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Diffstat (limited to 'boost/hana/greater.hpp')
-rw-r--r-- | boost/hana/greater.hpp | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/boost/hana/greater.hpp b/boost/hana/greater.hpp new file mode 100644 index 0000000000..ee75bb806a --- /dev/null +++ b/boost/hana/greater.hpp @@ -0,0 +1,71 @@ +/*! +@file +Defines `boost::hana::greater`. + +@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_GREATER_HPP +#define BOOST_HANA_GREATER_HPP + +#include <boost/hana/fwd/greater.hpp> + +#include <boost/hana/concept/orderable.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/concepts.hpp> +#include <boost/hana/detail/has_common_embedding.hpp> +#include <boost/hana/detail/nested_than.hpp> // required by fwd decl +#include <boost/hana/if.hpp> + + +BOOST_HANA_NAMESPACE_BEGIN + //! @cond + template <typename X, typename Y> + constexpr decltype(auto) greater_t::operator()(X&& x, Y&& y) const { + using T = typename hana::tag_of<X>::type; + using U = typename hana::tag_of<Y>::type; + using Greater = BOOST_HANA_DISPATCH_IF(decltype(greater_impl<T, U>{}), + hana::Orderable<T>::value && + hana::Orderable<U>::value + ); + + #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS + static_assert(hana::Orderable<T>::value, + "hana::greater(x, y) requires 'x' to be Orderable"); + + static_assert(hana::Orderable<U>::value, + "hana::greater(x, y) requires 'y' to be Orderable"); + #endif + + return Greater::apply(static_cast<X&&>(x), static_cast<Y&&>(y)); + } + //! @endcond + template <typename T, typename U, bool condition> + struct greater_impl<T, U, when<condition>> : default_ { + template <typename X, typename Y> + static constexpr decltype(auto) apply(X&& x, Y&& y) { + return hana::less(static_cast<Y&&>(y), + static_cast<X&&>(x)); + } + }; + + // Cross-type overload + template <typename T, typename U> + struct greater_impl<T, U, when< + detail::has_nontrivial_common_embedding<Orderable, T, U>::value + >> { + using C = typename hana::common<T, U>::type; + template <typename X, typename Y> + static constexpr decltype(auto) apply(X&& x, Y&& y) { + return hana::greater(hana::to<C>(static_cast<X&&>(x)), + hana::to<C>(static_cast<Y&&>(y))); + } + }; +BOOST_HANA_NAMESPACE_END + +#endif // !BOOST_HANA_GREATER_HPP |