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container_hash/doc/ref.xml
Daniel James 53fbb04e88 Move 'functional' headers and update paths
2017-12-29 13:58:48 +00:00

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<!--
Copyright Daniel James 2005-2009
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-->
<library-reference>
<section id="hash.reference.specification">
<para>For the full specification, see section 6.3 of the
<ulink url="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf">C++ Standard Library Technical Report</ulink>
and issue 6.18 of the
<ulink url="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1837.pdf">Library Extension Technical Report Issues List</ulink> (page 63).
</para>
</section>
<header name="boost/container_hash/hash.hpp">
<para>
Defines <code><classname>boost::hash</classname></code>,
and helper functions.
</para>
<namespace name="boost">
<!--
boost::hash
-->
<struct name="hash">
<template>
<template-type-parameter name="T"/>
</template>
<inherit access="public">
<classname>std::unary_function&lt;T, std::size_t&gt;</classname>
</inherit>
<purpose><simpara>A <ulink url="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf">TR1</ulink> compliant hash function object.</simpara></purpose>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>T const&amp;</paramtype>
</parameter>
<returns><para>
<programlisting><functionname>hash_value</functionname>(val)</programlisting>
</para></returns>
<notes>
<para>
The call to <code><functionname>hash_value</functionname></code>
is unqualified, so that custom overloads can be
found via argument dependent lookup.
</para>
<para>
This is not defined when the macro <code>BOOST_HASH_NO_EXTENSIONS</code>
is defined. The specializations are still defined, so only the specializations
required by TR1 are defined.
</para>
<para>
Forward declared in
<code>&lt;boost/container_hash/hash_fwd.hpp&gt;</code>
</para>
<para>
This hash function is not intended for general use, and isn't
guaranteed to be equal during separate runs of a program - so
please don't use it for any persistent storage or communication.
</para>
</notes>
<throws><para>
Only throws if
<code><functionname>hash_value</functionname>(T)</code> throws.
</para></throws>
</method>
</struct>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>bool</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>bool</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>char</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>char</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>signed char</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>signed char</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>unsigned char</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>unsigned char</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>wchar_t</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>wchar_t</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>char16_t</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>char16_t</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>char32_t</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>char32_t</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>short</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>short</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>unsigned short</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>unsigned short</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>int</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>int</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>unsigned int</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>unsigned int</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>long</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>long</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>unsigned long</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>unsigned long</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>long long</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>long long</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>unsigned long long</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>unsigned long long</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>float</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>float</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>double</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>double</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>long double</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>long double</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>std::string</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>std::string const&amp;</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>std::wstring</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>std::wstring const&amp;</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>std::u16string</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>std::u16string const&amp;</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>std::u32string</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>std::u32string const&amp;</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
<para><functionname>hash_value</functionname>(val) in Boost.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template>
<template-type-parameter name="T"/>
</template>
<specialization>
<template-arg>T*</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>T*</paramtype>
</parameter>
<returns>
<para>Unspecified in TR1, except that equal arguments yield the same result.</para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
</struct-specialization>
<struct-specialization name="hash">
<template></template>
<specialization>
<template-arg>std::type_index</template-arg>
</specialization>
<method name="operator()" cv="const">
<type>std::size_t</type>
<parameter name="val">
<paramtype>std::type_index</paramtype>
</parameter>
<returns>
<para><code>val.hash_code()</code></para>
</returns>
<throws><para>Doesn't throw</para></throws>
</method>
<notes>
<para>
Only available if it's in your standard library and Boost.Config
is aware of it.
</para>
</notes>
</struct-specialization>
<free-function-group name="Support functions (Boost extension).">
<!--
boost::hash_combine
-->
<function name="hash_combine">
<template>
<template-type-parameter name="T"/>
</template>
<type>void</type>
<parameter name="seed"><paramtype>size_t &amp;</paramtype></parameter>
<parameter name="v"><paramtype>T const&amp;</paramtype></parameter>
<purpose><simpara>
Called repeatedly to incrementally create a hash value from
several variables.
</simpara></purpose>
<effects>
Updates <code>seed</code> with a new hash value generated by
combining it with the result of
<code><functionname>hash_value</functionname>(v)</code>. Will
always produce the same result for the same combination of
<code>seed</code> and
<code><functionname>hash_value</functionname>(v)</code> during
the single run of a program.
