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### 3552. Parallel specialized memory algorithms should require forward iterators

Section: 20.2.2 [memory.syn] Status: WP Submitter: Tim Song Opened: 2021-05-16 Last modified: 2021-06-07

Priority: Not Prioritized

View all other issues in [memory.syn].

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Discussion:

The parallel versions of `uninitialized_{copy,move}{,_n}` are currently depicted as accepting input iterators for their source range. Similar to the non-uninitialized versions, they should require the source range to be at least forward.

[2021-05-20; Reflector poll]

Set status to Tentatively Ready after six votes in favour during reflector poll.

[2021-06-07 Approved at June 2021 virtual plenary. Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4885.

1. Modify 20.2.2 [memory.syn], header `<memory>` synopsis, as indicated:

   >       […]
   >     namespace std {
   >       […]

   >       template<class InputIterator, class NoThrowForwardIterator>
   >         NoThrowForwardIterator uninitialized_copy(InputIterator first, InputIterator last,
   >                                                   NoThrowForwardIterator result);
   >       template<class ExecutionPolicy, class InputForwardIterator, class NoThrowForwardIterator>
   >         NoThrowForwardIterator uninitialized_copy(ExecutionPolicy&& exec, // see 27.3.5 [algorithms.parallel.overloads]
   >                                                   InputForwardIterator first, InputForwardIterator last,
   >                                                   NoThrowForwardIterator result);
   >       template<class InputIterator, class Size, class NoThrowForwardIterator>
   >         NoThrowForwardIterator uninitialized_copy_n(InputIterator first, Size n,
   >                                                     NoThrowForwardIterator result);
   >       template<class ExecutionPolicy, class InputForwardIterator, class Size, class NoThrowForwardIterator>
   >         NoThrowForwardIterator uninitialized_copy_n(ExecutionPolicy&& exec, // see 27.3.5 [algorithms.parallel.overloads]
   >                                                     InputForwardIterator first, Size n,
   >                                                     NoThrowForwardIterator result);
   >       […]

   >       template<class InputIterator, class NoThrowForwardIterator>
   >         NoThrowForwardIterator uninitialized_move(InputIterator first, InputIterator last,
   >                                                   NoThrowForwardIterator result);
   >       template<class ExecutionPolicy, class InputForwardIterator, class NoThrowForwardIterator>
   >         NoThrowForwardIterator uninitialized_move(ExecutionPolicy&& exec, // see 27.3.5 [algorithms.parallel.overloads]
   >                                                   InputForwardIterator first, InputForwardIterator last,
   >                                                   NoThrowForwardIterator result);
   >       template<class InputIterator, class Size, class NoThrowForwardIterator>
   >         pair<InputIterator, NoThrowForwardIterator>
   >           uninitialized_move_n(InputIterator first, Size n, NoThrowForwardIterator result);
   >       template<class ExecutionPolicy, class InputForwardIterator, class Size, class NoThrowForwardIterator>
   >         pair<InputForwardIterator, NoThrowForwardIterator>
   >           uninitialized_move_n(ExecutionPolicy&& exec, // see 27.3.5 [algorithms.parallel.overloads]
   >                                InputForwardIterator first, Size n, NoThrowForwardIterator result);

   >       […]
   >     }