Permalink
Switch branches/tags
Nothing to show
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
79 lines (72 sloc) 2.55 KB
/*=============================================================================
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_UTILITY_WHILE_LOOP_HPP
#define SPROUT_UTILITY_WHILE_LOOP_HPP
#include <sprout/config.hpp>
#include <sprout/utility/pair/pair.hpp>
namespace sprout {
namespace detail {
template<typename T, typename Predicate>
inline SPROUT_CONSTEXPR sprout::pair<T, bool>
while_loop_check(T const& init, Predicate pred) {
return sprout::pair<T, bool>(init, !pred(init));
}
template<typename T, typename Predicate, typename UnaryOperation>
inline SPROUT_CONSTEXPR sprout::pair<T, bool>
while_loop_impl_1(sprout::pair<T, bool> const& current, Predicate pred, UnaryOperation unary_op, std::size_t n) {
return current.second || !pred(current.first) ? current
: n == 1 ? sprout::detail::while_loop_check<T>(unary_op(current.first), pred)
: sprout::detail::while_loop_impl_1(
sprout::detail::while_loop_impl_1(
current,
pred, unary_op, n / 2
),
pred, unary_op, n - n / 2
)
;
}
template<typename T, typename Predicate, typename UnaryOperation>
inline SPROUT_CONSTEXPR sprout::pair<T, bool>
while_loop_impl(sprout::pair<T, bool> const& current, Predicate pred, UnaryOperation unary_op, std::size_t n) {
return current.second || !pred(current.first) ? current
: sprout::detail::while_loop_impl(
sprout::detail::while_loop_impl_1(
current,
pred, unary_op, n
),
pred, unary_op, n * 2
)
;
}
} // namespace detail
//
// while_loop
//
// recursion depth:
// O(log N)
//
template<typename T, typename Predicate, typename UnaryOperation>
inline SPROUT_CONSTEXPR T
while_loop(T init, Predicate pred, UnaryOperation unary_op) {
typedef sprout::pair<T, bool> type;
return sprout::detail::while_loop_impl(type(init, false), pred, unary_op, 1).second;
}
//
// flat_while_loop
//
// recursion depth:
// 0
//
template<typename T, typename Predicate, typename UnaryOperation>
inline SPROUT_CXX14_CONSTEXPR T
flat_while_loop(T init, Predicate pred, UnaryOperation unary_op) {
for (; pred(init); init = unary_op(init))
;
return init;
}
} // namespace sprout
#endif // #ifndef SPROUT_UTILITY_WHILE_LOOP_HPP