75 lines
2.2 KiB
C++
75 lines
2.2 KiB
C++
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/*!
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@file
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Defines `boost::hana::fill`.
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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_FILL_HPP
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#define BOOST_HANA_FILL_HPP
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#include <boost/hana/fwd/fill.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/transform.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 Value>
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constexpr auto fill_t::operator()(Xs&& xs, Value&& value) const {
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using S = typename hana::tag_of<Xs>::type;
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using Fill = BOOST_HANA_DISPATCH_IF(fill_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::fill(xs, value) requires 'xs' to be a Functor");
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#endif
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return Fill::apply(static_cast<Xs&&>(xs),
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static_cast<Value&&>(value));
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}
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//! @endcond
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template <typename Fun, bool condition>
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struct fill_impl<Fun, when<condition>> : default_ {
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template <typename Xs, typename Value>
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static constexpr auto apply(Xs&& xs, Value&& v) {
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return hana::transform(static_cast<Xs&&>(xs),
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hana::always(static_cast<Value&&>(v))
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);
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}
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};
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template <typename S>
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struct fill_impl<S, when<Sequence<S>::value>> {
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//! @cond
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template <typename V>
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struct filler {
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V const& v;
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template <typename ...Xs>
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constexpr auto operator()(Xs const& ...xs) const {
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return hana::make<S>(((void)xs, v)...);
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}
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};
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//! @endcond
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template <typename Xs, typename V>
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static constexpr auto apply(Xs const& xs, V const& v) {
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return hana::unpack(xs, filler<V>{v});
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FILL_HPP
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