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77 lines
2.4 KiB
C++
77 lines
2.4 KiB
C++
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/*!
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@file
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Defines `boost::hana::transform`.
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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_TRANSFORM_HPP
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#define BOOST_HANA_TRANSFORM_HPP
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#include <boost/hana/fwd/transform.hpp>
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#include <boost/hana/bool.hpp>
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#include <boost/hana/concept/functor.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/core/make.hpp>
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#include <boost/hana/functional/always.hpp>
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#include <boost/hana/fwd/adjust_if.hpp>
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#include <boost/hana/unpack.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename Xs, typename F>
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constexpr auto transform_t::operator()(Xs&& xs, F&& f) const {
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using S = typename hana::tag_of<Xs>::type;
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using Transform = BOOST_HANA_DISPATCH_IF(transform_impl<S>,
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hana::Functor<S>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Functor<S>::value,
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"hana::transform(xs, f) requires 'xs' to be a Functor");
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#endif
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return Transform::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f));
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}
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//! @endcond
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template <typename Fun, bool condition>
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struct transform_impl<Fun, when<condition>> : default_ {
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template <typename Xs, typename F>
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static constexpr auto apply(Xs&& xs, F&& f) {
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return hana::adjust_if(static_cast<Xs&&>(xs),
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hana::always(hana::true_c),
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static_cast<F&&>(f));
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}
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};
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template <typename S>
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struct transform_impl<S, when<Sequence<S>::value>> {
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//! @cond
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template <typename F>
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struct transformer {
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F f;
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template <typename ...Xs>
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constexpr auto operator()(Xs&& ...xs) const {
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return hana::make<S>((*f)(static_cast<Xs&&>(xs))...);
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}
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};
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//! @endcond
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template <typename Xs, typename F>
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static constexpr auto apply(Xs&& xs, F&& f) {
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// We use a pointer to workaround a Clang 3.5 ICE
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return hana::unpack(static_cast<Xs&&>(xs),
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transformer<decltype(&f)>{&f});
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_TRANSFORM_HPP
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