mirror of
https://github.com/ecency/ecency-mobile.git
synced 2024-12-21 04:11:50 +03:00
54 lines
1.5 KiB
C++
54 lines
1.5 KiB
C++
/*!
|
|
@file
|
|
Defines `boost::hana::back`.
|
|
|
|
@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_BACK_HPP
|
|
#define BOOST_HANA_BACK_HPP
|
|
|
|
#include <boost/hana/fwd/back.hpp>
|
|
|
|
#include <boost/hana/at.hpp>
|
|
#include <boost/hana/concept/iterable.hpp>
|
|
#include <boost/hana/config.hpp>
|
|
#include <boost/hana/core/dispatch.hpp>
|
|
#include <boost/hana/length.hpp>
|
|
|
|
#include <cstddef>
|
|
|
|
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
|
//! @cond
|
|
template <typename Xs>
|
|
constexpr decltype(auto) back_t::operator()(Xs&& xs) const {
|
|
using It = typename hana::tag_of<Xs>::type;
|
|
using Back = BOOST_HANA_DISPATCH_IF(back_impl<It>,
|
|
hana::Iterable<It>::value
|
|
);
|
|
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
|
static_assert(hana::Iterable<It>::value,
|
|
"hana::back(xs) requires 'xs' to be an Iterable");
|
|
#endif
|
|
|
|
return Back::apply(static_cast<Xs&&>(xs));
|
|
}
|
|
//! @endcond
|
|
|
|
template <typename It, bool condition>
|
|
struct back_impl<It, when<condition>> : default_ {
|
|
template <typename Xs>
|
|
static constexpr decltype(auto) apply(Xs&& xs) {
|
|
constexpr std::size_t len = decltype(hana::length(xs))::value;
|
|
static_assert(len > 0, "hana::back(xs) requires 'xs' to be non-empty");
|
|
return hana::at_c<len - 1>(static_cast<Xs&&>(xs));
|
|
}
|
|
};
|
|
BOOST_HANA_NAMESPACE_END
|
|
|
|
#endif // !BOOST_HANA_BACK_HPP
|