cppdraft_translate/cppdraft/range/repeat.md

[range.repeat]

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 torepeat_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 {templateconcept integer-like-with-usable-difference-type = // exposition only**is-signed-integer-like || (is-integer-like && weakly_incrementable); template<move_constructible T, semiregular Bound = unreachable_sentinel_t>requires (is_object_v && same_as<T, remove_cv_t> &&(integer-like-with-usable-difference-type ||same_as<Bound, unreachable_sentinel_t>))class repeat_view : public view_interface<repeat_view<T, Bound>> {private:// [range.repeat.iterator], class repeat_view​::​iteratorstruct iterator; // exposition only**movable-box value_; // exposition only, see [range.move.wrap] Bound bound_ = Bound(); // exposition onlypublic: repeat_view() requires default_initializable = default; constexpr explicit repeat_view(const T& value, Bound bound = Bound())requires copy_constructible; 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 (<Bound, unreachable_sentinel_t>); constexpr unreachable_sentinel_t end() const noexcept; constexpr auto size() const requires (<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](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<T>;

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Preconditions: If Bound is not unreachable_sentinel_t,bound ≥ 0.

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Effects: Initializes value_ with value andbound_ 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) andbound_ with bound.

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template<class... TArgs, class... BoundArgs> requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<T, TArgs...> && [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<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_ withmake_from_tuple(std​::​move(value_args)) and initializes bound_ withmake_from_tuple(std​::​move(bound_args)).

The behavior is undefined ifBound is not unreachable_sentinel_t andbound_ 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](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<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](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<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]

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namespace std::ranges {template<move_constructible T, semiregular Bound>requires (is_object_v && same_as<T, remove_cv_t> &&(integer-like-with-usable-difference-type ||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 onlyconstexpr explicit iterator(const T* value, index-type b = index-type()); // exposition onlypublic: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 andcurrent_ 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,current_>0.

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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,current_+n≥0.

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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,current_−n≥0.

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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_);