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https://github.com/bolero-MURAKAMI/Sprout.git
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76 lines
2.5 KiB
C++
76 lines
2.5 KiB
C++
/*=============================================================================
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Copyright (c) 2011 RiSK (sscrisk)
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https://github.com/sscrisk/CEL---ConstExpr-Library
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Copyright (c) 2011-2016 Bolero MURAKAMI
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https://github.com/bolero-MURAKAMI/Sprout
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#ifndef SPROUT_ALGORITHM_PARTITION_POINT_HPP
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#define SPROUT_ALGORITHM_PARTITION_POINT_HPP
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#include <iterator>
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#include <sprout/config.hpp>
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#include <sprout/detail/predef.hpp>
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#include <sprout/iterator/operation.hpp>
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namespace sprout {
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#if defined(SPROUT_CONFIG_DISABLE_CXX14_CONSTEXPR) || SPROUT_GCC_IN_RANGE((5, 1, 0), (5, 1, 1))
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namespace detail {
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template<typename ForwardIterator, typename Predicate>
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inline SPROUT_CONSTEXPR ForwardIterator
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partition_point_impl(ForwardIterator first, ForwardIterator last, Predicate pred, ForwardIterator mid) {
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return mid == last ? mid
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: pred(*mid) ? sprout::detail::partition_point_impl(
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sprout::next(mid), last, pred,
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sprout::next(mid, 1 + (sprout::distance(mid, last) - 1) / 2)
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)
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: sprout::detail::partition_point_impl(
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first, mid, pred,
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sprout::next(first, sprout::distance(first, mid) / 2)
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)
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;
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}
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} // namespace detail
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// 25.3.13 Partitions
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//
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// recursion depth:
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// O(log N)
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//
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template<typename ForwardIterator, typename Predicate>
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inline SPROUT_CONSTEXPR ForwardIterator
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partition_point(ForwardIterator first, ForwardIterator last, Predicate pred) {
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return sprout::detail::partition_point_impl(
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first, last, pred,
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sprout::next(first, sprout::distance(first, last) / 2)
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);
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}
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#else
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// 25.3.13 Partitions
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//
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// recursion depth:
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// 0
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//
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template<typename ForwardIterator, typename Predicate>
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inline SPROUT_CXX14_CONSTEXPR ForwardIterator
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partition_point(ForwardIterator first, ForwardIterator last, Predicate pred) {
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typedef typename std::iterator_traits<ForwardIterator>::difference_type difference_type;
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for (difference_type len = sprout::distance(first, last); len != 0; ) {
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difference_type const half = len / 2;
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ForwardIterator const mid = sprout::next(first, half);
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if (pred(*mid)) {
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first = sprout::next(mid);
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len -= half + 1;
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} else {
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len = half;
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}
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}
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return first;
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}
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#endif
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} // namespace sprout
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#endif // #ifndef SPROUT_ALGORITHM_PARTITION_POINT_HPP
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