mirror of
https://github.com/ecency/ecency-mobile.git
synced 2024-12-23 05:13:04 +03:00
62 lines
1.8 KiB
C++
62 lines
1.8 KiB
C++
/*!
|
|
@file
|
|
Defines `boost::hana::if_`.
|
|
|
|
@copyright Louis Dionne 2013-2016
|
|
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_IF_HPP
|
|
#define BOOST_HANA_IF_HPP
|
|
|
|
#include <boost/hana/fwd/if.hpp>
|
|
|
|
#include <boost/hana/concept/logical.hpp>
|
|
#include <boost/hana/config.hpp>
|
|
#include <boost/hana/core/dispatch.hpp>
|
|
#include <boost/hana/eval_if.hpp>
|
|
|
|
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
|
//! @cond
|
|
template <typename Cond, typename Then, typename Else>
|
|
constexpr decltype(auto) if_t::operator()(Cond&& cond, Then&& then, Else&& else_) const {
|
|
using Bool = typename hana::tag_of<Cond>::type;
|
|
using If = BOOST_HANA_DISPATCH_IF(if_impl<Bool>,
|
|
hana::Logical<Bool>::value
|
|
);
|
|
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
|
static_assert(hana::Logical<Bool>::value,
|
|
"hana::if_(cond, then, else) requires 'cond' to be a Logical");
|
|
#endif
|
|
|
|
return If::apply(static_cast<Cond&&>(cond),
|
|
static_cast<Then&&>(then),
|
|
static_cast<Else&&>(else_));
|
|
}
|
|
//! @endcond
|
|
|
|
namespace detail {
|
|
template <typename T>
|
|
struct hold {
|
|
T value;
|
|
constexpr T&& operator()() && { return static_cast<T&&>(value); }
|
|
};
|
|
}
|
|
|
|
template <typename L, bool condition>
|
|
struct if_impl<L, when<condition>> : default_ {
|
|
template <typename C, typename T, typename E>
|
|
static constexpr auto apply(C&& c, T&& t, E&& e) {
|
|
return hana::eval_if(static_cast<C&&>(c),
|
|
detail::hold<T&&>{static_cast<T&&>(t)},
|
|
detail::hold<E&&>{static_cast<E&&>(e)}
|
|
);
|
|
}
|
|
};
|
|
BOOST_HANA_NAMESPACE_END
|
|
|
|
#endif // !BOOST_HANA_IF_HPP
|