24 Ranges library [ranges]

24.7 Range adaptors [range.adaptors]

24.7.7 Take view [range.take]

24.7.7.2 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(); // exposition only range_difference_t<V> count_ = 0; // exposition only // [range.take.sentinel], class template take_­view​::​sentinel template<bool> struct sentinel; // exposition only public: take_view() = default; constexpr 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 (!simple-view<V>) { if constexpr (sized_­range<V>) { if constexpr (random_­access_­range<V>) return ranges::begin(base_); else { auto sz = size(); return counted_iterator{ranges::begin(base_), 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 = size(); return counted_iterator{ranges::begin(base_), sz}; } } else return counted_iterator{ranges::begin(base_), count_}; } constexpr auto end() requires (!simple-view<V>) { if constexpr (sized_­range<V>) { if constexpr (random_­access_­range<V>) return ranges::begin(base_) + size(); else 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_) + size(); else 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_)); } }; template<class R> take_view(R&&, range_difference_t<R>) -> take_view<views::all_t<R>>; }
constexpr take_view(V base, range_difference_t<V> count);
Effects: Initializes base_­ with std​::​move(base) and count_­ with count.