mirror of
https://github.com/bolero-MURAKAMI/Sprout
synced 2024-11-12 21:09:01 +00:00
80 lines
2.6 KiB
C++
80 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_UTILITY_WHILE_LOOP_HPP
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#define SPROUT_UTILITY_WHILE_LOOP_HPP
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#include <sprout/config.hpp>
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#include <sprout/utility/pair/pair.hpp>
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namespace sprout {
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#ifdef SPROUT_CONFIG_DISABLE_CXX14_CONSTEXPR
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namespace detail {
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template<typename T, typename Predicate>
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inline SPROUT_CONSTEXPR sprout::pair<T, bool>
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while_loop_check(T const& init, Predicate pred) {
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return sprout::pair<T, bool>(init, !pred(init));
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}
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template<typename T, typename Predicate, typename UnaryOperation>
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inline SPROUT_CONSTEXPR sprout::pair<T, bool>
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while_loop_impl_1(sprout::pair<T, bool> const& current, Predicate pred, UnaryOperation unary_op, std::size_t n) {
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return current.second || !pred(current.first) ? current
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: n == 1 ? sprout::detail::while_loop_check<T>(unary_op(current.first), pred)
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: sprout::detail::while_loop_impl_1(
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sprout::detail::while_loop_impl_1(
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current,
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pred, unary_op, n / 2
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),
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pred, unary_op, n - n / 2
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)
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;
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}
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template<typename T, typename Predicate, typename UnaryOperation>
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inline SPROUT_CONSTEXPR sprout::pair<T, bool>
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while_loop_impl(sprout::pair<T, bool> const& current, Predicate pred, UnaryOperation unary_op, std::size_t n) {
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return current.second || !pred(current.first) ? current
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: sprout::detail::while_loop_impl(
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sprout::detail::while_loop_impl_1(
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current,
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pred, unary_op, n
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),
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pred, unary_op, 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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// while_loop
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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 T, typename Predicate, typename UnaryOperation>
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inline SPROUT_CONSTEXPR T
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while_loop(T init, Predicate pred, UnaryOperation unary_op) {
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typedef sprout::pair<T, bool> type;
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return sprout::detail::while_loop_impl(type(init, false), pred, unary_op, 1).second;
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}
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#else
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//
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// while_loop
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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 T, typename Predicate, typename UnaryOperation>
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inline SPROUT_CXX14_CONSTEXPR T
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while_loop(T init, Predicate pred, UnaryOperation unary_op) {
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for (; pred(init); init = unary_op(init))
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;
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return init;
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}
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#endif
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} // namespace sprout
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#endif // #ifndef SPROUT_UTILITY_WHILE_LOOP_HPP
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