Edit: /usr/include/boost/hana/cycle.hpp (4275B)
/*!
@file
Defines `boost::hana::cycle`.
@copyright Louis Dionne 2013-2017
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
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template
constexpr auto cycle_t::operator()(Xs&& xs, N const& n) const {
using M = typename hana::tag_of::type;
using Cycle = BOOST_HANA_DISPATCH_IF(cycle_impl,
hana::MonadPlus::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::MonadPlus::value,
"hana::cycle(xs, n) requires 'xs' to be a MonadPlus");
static_assert(hana::IntegralConstant::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), n);
}
//! @endcond
namespace detail {
template
struct cycle_helper;
template
struct cycle_helper {
template
static constexpr auto apply(Xs const&)
{ return hana::empty(); }
};
template
struct cycle_helper {
template
static constexpr auto apply(Xs const& xs)
{ return cycle_helper::apply(hana::concat(xs, xs)); }
};
template
struct cycle_helper {
template
static constexpr auto apply(Xs const& xs)
{ return hana::concat(xs, cycle_helper::apply(xs)); }
};
}
template
struct cycle_impl> : default_ {
template
static constexpr auto apply(Xs const& xs, N const&) {
constexpr std::size_t n = N::value;
return detail::cycle_helper::apply(xs);
}
};
namespace detail {
template
struct cycle_indices {
static constexpr auto compute_value() {
detail::array 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
struct cycle_impl::value>> {
template
static constexpr auto cycle_helper(Xs&& xs, std::index_sequence) {
constexpr auto indices = Indices::value;
(void)indices; // workaround GCC warning when sizeof...(i) == 0
return hana::make(hana::at_c(xs)...);
}
template
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;
return cycle_helper(static_cast(xs),
std::make_index_sequence{});
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_CYCLE_HPP