62 lines
1.9 KiB
C++
62 lines
1.9 KiB
C++
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/*!
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@file
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Defines `boost::hana::or_`.
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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_OR_HPP
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#define BOOST_HANA_OR_HPP
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#include <boost/hana/fwd/or.hpp>
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#include <boost/hana/concept/logical.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/detail/variadic/foldl1.hpp>
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#include <boost/hana/if.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename X, typename Y>
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constexpr decltype(auto) or_t::operator()(X&& x, Y&& y) const {
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using Bool = typename hana::tag_of<X>::type;
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using Or = BOOST_HANA_DISPATCH_IF(or_impl<Bool>,
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hana::Logical<Bool>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Logical<Bool>::value,
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"hana::or_(x, y) requires 'x' to be a Logical");
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#endif
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return Or::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
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}
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template <typename X, typename ...Y>
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constexpr decltype(auto) or_t::operator()(X&& x, Y&& ...y) const {
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return detail::variadic::foldl1(
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*this,
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static_cast<X&&>(x),
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static_cast<Y&&>(y)...
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);
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}
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//! @endcond
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template <typename L, bool condition>
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struct or_impl<L, when<condition>> : hana::default_ {
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template <typename X, typename Y>
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static constexpr decltype(auto) apply(X&& x, Y&& y) {
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//! @todo How to forward `x` here? Since the arguments to `if_`
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//! can be evaluated in any order, we have to be careful not to
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//! use `x` in a moved-from state.
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return hana::if_(x, x, static_cast<Y&&>(y));
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_OR_HPP
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