blockquote>
<b>Effects:</b> Constructs a <code>composite_key_compare</code> that stores
copies of the comparison predicate objects supplied in <code>x</code>.
</blockquote>
<code>const key_comp_tuple& key_comps()const;</code>
<blockquote>
<b>Returns:</b> a constant reference to a tuple holding the
comparison predicate objects internally stored by the
<code>composite_key_compare</code>.
</blockquote>
<code>key_comp_tuple& key_comps();</code>
<blockquote>
<b>Returns:</b> a reference to a tuple holding the
comparison predicate objects internally stored by the
<code>composite_key_compare</code>.
</blockquote>
<code>
template<typename CompositeKey1,typename CompositeKey2><br>
bool operator()(<br>
const composite_key_result<CompositeKey1> & x,<br>
const composite_key_result<CompositeKey2> & y)const;<br>
template<typename CompositeKey,typename Value0,...,typename Valuen><br>
bool operator()(<br>
const composite_key_result<CompositeKey>& x,<br>
const tuple<Value0,...,Valuen>& y)const;<br>
template<typename Value0,...,typename Valuen,typename CompositeKey><br>
bool operator()(<br>
const tuple<Value0,...,Valuen>& x,<br>
const composite_key_result<CompositeKey>& y)const;<br>
</code>
<blockquote>
<b>Requires:</b> The expressions
<code>key_comps().get<i>()(x<sub>i</sub>,y<sub>i</sub>)</code> and
<code>key_comps().get<i>()(y<sub>i</sub>,x<sub>i</sub>)</code>
are valid for all <code>i</code>
in <code>[0,min(length(x),length(y)))</code>.</br>
<b>Returns:</b> <code>true</code> if and only if there exists some
<code>j</code> in the range <code>[0,min(length(x),length(y)))</code>
such that
<blockquote>
<code>!key_comps().get<i>()(x<sub>i</sub>,y<sub>i</sub>) && !key_comps().get<i>()(y<sub>i</sub>,x<sub>i</sub>)</code>
for all <code>i</code> in <code>[0,j)</code>,<br>
<code> key_comps().get<j>()(x<sub>j</sub>,y<sub>j</sub>)</code>.
</blockquote>
<b>Complexity:</b> No more key extraction operations and comparisons
are performed than those necessary for the evaluation of the expression above,
starting at <code>i==0</code>. The evaluation is short-circuited as soon as
the result is determined to be <code>false</code>.
</blockquote>
<h3><a name="composite_key_result_less">Template class
<code>composite_key_result_less</code></a></h3>
<p>
<code>composite_key_result</code> acts as a particularization of
<code>composite_key_compare</code> where all the comparison predicates supplied
are instantiations of <code>std::less</code>.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_result_less</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>first_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
<code>CompositeKeyResult</code> must be an instantiation of
<code>composite_key_result</code> for some type
<code>composite_key<KeyFromValue0,...,KeyFromValuen></code>.
<code>composite_key_result_less<CompositeKeyResult>::operator()</code> is
then equivalent to
<code>composite_key_compare<Compare0,...,Comparen>::operator()</code>, taking
<blockquote>
<code>Comparei = std::less<KeyFromValuei::result_type></code> for all
<code>i = 0,...,n</code>.
</blockquote>
</p>
<p>
In addition to the requirements on <code>Comparei</code> imposed by
<code>composite_key_compare</code>, each of these types must be
<a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
<code>Default Constructible</code></a>. <code>composite_key_result_less</code>
is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
<code>Default Constructible</code></a> and
<a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>.
</p>
<h3><a name="composite_key_result_greater">Template class
<code>composite_key_result_greater</code></a></h3>
<p>
<code>composite_key_result</code> acts as a particularization of
<code>composite_key_compare</code> where all the comparison predicates supplied
are instantiations of <code>std::greater</code>.
</p>
<blockquote><pre>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKeyResult</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>composite_key_result_greater</span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>first_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
</pre></blockquote>
<p>
<code>CompositeKeyResult</code> must be an instantiation of
<code>composite_key_result</code> for some type
<code>composite_key<KeyFromValue0,...,KeyFromValuen></code>.
<code>composite_key_result_greater<CompositeKeyResult>::operator()</code> is
then equivalent to
<code>composite_key_compare<Compare0,...,Comparen>::operator()</code>, taking
<blockquote>
<code>Comparei = std::greater<KeyFromValuei::result_type></code> for all
<code>i = 0,...,n</code>.
</blockquote>
</p>
<p>
In addition to the requirements on <code>Comparei</code> imposed by
<code>composite_key_compare</code>, each of these types must be
<a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
<code>Default Constructible</code></a>. <code>composite_key_result_greater</code>
is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
<code>Default Constructible</code></a> and
<a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a>.
</p>
<h3><a name="less_composite_key_result">Specialization of <code>std::less</code> for
<code>composite_key</code> results</a></h3>
<p>
<code>std::less<CompositeKeyResult></code>, for <code>CompositeKeyResult</code>
being an instantiation of <code>composite_key_result</code>, has the same interface
and functionality that <code>composite_key_result_less<CompositeKeyResult></code>.
