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< title > The MPL Reference Manual: apply_wrap</ title >
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< table class = "header" >< tr class = "header" >< td class = "header-group navigation-bar" >< span class = "navigation-group" >< a href = "./apply.html" class = "navigation-link" > Prev</ a > < a href = "./unpack-args.html" class = "navigation-link" > Next</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./apply.html" class = "navigation-link" > Back</ a > < a href = "./unpack-args.html" class = "navigation-link" > Along</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./invocation.html" class = "navigation-link" > Up</ a > < a href = "../refmanual.html" class = "navigation-link" > Home</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./refmanual_toc.html" class = "navigation-link" > Full TOC</ a ></ span ></ td >
< td class = "header-group page-location" >< a href = "../refmanual.html" class = "navigation-link" > Front Page</ a > / < a href = "./metafunctions.html" class = "navigation-link" > Metafunctions</ a > / < a href = "./invocation.html" class = "navigation-link" > Invocation</ a > / < a href = "./apply-wrap.html" class = "navigation-link" > apply_wrap</ a ></ td >
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< div class = "section" id = "apply-wrap" >
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< h1 >< a class = "toc-backref" href = "./invocation.html#id1526" > apply_wrap</ a ></ h1 >
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< div class = "section" id = "id894" >
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< h3 >< a class = "subsection-title" href = "#synopsis" name = "synopsis" > Synopsis</ a ></ h3 >
< pre class = "literal-block" >
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template<
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typename F
>
struct apply_wrap0
{
typedef < em > unspecified</ em > type;
};
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template<
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typename F, typename A1
>
struct apply_wrap1
{
typedef < em > unspecified</ em > type;
};
< em > ...</ em >
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template<
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typename F, typename A1,< em > ...</ em > typename An
>
struct < a href = "./apply-wrap.html" class = "identifier" > apply_wrap</ a >< em > n</ em >
{
typedef < em > unspecified</ em > type;
};
</ pre >
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< div class = "section" id = "id895" >
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< h3 >< a class = "subsection-title" href = "#description" name = "description" > Description</ a ></ h3 >
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< p > Invokes a < a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class</ a > < tt class = "literal" >< span class = "pre" > F</ span ></ tt > with arguments < tt class = "literal" >< span class = "pre" > A1</ span ></ tt > ,... < tt class = "literal" >< span class = "pre" > An</ span ></ tt > .</ p >
< p > In essence, < tt class = "literal" >< span class = "pre" >< a href = "./apply-wrap.html" class = "identifier" > apply_wrap</ a ></ span ></ tt > forms are nothing more than syntactic wrappers around
< tt class = "literal" >< span class = "pre" > F::< a href = "./apply.html" class = "identifier" > apply</ a > < A1,...</ span > < span class = "pre" > An> ::type</ span ></ tt > / < tt class = "literal" >< span class = "pre" > F::< a href = "./apply.html" class = "identifier" > apply</ a > ::type</ span ></ tt > expressions (hence the name).