</effects>
<notes>
<para><functionname>hash_value</functionname> is called without
qualification, so that overloads can be found via ADL.</para>
<para>This is an extension to TR1</para>
<para>
Forward declared in
<code>&lt;boost/container_hash/hash_fwd.hpp&gt;</code>
</para>
<para>
This hash function is not intended for general use, and isn't
guaranteed to be equal during separate runs of a program - so
please don't use it for any persistent storage or communication.
</para>
</notes>
<throws>
Only throws if <functionname>hash_value</functionname>(T) throws.
Strong exception safety, as long as <functionname>hash_value</functionname>(T)
also has strong exception safety.
</throws>
</function>
<!--
boost::hash_range
-->
<overloaded-function name="hash_range">
<signature>
<template>
<template-type-parameter name="It"/>
</template>
<type>std::size_t</type>
<parameter name="first"><paramtype>It</paramtype></parameter>
<parameter name="last"><paramtype>It</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="It"/>
</template>
<type>void</type>
<parameter name="seed"><paramtype>std::size_t&amp;</paramtype></parameter>
<parameter name="first"><paramtype>It</paramtype></parameter>
<parameter name="last"><paramtype>It</paramtype></parameter>
</signature>
<purpose><simpara>
Calculate the combined hash value of the elements of an iterator
range.
</simpara></purpose>
<effects>
<para>For the two argument overload:
<programlisting>
size_t seed = 0;
for(; first != last; ++first)
{
<functionname>hash_combine</functionname>(seed, *first);
}
return seed;
</programlisting>
</para>
<para>For the three arguments overload:</para>
<programlisting>
for(; first != last; ++first)
{
<functionname>hash_combine</functionname>(seed, *first);
}
</programlisting>
</effects>
<notes>
<para>
<code>hash_range</code> is sensitive to the order of the elements
so it wouldn't be appropriate to use this with an unordered
container.
</para>
<para>This is an extension to TR1</para>
<para>
Forward declared in
<code>&lt;boost/container_hash/hash_fwd.hpp&gt;</code>
</para>
<para>
This hash function is not intended for general use, and isn't
guaranteed to be equal during separate runs of a program - so
please don't use it for any persistent storage or communication.
</para>
</notes>
<throws><para>
Only throws if <code><functionname>hash_value</functionname>(std::iterator_traits&lt;It&gt;::value_type)</code>
throws. <code>hash_range(std::size_t&amp;, It, It)</code> has basic exception safety as long as
<code><functionname>hash_value</functionname>(std::iterator_traits&lt;It&gt;::value_type)</code>
has basic exception safety.
</para></throws>
</overloaded-function>
</free-function-group>
<free-function-group name="Overloadable hash implementation (Boost extension).">
<!--
boost::hash_value - integers
-->
<overloaded-function name="hash_value">
<purpose><simpara>
Implementation of the hash function.
</simpara></purpose>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>bool</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>char</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>signed char</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>unsigned char</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>wchar_t</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>char16_t</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>char32_t</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>short</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>unsigned short</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>int</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>unsigned int</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>long</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>unsigned long</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>long long</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>unsigned long long</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>float</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>double</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>long double</paramtype></parameter>
</signature>
<signature>
<template><template-type-parameter name="T"/></template>
<type>std::size_t</type>
<parameter name="val"><paramtype>T* const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T"/>
<template-nontype-parameter name="N"><type>unsigned</type></template-nontype-parameter>
</template>
<type>std::size_t</type>
<parameter><paramtype>T (&amp;val)[N]</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T"/>
<template-nontype-parameter name="N"><type>unsigned</type></template-nontype-parameter>
</template>
<type>std::size_t</type>
<parameter><paramtype>const T (&amp;val)[N]</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="Ch"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val">
<paramtype>std::basic_string&lt;Ch, std::char_traits&lt;Ch&gt;, A&gt; const&amp;</paramtype>
</parameter>
</signature>
<signature>
<template>
<template-type-parameter name="A"/>
<template-type-parameter name="B"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::pair&lt;A, B&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::vector&lt;T, A&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::list&lt;T, A&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::deque&lt;T, A&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="K"/>
<template-type-parameter name="C"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::set&lt;K, C, A&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="K"/>
<template-type-parameter name="C"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::multiset&lt;K, C, A&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="K"/>
<template-type-parameter name="T"/>
<template-type-parameter name="C"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::map&lt;K, T, C, A&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="K"/>
<template-type-parameter name="T"/>
<template-type-parameter name="C"/>
<template-type-parameter name="A"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::multimap&lt;K, T, C, A&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::complex&lt;T&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::type_index</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T"/>
<template-nontype-parameter name="N">
<type>std::size_t</type>
</template-nontype-parameter>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::array&lt;T, N&gt; const&amp;</paramtype></parameter>
</signature>
<signature>
<template>
<template-type-parameter name="T" pack="1"/>
</template>
<type>std::size_t</type>
<parameter name="val"><paramtype>std::tuple&lt;T...&gt;</paramtype></parameter>
</signature>
<description><para>
Generally shouldn't be called directly by users, instead they should use
<classname>boost::hash</classname>, <functionname>boost::hash_range</functionname>
or <functionname>boost::hash_combine</functionname> which
call <code>hash_value</code> without namespace qualification so that overloads
for custom types are found via ADL.
