110 lines
3.4 KiB
C++
110 lines
3.4 KiB
C++
|
/*!
|
||
|
|
@file
|
||
|
|
Defines `boost::hana::common` and `boost::hana::common_t`.
|
||
|
|
|
||
|
|
@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_CORE_COMMON_HPP
|
||
|
|
#define BOOST_HANA_CORE_COMMON_HPP
|
||
|
|
|
||
|
|
#include <boost/hana/fwd/core/common.hpp>
|
||
|
|
|
||
|
|
#include <boost/hana/concept/constant.hpp>
|
||
|
|
#include <boost/hana/config.hpp>
|
||
|
|
#include <boost/hana/core/when.hpp>
|
||
|
|
#include <boost/hana/detail/canonical_constant.hpp>
|
||
|
|
#include <boost/hana/detail/std_common_type.hpp>
|
||
|
|
#include <boost/hana/detail/void_t.hpp>
|
||
|
|
|
||
|
|
#include <type_traits>
|
||
|
|
|
||
|
|
|
||
|
|
namespace boost { namespace hana {
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
// common
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
//! @cond
|
||
|
|
template <typename T, typename U, typename>
|
||
|
|
struct common : common<T, U, when<true>> { };
|
||
|
|
//! @endcond
|
||
|
|
|
||
|
|
template <typename T, typename U, bool condition>
|
||
|
|
struct common<T, U, when<condition>>
|
||
|
|
: detail::std_common_type<T, U>
|
||
|
|
{ };
|
||
|
|
|
||
|
|
template <typename T>
|
||
|
|
struct common<T, T> {
|
||
|
|
using type = T;
|
||
|
|
};
|
||
|
|
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
// has_common
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
template <typename T, typename U, typename>
|
||
|
|
struct has_common : std::false_type { };
|
||
|
|
|
||
|
|
template <typename T, typename U>
|
||
|
|
struct has_common<T, U, detail::void_t<typename common<T, U>::type>>
|
||
|
|
: std::true_type
|
||
|
|
{ };
|
||
|
|
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
// Provided common data types for Constants
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
namespace constant_detail {
|
||
|
|
//! @todo
|
||
|
|
//! This is an awful hack to avoid having
|
||
|
|
//! @code
|
||
|
|
//! common<integral_constant_tag<int>, integral_constant_tag<long>>
|
||
|
|
//! ==
|
||
|
|
//! CanonicalConstant<long>
|
||
|
|
//! @endcode
|
||
|
|
template <typename A, typename B, typename C>
|
||
|
|
struct which {
|
||
|
|
using type = detail::CanonicalConstant<C>;
|
||
|
|
};
|
||
|
|
|
||
|
|
template <template <typename ...> class A, typename T, typename U, typename C>
|
||
|
|
struct which<A<T>, A<U>, C> {
|
||
|
|
using type = A<C>;
|
||
|
|
};
|
||
|
|
}
|
||
|
|
|
||
|
|
template <typename A, typename B>
|
||
|
|
struct common<A, B, when<
|
||
|
|
hana::Constant<A>::value &&
|
||
|
|
hana::Constant<B>::value &&
|
||
|
|
has_common<typename A::value_type, typename B::value_type>::value
|
||
|
|
>> {
|
||
|
|
using type = typename constant_detail::which<
|
||
|
|
A, B,
|
||
|
|
typename common<typename A::value_type,
|
||
|
|
typename B::value_type>::type
|
||
|
|
>::type;
|
||
|
|
};
|
||
|
|
|
||
|
|
template <typename A, typename B>
|
||
|
|
struct common<A, B, when<
|
||
|
|
hana::Constant<A>::value &&
|
||
|
|
!hana::Constant<B>::value &&
|
||
|
|
has_common<typename A::value_type, B>::value
|
||
|
|
>> {
|
||
|
|
using type = typename common<typename A::value_type, B>::type;
|
||
|
|
};
|
||
|
|
|
||
|
|
template <typename A, typename B>
|
||
|
|
struct common<A, B, when<
|
||
|
|
!hana::Constant<A>::value &&
|
||
|
|
hana::Constant<B>::value &&
|
||
|
|
has_common<A, typename B::value_type>::value
|
||
|
|
>> {
|
||
|
|
using type = typename common<A, typename B::value_type>::type;
|
||
|
|
};
|
||
|
|
}} // end namespace boost::hana
|
||
|
|
|
||
|
|
#endif // !BOOST_HANA_CORE_COMMON_HPP
|