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328 lines
11 KiB
C++
328 lines
11 KiB
C++
/// \file
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// Range v3 library
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//
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// Copyright Eric Niebler 2013-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_TAKE_HPP
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#define RANGES_V3_VIEW_TAKE_HPP
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#include <type_traits>
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#include <range/v3/range_fwd.hpp>
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#include <range/v3/algorithm/min.hpp>
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#include <range/v3/functional/bind_back.hpp>
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#include <range/v3/iterator/counted_iterator.hpp>
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#include <range/v3/iterator/default_sentinel.hpp>
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#include <range/v3/range/concepts.hpp>
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#include <range/v3/range/traits.hpp>
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#include <range/v3/utility/static_const.hpp>
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#include <range/v3/view/all.hpp>
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#include <range/v3/view/view.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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/// \addtogroup group-views
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/// @{
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template<typename Rng>
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struct take_view : view_interface<take_view<Rng>, finite>
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{
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private:
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CPP_assert(view_<Rng>);
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Rng base_ = Rng();
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range_difference_t<Rng> count_ = 0;
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template<bool Const>
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struct sentinel
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{
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private:
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using Base = meta::conditional_t<Const, Rng const, Rng>;
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using CI = counted_iterator<iterator_t<Base>>;
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sentinel_t<Base> end_ = sentinel_t<Base>();
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public:
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sentinel() = default;
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constexpr explicit sentinel(sentinel_t<Base> last)
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: end_(std::move(last))
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{}
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template(bool Other)(
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requires Const AND CPP_NOT(Other) AND
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convertible_to<sentinel_t<Rng>,
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sentinel_t<Base>>)
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constexpr sentinel(sentinel<Other> that)
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: end_(std::move(that.end_))
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{}
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constexpr sentinel_t<Base> base() const
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{
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return end_;
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}
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#ifdef RANGES_WORKAROUND_MSVC_756601
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template<typename = void>
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#endif // RANGES_WORKAROUND_MSVC_756601
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friend constexpr bool operator==(sentinel const & x, CI const & y)
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{
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return y.count() == 0 || y.base() == x.end_;
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}
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#ifdef RANGES_WORKAROUND_MSVC_756601
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template<typename = void>
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#endif // RANGES_WORKAROUND_MSVC_756601
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friend constexpr bool operator==(CI const & y, sentinel const & x)
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{
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return y.count() == 0 || y.base() == x.end_;
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}
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#ifdef RANGES_WORKAROUND_MSVC_756601
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template<typename = void>
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#endif // RANGES_WORKAROUND_MSVC_756601
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friend constexpr bool operator!=(sentinel const & x, CI const & y)
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{
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return y.count() != 0 && y.base() != x.end_;
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}
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#ifdef RANGES_WORKAROUND_MSVC_756601
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template<typename = void>
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#endif // RANGES_WORKAROUND_MSVC_756601
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friend constexpr bool operator!=(CI const & y, sentinel const & x)
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{
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return y.count() != 0 && y.base() != x.end_;
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}
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};
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#if RANGES_CXX_IF_CONSTEXPR < RANGES_CXX_IF_CONSTEXPR_17
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template<typename Take>
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static auto begin_random_access_(Take & take, std::true_type)
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{
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return ranges::begin(take.base_);
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}
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template<typename Take>
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static auto begin_random_access_(Take & take, std::false_type)
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{
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auto s = static_cast<range_difference_t<Rng>>(take.size());
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return make_counted_iterator(ranges::begin(take.base_), s);
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}
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template<typename Take>
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static auto begin_sized_(Take & take, std::true_type)
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{
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return begin_random_access_(
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take, meta::bool_<random_access_range<decltype((take.base_))>>{});
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}
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template<typename Take>
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static auto begin_sized_(Take & take, std::false_type)
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{
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return make_counted_iterator(ranges::begin(take.base_), take.count_);
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}
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template<typename Take>
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static auto end_random_access_(Take & take, std::true_type)
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{
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return ranges::begin(take.base_) +
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static_cast<range_difference_t<Rng>>(take.size());
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}
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static auto end_random_access_(detail::ignore_t, std::false_type)
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{
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return default_sentinel;
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}
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template<typename Take>
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static auto end_sized_(Take & take, std::true_type, std::false_type) // sized
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{
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return end_random_access_(
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take, meta::bool_<random_access_range<decltype((take.base_))>>{});
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}
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static auto end_sized_(detail::ignore_t, std::false_type,
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std::true_type) // infinite
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{
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return default_sentinel;
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}
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static auto end_sized_(take_view & take, std::false_type, std::false_type)
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{
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return sentinel<false>{ranges::end(take.base_)};
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}
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static auto end_sized_(take_view const & take, std::false_type, std::false_type)
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{
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return sentinel<true>{ranges::end(take.base_)};
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}
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#endif
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public:
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take_view() = default;
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constexpr take_view(Rng base, range_difference_t<Rng> cnt)
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: base_(std::move(base))
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, count_(cnt)
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{}
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constexpr Rng base() const
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{
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return base_;
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}
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CPP_auto_member
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constexpr auto CPP_fun(begin)()(
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requires(!simple_view<Rng>()))
