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The identity metafunction. Returns X unchanged.
#include <boost/mpl/identity.hpp>
Parameter | Requirement | Description |
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X | Any type | An argument to be returned. |
For an arbitrary type x:
typedef identity<x>::type r;
Return type: | A type. |
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Semantics: | Equivalent to typedef x r; |
Postcondition: | is_same<r,x>::value == true. |
typedef apply< identity<_1>, char >::type t1; typedef apply< identity<_2>, char,int >::type t2; BOOST_MPL_ASSERT(( is_same< t1, char > )); BOOST_MPL_ASSERT(( is_same< t2, int > ));