25 Ranges library [ranges]

25.6 Range factories [range.factories]

25.6.5 Repeat view [range.repeat]

25.6.5.1 Overview [range.repeat.overview]

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repeat_view generates a sequence of elements by repeatedly producing the same value.
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The name views​::​repeat denotes a customization point object ([customization.point.object]).
Given subexpressions E and F, the expressions views​::​repeat(E) and views​::​repeat(E, F) are expression-equivalent to repeat_view<decay_t<decltype((E))>>(E) and repeat_view(E, F), respectively.
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[Example 1: for (int i : views::repeat(17, 4)) cout << i << ' '; // prints 17 17 17 17 — end example]

25.6.5.2 Class template repeat_view [range.repeat.view]

namespace std::ranges { template<class T> concept integer-like-with-usable-difference-type = // exposition only is-signed-integer-like<T> || (is-integer-like<T> && weakly_incrementable<T>); template<move_constructible T, semiregular Bound = unreachable_sentinel_t> requires (is_object_v<T> && same_as<T, remove_cv_t<T>> && (integer-like-with-usable-difference-type<Bound> || same_as<Bound, unreachable_sentinel_t>)) class repeat_view : public view_interface<repeat_view<T, Bound>> { private: // [range.repeat.iterator], class repeat_view​::​iterator struct iterator; // exposition only movable-box<T> value_; // exposition only, see [range.move.wrap] Bound bound_ = Bound(); // exposition only public: repeat_view() requires default_initializable<T> = default; constexpr explicit repeat_view(const T& value, Bound bound = Bound()) requires copy_constructible<T>; constexpr explicit repeat_view(T&& value, Bound bound = Bound()); template<class... TArgs, class... BoundArgs> requires constructible_from<T, TArgs...> && constructible_from<Bound, BoundArgs...> constexpr explicit repeat_view(piecewise_construct_t, tuple<TArgs...> value_args, tuple<BoundArgs...> bound_args = tuple<>{}); constexpr iterator begin() const; constexpr iterator end() const requires (!same_as<Bound, unreachable_sentinel_t>); constexpr unreachable_sentinel_t end() const noexcept; constexpr auto size() const requires (!same_as<Bound, unreachable_sentinel_t>); }; template<class T, class Bound = unreachable_sentinel_t> repeat_view(T, Bound = Bound()) -> repeat_view<T, Bound>; }
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constexpr explicit repeat_view(const T& value, Bound bound = Bound()) requires copy_constructible<T>;
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Preconditions: If Bound is not unreachable_sentinel_t, bound  ≥ 0.
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Effects: Initializes value_ with value and bound_ with bound.
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constexpr explicit repeat_view(T&& value, Bound bound = Bound());
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Preconditions: If Bound is not unreachable_sentinel_t, bound  ≥ 0.
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Effects: Initializes value_ with std​::​move(value) and bound_ with bound.
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template<class... TArgs, class... BoundArgs> requires constructible_from<T, TArgs...> && constructible_from<Bound, BoundArgs...> constexpr explicit repeat_view(piecewise_construct_t, tuple<TArgs...> value_args, tuple<BoundArgs...> bound_args = tuple<>{});
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Effects: Initializes value_ with make_from_tuple<T>(std​::​move(value_args)) and initializes bound_ with make_from_tuple<Bound>(std​::​move(bound_args)).
The behavior is undefined if Bound is not unreachable_sentinel_t and bound_ is negative.
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constexpr iterator begin() const;
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Effects: Equivalent to: return iterator(addressof(*value_));
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constexpr iterator end() const requires (!same_as<Bound, unreachable_sentinel_t>);
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Effects: Equivalent to: return iterator(addressof(*value_), bound_);
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constexpr unreachable_sentinel_t end() const noexcept;
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Effects: Equivalent to: return unreachable_sentinel;
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constexpr auto size() const requires (!same_as<Bound, unreachable_sentinel_t>);
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Effects: Equivalent to: return to-unsigned-like(bound_);

