115 lines
4.0 KiB
C++
115 lines
4.0 KiB
C++
/*!
|
|
@file
|
|
Defines `boost::hana::minus`.
|
|
|
|
@copyright Louis Dionne 2013-2016
|
|
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_MINUS_HPP
|
|
#define BOOST_HANA_MINUS_HPP
|
|
|
|
#include <boost/hana/fwd/minus.hpp>
|
|
|
|
#include <boost/hana/concept/constant.hpp>
|
|
#include <boost/hana/concept/group.hpp>
|
|
#include <boost/hana/config.hpp>
|
|
#include <boost/hana/core/common.hpp>
|
|
#include <boost/hana/core/to.hpp>
|
|
#include <boost/hana/core/dispatch.hpp>
|
|
#include <boost/hana/detail/canonical_constant.hpp>
|
|
#include <boost/hana/detail/has_common_embedding.hpp>
|
|
#include <boost/hana/fwd/negate.hpp>
|
|
#include <boost/hana/plus.hpp>
|
|
#include <boost/hana/value.hpp>
|
|
|
|
#include <type_traits>
|
|
|
|
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
|
//! @cond
|
|
template <typename X, typename Y>
|
|
constexpr decltype(auto) minus_t::operator()(X&& x, Y&& y) const {
|
|
using T = typename hana::tag_of<X>::type;
|
|
using U = typename hana::tag_of<Y>::type;
|
|
using Minus = BOOST_HANA_DISPATCH_IF(decltype(minus_impl<T, U>{}),
|
|
hana::Group<T>::value &&
|
|
hana::Group<U>::value
|
|
);
|
|
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
|
static_assert(hana::Group<T>::value,
|
|
"hana::minus(x, y) requires 'x' to be in a Group");
|
|
|
|
static_assert(hana::Group<U>::value,
|
|
"hana::minus(x, y) requires 'y' to be in a Group");
|
|
#endif
|
|
|
|
return Minus::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
|
|
}
|
|
//! @endcond
|
|
|
|
template <typename T, typename U, bool condition>
|
|
struct minus_impl<T, U, when<condition>> : default_ {
|
|
template <typename ...Args>
|
|
static constexpr auto apply(Args&& ...) = delete;
|
|
};
|
|
|
|
template <typename T, bool condition>
|
|
struct minus_impl<T, T, when<condition>> : default_ {
|
|
template <typename X, typename Y>
|
|
static constexpr decltype(auto) apply(X&& x, Y&& y) {
|
|
return hana::plus(static_cast<X&&>(x),
|
|
hana::negate(static_cast<Y&&>(y)));
|
|
}
|
|
};
|
|
|
|
// Cross-type overload
|
|
template <typename T, typename U>
|
|
struct minus_impl<T, U, when<
|
|
detail::has_nontrivial_common_embedding<Group, T, U>::value
|
|
>> {
|
|
using C = typename common<T, U>::type;
|
|
template <typename X, typename Y>
|
|
static constexpr decltype(auto) apply(X&& x, Y&& y) {
|
|
return hana::minus(hana::to<C>(static_cast<X&&>(x)),
|
|
hana::to<C>(static_cast<Y&&>(y)));
|
|
}
|
|
};
|
|
|
|
//////////////////////////////////////////////////////////////////////////
|
|
// Model for arithmetic data types
|
|
//////////////////////////////////////////////////////////////////////////
|
|
template <typename T>
|
|
struct minus_impl<T, T, when<std::is_arithmetic<T>::value &&
|
|
!std::is_same<bool, T>::value>> {
|
|
template <typename X, typename Y>
|
|
static constexpr decltype(auto) apply(X&& x, Y&& y)
|
|
{ return static_cast<X&&>(x) - static_cast<Y&&>(y); }
|
|
};
|
|
|
|
//////////////////////////////////////////////////////////////////////////
|
|
// Model for Constants over a Group
|
|
//////////////////////////////////////////////////////////////////////////
|
|
namespace detail {
|
|
template <typename C, typename X, typename Y>
|
|
struct constant_from_minus {
|
|
static constexpr auto value = hana::minus(hana::value<X>(), hana::value<Y>());
|
|
using hana_tag = detail::CanonicalConstant<typename C::value_type>;
|
|
};
|
|
}
|
|
|
|
template <typename C>
|
|
struct minus_impl<C, C, when<
|
|
hana::Constant<C>::value &&
|
|
Group<typename C::value_type>::value
|
|
>> {
|
|
template <typename X, typename Y>
|
|
static constexpr decltype(auto) apply(X const&, Y const&)
|
|
{ return hana::to<C>(detail::constant_from_minus<C, X, Y>{}); }
|
|
};
|
|
BOOST_HANA_NAMESPACE_END
|
|
|
|
#endif // !BOOST_HANA_MINUS_HPP
|