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< title > The MPL Reference Manual: lambda< / title >
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< table class = "header" > < tr class = "header" > < td class = "header-group navigation-bar" > < span class = "navigation-group" > < a href = "./placeholders.html" class = "navigation-link" > Prev< / a > < a href = "./bind.html" class = "navigation-link" > Next< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./placeholders.html" class = "navigation-link" > Back< / a > < a href = "./bind.html" class = "navigation-link" > Along< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./composition-and-argument-binding.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 = "./composition-and-argument-binding.html" class = "navigation-link" > Composition and Argument Binding< / a > / < a href = "./lambda.html" class = "navigation-link" > lambda< / a > < / td >
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< / tr > < / table > < div class = "header-separator" > < / div >
< div class = "section" id = "lambda" >
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< h1 > < a class = "toc-backref" href = "./composition-and-argument-binding.html#id1530" > lambda< / a > < / h1 >
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< div class = "section" id = "id922" >
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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 X
, typename Tag = < em > unspecified< / em >
>
struct < a href = "./lambda.html" class = "identifier" > lambda< / a >
{
typedef < em > unspecified< / em > type;
};
< / pre >
< / div >
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< div class = "section" id = "id923" >
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< h3 > < a class = "subsection-title" href = "#description" name = "description" > Description< / a > < / h3 >
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< p > If < tt class = "literal" > < span class = "pre" > X< / span > < / tt > is a < a class = "reference internal" href = "./placeholder-expression.html" > Placeholder Expression< / a > , transforms < tt class = "literal" > < span class = "pre" > X< / span > < / tt > into a corresponding
< a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class< / a > , otherwise < tt class = "literal" > < span class = "pre" > X< / span > < / tt > is returned unchanged.< / p >
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< / div >
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< div class = "section" id = "id924" >
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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/lambda.hpp" class = "header" > boost/mpl/lambda.hpp< / a > >
< / pre >
< / div >
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< div class = "section" id = "id925" >
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< h3 > < a class = "subsection-title" href = "#parameters" name = "parameters" > Parameters< / a > < / h3 >
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< table border = "1" class = "docutils table" >
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< colgroup >
< col width = "18%" / >
< col width = "27%" / >
< col width = "55%" / >
< / colgroup >
< thead valign = "bottom" >
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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 >
< tbody valign = "top" >
< tr > < td > < tt class = "literal" > < span class = "pre" > X< / span > < / tt > < / td >
< td > Any type< / td >
< td > An expression to transform.< / td >
< / tr >
< tr > < td > < tt class = "literal" > < span class = "pre" > Tag< / span > < / tt > < / td >
< td > Any type< / td >
< td > A tag determining transform semantics.< / td >
< / tr >
< / tbody >
< / table >
< / div >
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< div class = "section" id = "id926" >
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< h3 > < a class = "subsection-title" href = "#expression-semantics" name = "expression-semantics" > Expression semantics< / a > < / h3 >
< p > For arbitrary types < tt class = "literal" > < span class = "pre" > x< / span > < / tt > and < tt class = "literal" > < span class = "pre" > tag< / span > < / tt > :< / p >
< pre class = "literal-block" >
typedef < a href = "./lambda.html" class = "identifier" > lambda< / a > < x> ::type f;
< / 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" >
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< tr class = "field" > < th class = "field-name" > Return type:< / th > < td class = "field-body" > < p class = "first" > < a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class< / a > .< / p >
< / td >
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< / tr >
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< tr class = "field" > < th class = "field-name" > Semantics:< / th > < td class = "field-body" > < p class = "first" > If < tt class = "literal" > < span class = "pre" > x< / span > < / tt > is a < a class = "reference internal" href = "./placeholder-expression.html" > Placeholder Expression< / a > in a general form < tt class = "literal" > < span class = "pre" > X< a1,...an> < / span > < / tt > , where
< tt class = "literal" > < span class = "pre" > X< / span > < / tt > is a class template and < tt class = "literal" > < span class = "pre" > a1< / span > < / tt > ,... < tt class = "literal" > < span class = "pre" > an< / span > < / tt > are arbitrary types, equivalent
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to< / p >
< pre class = "literal-block" >
typedef < a href = "./protect.html" class = "identifier" > protect< / a > < < a href = "./bind.html" class = "identifier" > bind< / a > <
< a href = "./quote.html" class = "identifier" > quote< / a > < em > n< / em > < X>
