mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
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82 lines
2.6 KiB
C++
82 lines
2.6 KiB
C++
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/*=============================================================================
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Copyright (c) 2011-2015 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_UNTIL_LOOP_HPP
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#define SPROUT_UTILITY_UNTIL_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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until_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 UnaryOperation, typename Predicate>
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inline SPROUT_CONSTEXPR sprout::pair<T, bool>
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until_loop_impl_1(sprout::pair<T, bool> const& current, UnaryOperation unary_op, Predicate pred, std::size_t n) {
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return current.second || pred(current.first) ? current
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: n == 1 ? sprout::detail::until_loop_check<T>(unary_op(current.first), pred)
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: sprout::detail::until_loop_impl_1(
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sprout::detail::until_loop_impl_1(
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current,
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unary_op, pred, n / 2
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),
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unary_op, pred, n - n / 2
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)
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;
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}
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template<typename T, typename UnaryOperation, typename Predicate>
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inline SPROUT_CONSTEXPR sprout::pair<T, bool>
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until_loop_impl(sprout::pair<T, bool> const& current, UnaryOperation unary_op, Predicate pred, std::size_t n) {
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return current.second || pred(current.first) ? current
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: sprout::detail::until_loop_impl(
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sprout::detail::until_loop_impl_1(
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current,
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unary_op, pred, n
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),
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unary_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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// until_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 UnaryOperation, typename Predicate>
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inline SPROUT_CONSTEXPR T
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until_loop(T init, UnaryOperation unary_op, Predicate pred) {
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typedef sprout::pair<T, bool> type;
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return sprout::detail::until_loop_impl(type(init, false), unary_op, pred, 1).second;
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}
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#else
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//
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// until_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 UnaryOperation, typename Predicate>
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inline SPROUT_CXX14_CONSTEXPR T
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until_loop(T init, UnaryOperation unary_op, Predicate pred) {
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while (!pred(init)) {
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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_UNTIL_LOOP_HPP
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