From Jason Turner

[alg.reverse]

C++17 → C++20 3.4 KB 52 lines
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Archived: C++17 | C++20
Markdown: C++17 | C++20
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  ### Reverse <a id="alg.reverse">[[alg.reverse]]</a>
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  ``` cpp
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  template<class BidirectionalIterator>
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- void reverse(BidirectionalIterator first, BidirectionalIterator last);
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  template<class ExecutionPolicy, class BidirectionalIterator>
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  void reverse(ExecutionPolicy&& exec,
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  BidirectionalIterator first, BidirectionalIterator last);
 
 
 
 
 
 
 
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  ```
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- *Requires:* `*first` shall be swappable ([[swappable.requirements]]).
 
 
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  *Effects:* For each non-negative integer `i < (last - first) / 2`,
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- applies `iter_swap` to all pairs of iterators
 
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  `first + i, (last - i) - 1`.
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- *Requires:* `BidirectionalIterator` shall satisfy the requirements of
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- `ValueSwappable` ([[swappable.requirements]]).
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  *Complexity:* Exactly `(last - first)/2` swaps.
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  ``` cpp
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  template<class BidirectionalIterator, class OutputIterator>
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- OutputIterator
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  reverse_copy(BidirectionalIterator first, BidirectionalIterator last,
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  OutputIterator result);
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  template<class ExecutionPolicy, class BidirectionalIterator, class ForwardIterator>
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  ForwardIterator
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  reverse_copy(ExecutionPolicy&& exec,
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  BidirectionalIterator first, BidirectionalIterator last,
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  ForwardIterator result);
 
 
 
 
 
 
 
 
 
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  ```
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- *Requires:* The ranges \[`first`, `last`) and \[`result`,
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- `result + (last - first)`) shall not overlap.
 
 
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  *Effects:* Copies the range \[`first`, `last`) to the range \[`result`,
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- `result + (last - first)`) such that for every non-negative integer
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- `i < (last - first)` the following assignment takes place:
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- `*(result + (last - first) - 1 - i) = *(first + i)`.
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- *Returns:* `result + (last - first)`.
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- *Complexity:* Exactly `last - first` assignments.
 
 
 
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  ### Reverse <a id="alg.reverse">[[alg.reverse]]</a>
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  ``` cpp
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  template<class BidirectionalIterator>
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+ constexpr void reverse(BidirectionalIterator first, BidirectionalIterator last);
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  template<class ExecutionPolicy, class BidirectionalIterator>
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  void reverse(ExecutionPolicy&& exec,
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  BidirectionalIterator first, BidirectionalIterator last);
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+
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+ template<bidirectional_iterator I, sentinel_for<I> S>
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+ requires permutable<I>
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+ constexpr I ranges::reverse(I first, S last);
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+ template<bidirectional_range R>
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+ requires permutable<iterator_t<R>>
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+ constexpr borrowed_iterator_t<R> ranges::reverse(R&& r);
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  ```
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+ *Preconditions:* For the overloads in namespace `std`,
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+ `BidirectionalIterator` meets the *Cpp17ValueSwappable*
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+ requirements [[swappable.requirements]].
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  *Effects:* For each non-negative integer `i < (last - first) / 2`,
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+ applies `std::iter_swap`, or `ranges::iter_swap` for the overloads in
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+ namespace `ranges`, to all pairs of iterators
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  `first + i, (last - i) - 1`.
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+ *Returns:* `last` for the overloads in namespace `ranges`.
 
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  *Complexity:* Exactly `(last - first)/2` swaps.
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  ``` cpp
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  template<class BidirectionalIterator, class OutputIterator>
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+ constexpr OutputIterator
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  reverse_copy(BidirectionalIterator first, BidirectionalIterator last,
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  OutputIterator result);
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  template<class ExecutionPolicy, class BidirectionalIterator, class ForwardIterator>
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  ForwardIterator
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  reverse_copy(ExecutionPolicy&& exec,
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  BidirectionalIterator first, BidirectionalIterator last,
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  ForwardIterator result);
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+
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+ template<bidirectional_iterator I, sentinel_for<I> S, weakly_incrementable O>
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+ requires indirectly_copyable<I, O>
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+ constexpr ranges::reverse_copy_result<I, O>
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+ ranges::reverse_copy(I first, S last, O result);
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+ template<bidirectional_range R, weakly_incrementable O>
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+ requires indirectly_copyable<iterator_t<R>, O>
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+ constexpr ranges::reverse_copy_result<borrowed_iterator_t<R>, O>
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+ ranges::reverse_copy(R&& r, O result);
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  ```
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+ Let N be `last - first`.
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+
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+ *Preconditions:* The ranges \[`first`, `last`) and \[`result`,
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+ `result + `N) do not overlap.
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  *Effects:* Copies the range \[`first`, `last`) to the range \[`result`,
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+ `result + `N) such that for every non-negative integer `i < `N the
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+ following assignment takes place:
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+ `*(result + `N` - 1 - i) = *(first + i)`.
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+ *Returns:*
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+ - `result + `N for the overloads in namespace `std`.
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+ - `{last, result + `N`}` for the overloads in namespace `ranges`.
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+
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+ *Complexity:* Exactly N assignments.
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