[range.take.while] (original) (raw)
25 Ranges library [ranges]
25.7 Range adaptors [range.adaptors]
25.7.11 Take while view [range.take.while]
25.7.11.1 Overview [range.take.while.overview]
Given a unary predicate pred and a view r,take_while_view produces a view of the range [ranges::begin(r), ranges::find_if_not(r, pred)).
Given subexpressions E and F, the expression views::take_while(E, F)is expression-equivalent to take_while_view(E, F).
[Example 1: auto input = istringstream{"0 1 2 3 4 5 6 7 8 9"};auto small = [](const auto x) noexcept { return x < 5; };auto small_ints = views::istream<int>(input) | views::take_while(small);for (const auto i : small_ints) { cout << i << ' '; } auto i = 0; input >> i; cout << i; — _end example_]
25.7.11.2 Class template take_while_view [range.take.while.view]
namespace std::ranges { template<view V, class Pred> requires input_range<V> && is_object_v<Pred> && indirect_unary_predicate<const Pred, iterator_t<V>> class take_while_view : public view_interface<take_while_view<V, Pred>> { template<bool> class sentinel; V base_ = V(); movable-box<Pred> pred_; public: take_while_view() requires default_initializable<V> && default_initializable<Pred> = default;constexpr explicit take_while_view(V base, Pred pred);constexpr V base() const & requires copy_constructible<V> { return base_; } constexpr V base() && { return std::move(base_); } constexpr const Pred& pred() const;constexpr auto begin() requires (<V>) { return ranges::begin(base_); } constexpr auto begin() const requires range<const V> && indirect_unary_predicate<const Pred, iterator_t<const V>> { return ranges::begin(base_); } constexpr auto end() requires (
<V>) { return sentinel<false>(ranges::end(base_), addressof(*pred_)); } constexpr auto end() const requires range<const V> && indirect_unary_predicate<const Pred, iterator_t<const V>> { return sentinel<true>(ranges::end(base_), addressof(*pred_)); } };template<class R, class Pred> take_while_view(R&&, Pred) -> take_while_view<views::all_t<R>, Pred>;}
constexpr explicit take_while_view(V base, Pred pred);
Effects: Initializes base_ with std::move(base) and_pred__ with std::move(pred).
constexpr const Pred& pred() const;
Effects: Equivalent to: return *pred_;
25.7.11.3 Class template take_while_view::sentinel [range.take.while.sentinel]
namespace std::ranges { template<view V, class Pred> requires input_range<V> && is_object_v<Pred> && indirect_unary_predicate<const Pred, iterator_t<V>> template<bool Const> class take_while_view<V, Pred>::sentinel { using Base = maybe-const<Const, V>; sentinel_t<_Base_> end_ = sentinel_t<_Base_>(); const Pred* pred_ = nullptr; public: sentinel() = default;constexpr explicit sentinel(sentinel_t<_Base_> end, const Pred* pred);constexpr sentinel(sentinel<!Const> s) requires Const && convertible_to<sentinel_t<V>, sentinel_t<_Base_>>;constexpr sentinel_t<_Base_> base() const { return end_; } friend constexpr bool operator==(const iterator_t<_Base_>& x, const sentinel& y);template<bool OtherConst = !Const> requires sentinel_for<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr bool operator==(const iterator_t<_maybe-const_<OtherConst, V>>& x,const sentinel& y);};}
constexpr explicit _sentinel_(sentinel_t<_Base_> end, const Pred* pred);
Effects: Initializes end_ with end and pred_ with pred.
constexpr _sentinel_(_sentinel_<!Const> s) requires Const && [convertible_to](concept.convertible#concept:convertible%5Fto "18.4.4 Concept convertible_to [concept.convertible]")<sentinel_t<V>, sentinel_t<_Base_>>;
Effects: Initializes end_ with std::move(s.end_) and_pred__ with s.pred_.
friend constexpr bool operator==(const iterator_t<_Base_>& x, const _sentinel_& y);template<bool OtherConst = !Const> requires [sentinel_for](iterator.concept.sentinel#concept:sentinel%5Ffor "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<sentinel_t<_Base_>, iterator_t<_maybe-const_<OtherConst, V>>> friend constexpr bool operator==(const iterator_t<_maybe-const_<OtherConst, V>>& x,const _sentinel_& y);
Effects: Equivalent to:return y.end_ == x || !invoke(*y.pred_, *x);