Synopsis

template<
      typename X
    >
struct always
{
    // |unspecified|
    // |...|
};

Description

always<X> specialization is a variadic |Metafunction Class| always returning the same type, X, regardless of the number and types of passed arguments.

Header

#include <boost/mpl/always.hpp>

Model of

|Metafunction Class|

Parameters

Expression semantics

For an arbitrary type x:

typedef always<x> f;

struct f : bind< identity<_1>, x > {};

Example

typedef always<true_> always_true;
BOOST_MPL_ASSERT(( apply< always_true,false_> ));
BOOST_MPL_ASSERT(( apply< always_true,false_,false_ > ));
BOOST_MPL_ASSERT(( apply< always_true,false_,false_,false_ > ));

See also

|Metafunctions|, |Metafunction Class|, |identity|, |bind|, |apply|