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