/*!
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@file
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Defines `boost::hana::find_if`.
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@copyright Louis Dionne 2013-2017
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@copyright Jason Rice 2017
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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_FIND_IF_HPP
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#define BOOST_HANA_FIND_IF_HPP
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#include <boost/hana/fwd/find_if.hpp>
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#include <boost/hana/accessors.hpp>
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#include <boost/hana/at.hpp>
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#include <boost/hana/bool.hpp>
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#include <boost/hana/concept/iterable.hpp>
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#include <boost/hana/concept/searchable.hpp>
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#include <boost/hana/concept/struct.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/first.hpp>
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#include <boost/hana/functional/compose.hpp>
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#include <boost/hana/index_if.hpp>
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#include <boost/hana/second.hpp>
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#include <boost/hana/transform.hpp>
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#include <cstddef>
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#include <utility>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename Xs, typename Pred>
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constexpr auto find_if_t::operator()(Xs&& xs, Pred&& pred) const {
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using S = typename hana::tag_of<Xs>::type;
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using FindIf = BOOST_HANA_DISPATCH_IF(find_if_impl<S>,
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hana::Searchable<S>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Searchable<S>::value,
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"hana::find_if(xs, pred) requires 'xs' to be a Searchable");
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#endif
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return FindIf::apply(static_cast<Xs&&>(xs), static_cast<Pred&&>(pred));
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}
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//! @endcond
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template <typename S, bool condition>
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struct find_if_impl<S, when<condition>> : default_ {
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template <typename ...Args>
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static constexpr auto apply(Args&& ...) = delete;
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};
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namespace detail {
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template <typename Xs>
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struct partial_at {
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Xs const& xs;
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template <typename I>
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constexpr decltype(auto) operator()(I i) const {
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return hana::at(xs, i);
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}
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};
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}
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template <typename Tag>
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struct find_if_impl<Tag, when<Iterable<Tag>::value>> {
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template <typename Xs, typename Pred>
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static constexpr auto apply(Xs&& xs, Pred&& pred) {
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using Result = decltype(hana::index_if(
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static_cast<Xs&&>(xs), static_cast<Pred&&>(pred)));
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return hana::transform(Result{},
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detail::partial_at<std::decay_t<Xs>>{static_cast<Xs&&>(xs)});
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}
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};
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template <typename T, std::size_t N>
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struct find_if_impl<T[N]> {
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template <typename Xs>
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static constexpr auto find_if_helper(Xs&&, hana::false_)
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{ return hana::nothing; }
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template <typename Xs>
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static constexpr auto find_if_helper(Xs&& xs, hana::true_)
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{ return hana::just(static_cast<Xs&&>(xs)[0]); }
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template <typename Xs, typename Pred>
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static constexpr auto apply(Xs&& xs, Pred&& pred) {
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return find_if_helper(static_cast<Xs&&>(xs),
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hana::bool_c<decltype(
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static_cast<Pred&&>(pred)(static_cast<Xs&&>(xs)[0])
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)::value>
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);
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}
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};
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namespace struct_detail {
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template <typename X>
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struct get_member {
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X x;
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template <typename Member>
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constexpr decltype(auto) operator()(Member&& member) && {
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return hana::second(static_cast<Member&&>(member))(
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static_cast<X&&>(x)
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);
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}
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};
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}
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template <typename S>
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struct find_if_impl<S, when<hana::Struct<S>::value>> {
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template <typename X, typename Pred>
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static constexpr decltype(auto) apply(X&& x, Pred&& pred) {
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return hana::transform(
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hana::find_if(hana::accessors<S>(),
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hana::compose(static_cast<Pred&&>(pred), hana::first)
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),
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struct_detail::get_member<X>{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_FIND_IF_HPP
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