They provide a more concise notation and higher portability than their
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underlaying constructs at the cost of an extra template instantiation.</ p >
</ div >
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< div class = "section" id = "id896" >
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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/apply_wrap.hpp" class = "header" > boost/mpl/apply_wrap.hpp</ a > >
</ pre >
</ div >
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< div class = "section" id = "id897" >
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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" > F</ span ></ tt ></ td >
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< td >< a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class</ a ></ td >
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< td > A metafunction class to invoke.</ td >
</ tr >
< tr >< td >< tt class = "literal" >< span class = "pre" > A1</ span ></ tt > ,... < tt class = "literal" >< span class = "pre" > An</ span ></ tt ></ td >
< td > Any type</ td >
< td > Invocation arguments.</ td >
</ tr >
</ tbody >
</ table >
</ div >
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< div class = "section" id = "id898" >
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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 = "./metafunction-class.html" > Metafunction Class</ a > < tt class = "literal" >< span class = "pre" > f</ span ></ tt > and arbitrary types < tt class = "literal" >< span class = "pre" > a1</ span ></ tt > ,... < tt class = "literal" >< span class = "pre" > an</ span ></ tt > :</ p >
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< pre class = "literal-block" >
typedef < a href = "./apply-wrap.html" class = "identifier" > apply_wrap</ a >< em > n</ em > < f,a1,< em > ...</ em > an> ::type t;
</ 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" />
< tbody valign = "top" >
< tr class = "field" >< th class = "field-name" > Return type:</ th >< td class = "field-body" > Any type.</ td >
</ tr >
< tr class = "field" >< th class = "field-name" > Semantics:</ th >< td class = "field-body" > If < tt class = "literal" >< span class = "pre" > n</ span > < span class = "pre" > > </ span > < span class = "pre" > 0</ span ></ tt > , equivalent to < tt class = "literal" >< span class = "pre" > typedef</ span > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply</ a > < a1,...</ span > < span class = "pre" > an> ::type</ span > < span class = "pre" > t;</ span ></ tt > ,
otherwise equivalent to either < tt class = "literal" >< span class = "pre" > typedef</ span > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply</ a > ::type</ span > < span class = "pre" > t;</ span ></ tt > or
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< tt class = "literal" >< span class = "pre" > typedef</ span > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply</ a > <> ::type</ span > < span class = "pre" > t;</ span ></ tt > depending on whether < tt class = "literal" >< span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply</ a ></ span ></ tt > is
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a class or a class template.</ td >
</ tr >
</ tbody >
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< div class = "section" id = "id899" >
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< h3 >< a class = "subsection-title" href = "#example" name = "example" > Example</ a ></ h3 >
< pre class = "literal-block" >
struct f0
{
template< typename T = int > struct < a href = "./apply.html" class = "identifier" > apply</ a >
{
typedef char type;
};
};
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struct g0
{
struct < a href = "./apply.html" class = "identifier" > apply</ a > { typedef char type; };
};
struct f2
{
template< typename T1, typename T2 > struct < a href = "./apply.html" class = "identifier" > apply</ a >
{
typedef T2 type;
};
};
typedef < a href = "./apply-wrap.html" class = "identifier" > apply_wrap</ a >< tt class = "literal" >< span class = "pre" > 0</ span ></ tt > < f0 > ::type r1;
typedef < a href = "./apply-wrap.html" class = "identifier" > apply_wrap</ a >< tt class = "literal" >< span class = "pre" > 0</ span ></ tt > < g0 > ::type r2;
typedef < a href = "./apply-wrap.html" class = "identifier" > apply_wrap</ a >< tt class = "literal" >< span class = "pre" > 2</ span ></ tt > < f2,int,char > ::type r3;
< a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT</ a > (( is_same< r1,char> ));
< a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT</ a > (( is_same< r2,char> ));
< a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT</ a > (( is_same< r3,char> ));
</ pre >
</ div >
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< div class = "section" id = "id900" >
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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 = "./metafunctions.html" > Metafunctions</ a > , < a class = "reference internal" href = "./invocation.html" > invocation</ a > , < a class = "reference internal" href = "./apply.html" > apply</ a > , < a class = "reference internal" href = "./lambda.html" > lambda</ a > , < a class = "reference internal" href = "./quote.html" > quote</ a > , < a class = "reference internal" href = "./bind.html" > bind</ a > , < a class = "reference internal" href = "./protect.html" > protect</ a ></ p >
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<!-- Metafunctions/Invocation//unpack_args |30 -->
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< table class = "footer" >< tr class = "footer" >< td class = "header-group navigation-bar" >< span class = "navigation-group" >< a href = "./apply.html" class = "navigation-link" > Prev</ a > < a href = "./unpack-args.html" class = "navigation-link" > Next</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./apply.html" class = "navigation-link" > Back</ a > < a href = "./unpack-args.html" class = "navigation-link" > Along</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./invocation.html" class = "navigation-link" > Up</ a > < a href = "../refmanual.html" class = "navigation-link" > Home</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./refmanual_toc.html" class = "navigation-link" > Full TOC</ a ></ span ></ td >
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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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