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< title > The MPL Reference Manual: Metafunction Class< / title >
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< table class = "header" > < tr class = "header" > < td class = "header-group navigation-bar" > < span class = "navigation-group" > < a href = "./metafunction.html" class = "navigation-link" > Prev< / a > < a href = "./lambda-expression.html" class = "navigation-link" > Next< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./metafunction.html" class = "navigation-link" > Back< / a > < a href = "./lambda-expression.html" class = "navigation-link" > Along< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./metafunctions-concepts.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 = "./metafunctions-concepts.html" class = "navigation-link" > Concepts< / a > / < a href = "./metafunction-class.html" class = "navigation-link" > Metafunction Class< / a > < / td >
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< div class = "section" id = "metafunction-class" >
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< h1 > < a class = "toc-backref" href = "./metafunctions-concepts.html#id1513" > Metafunction Class< / a > < / h1 >
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< div class = "section" id = "summary" >
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< h3 > Summary< / h3 >
< p > A < em > metafunction class< / em > is a certain form of metafunction representation
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that enables higher-order metaprogramming. More precisely, it's a class
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with a publicly-accessible nested < a class = "reference internal" href = "./metafunction.html" > Metafunction< / a > called < tt class = "literal" > < span class = "pre" > < a href = "./apply.html" class = "identifier" > apply< / a > < / span > < / tt > .
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Correspondingly, a metafunction class invocation is defined as invocation
of its nested < tt class = "literal" > < span class = "pre" > < a href = "./apply.html" class = "identifier" > apply< / a > < / span > < / tt > metafunction.< / p >
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< h3 > < a class = "subsection-title" href = "#expression-requirements" name = "expression-requirements" > Expression requirements< / a > < / h3 >
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< p > In the following table and subsequent specifications, < tt class = "literal" > < span class = "pre" > f< / span > < / tt > is a < a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class< / a > .< / p >
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< tr > < th class = "head" > Expression< / th >
< th class = "head" > Type< / th >
< th class = "head" > Complexity< / th >
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< tr > < td > < tt class = "literal" > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply< / a > ::type< / span > < / tt > < / td >
< td > Any type< / td >
< td > Unspecified.< / td >
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< tr > < td > < tt class = "literal" > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply< / a > < > ::type< / span > < / tt > < / td >
< td > Any type< / td >
< td > Unspecified.< / td >
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< tr > < td > < tt class = "literal" > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply< / a > < a1,...an> ::type< / span > < / tt > < / td >
< td > Any type< / td >
< td > Unspecified.< / td >
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< h3 > < a class = "subsection-title" href = "#expression-semantics" name = "expression-semantics" > Expression semantics< / a > < / h3 >
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typedef f::< a href = "./apply.html" class = "identifier" > apply< / a > ::type x;
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< tr class = "field" > < th class = "field-name" > Precondition:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > f< / span > < / tt > is a nullary < a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class< / a > ; < tt class = "literal" > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply< / a > ::type< / span > < / tt > is a < em > type-name< / em > .< / td >
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< / tr >
< tr class = "field" > < th class = "field-name" > Semantics:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > x< / span > < / tt > is the result of the metafunction class invocation.< / td >
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typedef f::< a href = "./apply.html" class = "identifier" > apply< / a > < > ::type x;
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< tr class = "field" > < th class = "field-name" > Precondition:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > f< / span > < / tt > is a nullary < a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class< / a > ; < tt class = "literal" > < span class = "pre" > f::< a href = "./apply.html" class = "identifier" > apply< / a > < > ::type< / span > < / tt > is a < em > type-name< / em > .< / td >
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< / tr >
< tr class = "field" > < th class = "field-name" > Semantics:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > x< / span > < / tt > is the result of the metafunction class invocation.< / td >
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typedef f::< a href = "./apply.html" class = "identifier" > apply< / a > < a1,< em > ...< / em > a< em > n< / em > > ::type x;
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< tr class = "field" > < th class = "field-name" > Precondition:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > f< / span > < / tt > is an < em > n< / em > -ary metafunction class; < tt class = "literal" > < span class = "pre" > < a href = "./apply.html" class = "identifier" > apply< / a > < / span > < / tt > is a < a class = "reference internal" href = "./metafunction.html" > Metafunction< / a > .< / td >
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< / tr >
< tr class = "field" > < th class = "field-name" > Semantics:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > x< / span > < / tt > is the result of the metafunction class
invocation with the actual arguments < tt class = "literal" > < span class = "pre" > a1< / span > < / tt > ,... < tt class = "literal" > < span class = "pre" > an< / span > < / tt > .< / td >
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< h3 > < a class = "subsection-title" href = "#models" name = "models" > Models< / a > < / h3 >
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< li > < a class = "reference internal" href = "./always.html" > always< / a > < / li >
< li > < a class = "reference internal" href = "./arg.html" > arg< / a > < / li >
< li > < a class = "reference internal" href = "./quote.html" > quote< / a > < / li >
< li > < a class = "reference internal" href = "./numeric-cast.html" > numeric_cast< / a > < / li >
< li > < a class = "reference internal" href = "./unpack-args.html" > unpack_args< / a > < / li >
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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 = "./metafunction.html" > Metafunction< / a > , < a class = "reference internal" href = "./lambda-expression.html" > Lambda Expression< / a > , < a class = "reference internal" href = "./invocation.html" > invocation< / a > , < a class = "reference internal" href = "./apply-wrap.html" > apply_wrap< / a > , < a class = "reference internal" href = "./bind.html" > bind< / a > , < a class = "reference internal" href = "./quote.html" > quote< / a > < / p >
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< table class = "footer" > < tr class = "footer" > < td class = "header-group navigation-bar" > < span class = "navigation-group" > < a href = "./metafunction.html" class = "navigation-link" > Prev< / a > < a href = "./lambda-expression.html" class = "navigation-link" > Next< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./metafunction.html" class = "navigation-link" > Back< / a > < a href = "./lambda-expression.html" class = "navigation-link" > Along< / a > < / span > < span class = "navigation-group-separator" > | < / span > < span class = "navigation-group" > < a href = "./metafunctions-concepts.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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