mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
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70 lines
2.6 KiB
C++
70 lines
2.6 KiB
C++
/*=============================================================================
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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_FOLD_WHILE_HPP
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#define SPROUT_ALGORITHM_FOLD_WHILE_HPP
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#include <iterator>
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#include <sprout/config.hpp>
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#include <sprout/iterator/operation.hpp>
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#include <sprout/utility/pair/pair.hpp>
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namespace sprout {
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namespace detail {
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template<typename InputIterator, typename T, typename BinaryOperation, typename Predicate>
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inline SPROUT_CONSTEXPR sprout::pair<InputIterator, T>
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fold_while_impl_1(
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sprout::pair<InputIterator, T> const& current,
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InputIterator last, BinaryOperation binary_op, Predicate pred, typename std::iterator_traits<InputIterator>::difference_type n
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)
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{
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typedef sprout::pair<InputIterator, T> type;
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return current.first == last || !pred(current.second) ? current
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: n == 1 ? type(sprout::next(current.first), binary_op(current.second, *current.first))
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: sprout::detail::fold_while_impl_1(
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sprout::detail::fold_while_impl_1(
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current,
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last, binary_op, pred, n / 2
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),
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last, binary_op, pred, n - n / 2
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)
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;
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}
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template<typename InputIterator, typename T, typename BinaryOperation, typename Predicate>
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inline SPROUT_CONSTEXPR sprout::pair<InputIterator, T>
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fold_while_impl(
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sprout::pair<InputIterator, T> const& current,
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InputIterator last, BinaryOperation binary_op, Predicate pred, typename std::iterator_traits<InputIterator>::difference_type n
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)
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{
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return current.first == last || !pred(current.second) ? current
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: sprout::detail::fold_while_impl(
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sprout::detail::fold_while_impl_1(
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current,
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last, binary_op, pred, n
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),
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last, binary_op, pred, n * 2
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)
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;
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}
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} // namespace detail
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//
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// fold_while
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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 InputIterator, typename T, typename BinaryOperation, typename Predicate>
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inline SPROUT_CONSTEXPR T
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fold_while(InputIterator first, InputIterator last, T init, BinaryOperation binary_op, Predicate pred) {
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typedef sprout::pair<InputIterator, T> type;
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return sprout::detail::fold_while_impl(type(first, init), last, binary_op, pred, 1).second;
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}
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} // namespace sprout
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#endif // #ifndef SPROUT_ALGORITHM_FOLD_WHILE_HPP
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