mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
synced 2024-11-25 00:43:44 +00:00
70 lines
2.6 KiB
C++
70 lines
2.6 KiB
C++
/*=============================================================================
|
|
Copyright (c) 2011-2017 Bolero MURAKAMI
|
|
https://github.com/bolero-MURAKAMI/Sprout
|
|
|
|
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
|
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
|
=============================================================================*/
|
|
#ifndef SPROUT_ALGORITHM_FOLD_WHILE_HPP
|
|
#define SPROUT_ALGORITHM_FOLD_WHILE_HPP
|
|
|
|
#include <iterator>
|
|
#include <sprout/config.hpp>
|
|
#include <sprout/iterator/operation.hpp>
|
|
#include <sprout/utility/pair/pair.hpp>
|
|
|
|
namespace sprout {
|
|
namespace detail {
|
|
template<typename InputIterator, typename T, typename BinaryOperation, typename Predicate>
|
|
inline SPROUT_CONSTEXPR sprout::pair<InputIterator, T>
|
|
fold_while_impl_1(
|
|
sprout::pair<InputIterator, T> const& current,
|
|
InputIterator const& last, BinaryOperation binary_op, Predicate pred, typename std::iterator_traits<InputIterator>::difference_type n
|
|
)
|
|
{
|
|
typedef sprout::pair<InputIterator, T> type;
|
|
return current.first == last || !pred(current.second) ? current
|
|
: n == 1 ? type(sprout::next(current.first), binary_op(current.second, *current.first))
|
|
: sprout::detail::fold_while_impl_1(
|
|
sprout::detail::fold_while_impl_1(
|
|
current,
|
|
last, binary_op, pred, n / 2
|
|
),
|
|
last, binary_op, pred, n - n / 2
|
|
)
|
|
;
|
|
}
|
|
template<typename InputIterator, typename T, typename BinaryOperation, typename Predicate>
|
|
inline SPROUT_CONSTEXPR sprout::pair<InputIterator, T>
|
|
fold_while_impl(
|
|
sprout::pair<InputIterator, T> const& current,
|
|
InputIterator const& last, BinaryOperation binary_op, Predicate pred, typename std::iterator_traits<InputIterator>::difference_type n
|
|
)
|
|
{
|
|
return current.first == last || !pred(current.second) ? current
|
|
: sprout::detail::fold_while_impl(
|
|
sprout::detail::fold_while_impl_1(
|
|
current,
|
|
last, binary_op, pred, n
|
|
),
|
|
last, binary_op, pred, n * 2
|
|
)
|
|
;
|
|
}
|
|
} // namespace detail
|
|
|
|
//
|
|
// fold_while
|
|
//
|
|
// recursion depth:
|
|
// O(log N)
|
|
//
|
|
template<typename InputIterator, typename T, typename BinaryOperation, typename Predicate>
|
|
inline SPROUT_CONSTEXPR T
|
|
fold_while(InputIterator first, InputIterator last, T init, BinaryOperation binary_op, Predicate pred) {
|
|
typedef sprout::pair<InputIterator, T> type;
|
|
return sprout::detail::fold_while_impl(type(first, init), last, binary_op, pred, 1).second;
|
|
}
|
|
} // namespace sprout
|
|
|
|
#endif // #ifndef SPROUT_ALGORITHM_FOLD_WHILE_HPP
|