Sprout/sprout/range/adaptor/adapted_taken.hpp

#ifndef SPROUT_RANGE_ADAPTOR_ADAPTED_TAKEN_HPP
#define SPROUT_RANGE_ADAPTOR_ADAPTED_TAKEN_HPP

#include <sprout/config.hpp>
#include <sprout/utility/lvalue_forward.hpp>
#include <sprout/range/adaptor/taken.hpp>
#include <sprout/range/adaptor/dropped.hpp>
#include <sprout/range/adaptor/jointed.hpp>

namespace sprout {
	namespace adaptors {
		//
		// adapt_take_holder
		//
		template<typename Adaptor, typename Difference>
		class adapt_take_holder {
		public:
			typedef Adaptor adaptor_type;
			typedef Difference difference_type;
		private:
			adaptor_type adaptor_;
			difference_type distance_;
		public:
			explicit SPROUT_CONSTEXPR adapt_take_holder(adaptor_type const& adaptor, difference_type distance)
				: adaptor_(adaptor), distance_(distance)
			{}
			SPROUT_CONSTEXPR adaptor_type const& adaptor() const {
				return adaptor_;
			}
			SPROUT_CONSTEXPR difference_type const& distance() const {
				return distance_;
			}
		};

		//
		// adapted_taken_forwarder
		//
		class adapted_taken_forwarder {
		public:
			template<typename Adaptor, typename Difference>
			SPROUT_CONSTEXPR sprout::adaptors::adapt_take_holder<Adaptor, Difference>
			operator()(Adaptor const& adaptor, Difference distance) {
				return sprout::adaptors::adapt_take_holder<Adaptor, Difference>(adaptor, distance);
			}
		};

		//
		// adapted_taken
		//
		namespace {
			SPROUT_STATIC_CONSTEXPR sprout::adaptors::adapted_taken_forwarder adapted_taken{};
		}	// anonymous-namespace

		//
		// operator|
		//
		template<typename Range, typename Adaptor, typename Difference>
		inline SPROUT_CONSTEXPR auto
		operator|(Range&& lhs, sprout::adaptors::adapt_take_holder<Adaptor, Difference> const& rhs)
		-> decltype(
			sprout::lvalue_forward<Range>(lhs) | sprout::adaptors::taken(rhs.distance()) | rhs.adaptor()
				| sprout::adaptors::jointed(sprout::lvalue_forward<Range>(lhs) | sprout::adaptors::dropped(rhs.distance()))
			)
		{
			return sprout::lvalue_forward<Range>(lhs) | sprout::adaptors::taken(rhs.distance()) | rhs.adaptor()
				| sprout::adaptors::jointed(sprout::lvalue_forward<Range>(lhs) | sprout::adaptors::dropped(rhs.distance()))
				;
		}
	}	// namespace adaptors
}	// namespace sprout

#endif	// #ifndef SPROUT_RANGE_ADAPTOR_ADAPTED_TAKEN_HPP