79 lines
2.5 KiB
C++
79 lines
2.5 KiB
C++
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/*!
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@file
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Defines `boost::hana::adjust_if`.
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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_ADJUST_IF_HPP
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#define BOOST_HANA_ADJUST_IF_HPP
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#include <boost/hana/fwd/adjust_if.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/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/if.hpp>
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#include <boost/hana/transform.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename Xs, typename Pred, typename F>
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constexpr auto adjust_if_t::operator()(Xs&& xs, Pred const& pred, F const& f) const {
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using S = typename hana::tag_of<Xs>::type;
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using AdjustIf = BOOST_HANA_DISPATCH_IF(adjust_if_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::adjust_if(xs, pred, f) requires 'xs' to be a Functor");
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#endif
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return AdjustIf::apply(static_cast<Xs&&>(xs), pred, f);
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}
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//! @endcond
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namespace detail {
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template <typename Pred, typename F>
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struct apply_if {
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Pred const& pred;
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F const& f;
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template <typename X>
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constexpr decltype(auto) helper(bool cond, X&& x) const
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{ return cond ? f(static_cast<X&&>(x)) : static_cast<X&&>(x); }
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template <typename X>
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constexpr decltype(auto) helper(hana::true_, X&& x) const
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{ return f(static_cast<X&&>(x)); }
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template <typename X>
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constexpr decltype(auto) helper(hana::false_, X&& x) const
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{ return static_cast<X&&>(x); }
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template <typename X>
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constexpr decltype(auto) operator()(X&& x) const {
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auto cond = hana::if_(pred(x), hana::true_c, hana::false_c);
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return this->helper(cond, static_cast<X&&>(x));
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}
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};
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}
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template <typename Fun, bool condition>
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struct adjust_if_impl<Fun, when<condition>> : default_ {
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template <typename Xs, typename Pred, typename F>
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static constexpr auto apply(Xs&& xs, Pred const& pred, F const& f) {
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return hana::transform(static_cast<Xs&&>(xs),
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detail::apply_if<Pred, F>{pred, f});
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_ADJUST_IF_HPP
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