[range.take.view] (original) (raw)
25 Ranges library [ranges]
25.7.10.2 Class template take_view [range.take.view]
namespace std::ranges { template<view V> class take_view : public view_interface<take_view<V>> { private: V base_ = V(); range_difference_t<V> count_ = 0; template<bool> class sentinel; public: take_view() requires default_initializable<V> = default;constexpr explicit take_view(V base, range_difference_t<V> count);constexpr V base() const & requires copy_constructible<V> { return base_; } constexpr V base() && { return std::move(base_); } constexpr auto begin() requires (
<V>) { if constexpr (sized_range<V>) { if constexpr (random_access_range<V>) { return ranges::begin(base_);} else { auto sz = range_difference_t<V>(size());return counted_iterator(ranges::begin(base_), sz);} } else if constexpr (sized_sentinel_for<sentinel_t<V>, iterator_t<V>>) { auto it = ranges::begin(base_);auto sz = std::min(count_, ranges::end(base_) - it);return counted_iterator(std::move(it), sz);} else { return counted_iterator(ranges::begin(base_), count_);} } constexpr auto begin() const requires range<const V> { if constexpr (sized_range<const V>) { if constexpr (random_access_range<const V>) { return ranges::begin(base_);} else { auto sz = range_difference_t<const V>(size());return counted_iterator(ranges::begin(base_), sz);} } else if constexpr (sized_sentinel_for<sentinel_t<const V>, iterator_t<const V>>) { auto it = ranges::begin(base_);auto sz = std::min(count_, ranges::end(base_) - it);return counted_iterator(std::move(it), sz);} else { return counted_iterator(ranges::begin(base_), count_);} } constexpr auto end() requires (<V>) { if constexpr (sized_range<V>) { if constexpr (random_access_range<V>) return ranges::begin(base_) + range_difference_t<V>(size());else return default_sentinel;} else if constexpr (sized_sentinel_for<sentinel_t<V>, iterator_t<V>>) { return default_sentinel;} else { return sentinel<false>{ranges::end(base_)};} } constexpr auto end() const requires range<const V> { if constexpr (sized_range<const V>) { if constexpr (random_access_range<const V>) return ranges::begin(base_) + range_difference_t<const V>(size());else return default_sentinel;} else if constexpr (sized_sentinel_for<sentinel_t<const V>, iterator_t<const V>>) { return default_sentinel;} else { return sentinel<true>{ranges::end(base_)};} } constexpr auto size() requires sized_range<V> { auto n = ranges::size(base_);return ranges::min(n, static_cast<decltype(n)>(count_));} constexpr auto size() const requires sized_range<const V> { auto n = ranges::size(base_);return ranges::min(n, static_cast<decltype(n)>(count_));} constexpr auto reserve_hint() { if constexpr (approximately_sized_range<V>) { auto n = static_cast<range_difference_t<V>>(ranges::reserve_hint(base_));return to-unsigned-like(ranges::min(n, count_));} return to-unsigned-like(count_);} constexpr auto reserve_hint() const { if constexpr (approximately_sized_range<const V>) { auto n = static_cast<range_difference_t<const V>>(ranges::reserve_hint(base_));return to-unsigned-like(ranges::min(n, count_));} return to-unsigned-like(count_);} };template<class R> take_view(R&&, range_difference_t<R>) -> take_view<views::all_t<R>>;}
constexpr explicit take_view(V base, range_difference_t<V> count);
Preconditions: count >= 0 is true.
Effects: Initializes base_ with std::move(base) and_count__ with count.