, < a href = "./lambda.html" class = "identifier" > lambda< / a > < a1> ::type,< em > ...< / em > < a href = "./lambda.html" class = "identifier" > lambda< / a > < a< em > n< / em > > ::type
> > f;
< / pre >
< p class = "last" > otherwise, < tt class = "literal" > < span class = "pre" > f< / span > < / tt > is identical to < tt class = "literal" > < span class = "pre" > x< / span > < / tt > .< / p >
< / td >
< / tr >
< / tbody >
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<!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
< pre class = "literal-block" >
typedef < a href = "./lambda.html" class = "identifier" > lambda< / a > < x,tag> ::type f;
< / 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" >
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< tr class = "field" > < th class = "field-name" > Return type:< / th > < td class = "field-body" > < p class = "first" > < a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class< / a > .< / p >
< / td >
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< / tr >
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< tr class = "field" > < th class = "field-name" > Semantics:< / th > < td class = "field-body" > < p class = "first" > If < tt class = "literal" > < span class = "pre" > x< / span > < / tt > is a < a class = "reference internal" href = "./placeholder-expression.html" > Placeholder Expression< / a > in a general form < tt class = "literal" > < span class = "pre" > X< a1,...an> < / span > < / tt > , where
< tt class = "literal" > < span class = "pre" > X< / span > < / tt > is a class template and < tt class = "literal" > < span class = "pre" > a1< / span > < / tt > ,... < tt class = "literal" > < span class = "pre" > an< / span > < / tt > are arbitrary types, equivalent
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to< / p >
< pre class = "literal-block" >
typedef < a href = "./protect.html" class = "identifier" > protect< / a > < < a href = "./bind.html" class = "identifier" > bind< / a > <
< a href = "./quote.html" class = "identifier" > quote< / a > < em > n< / em > < X,tag>
, < a href = "./lambda.html" class = "identifier" > lambda< / a > < a1,tag> ::type,< em > ...< / em > < a href = "./lambda.html" class = "identifier" > lambda< / a > < a< em > n< / em > ,tag> ::type
> > f;
< / pre >
< p class = "last" > otherwise, < tt class = "literal" > < span class = "pre" > f< / span > < / tt > is identical to < tt class = "literal" > < span class = "pre" > x< / span > < / tt > .< / p >
< / td >
< / tr >
< / tbody >
< / table >
< / div >
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< div class = "section" id = "id927" >
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< h3 > < a class = "subsection-title" href = "#example" name = "example" > Example< / a > < / h3 >
< pre class = "literal-block" >
template< typename N1, typename N2 > struct int_plus
: < a href = "./int.html" class = "identifier" > int_< / a > < ( N1::value + N2::value )>
{
};
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typedef < a href = "./lambda.html" class = "identifier" > lambda< / a > < int_plus< < a href = "./placeholders.html" class = "identifier" > _1< / a > , < a href = "./int.html" class = "identifier" > int_< / a > < 42> > > ::type f1;
typedef < a href = "./bind.html" class = "identifier" > bind< / a > < < a href = "./quote.html" class = "identifier" > quote< / a > < tt class = "literal" > < span class = "pre" > 2< / span > < / tt > < int_plus> , < a href = "./placeholders.html" class = "identifier" > _1< / a > , < a href = "./int.html" class = "identifier" > int_< / a > < 42> > f2;
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typedef f1::< a href = "./apply.html" class = "identifier" > apply< / a > < 42> ::type r1;
typedef f2::< a href = "./apply.html" class = "identifier" > apply< / a > < 42> ::type r2;
< a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION< / a > ( r1::value, ==, 84 );
< a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION< / a > ( r2::value, ==, 84 );
< / pre >
< / div >
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< div class = "section" id = "id928" >
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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 = "./composition-and-argument-binding.html" > Composition and Argument Binding< / a > , < a class = "reference internal" href = "./invocation.html" > invocation< / a > , < a class = "reference internal" href = "./placeholders.html" > Placeholders< / a > , < a class = "reference internal" href = "./bind.html" > bind< / a > , < a class = "reference internal" href = "./quote.html" > quote< / a > , < a class = "reference internal" href = "./protect.html" > protect< / a > , < a class = "reference internal" href = "./apply.html" > apply< / a > < / p >
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< table class = "footer" > < tr class = "footer" > < td class = "header-group navigation-bar" > < span class = "navigation-group" > < a href = "./placeholders.html" class = "navigation-link" > Prev< / a > < a href = "./bind.html" class = "navigation-link" > Next< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./placeholders.html" class = "navigation-link" > Back< / a > < a href = "./bind.html" class = "navigation-link" > Along< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./composition-and-argument-binding.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 > < 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
file LICENSE_1_0.txt or copy at < a class = "reference external" href = "http://www.boost.org/LICENSE_1_0.txt" target = "_top" > http://www.boost.org/LICENSE_1_0.txt< / a > )< / div > < / td > < / tr > < / table > < / body >
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