</para></description>
<notes>
<para>This is an extension to TR1</para>
<para>
This hash function is not intended for general use, and isn't
guaranteed to be equal during separate runs of a program - so
please don't use it for any persistent storage or communication.
</para>
</notes>
<throws>
Only throws if a user supplied version of
<code><functionname>hash_value</functionname></code>
throws for an element of a container, or
one of the types stored in a pair.
</throws>
<returns>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>Types</entry>
<entry>Returns</entry>
</row>
</thead>
<tbody>
<row>
<entry><code>bool</code>,
<code>char</code>, <code>signed char</code>, <code>unsigned char</code>,
<code>wchar_t</code>, <code>char16_t</code>, <code>char32_t</code>,
<code>short</code>, <code>unsigned short</code>,
<code>int</code>, <code>unsigned int</code>, <code>long</code>, <code>unsigned long</code>
</entry>
<entry><code>val</code></entry>
</row>
<row>
<entry><code>long long</code>, <code>unsigned long long</code></entry>
<entry><code>val</code> when <code>abs(val) &lt;= std::numeric_limits&lt;std::size_t&gt;::max()</code>.</entry>
</row>
<row>
<entry><code>float</code>, <code>double</code>, <code>long double</code></entry>
<entry>An unspecified value, except that equal arguments shall yield the same result.</entry>
</row>
<row>
<entry><code>T*</code></entry>
<entry>An unspecified value, except that equal arguments shall yield the same result.</entry>
</row>
<row>
<entry>
<code>T&#160;val[N]</code>,
<code>const&#160;T&#160;val[N]</code>
</entry>
<entry><code>hash_range(val, val+N)</code></entry>
</row>
<row>
<entry>
<code>std:basic_string&lt;Ch,&#160;std::char_traits&lt;Ch&gt;,&#160;A&gt;</code>,
<code>std::vector&lt;T,&#160;A&gt;</code>,
<code>std::list&lt;T,&#160;A&gt;</code>,
<code>std::deque&lt;T,&#160;A&gt;</code>,
<code>std::set&lt;K,&#160;C,&#160;A&gt;</code>,
<code>std::multiset&lt;K,&#160;C,&#160;A&gt;</code>,
<code>std::map&lt;K,&#160;T,&#160;C,&#160;A&gt;</code>,
<code>std::multimap&lt;K,&#160;T,&#160;C,&#160;A&gt;</code>,
<code>std::array&lt;T,&#160;N&gt;</code>
</entry>
<entry><code>hash_range(val.begin(), val.end())</code></entry>
</row>
<row>
<entry><code>std::pair&lt;A, B&gt;</code></entry>
<entry><programlisting>size_t seed = 0;
<functionname>hash_combine</functionname>(seed, val.first);
<functionname>hash_combine</functionname>(seed, val.second);
return seed;</programlisting></entry>
</row>
<row>
<entry><code>std::tuple&lt;T...&gt;</code></entry>
<entry><programlisting>size_t seed = 0;
<functionname>hash_combine</functionname>(seed, get&lt;0&gt;(val));
<functionname>hash_combine</functionname>(seed, get&lt;1&gt;(val));
// ....
return seed;</programlisting></entry>
</row>
<row>
<entry>
<code>std::complex&lt;T&gt;</code>
</entry>
<entry>When <code>T</code> is a built in type and <code>val.imag() == 0</code>, the result is equal to <code>hash_value(val.real())</code>. Otherwise an unspecified value, except that equal arguments shall yield the same result.</entry>
</row>
<row>
<entry>
<code>std::type_index</code>
</entry>
<entry><code>val.hash_code()</code></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</returns>
</overloaded-function>
</free-function-group>
</namespace>
</header>
</library-reference>
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