</p>
<blockquote><pre>
<span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>less</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>></span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>first_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
<span class=special>}</span> <span class=comment>// namespace std</span>
</pre></blockquote>
<h3><a name="greater_composite_key_result">Specialization of <code>std::greater</code> for
<code>composite_key</code> results</a></h3>
<p>
<code>std::greater<CompositeKeyResult></code>, for <code>CompositeKeyResult</code>
being an instantiation of <code>composite_key_result</code>, has the same interface
and functionality that <code>composite_key_result_greater<CompositeKeyResult></code>.
</p>
<blockquote><pre>
<span class=keyword>namespace</span> <span class=identifier>std</span><span class=special>{</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>struct</span> <span class=identifier>greater</span><span class=special><</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>></span> <span class=special>></span>
<span class=special>{</span>
<span class=keyword>typedef</span> <span class=identifier>CompositeKeyResult</span> <span class=identifier>first_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=identifier>first_argument_type</span> <span class=identifier>second_argument_type</span><span class=special>;</span>
<span class=keyword>typedef</span> <span class=keyword>bool</span> <span class=identifier>result_type</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey2</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey1</span><span class=special>></span> <span class=special>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey2</span><span class=special>></span> <span class=special>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>Value0</span><span class=special>,...,</span><span class=keyword>typename</span> <span class=identifier>Valuen</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>CompositeKey</span><span class=special>></span>
<span class=keyword>bool</span> <span class=keyword>operator</span><span class=special>()(</span>
<span class=keyword>const</span> <span class=identifier>tuple</span><span class=special><</span><span class=identifier>Value0</span><span class=special>,...,</span><span class=identifier>Valuen</span><span class=special>>&</span> <span class=identifier>x</span><span class=special>,</span>
<span class=keyword>const</span> <span class=identifier>composite_key_result</span><span class=special><</span><span class=identifier>CompositeKey</span><span class=special>>&</span> <span class=identifier>y</span><span class=special>)</span><span class=keyword>const</span><span class=special>;</span>
<span class=special>};</span>
<span class=special>}</span> <span class=comment>// namespace std</span>
</pre></blockquote>
<h3><a name="ordering_semantics">Ordering semantics</a></h3>
<p>
Consider an instantiation of <code>composite_key_compare</code> with
types <code>Compare0</code>, ... , <code>Comparen</code> such that each
<code>Comparei</code> is a
<a href="http://www.sgi.com/tech/stl/StrictWeakOrdering.html"><code>Strict
Weak Ordering</code></a> on a certain type <code>Ti</code>. Then the following
properties hold.
</p>
<p>
Let <code>CompositeKey</code> be a type of the form
<code>composite_key<Value,KeyFromValue0,...,KeyFromValuej></code>,
with <code>j <= n</code>, such that
<blockquote>
<code>KeyFromValuei::result_type = Ti</code>, for all <code>i = 0,...,j</code>.
</blockquote>
Then, <code>composite_key_compare</code> is a
<a href="http://www.sgi.com/tech/stl/StrictWeakOrdering.html"><code>Strict
Weak Ordering</code></a> on elements of type
<code>composite_key_result<CompositeKey></code>, and the order induced
is lexicographical. Also, the following types are
<a href="ord_indices.html#set_operations"><code>Compatible Keys</code></a> of
<code>composite_key_compare</code> with respect to
<code>composite_key_result<CompositeKey></code>:
<blockquote>
<code>tuple<Q0,...,Qk></code>, <code>k <= n</code><br>
<code>composite_key_result<composite_key<K0,...,Kk> ></code>, with
<code>Ki::result_type = Qi</code> for all <code>i = 0,...,k</code>.
</blockquote>
provided that each <code>Qi</code> is either <code>Ti</code> or a
<a href="ord_indices.html#set_operations"><code>Compatible Key</code></a>
of <code>Comparei</code>. In this case, the comparison is done
lexicographically only on the first <code>1+min(j,k)</code> elements.
</p>
<p>
The rationale of this design is simple:
<code>composite_key_result</code>s are regarded as "virtual" tuples
with each element being the result of the corresponding elementary key
extractor. Accordingly, these objects and actual tuples are compared
lexicographically taking the minimum length of the operands considered.
</p>
<p>
Analogous properties hold for
<code>composite_key_result::operator<</code>. As for
<code>operator==</code>, the semantics is compatible with that of
less-than comparison, with the additional constraint that only objects
of the same length can be tested for equality. In this regard,
the equivalence classes induced by <code>x==y</code> are subsets
of those associated to <code>!(x<y)&&!(y<x)</code>.
</p>
<hr>
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Sequenced indices
</a></div>
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Boost.MultiIndex reference
</a></div>
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Compiler specifics
</a></div><br clear="all" style="clear: all;">
<br>
<p>Revised September 3rd 2004</p>
<p>© Copyright 2003-2004 Joaquín M López Muñoz.
Distributed under the Boost Software
License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt">
LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">
http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
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