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< title > The MPL Reference Manual: numeric_cast</ title >
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< 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 = "./miscellaneous.html" class = "navigation-link" > Miscellaneous</ a > / < a href = "./numeric-cast.html" class = "navigation-link" > numeric_cast</ a ></ td >
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< div class = "section" id = "numeric-cast" >
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< h1 >< a class = "toc-backref" href = "./miscellaneous.html#id1568" > numeric_cast</ a ></ h1 >
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< div class = "section" id = "id1181" >
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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 SourceTag
, typename TargetTag
>
struct < a href = "./numeric-cast.html" class = "identifier" > numeric_cast</ a > ;
</ pre >
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< div class = "section" id = "id1182" >
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< h3 >< a class = "subsection-title" href = "#description" name = "description" > Description</ a ></ h3 >
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< p > Each < tt class = "literal" >< span class = "pre" >< a href = "./numeric-cast.html" class = "identifier" > numeric_cast</ a ></ span ></ tt > specialization is a user-specialized unary < a class = "reference internal" href = "./metafunction-class.html" > Metafunction Class</ a >
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providing a conversion between two numeric types.</ p >
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< div class = "section" id = "id1183" >
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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/numeric_cast.hpp" class = "header" > boost/mpl/numeric_cast.hpp</ a > >
</ pre >
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< div class = "section" id = "id1184" >
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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" > SourceTag</ span ></ tt ></ td >
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< td >< a class = "reference internal" href = "./integral-constant.html" > Integral Constant</ a ></ td >
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< td > A tag for the conversion's source type.</ td >
</ tr >
< tr >< td >< tt class = "literal" >< span class = "pre" > TargetTag</ span ></ tt ></ td >
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< td >< a class = "reference internal" href = "./integral-constant.html" > Integral Constant</ a ></ td >
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< td > A tag for the conversion's destination type.</ td >
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< div class = "section" id = "id1185" >
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< h3 >< a class = "subsection-title" href = "#expression-semantics" name = "expression-semantics" > Expression semantics</ a ></ h3 >
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< p > If < tt class = "literal" >< span class = "pre" > x</ span ></ tt > and < tt class = "literal" >< span class = "pre" > y</ span ></ tt > are two numeric types, < tt class = "literal" >< span class = "pre" > x</ span ></ tt > is convertible to < tt class = "literal" >< span class = "pre" > y</ span ></ tt > , and
< tt class = "literal" >< span class = "pre" > x_tag</ span ></ tt > and < tt class = "literal" >< span class = "pre" > y_tag</ span ></ tt > are the types' corresponding < a class = "reference internal" href = "./integral-constant.html" > Integral Constant</ a > tags:</ p >
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< pre class = "literal-block" >
typedef < a href = "./apply-wrap.html" class = "identifier" > apply_wrap</ a >< tt class = "literal" >< span class = "pre" > 2</ span ></ tt > < < a href = "./numeric-cast.html" class = "identifier" > numeric_cast</ a > < x_tag,y_tag> ,x > ::type r;
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< table class = "docutils field-list" frame = "void" rules = "none" >
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< col class = "field-name" />
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< tr class = "field" >< th class = "field-name" > Return type:</ th >< td class = "field-body" > A type.</ td >
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< tr class = "field" >< th class = "field-name" > Semantics:</ th >< td class = "field-body" >< tt class = "literal" >< span class = "pre" > r</ span ></ tt > is a value of < tt class = "literal" >< span class = "pre" > x</ span ></ tt > converted to the type of < tt class = "literal" >< span class = "pre" > y</ span ></ tt > .</ td >
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< div class = "section" id = "id1186" >
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< h3 >< a class = "subsection-title" href = "#complexity" name = "complexity" > Complexity</ a ></ h3 >
< p > Unspecified.</ p >
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< div class = "section" id = "id1187" >
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< h3 >< a class = "subsection-title" href = "#example" name = "example" > Example</ a ></ h3 >
< pre class = "literal-block" >
struct complex_tag : < a href = "./int.html" class = "identifier" > int_</ a > < 10> {};
template< typename Re, typename Im > struct complex
{
typedef complex_tag tag;
typedef complex type;
typedef Re real;
typedef Im imag;
};
template< typename C > struct real : C::real {};
template< typename C > struct imag : C::imag {};
namespace boost { namespace mpl {
template<> struct < a href = "./numeric-cast.html" class = "identifier" > numeric_cast</ a > < integral_c_tag,complex_tag >
{
template< typename N > struct < a href = "./apply.html" class = "identifier" > apply</ a >
: complex< N, < a href = "./integral-c.html" class = "identifier" > integral_c</ a > < typename N::< a href = "./value-type.html" class = "identifier" > value_type</ a > , 0 > >
{
};
};
template<>
struct plus_impl< complex_tag,complex_tag >
{
template< typename N1, typename N2 > struct < a href = "./apply.html" class = "identifier" > apply</ a >
: complex<
< a href = "./plus.html" class = "identifier" > plus</ a > < typename N1::real, typename N2::real >
, < a href = "./plus.html" class = "identifier" > plus</ a > < typename N1::imag, typename N2::imag >
>
{
};
};
}}
typedef < a href = "./int.html" class = "identifier" > int_</ a > < 2> i;
typedef complex< < a href = "./int.html" class = "identifier" > int_</ a > < 5> , < a href = "./int.html" class = "identifier" > int_</ a > < -1> > c1;
typedef complex< < a href = "./int.html" class = "identifier" > int_</ a > < -5> , < a href = "./int.html" class = "identifier" > int_</ a > < 1> > c2;
typedef < a href = "./plus.html" class = "identifier" > plus</ a > < c1,i> r4;
< a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION</ a > ( real< r4> ::value, ==, 7 );
< a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION</ a > ( imag< r4> ::value, ==, -1 );
typedef < a href = "./plus.html" class = "identifier" > plus</ a > < i,c2> r5;
< a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION</ a > ( real< r5> ::value, ==, -3 );
< a href = "./assert-relation.html" class = "identifier" > BOOST_MPL_ASSERT_RELATION</ a > ( imag< r5> ::value, ==, 1 );
</ pre >
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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 = "./numeric-metafunction.html" > Numeric Metafunction</ a > , < a class = "reference internal" href = "./plus.html" > plus</ a > , < a class = "reference internal" href = "./minus.html" > minus</ a > , < a class = "reference internal" href = "./times.html" > times</ a ></ p >
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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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