mirror of
https://github.com/ecency/ecency-mobile.git
synced 2024-12-22 12:51:42 +03:00
86 lines
3.0 KiB
C++
86 lines
3.0 KiB
C++
/*!
|
|
@file
|
|
Defines `boost::hana::drop_front_exactly`.
|
|
|
|
@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_DROP_FRONT_EXACTLY_HPP
|
|
#define BOOST_HANA_DROP_FRONT_EXACTLY_HPP
|
|
|
|
#include <boost/hana/fwd/drop_front_exactly.hpp>
|
|
|
|
#include <boost/hana/bool.hpp>
|
|
#include <boost/hana/concept/integral_constant.hpp>
|
|
#include <boost/hana/concept/iterable.hpp>
|
|
#include <boost/hana/config.hpp>
|
|
#include <boost/hana/core/dispatch.hpp>
|
|
#include <boost/hana/drop_front.hpp>
|
|
#include <boost/hana/integral_constant.hpp>
|
|
#include <boost/hana/is_empty.hpp>
|
|
|
|
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
|
//! @cond
|
|
template <typename Xs, typename N>
|
|
constexpr auto drop_front_exactly_t::operator()(Xs&& xs, N const& n) const {
|
|
using It = typename hana::tag_of<Xs>::type;
|
|
using DropFrontExactly = BOOST_HANA_DISPATCH_IF(drop_front_exactly_impl<It>,
|
|
hana::Iterable<It>::value &&
|
|
hana::IntegralConstant<N>::value
|
|
);
|
|
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
|
static_assert(hana::Iterable<It>::value,
|
|
"hana::drop_front_exactly(xs, n) requires 'xs' to be an Iterable");
|
|
|
|
static_assert(hana::IntegralConstant<N>::value,
|
|
"hana::drop_front_exactly(xs, n) requires 'n' to be an IntegralConstant");
|
|
#endif
|
|
|
|
static_assert(N::value >= 0,
|
|
"hana::drop_front_exactly(xs, n) requires 'n' to be non-negative");
|
|
|
|
return DropFrontExactly::apply(static_cast<Xs&&>(xs), n);
|
|
}
|
|
|
|
template <typename Xs>
|
|
constexpr auto drop_front_exactly_t::operator()(Xs&& xs) const {
|
|
return (*this)(static_cast<Xs&&>(xs), hana::size_c<1>);
|
|
}
|
|
//! @endcond
|
|
|
|
namespace detail {
|
|
template <typename Xs, typename N>
|
|
constexpr void check_dfe_overflow(Xs const& xs, N const&, hana::true_) {
|
|
constexpr bool n_overflew_length = decltype(
|
|
hana::is_empty(hana::drop_front(xs, hana::size_c<N::value - 1>))
|
|
)::value;
|
|
static_assert(!n_overflew_length,
|
|
"hana::drop_front_exactly(xs, n) requires 'n' to be less than or "
|
|
"equal to the number of elements in 'xs'");
|
|
}
|
|
|
|
template <typename Xs, typename N>
|
|
constexpr void check_dfe_overflow(Xs const&, N const&, hana::false_) { }
|
|
}
|
|
|
|
template <typename It, bool condition>
|
|
struct drop_front_exactly_impl<It, when<condition>> : default_ {
|
|
template <typename Xs, typename N>
|
|
static constexpr auto apply(Xs&& xs, N const& n) {
|
|
auto result = hana::drop_front(static_cast<Xs&&>(xs), n);
|
|
constexpr bool check_for_overflow =
|
|
decltype(hana::is_empty(result))::value && N::value != 0;
|
|
|
|
detail::check_dfe_overflow(xs, n, hana::bool_c<check_for_overflow>);
|
|
|
|
return result; // NRVO applied
|
|
}
|
|
};
|
|
BOOST_HANA_NAMESPACE_END
|
|
|
|
#endif // !BOOST_HANA_DROP_FRONT_EXACTLY_HPP
|