101 lines
3.9 KiB
C++
101 lines
3.9 KiB
C++
/*!
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@file
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Defines `boost::hana::remove_range` and `boost::hana::remove_range_c`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_REMOVE_RANGE_HPP
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#define BOOST_HANA_REMOVE_RANGE_HPP
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#include <boost/hana/fwd/remove_range.hpp>
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#include <boost/hana/at.hpp>
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#include <boost/hana/concept/integral_constant.hpp>
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#include <boost/hana/concept/sequence.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/core/make.hpp>
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#include <boost/hana/integral_constant.hpp>
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#include <boost/hana/length.hpp>
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#include <cstddef>
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#include <utility>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename Xs, typename From, typename To>
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constexpr auto remove_range_t::operator()(Xs&& xs, From const& from, To const& to) const {
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using S = typename hana::tag_of<Xs>::type;
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using RemoveRange = BOOST_HANA_DISPATCH_IF(remove_range_impl<S>,
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hana::Sequence<S>::value &&
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hana::IntegralConstant<From>::value &&
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hana::IntegralConstant<To>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Sequence<S>::value,
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"hana::remove_range(xs, from, to) requires 'xs' to be a Sequence");
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static_assert(hana::IntegralConstant<From>::value,
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"hana::remove_range(xs, from, to) requires 'from' to be an IntegralConstant");
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static_assert(hana::IntegralConstant<To>::value,
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"hana::remove_range(xs, from, to) requires 'to' to be an IntegralConstant");
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#endif
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return RemoveRange::apply(static_cast<Xs&&>(xs), from, to);
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}
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//! @endcond
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template <typename S, bool condition>
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struct remove_range_impl<S, when<condition>> : default_ {
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template <std::size_t offset, typename Xs, std::size_t ...before, std::size_t ...after>
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static constexpr auto
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remove_range_helper(Xs&& xs, std::index_sequence<before...>,
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std::index_sequence<after...>)
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{
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return hana::make<S>(
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hana::at_c<before>(static_cast<Xs&&>(xs))...,
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hana::at_c<offset + after>(static_cast<Xs&&>(xs))...
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);
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}
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template <typename Xs, typename From, typename To>
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static constexpr auto apply(Xs&& xs, From const&, To const&) {
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constexpr std::size_t from = From::value;
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constexpr std::size_t to = To::value;
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constexpr std::size_t len = decltype(hana::length(xs))::value;
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constexpr std::size_t before = from == to ? len : from;
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constexpr std::size_t after = from == to ? 0 : len - to;
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static_assert(from <= to,
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"hana::remove_range(xs, from, to) requires '[from, to)' to be a "
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"valid interval, meaning that 'from <= to'");
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static_assert(from == to || from >= 0,
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"hana::remove_range(xs, from, to) requires 'from' to be non-negative");
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static_assert(from == to || to <= len,
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"hana::remove_range(xs, from, to) requires 'to <= length(xs)'");
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return remove_range_helper<to>(static_cast<Xs&&>(xs),
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std::make_index_sequence<before>{},
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std::make_index_sequence<after>{});
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}
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};
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template <std::size_t from, std::size_t to>
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struct remove_range_c_t {
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template <typename Xs>
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constexpr decltype(auto) operator()(Xs&& xs) const {
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return hana::remove_range(static_cast<Xs&&>(xs),
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hana::size_c<from>,
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hana::size_c<to>);
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_REMOVE_RANGE_HPP
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