mirror of https://github.com/axmolengine/axmol.git
124 lines
3.3 KiB
C++
124 lines
3.3 KiB
C++
/// \file
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// Range v3 library
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//
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// Copyright Casey Carter 2018-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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//
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#ifndef RANGES_V3_VIEW_ENUMERATE_HPP
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#define RANGES_V3_VIEW_ENUMERATE_HPP
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#include <range/v3/core.hpp>
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#include <range/v3/iterator/unreachable_sentinel.hpp>
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#include <range/v3/view/all.hpp>
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#include <range/v3/view/facade.hpp>
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#include <range/v3/view/zip.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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/// \cond
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namespace detail
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{
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// Counts from zero up.
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// See https://github.com/ericniebler/range-v3/issues/1141
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// for why we don't just use iota_view.
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template<typename Size, typename Diff>
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struct index_view : view_facade<index_view<Size, Diff>, infinite>
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{
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private:
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friend range_access;
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struct cursor
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{
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using difference_type = Diff;
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private:
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friend range_access;
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Size index_{0};
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Size read() const
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{
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return index_;
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}
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void next()
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{
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++index_;
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}
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bool equal(cursor const & that) const
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{
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return that.index_ == index_;
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}
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void prev()
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{
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--index_;
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}
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void advance(Diff n)
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{
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index_ += static_cast<Size>(n);
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}
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Diff distance_to(cursor const & that) const
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{
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return static_cast<Diff>(static_cast<Diff>(that.index_) -
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static_cast<Diff>(index_));
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}
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public:
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cursor() = default;
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};
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cursor begin_cursor() const
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{
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return cursor{};
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}
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unreachable_sentinel_t end_cursor() const
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{
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return unreachable;
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}
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public:
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index_view() = default;
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};
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} // namespace detail
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template<typename Size, typename Diff>
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RANGES_INLINE_VAR constexpr bool enable_borrowed_range<detail::index_view<Size, Diff>> =
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true;
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/// \endcond
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/// \addtogroup group-views
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/// @{
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namespace views
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{
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/// Lazily pairs each element in a source range with
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/// its corresponding index.
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struct enumerate_fn
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{
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template(typename Rng)(
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requires viewable_range<Rng>)
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auto operator()(Rng && rng) const
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{
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using D = range_difference_t<Rng>;
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using S = detail::iter_size_t<iterator_t<Rng>>;
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return zip(detail::index_view<S, D>(), all(static_cast<Rng &&>(rng)));
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}
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};
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/// \relates enumerate_fn
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/// \ingroup group-views
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RANGES_INLINE_VARIABLE(view_closure<enumerate_fn>, enumerate)
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} // namespace views
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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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