98 lines
3.4 KiB
C++
98 lines
3.4 KiB
C++
|
/*!
|
||
|
|
@file
|
||
|
|
Defines `boost::hana::minimum`.
|
||
|
|
|
||
|
|
@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_MINIMUM_HPP
|
||
|
|
#define BOOST_HANA_MINIMUM_HPP
|
||
|
|
|
||
|
|
#include <boost/hana/fwd/minimum.hpp>
|
||
|
|
|
||
|
|
#include <boost/hana/concept/foldable.hpp>
|
||
|
|
#include <boost/hana/config.hpp>
|
||
|
|
#include <boost/hana/core/dispatch.hpp>
|
||
|
|
#include <boost/hana/detail/nested_by.hpp> // required by fwd decl
|
||
|
|
#include <boost/hana/fold_left.hpp>
|
||
|
|
#include <boost/hana/if.hpp>
|
||
|
|
#include <boost/hana/less.hpp>
|
||
|
|
|
||
|
|
|
||
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
||
|
|
//! @cond
|
||
|
|
template <typename Xs>
|
||
|
|
constexpr decltype(auto) minimum_t::operator()(Xs&& xs) const {
|
||
|
|
using S = typename hana::tag_of<Xs>::type;
|
||
|
|
using Minimum = BOOST_HANA_DISPATCH_IF(minimum_impl<S>,
|
||
|
|
hana::Foldable<S>::value
|
||
|
|
);
|
||
|
|
|
||
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
||
|
|
static_assert(hana::Foldable<S>::value,
|
||
|
|
"hana::minimum(xs) requires 'xs' to be Foldable");
|
||
|
|
#endif
|
||
|
|
|
||
|
|
return Minimum::apply(static_cast<Xs&&>(xs));
|
||
|
|
}
|
||
|
|
|
||
|
|
template <typename Xs, typename Predicate>
|
||
|
|
constexpr decltype(auto) minimum_t::operator()(Xs&& xs, Predicate&& pred) const {
|
||
|
|
using S = typename hana::tag_of<Xs>::type;
|
||
|
|
using Minimum = BOOST_HANA_DISPATCH_IF(minimum_pred_impl<S>,
|
||
|
|
hana::Foldable<S>::value
|
||
|
|
);
|
||
|
|
|
||
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
||
|
|
static_assert(hana::Foldable<S>::value,
|
||
|
|
"hana::minimum(xs, predicate) requires 'xs' to be Foldable");
|
||
|
|
#endif
|
||
|
|
|
||
|
|
return Minimum::apply(static_cast<Xs&&>(xs),
|
||
|
|
static_cast<Predicate&&>(pred));
|
||
|
|
}
|
||
|
|
//! @endcond
|
||
|
|
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
// minimum (with a custom predicate)
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
namespace detail {
|
||
|
|
template <typename Pred>
|
||
|
|
struct min_by {
|
||
|
|
Pred pred;
|
||
|
|
|
||
|
|
template <typename X, typename Y>
|
||
|
|
constexpr decltype(auto) operator()(X&& x, Y&& y) const {
|
||
|
|
auto result = (*pred)(x, y);
|
||
|
|
return hana::if_(result, static_cast<X&&>(x),
|
||
|
|
static_cast<Y&&>(y));
|
||
|
|
}
|
||
|
|
};
|
||
|
|
}
|
||
|
|
|
||
|
|
template <typename T, bool condition>
|
||
|
|
struct minimum_pred_impl<T, when<condition>> : default_ {
|
||
|
|
template <typename Xs, typename Pred>
|
||
|
|
static constexpr decltype(auto) apply(Xs&& xs, Pred const& pred) {
|
||
|
|
// We use a pointer instead of a reference to avoid a Clang ICE.
|
||
|
|
return hana::fold_left(static_cast<Xs&&>(xs),
|
||
|
|
detail::min_by<decltype(&pred)>{&pred}
|
||
|
|
);
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
// minimum (without a custom predicate)
|
||
|
|
//////////////////////////////////////////////////////////////////////////
|
||
|
|
template <typename T, bool condition>
|
||
|
|
struct minimum_impl<T, when<condition>> : default_ {
|
||
|
|
template <typename Xs>
|
||
|
|
static constexpr decltype(auto) apply(Xs&& xs)
|
||
|
|
{ return hana::minimum(static_cast<Xs&&>(xs), hana::less); }
|
||
|
|
};
|
||
|
|
BOOST_HANA_NAMESPACE_END
|
||
|
|
|
||
|
|
#endif // !BOOST_HANA_MINIMUM_HPP
|