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/*!
@file
Defines `boost::hana::minus`.
Copyright Louis Dionne 2013-2022
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>
namespace boost { namespace hana {
//! @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>{}); }
};
}} // end namespace boost::hana
#endif // !BOOST_HANA_MINUS_HPP
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