97 lines
2.9 KiB
C++
97 lines
2.9 KiB
C++
/*!
|
|
@file
|
|
Adapts `std::integral_constant` for use with Hana.
|
|
|
|
@copyright Louis Dionne 2013-2017
|
|
Distributed under the Boost Software License, Version 1.0.
|
|
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
|
|
*/
|
|
|
|
#ifndef BOOST_HANA_EXT_STD_INTEGRAL_CONSTANT_HPP
|
|
#define BOOST_HANA_EXT_STD_INTEGRAL_CONSTANT_HPP
|
|
|
|
#include <boost/hana/concept/integral_constant.hpp>
|
|
#include <boost/hana/config.hpp>
|
|
#include <boost/hana/core/when.hpp>
|
|
#include <boost/hana/fwd/core/to.hpp>
|
|
#include <boost/hana/fwd/core/tag_of.hpp>
|
|
#include <boost/hana/fwd/integral_constant.hpp>
|
|
|
|
#include <type_traits>
|
|
|
|
|
|
#ifdef BOOST_HANA_DOXYGEN_INVOKED
|
|
namespace std {
|
|
//! @ingroup group-ext-std
|
|
//! Adapter for `std::integral_constant`s.
|
|
//!
|
|
//! Provided models
|
|
//! ---------------
|
|
//! 1. `Constant` and `IntegralConstant`\n
|
|
//! A `std::integral_constant` is a model of the `IntegralConstant` and
|
|
//! `Constant` concepts, just like `hana::integral_constant`s are. As a
|
|
//! consequence, they are also implicitly a model of the concepts provided
|
|
//! for all models of `Constant`.
|
|
//! @include example/ext/std/integral_constant.cpp
|
|
template <typename T, T v>
|
|
struct integral_constant { };
|
|
}
|
|
#endif
|
|
|
|
|
|
namespace boost { namespace hana {
|
|
namespace ext { namespace std {
|
|
template <typename T>
|
|
struct integral_constant_tag { using value_type = T; };
|
|
}}
|
|
|
|
namespace detail {
|
|
template <typename T, T v>
|
|
constexpr bool
|
|
is_std_integral_constant(std::integral_constant<T, v>*)
|
|
{ return true; }
|
|
|
|
constexpr bool is_std_integral_constant(...)
|
|
{ return false; }
|
|
|
|
|
|
template <typename T, T v>
|
|
constexpr bool
|
|
is_hana_integral_constant(hana::integral_constant<T, v>*)
|
|
{ return true; }
|
|
|
|
constexpr bool is_hana_integral_constant(...)
|
|
{ return false; }
|
|
}
|
|
|
|
template <typename T>
|
|
struct tag_of<T, when<
|
|
detail::is_std_integral_constant((T*)0) &&
|
|
!detail::is_hana_integral_constant((T*)0)
|
|
>> {
|
|
using type = ext::std::integral_constant_tag<
|
|
typename hana::tag_of<typename T::value_type>::type
|
|
>;
|
|
};
|
|
|
|
//////////////////////////////////////////////////////////////////////////
|
|
// Constant/IntegralConstant
|
|
//////////////////////////////////////////////////////////////////////////
|
|
template <typename T>
|
|
struct IntegralConstant<ext::std::integral_constant_tag<T>> {
|
|
static constexpr bool value = true;
|
|
};
|
|
|
|
template <typename T, typename C>
|
|
struct to_impl<ext::std::integral_constant_tag<T>, C, when<
|
|
hana::IntegralConstant<C>::value
|
|
>> : embedding<is_embedded<typename C::value_type, T>::value> {
|
|
template <typename N>
|
|
static constexpr auto apply(N const&) {
|
|
return std::integral_constant<T, N::value>{};
|
|
}
|
|
};
|
|
}} // end namespace boost::hana
|
|
|
|
#endif // !BOOST_HANA_EXT_STD_INTEGRAL_CONSTANT_HPP
|