mirror of https://github.com/axmolengine/axmol.git
127 lines
4.0 KiB
C++
127 lines
4.0 KiB
C++
/// \file
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// Range v3 library
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//
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// Copyright Eric Niebler 2021-present
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//
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// Use, modification and distribution is subject to the
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// Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// Project home: https://github.com/ericniebler/range-v3
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#ifndef RANGES_V3_ALGORITHM_FOLD_RIGHT_HPP
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#define RANGES_V3_ALGORITHM_FOLD_RIGHT_HPP
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#include <meta/meta.hpp>
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#include <range/v3/algorithm/fold_left.hpp>
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#include <range/v3/functional/identity.hpp>
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#include <range/v3/functional/invoke.hpp>
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#include <range/v3/iterator/operations.hpp>
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#include <range/v3/range/access.hpp>
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#include <range/v3/range/concepts.hpp>
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#include <range/v3/utility/optional.hpp>
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#include <range/v3/detail/prologue.hpp>
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namespace ranges
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{
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namespace detail
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{
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template<typename F>
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struct flipped
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{
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F f;
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template(class T, class U)(requires invocable<F &, U, T>) //
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invoke_result_t<F &, U, T>
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operator()(T &&, U &&);
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};
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} // namespace detail
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// clang-format off
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/// \concept indirectly_binary_right_foldable
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/// \brief The \c indirectly_binary_right_foldable concept
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template<class F, class T, class I>
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CPP_concept indirectly_binary_right_foldable =
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indirectly_binary_left_foldable<detail::flipped<F>, T, I>;
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// clang-format on
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/// \addtogroup group-algorithms
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/// @{
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RANGES_FUNC_BEGIN(fold_right)
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template(typename I, typename S, typename T, typename Op)(
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requires sentinel_for<S, I> AND bidirectional_iterator<I> AND
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indirectly_binary_right_foldable<Op, T, I>) //
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constexpr auto
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RANGES_FUNC(fold_right)(I first, S last, T init, Op op)
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{
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using U = std::decay_t<invoke_result_t<Op &, iter_reference_t<I>, T>>;
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if(first == last)
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{
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return U(std::move(init));
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}
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I tail = next(first, last);
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U accum = invoke(op, *--tail, std::move(init));
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while(first != tail)
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{
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accum = invoke(op, *--tail, std::move(accum));
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}
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return accum;
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}
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template(typename Rng, typename T, typename Op)(
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requires bidirectional_range<Rng> AND
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indirectly_binary_right_foldable<Op, T, iterator_t<Rng>>) //
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constexpr auto
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RANGES_FUNC(fold_right)(Rng && rng, T init, Op op)
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{
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return (*this)(begin(rng), end(rng), std::move(init), std::move(op));
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}
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RANGES_FUNC_END(fold_right)
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RANGES_FUNC_BEGIN(fold_right_last)
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template(typename I, typename S, typename Op)(
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requires sentinel_for<S, I> AND bidirectional_iterator<I> AND
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indirectly_binary_right_foldable<Op, iter_value_t<I>, I>
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AND constructible_from<iter_value_t<I>, iter_reference_t<I>>) //
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constexpr auto
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RANGES_FUNC(fold_right_last)(I first, S last, Op op)
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{
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using U = invoke_result_t<fold_right_fn, I, S, iter_value_t<I>, Op>;
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if(first == last)
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{
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return optional<U>();
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}
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I tail = prev(next(first, std::move(last)));
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return optional<U>(
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in_place,
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fold_right_fn{}(
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std::move(first), tail, iter_value_t<I>(*tail), std::move(op)));
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}
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template(typename R, typename Op)(
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requires bidirectional_range<R> AND
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indirectly_binary_right_foldable<Op, range_value_t<R>, iterator_t<R>>
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AND constructible_from<range_value_t<R>, range_reference_t<R>>) //
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constexpr auto
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RANGES_FUNC(fold_right_last)(R && rng, Op op)
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{
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return (*this)(begin(rng), end(rng), std::move(op));
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}
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RANGES_FUNC_END(fold_right_last)
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/// @}
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} // namespace ranges
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#include <range/v3/detail/epilogue.hpp>
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#endif
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