mirror of
https://github.com/ecency/ecency-mobile.git
synced 2024-12-25 14:22:14 +03:00
100 lines
3.4 KiB
C++
100 lines
3.4 KiB
C++
/*!
|
|
@file
|
|
Defines `boost::hana::slice` and `boost::hana::slice_c`.
|
|
|
|
@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_SLICE_HPP
|
|
#define BOOST_HANA_SLICE_HPP
|
|
|
|
#include <boost/hana/fwd/slice.hpp>
|
|
|
|
#include <boost/hana/at.hpp>
|
|
#include <boost/hana/concept/foldable.hpp>
|
|
#include <boost/hana/concept/sequence.hpp>
|
|
#include <boost/hana/config.hpp>
|
|
#include <boost/hana/core/dispatch.hpp>
|
|
#include <boost/hana/core/make.hpp>
|
|
#include <boost/hana/range.hpp>
|
|
#include <boost/hana/unpack.hpp>
|
|
|
|
#include <cstddef>
|
|
#include <utility>
|
|
|
|
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
|
//! @cond
|
|
template <typename Xs, typename Indices>
|
|
constexpr auto slice_t::operator()(Xs&& xs, Indices&& indices) const {
|
|
using S = typename hana::tag_of<Xs>::type;
|
|
using Slice = BOOST_HANA_DISPATCH_IF(slice_impl<S>,
|
|
hana::Sequence<S>::value &&
|
|
hana::Foldable<Indices>::value
|
|
);
|
|
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
|
static_assert(hana::Sequence<S>::value,
|
|
"hana::slice(xs, indices) requires 'xs' to be a Sequence");
|
|
|
|
static_assert(hana::Foldable<Indices>::value,
|
|
"hana::slice(xs, indices) requires 'indices' to be Foldable");
|
|
#endif
|
|
|
|
return Slice::apply(static_cast<Xs&&>(xs), static_cast<Indices&&>(indices));
|
|
}
|
|
//! @endcond
|
|
|
|
namespace detail {
|
|
template <typename Xs>
|
|
struct take_arbitrary {
|
|
Xs& xs;
|
|
using S = typename hana::tag_of<Xs>::type;
|
|
|
|
template <typename ...N>
|
|
constexpr auto operator()(N const& ...) const {
|
|
return hana::make<S>(hana::at_c<N::value>(xs)...);
|
|
}
|
|
};
|
|
}
|
|
|
|
template <typename S, bool condition>
|
|
struct slice_impl<S, when<condition>> : default_ {
|
|
template <std::size_t from, typename Xs, std::size_t ...i>
|
|
static constexpr auto from_offset(Xs&& xs, std::index_sequence<i...>) {
|
|
return hana::make<S>(hana::at_c<from + i>(static_cast<Xs&&>(xs))...);
|
|
}
|
|
|
|
template <typename Xs, typename T, T from, T to>
|
|
static constexpr auto apply(Xs&& xs, hana::range<T, from, to> const&) {
|
|
return slice_impl::from_offset<from>(
|
|
static_cast<Xs&&>(xs), std::make_index_sequence<to - from>{}
|
|
);
|
|
}
|
|
|
|
//! @todo
|
|
//! Since we have the right to specify the same index more than once,
|
|
//! we can't move from the elements of the source sequence even if it
|
|
//! is a temporary object: we could end up double-moving. Perhaps it
|
|
//! would be possible to determine the indices from which we can move
|
|
//! without incurring a too large compile-time penalty?
|
|
template <typename Xs, typename Indices>
|
|
static constexpr auto apply(Xs const& xs, Indices const& indices) {
|
|
return hana::unpack(indices, detail::take_arbitrary<Xs const>{xs});
|
|
}
|
|
};
|
|
|
|
template <std::size_t from, std::size_t to>
|
|
struct slice_c_t {
|
|
template <typename Xs>
|
|
constexpr auto operator()(Xs&& xs) const {
|
|
return hana::slice(static_cast<Xs&&>(xs),
|
|
hana::range_c<std::size_t, from, to>);
|
|
}
|
|
};
|
|
BOOST_HANA_NAMESPACE_END
|
|
|
|
#endif // !BOOST_HANA_SLICE_HPP
|