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< title > The MPL Reference Manual: empty< / title >
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< td class = "header-group page-location" > < a href = "../refmanual.html" class = "navigation-link" > Front Page< / a > / < a href = "./sequences.html" class = "navigation-link" > Sequences< / a > / < a href = "./intrinsic-metafunctions.html" class = "navigation-link" > Intrinsic Metafunctions< / a > / < a href = "./empty.html" class = "navigation-link" > empty< / a > < / td >
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< h1 > < a class = "toc-backref" href = "./intrinsic-metafunctions.html#id1430" > empty< / a > < / h1 >
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< div class = "section" id = "id220" >
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< h3 > < a class = "subsection-title" href = "#synopsis" name = "synopsis" > Synopsis< / a > < / h3 >
< pre class = "literal-block" >
template<
typename Sequence
>
struct < a href = "./empty.html" class = "identifier" > empty< / a >
{
typedef < em > unspecified< / em > type;
};
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< div class = "section" id = "id221" >
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< h3 > < a class = "subsection-title" href = "#description" name = "description" > Description< / a > < / h3 >
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< p > Returns an < a class = "reference internal" href = "./integral-constant.html" > Integral Constant< / a > < tt class = "literal" > < span class = "pre" > c< / span > < / tt > such that < tt class = "literal" > < span class = "pre" > c::value< / span > < span class = "pre" > ==< / span > < span class = "pre" > true< / span > < / tt > if
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and only if the sequence is empty.< / p >
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< div class = "section" id = "id222" >
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< h3 > < a class = "subsection-title" href = "#header" name = "header" > Header< / a > < / h3 >
< pre class = "literal-block" >
#include < < a href = "../../../../boost/mpl/empty.hpp" class = "header" > boost/mpl/empty.hpp< / a > >
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< div class = "section" id = "id223" >
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< h3 > < a class = "subsection-title" href = "#model-of" name = "model-of" > Model of< / a > < / h3 >
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< p > < a class = "reference internal" href = "./tag-dispatched-metafunction.html" > Tag Dispatched Metafunction< / a > < / p >
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< div class = "section" id = "id224" >
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< h3 > < a class = "subsection-title" href = "#parameters" name = "parameters" > Parameters< / a > < / h3 >
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< tr > < th class = "head" > Parameter< / th >
< th class = "head" > Requirement< / th >
< th class = "head" > Description< / th >
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< / tr >
< / thead >
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< tr > < td > < tt class = "literal" > < span class = "pre" > Sequence< / span > < / tt > < / td >
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< td > < a class = "reference internal" href = "./forward-sequence.html" > Forward Sequence< / a > < / td >
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< td > A sequence to test.< / td >
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< div class = "section" id = "id225" >
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< h3 > < a class = "subsection-title" href = "#expression-semantics" name = "expression-semantics" > Expression semantics< / a > < / h3 >
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< p > For any < a class = "reference internal" href = "./forward-sequence.html" > Forward Sequence< / a > < tt class = "literal" > < span class = "pre" > s< / span > < / tt > :< / p >
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< pre class = "literal-block" >
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typedef < a href = "./empty.html" class = "identifier" > empty< / a > < s> ::type c;
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< / pre >
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< table class = "docutils field-list" frame = "void" rules = "none" >
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< col class = "field-name" / >
< col class = "field-body" / >
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< tr class = "field" > < th class = "field-name" > Return type:< / th > < td class = "field-body" > Boolean < a class = "reference internal" href = "./integral-constant.html" > Integral Constant< / a > .< / td >
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< / tr >
< tr class = "field" > < th class = "field-name" > Semantics:< / th > < td class = "field-body" > Equivalent to < tt class = "literal" > < span class = "pre" > typedef< / span > < span class = "pre" > is_same< < / span > < span class = "pre" > < a href = "./begin.html" class = "identifier" > begin< / a > < s> ::type,< a href = "./end.html" class = "identifier" > end< / a > < s> ::type< / span > < span class = "pre" > > ::type< / span > < span class = "pre" > c;< / span > < / tt > .< / td >
< / tr >
< tr class = "field" > < th class = "field-name" > Postcondition:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > < a href = "./empty.html" class = "identifier" > empty< / a > < s> ::value< / span > < span class = "pre" > ==< / span > < span class = "pre" > (< / span > < span class = "pre" > < a href = "./size.html" class = "identifier" > size< / a > < s> ::value< / span > < span class = "pre" > ==< / span > < span class = "pre" > 0< / span > < span class = "pre" > )< / span > < / tt > .< / td >
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< div class = "section" id = "id226" >
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< h3 > < a class = "subsection-title" href = "#complexity" name = "complexity" > Complexity< / a > < / h3 >
< p > Amortized constant time.< / p >
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< div class = "section" id = "id227" >
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< h3 > < a class = "subsection-title" href = "#example" name = "example" > Example< / a > < / h3 >
< pre class = "literal-block" >
typedef < a href = "./range-c.html" class = "identifier" > range_c< / a > < int,0,0> empty_range;
typedef < a href = "./vector.html" class = "identifier" > vector< / a > < long,float,double> types;
< a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT< / a > ( < a href = "./empty.html" class = "identifier" > empty< / a > < empty_range> );
< a href = "./assert-not.html" class = "identifier" > BOOST_MPL_ASSERT_NOT< / a > ( < a href = "./empty.html" class = "identifier" > empty< / a > < types> );
< / pre >
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< div class = "section" id = "id228" >
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< h3 > < a class = "subsection-title" href = "#see-also" name = "see-also" > See also< / a > < / h3 >
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< p > < a class = "reference internal" href = "./forward-sequence.html" > Forward Sequence< / a > , < a class = "reference internal" href = "./integral-constant.html" > Integral Constant< / a > , < a class = "reference internal" href = "./size.html" > size< / a > , < a class = "reference internal" href = "./begin.html" > begin< / a > / < a class = "reference internal" href = "./end.html" > end< / a > < / p >
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<!-- Sequences/Intrinsic Metafunctions//end -->
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< td > < div class = "copyright-footer" > < div class = "copyright" > Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams< / div >
Distributed under the Boost Software License, Version 1.0. (See accompanying
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