63e88f80
 Hu Chunming
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/*!
@file
Defines `boost::hana::transform`.
Copyright Louis Dionne 2013-2022
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_TRANSFORM_HPP
#define BOOST_HANA_TRANSFORM_HPP
#include <boost/hana/fwd/transform.hpp>
#include <boost/hana/bool.hpp>
#include <boost/hana/concept/functor.hpp>
#include <boost/hana/concept/sequence.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/core/make.hpp>
#include <boost/hana/functional/always.hpp>
#include <boost/hana/fwd/adjust_if.hpp>
#include <boost/hana/unpack.hpp>
namespace boost { namespace hana {
//! @cond
template <typename Xs, typename F>
constexpr auto transform_t::operator()(Xs&& xs, F&& f) const {
using S = typename hana::tag_of<Xs>::type;
using Transform = BOOST_HANA_DISPATCH_IF(transform_impl<S>,
hana::Functor<S>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Functor<S>::value,
"hana::transform(xs, f) requires 'xs' to be a Functor");
#endif
return Transform::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f));
}
//! @endcond
template <typename Fun, bool condition>
struct transform_impl<Fun, when<condition>> : default_ {
template <typename Xs, typename F>
static constexpr auto apply(Xs&& xs, F&& f) {
return hana::adjust_if(static_cast<Xs&&>(xs),
hana::always(hana::true_c),
static_cast<F&&>(f));
}
};
template <typename S>
struct transform_impl<S, when<Sequence<S>::value>> {
//! @cond
template <typename F>
struct transformer {
F f;
template <typename ...Xs>
constexpr auto operator()(Xs&& ...xs) const {
return hana::make<S>((*f)(static_cast<Xs&&>(xs))...);
}
};
//! @endcond
template <typename Xs, typename F>
static constexpr auto apply(Xs&& xs, F&& f) {
// We use a pointer to workaround a Clang 3.5 ICE
return hana::unpack(static_cast<Xs&&>(xs),
transformer<decltype(&f)>{&f});
}
};
}} // end namespace boost::hana
#endif // !BOOST_HANA_TRANSFORM_HPP
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