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Add mp_valid, mp_defer, mp_defer_if_valid.

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Peter Dimov
2015-07-16 00:40:40 +03:00
parent a5dd767f93
commit 61b897e857
5 changed files with 154 additions and 0 deletions
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24
include/boost/mp11/utility.hpp
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@@ -8,6 +8,8 @@
// See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt
#include <boost/mp11/integral.hpp>
namespace boost
{
@@ -63,8 +65,30 @@ template<bool C, class T, template<class...> class F, class... U> using mp_eval_
template<class C, class T, template<class...> class F, class... U> using mp_eval_if = typename detail::mp_eval_if_c_impl<static_cast<bool>(C::value), T, F, U...>::type;
// mp_valid
// implementation by Bruno Dutra (by the name is_evaluable)
namespace detail
{
template<template<class...> class F, class... T> struct mp_valid_impl
{
template<template<class...> class G, class = G<T...>> static mp_true check(int);
template<template<class...> class> static mp_false check(...);
using type = decltype(check<F>(0));
};
} // namespace detail
template<template<class...> class F, class... T> using mp_valid = typename detail::mp_valid_impl<F, T...>::type;
// mp_defer
template<template<class...> class F, class... T> struct mp_defer
{
using type = F<T...>;
};
// mp_defer_if_valid
template<template<class...> class F, class... T> using mp_defer_if_valid = mp_if<mp_valid<F, T...>, mp_defer<F, T...>, mp_inherit<>>;
} // namespace boost