Sprout/sprout/algorithm/partition_point.hpp

#ifndef SPROUT_ALGORITHM_PARTITION_POINT_HPP
#define SPROUT_ALGORITHM_PARTITION_POINT_HPP

#include <sprout/config.hpp>
#include <sprout/iterator/operation.hpp>
#include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT

namespace sprout {
	// Copyright (C) 2011 RiSK (sscrisk)

	namespace detail {
		template<typename ForwardIterator, typename Predicate>
		SPROUT_CONSTEXPR ForwardIterator partition_point_impl(ForwardIterator first, ForwardIterator last, Predicate pred, ForwardIterator mid) {
			return mid == last ? mid
				: pred(*mid) ? sprout::detail::partition_point_impl(
					sprout::next(mid),
					last,
					pred,
					sprout::next(mid, 1 + NS_SSCRISK_CEL_OR_SPROUT::distance(sprout::next(mid), last) / 2)
					)
				: sprout::detail::partition_point_impl(
					first,
					mid,
					pred,
					sprout::next(first, NS_SSCRISK_CEL_OR_SPROUT::distance(first, mid) / 2)
					)
				;
		}
	}	// namespace detail

	// 25.3.13 Partitions
	template<typename ForwardIterator, typename Predicate>
	SPROUT_CONSTEXPR ForwardIterator partition_point(ForwardIterator first, ForwardIterator last, Predicate pred) {
		return sprout::detail::partition_point_impl(first, last, pred, sprout::next(first, NS_SSCRISK_CEL_OR_SPROUT::distance(first, last) / 2));
	}
}	// namespace sprout

#endif	// #ifndef SPROUT_ALGORITHM_PARTITION_POINT_HPP