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{
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#if RANGES_CXX_IF_CONSTEXPR >= RANGES_CXX_IF_CONSTEXPR_17
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if constexpr(sized_range<Rng>)
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if constexpr(random_access_range<Rng>)
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return ranges::begin(base_);
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else
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{
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// cannot always delegate to size() member on GCC with ConceptsTS
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#if defined(__cpp_concepts) && __cpp_concepts <= 201507
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auto s = ranges::min(
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static_cast<range_difference_t<Rng>>(count_),
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static_cast<range_difference_t<Rng>>(ranges::size(base_)));
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#else
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auto s = static_cast<range_difference_t<Rng>>(size());
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#endif
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return make_counted_iterator(ranges::begin(base_), s);
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}
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else
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return make_counted_iterator(ranges::begin(base_), count_);
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#else
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return begin_sized_(*this, meta::bool_<sized_range<Rng>>{});
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#endif
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}
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CPP_auto_member
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constexpr auto CPP_fun(begin)()(const //
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requires range<Rng const>)
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{
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#if RANGES_CXX_IF_CONSTEXPR >= RANGES_CXX_IF_CONSTEXPR_17
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if constexpr(sized_range<Rng const>)
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if constexpr(random_access_range<Rng const>)
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return ranges::begin(base_);
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else
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{
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auto s = static_cast<range_difference_t<Rng>>(size());
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return make_counted_iterator(ranges::begin(base_), s);
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}
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else
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return make_counted_iterator(ranges::begin(base_), count_);
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#else
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return begin_sized_(*this, meta::bool_<sized_range<Rng const>>{});
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#endif
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}
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CPP_auto_member
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constexpr auto CPP_fun(end)()(
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requires(!simple_view<Rng>()))
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{
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#if RANGES_CXX_IF_CONSTEXPR >= RANGES_CXX_IF_CONSTEXPR_17
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if constexpr(sized_range<Rng>)
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if constexpr(random_access_range<Rng>)
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return ranges::begin(base_) +
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static_cast<range_difference_t<Rng>>(size());
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else
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return default_sentinel;
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// Not to spec: Infinite ranges:
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else if constexpr(is_infinite<Rng>::value)
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return default_sentinel;
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else
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return sentinel<false>{ranges::end(base_)};
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#else
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return end_sized_(*this, meta::bool_<sized_range<Rng>>{}, is_infinite<Rng>{});
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#endif
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}
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CPP_auto_member
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constexpr auto CPP_fun(end)()(const //
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requires range<Rng const>)
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{
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#if RANGES_CXX_IF_CONSTEXPR >= RANGES_CXX_IF_CONSTEXPR_17
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if constexpr(sized_range<Rng const>)
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if constexpr(random_access_range<Rng const>)
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return ranges::begin(base_) +
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static_cast<range_difference_t<Rng>>(size());
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else
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return default_sentinel;
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// Not to spec: Infinite ranges:
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else if constexpr(is_infinite<Rng const>::value)
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return default_sentinel;
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else
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return sentinel<true>{ranges::end(base_)};
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#else
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return end_sized_(
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*this, meta::bool_<sized_range<Rng const>>{}, is_infinite<Rng const>{});
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#endif
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}
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CPP_auto_member
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constexpr auto CPP_fun(size)()(
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requires sized_range<Rng>)
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{
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auto n = ranges::size(base_);
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return ranges::min(n, static_cast<decltype(n)>(count_));
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}
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CPP_auto_member
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constexpr auto CPP_fun(size)()(const //
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requires sized_range<Rng const>)
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{
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auto n = ranges::size(base_);
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return ranges::min(n, static_cast<decltype(n)>(count_));
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}
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};
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template<typename Rng>
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RANGES_INLINE_VAR constexpr bool enable_borrowed_range<take_view<Rng>> = //
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enable_borrowed_range<Rng>;
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#if RANGES_CXX_DEDUCTION_GUIDES >= RANGES_CXX_DEDUCTION_GUIDES_17
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template<typename Rng>
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take_view(Rng &&, range_difference_t<Rng>)
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-> take_view<views::all_t<Rng>>;
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#endif
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namespace views
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{
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struct take_base_fn
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{
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template(typename Rng)(
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requires viewable_range<Rng>)
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take_view<all_t<Rng>> operator()(Rng && rng, range_difference_t<Rng> n) const
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{
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return {all(static_cast<Rng &&>(rng)), n};
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}
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};
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struct take_fn : take_base_fn
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{
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using take_base_fn::operator();
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template(typename Int)(
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requires detail::integer_like_<Int>)
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constexpr auto operator()(Int n) const
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{
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return make_view_closure(bind_back(take_base_fn{}, n));
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}
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};
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/// \relates take_fn
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RANGES_INLINE_VARIABLE(take_fn, take)
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} // namespace views
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namespace cpp20
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{
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namespace views
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{
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using ranges::views::take;
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}
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template(typename Rng)(
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requires view_<Rng>)
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using take_view = ranges::take_view<Rng>;
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} // namespace cpp20
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/// @}
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} // namespace ranges
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#include <range/v3/detail/epilogue.hpp>
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#include <range/v3/detail/satisfy_boost_range.hpp>
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RANGES_SATISFY_BOOST_RANGE(::ranges::take_view)
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#endif
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