63 lines
1.9 KiB
C++
63 lines
1.9 KiB
C++
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/*!
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@file
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Defines `boost::hana::for_each`.
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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_FOR_EACH_HPP
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#define BOOST_HANA_FOR_EACH_HPP
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#include <boost/hana/fwd/for_each.hpp>
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#include <boost/hana/concept/foldable.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/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 void for_each_t::operator()(Xs&& xs, F&& f) const {
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using S = typename hana::tag_of<Xs>::type;
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using ForEach = BOOST_HANA_DISPATCH_IF(for_each_impl<S>,
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hana::Foldable<S>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Foldable<S>::value,
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"hana::for_each(xs, f) requires 'xs' to be Foldable");
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#endif
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return ForEach::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f));
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}
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//! @endcond
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namespace detail {
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template <typename F>
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struct on_each {
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F f;
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template <typename ...Xs>
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constexpr void operator()(Xs&& ...xs) const {
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using Swallow = int[];
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(void)Swallow{0, ((void)(*f)(static_cast<Xs&&>(xs)), 0)...};
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}
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};
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}
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template <typename T, bool condition>
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struct for_each_impl<T, when<condition>> : default_ {
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template <typename Xs, typename F>
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static constexpr void apply(Xs&& xs, F&& f) {
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// We use a pointer instead of a reference to avoid a Clang ICE.
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hana::unpack(static_cast<Xs&&>(xs),
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detail::on_each<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_FOR_EACH_HPP
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