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/*!
@file
Defines `boost::hana::remove_range` and `boost::hana::remove_range_c`.
@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_REMOVE_RANGE_HPP
#define BOOST_HANA_REMOVE_RANGE_HPP
#include <boost/hana/fwd/remove_range.hpp>
#include <boost/hana/at.hpp>
#include <boost/hana/concept/integral_constant.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/integral_constant.hpp>
#include <boost/hana/length.hpp>
#include <cstddef>
#include <utility>
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template <typename Xs, typename From, typename To>
constexpr auto remove_range_t::operator()(Xs&& xs, From const& from, To const& to) const {
using S = typename hana::tag_of<Xs>::type;
using RemoveRange = BOOST_HANA_DISPATCH_IF(remove_range_impl<S>,
hana::Sequence<S>::value &&
hana::IntegralConstant<From>::value &&
hana::IntegralConstant<To>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Sequence<S>::value,
"hana::remove_range(xs, from, to) requires 'xs' to be a Sequence");
static_assert(hana::IntegralConstant<From>::value,
"hana::remove_range(xs, from, to) requires 'from' to be an IntegralConstant");
static_assert(hana::IntegralConstant<To>::value,
"hana::remove_range(xs, from, to) requires 'to' to be an IntegralConstant");
#endif
return RemoveRange::apply(static_cast<Xs&&>(xs), from, to);
}
//! @endcond
template <typename S, bool condition>
struct remove_range_impl<S, when<condition>> : default_ {
template <std::size_t offset, typename Xs, std::size_t ...before, std::size_t ...after>
static constexpr auto
remove_range_helper(Xs&& xs, std::index_sequence<before...>,
std::index_sequence<after...>)
{
return hana::make<S>(
hana::at_c<before>(static_cast<Xs&&>(xs))...,
hana::at_c<offset + after>(static_cast<Xs&&>(xs))...
);
}
template <typename Xs, typename From, typename To>
static constexpr auto apply(Xs&& xs, From const&, To const&) {
constexpr std::size_t from = From::value;
constexpr std::size_t to = To::value;
constexpr std::size_t len = decltype(hana::length(xs))::value;
constexpr std::size_t before = from == to ? len : from;
constexpr std::size_t after = from == to ? 0 : len - to;
static_assert(from <= to,
"hana::remove_range(xs, from, to) requires '[from, to)' to be a "
"valid interval, meaning that 'from <= to'");
static_assert(from == to || from >= 0,
"hana::remove_range(xs, from, to) requires 'from' to be non-negative");
static_assert(from == to || to <= len,
"hana::remove_range(xs, from, to) requires 'to <= length(xs)'");
return remove_range_helper<to>(static_cast<Xs&&>(xs),
std::make_index_sequence<before>{},
std::make_index_sequence<after>{});
}
};
template <std::size_t from, std::size_t to>
struct remove_range_c_t {
template <typename Xs>
constexpr decltype(auto) operator()(Xs&& xs) const {
return hana::remove_range(static_cast<Xs&&>(xs),
hana::size_c<from>,
hana::size_c<to>);
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_REMOVE_RANGE_HPP
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