if_c

Synopsis

template< 
      bool c
    , typename T1
    , typename T2
    >
struct if_c
{
    typedef unspecified type;
};

Description

Returns one of its two arguments, T1 or T2, depending on the value of integral constant c. if_c<c,t1,t2>::type is a shorcut notation for if_< bool_<c>,t1,t2 >::type.

Header

#include <boost/mpl/if.hpp>

Parameters

Parameter	Requirement	Description
`c`	An integral constant	A selection condition.
`T1`, `T2`	Any type	Types to select from.

Expression semantics

For any integral constant c and arbitrary types t1, t2:

typedef if_c<c,t1,t2>::type t;

Return type:	Any type.
Semantics:	Equivalent to `typedef if_< bool_<c>,t1,t2 >::type t;`

Example

typedef if_c<true,char,long>::type t1;
typedef if_c<false,char,long>::type t2;

BOOST_MPL_ASSERT(( is_same<t1, char> ));
BOOST_MPL_ASSERT(( is_same<t2, long> ));