25.6.5.3 Class repeat_view​::​iterator [range.repeat.iterator]

namespace std::ranges { template<move_constructible T, semiregular Bound> requires (is_object_v<T> && same_as<T, remove_cv_t<T>> && (integer-like-with-usable-difference-type<Bound> || same_as<Bound, unreachable_sentinel_t>)) class repeat_view<T, Bound>::iterator { private: using index-type = // exposition only conditional_t<same_as<Bound, unreachable_sentinel_t>, ptrdiff_t, Bound>; const T* value_ = nullptr; // exposition only index-type current_ = index-type(); // exposition only constexpr explicit iterator(const T* value, index-type b = index-type()); // exposition only public: using iterator_concept = random_access_iterator_tag; using iterator_category = random_access_iterator_tag; using value_type = T; using difference_type = see below; iterator() = default; constexpr const T& operator*() const noexcept; constexpr iterator& operator++(); constexpr iterator operator++(int); constexpr iterator& operator--(); constexpr iterator operator--(int); constexpr iterator& operator+=(difference_type n); constexpr iterator& operator-=(difference_type n); constexpr const T& operator[](difference_type n) const noexcept; friend constexpr bool operator==(const iterator& x, const iterator& y); friend constexpr auto operator<=>(const iterator& x, const iterator& y); friend constexpr iterator operator+(iterator i, difference_type n); friend constexpr iterator operator+(difference_type n, iterator i); friend constexpr iterator operator-(iterator i, difference_type n); friend constexpr difference_type operator-(const iterator& x, const iterator& y); }; }
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If is-signed-integer-like<index-type> is true, the member typedef-name difference_type denotes index-type.
Otherwise, it denotes IOTA-DIFF-T(index-type) ([range.iota.view]).
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constexpr explicit iterator(const T* value, index-type b = index-type());
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Preconditions: If Bound is not unreachable_sentinel_t, b  ≥ 0.
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Effects: Initializes value_ with value and current_ with b.
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constexpr const T& operator*() const noexcept;
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Effects: Equivalent to: return *value_;
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constexpr iterator& operator++();
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Effects: Equivalent to: ++current_; return *this;
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constexpr iterator operator++(int);
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Effects: Equivalent to: auto tmp = *this; ++*this; return tmp;
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constexpr iterator& operator--();
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Preconditions: If Bound is not unreachable_sentinel_t, .
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Effects: Equivalent to: --current_; return *this;
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constexpr iterator operator--(int);
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Effects: Equivalent to: auto tmp = *this; --*this; return tmp;
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constexpr iterator& operator+=(difference_type n);
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Preconditions: If Bound is not unreachable_sentinel_t, .
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Effects: Equivalent to: current_ += n; return *this;
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constexpr iterator& operator-=(difference_type n);
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Preconditions: If Bound is not unreachable_sentinel_t, .
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Effects: Equivalent to: current_ -= n; return *this;
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constexpr const T& operator[](difference_type n) const noexcept;
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Effects: Equivalent to: return *(*this + n);
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friend constexpr bool operator==(const iterator& x, const iterator& y);
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Effects: Equivalent to: return x.current_ == y.current_;
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friend constexpr auto operator<=>(const iterator& x, const iterator& y);
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Effects: Equivalent to: return x.current_ <=> y.current_;
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friend constexpr iterator operator+(iterator i, difference_type n); friend constexpr iterator operator+(difference_type n, iterator i);
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Effects: Equivalent to: i += n; return i;
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friend constexpr iterator operator-(iterator i, difference_type n);
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Effects: Equivalent to: i -= n; return i;
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friend constexpr difference_type operator-(const iterator& x, const iterator& y);
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Effects: Equivalent to: return static_cast<difference_type>(x.current_) - static_cast<difference_type>(y.current_);