/*! @file Defines `boost::hana::remove_range` and `boost::hana::remove_range_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_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