#ifndef BOOST_TYPE_TRAITS_DETAIL_MP_DEFER_HPP_INCLUDED
|
#define BOOST_TYPE_TRAITS_DETAIL_MP_DEFER_HPP_INCLUDED
|
|
//
|
// Copyright 2015 Peter Dimov
|
//
|
// Distributed under the Boost Software License, Version 1.0.
|
// See accompanying file LICENSE_1_0.txt or copy at
|
// http://www.boost.org/LICENSE_1_0.txt
|
//
|
|
#include <boost/type_traits/integral_constant.hpp>
|
#include <boost/type_traits/conditional.hpp>
|
|
namespace boost
|
{
|
|
namespace type_traits_detail
|
{
|
|
// mp_valid
|
// implementation by Bruno Dutra (by the name is_evaluable)
|
|
template<template<class...> class F, class... T>
|
struct mp_valid_impl
|
{
|
template<template<class...> class G, class = G<T...>>
|
static boost::true_type check_s(int);
|
|
template<template<class...> class>
|
static boost::false_type check_s(...);
|
|
using type = decltype(check_s<F>(0));
|
};
|
|
template<template<class...> class F, class... T>
|
using mp_valid = typename mp_valid_impl<F, T...>::type;
|
|
// mp_defer
|
|
struct mp_empty
|
{
|
};
|
|
template<template<class...> class F, class... T> struct mp_defer_impl
|
{
|
using type = F<T...>;
|
};
|
|
template<template<class...> class F, class... T> using mp_defer = typename boost::conditional<mp_valid<F, T...>::value, mp_defer_impl<F, T...>, mp_empty>::type;
|
|
} // namespace type_traits_detail
|
|
} // namespace boost
|
|
#endif // #ifndef BOOST_TYPE_TRAITS_DETAIL_MP_DEFER_HPP_INCLUDED
|
