79 lines
2.5 KiB
C++
79 lines
2.5 KiB
C++
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/*!
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@file
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Defines `boost::hana::ap`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_AP_HPP
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#define BOOST_HANA_AP_HPP
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#include <boost/hana/fwd/ap.hpp>
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#include <boost/hana/chain.hpp>
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#include <boost/hana/concept/applicative.hpp>
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#include <boost/hana/concept/sequence.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/detail/variadic/foldl1.hpp>
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#include <boost/hana/functional/curry.hpp>
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#include <boost/hana/functional/partial.hpp>
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#include <boost/hana/transform.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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template <typename A, bool condition>
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struct ap_impl<A, when<condition>> : default_ {
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template <typename ...Args>
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static constexpr auto apply(Args&& ...args) = delete;
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};
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//! @cond
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template <typename F, typename X>
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constexpr decltype(auto) ap_t::operator()(F&& f, X&& x) const {
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using Function = typename hana::tag_of<F>::type;
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using Value = typename hana::tag_of<X>::type;
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using Ap = BOOST_HANA_DISPATCH_IF(ap_impl<Function>,
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hana::Applicative<Function>::value && hana::Applicative<Value>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Applicative<Function>::value,
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"hana::ap(f, x) requires 'f' to be an Applicative");
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static_assert(hana::Applicative<Value>::value,
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"hana::ap(f, x) requires 'x' to be an Applicative");
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#endif
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return Ap::apply(static_cast<F&&>(f), static_cast<X&&>(x));
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}
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template <typename F, typename ...Xs>
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constexpr decltype(auto) ap_t::operator()(F&& f, Xs&& ...xs) const {
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static_assert(sizeof...(xs) >= 1,
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"hana::ap must be called with at least two arguments");
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return detail::variadic::foldl1(
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*this,
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hana::transform(static_cast<F&&>(f), hana::curry<sizeof...(xs)>),
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static_cast<Xs&&>(xs)...
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);
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}
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//! @endcond
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template <typename S>
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struct ap_impl<S, when<Sequence<S>::value>> {
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template <typename F, typename X>
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static constexpr decltype(auto) apply(F&& f, X&& x) {
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return hana::chain(
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static_cast<F&&>(f),
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hana::partial(hana::transform, static_cast<X&&>(x))
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);
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_AP_HPP
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