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/*!
@file
Defines `boost::hana::ap`.
@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_AP_HPP
#define BOOST_HANA_AP_HPP
#include <boost/hana/fwd/ap.hpp>
#include <boost/hana/chain.hpp>
#include <boost/hana/concept/applicative.hpp>
#include <boost/hana/concept/sequence.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/detail/variadic/foldl1.hpp>
#include <boost/hana/functional/curry.hpp>
#include <boost/hana/functional/partial.hpp>
#include <boost/hana/transform.hpp>
BOOST_HANA_NAMESPACE_BEGIN
template <typename A, bool condition>
struct ap_impl<A, when<condition>> : default_ {
template <typename ...Args>
static constexpr auto apply(Args&& ...args) = delete;
};
//! @cond
template <typename F, typename X>
constexpr decltype(auto) ap_t::operator()(F&& f, X&& x) const {
using Function = typename hana::tag_of<F>::type;
using Value = typename hana::tag_of<X>::type;
using Ap = BOOST_HANA_DISPATCH_IF(ap_impl<Function>,
hana::Applicative<Function>::value && hana::Applicative<Value>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Applicative<Function>::value,
"hana::ap(f, x) requires 'f' to be an Applicative");
static_assert(hana::Applicative<Value>::value,
"hana::ap(f, x) requires 'x' to be an Applicative");
#endif
return Ap::apply(static_cast<F&&>(f), static_cast<X&&>(x));
}
template <typename F, typename ...Xs>
constexpr decltype(auto) ap_t::operator()(F&& f, Xs&& ...xs) const {
static_assert(sizeof...(xs) >= 1,
"hana::ap must be called with at least two arguments");
return detail::variadic::foldl1(
*this,
hana::transform(static_cast<F&&>(f), hana::curry<sizeof...(xs)>),
static_cast<Xs&&>(xs)...
);
}
//! @endcond
template <typename S>
struct ap_impl<S, when<Sequence<S>::value>> {
template <typename F, typename X>
static constexpr decltype(auto) apply(F&& f, X&& x) {
return hana::chain(
static_cast<F&&>(f),
hana::partial(hana::transform, static_cast<X&&>(x))
);
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_AP_HPP
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