mirror of
https://github.com/ecency/ecency-mobile.git
synced 2024-12-23 13:22:02 +03:00
128 lines
4.3 KiB
C++
128 lines
4.3 KiB
C++
/*!
|
|
@file
|
|
Defines `boost::hana::cycle`.
|
|
|
|
@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_CYCLE_HPP
|
|
#define BOOST_HANA_CYCLE_HPP
|
|
|
|
#include <boost/hana/fwd/cycle.hpp>
|
|
|
|
#include <boost/hana/at.hpp>
|
|
#include <boost/hana/concat.hpp>
|
|
#include <boost/hana/concept/integral_constant.hpp>
|
|
#include <boost/hana/concept/monad_plus.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/detail/array.hpp>
|
|
#include <boost/hana/empty.hpp>
|
|
#include <boost/hana/length.hpp>
|
|
|
|
#include <cstddef>
|
|
#include <utility>
|
|
|
|
|
|
BOOST_HANA_NAMESPACE_BEGIN
|
|
//! @cond
|
|
template <typename Xs, typename N>
|
|
constexpr auto cycle_t::operator()(Xs&& xs, N const& n) const {
|
|
using M = typename hana::tag_of<Xs>::type;
|
|
using Cycle = BOOST_HANA_DISPATCH_IF(cycle_impl<M>,
|
|
hana::MonadPlus<M>::value
|
|
);
|
|
|
|
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
|
|
static_assert(hana::MonadPlus<M>::value,
|
|
"hana::cycle(xs, n) requires 'xs' to be a MonadPlus");
|
|
|
|
static_assert(hana::IntegralConstant<N>::value,
|
|
"hana::cycle(xs, n) requires 'n' to be an IntegralConstant");
|
|
#endif
|
|
|
|
static_assert(N::value >= 0,
|
|
"hana::cycle(xs, n) requires 'n' to be non-negative");
|
|
|
|
return Cycle::apply(static_cast<Xs&&>(xs), n);
|
|
}
|
|
//! @endcond
|
|
|
|
namespace detail {
|
|
template <typename M, std::size_t n, bool = n % 2 == 0>
|
|
struct cycle_helper;
|
|
|
|
template <typename M>
|
|
struct cycle_helper<M, 0, true> {
|
|
template <typename Xs>
|
|
static constexpr auto apply(Xs const&)
|
|
{ return hana::empty<M>(); }
|
|
};
|
|
|
|
template <typename M, std::size_t n>
|
|
struct cycle_helper<M, n, true> {
|
|
template <typename Xs>
|
|
static constexpr auto apply(Xs const& xs)
|
|
{ return cycle_helper<M, n/2>::apply(hana::concat(xs, xs)); }
|
|
};
|
|
|
|
template <typename M, std::size_t n>
|
|
struct cycle_helper<M, n, false> {
|
|
template <typename Xs>
|
|
static constexpr auto apply(Xs const& xs)
|
|
{ return hana::concat(xs, cycle_helper<M, n-1>::apply(xs)); }
|
|
};
|
|
}
|
|
|
|
template <typename M, bool condition>
|
|
struct cycle_impl<M, when<condition>> : default_ {
|
|
template <typename Xs, typename N>
|
|
static constexpr auto apply(Xs const& xs, N const&) {
|
|
constexpr std::size_t n = N::value;
|
|
return detail::cycle_helper<M, n>::apply(xs);
|
|
}
|
|
};
|
|
|
|
namespace detail {
|
|
template <std::size_t N, std::size_t Len>
|
|
struct cycle_indices {
|
|
static constexpr auto compute_value() {
|
|
detail::array<std::size_t, N * Len> indices{};
|
|
// Avoid (incorrect) Clang warning about remainder by zero
|
|
// in the loop below.
|
|
std::size_t len = Len;
|
|
for (std::size_t i = 0; i < N * Len; ++i)
|
|
indices[i] = i % len;
|
|
return indices;
|
|
}
|
|
|
|
static constexpr auto value = compute_value();
|
|
};
|
|
}
|
|
|
|
template <typename S>
|
|
struct cycle_impl<S, when<Sequence<S>::value>> {
|
|
template <typename Indices, typename Xs, std::size_t ...i>
|
|
static constexpr auto cycle_helper(Xs&& xs, std::index_sequence<i...>) {
|
|
constexpr auto indices = Indices::value;
|
|
(void)indices; // workaround GCC warning when sizeof...(i) == 0
|
|
return hana::make<S>(hana::at_c<indices[i]>(xs)...);
|
|
}
|
|
|
|
template <typename Xs, typename N>
|
|
static constexpr auto apply(Xs&& xs, N const&) {
|
|
constexpr std::size_t n = N::value;
|
|
constexpr std::size_t len = decltype(hana::length(xs))::value;
|
|
using Indices = detail::cycle_indices<n, len>;
|
|
return cycle_helper<Indices>(static_cast<Xs&&>(xs),
|
|
std::make_index_sequence<n * len>{});
|
|
}
|
|
};
|
|
BOOST_HANA_NAMESPACE_END
|
|
|
|
#endif // !BOOST_HANA_CYCLE_HPP
|