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1088. std::promise should provide non-member swap overload

Section: 32.10.6 [futures.promise] Status: Resolved Submitter: Howard Hinnant Opened: 2009-03-22 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Addresses UK 342 [CD1]

std::promise is missing a non-member overload of swap. This is inconsistent with other types that provide a swap member function.

Add a non-member overload void swap(promise&& x,promise&& y){ x.swap(y); }

[ Summit: ]

Create an issue. Move to review, attention: Howard. Detlef will also look into it.

[ Post Summit Daniel provided wording. ]

[ 2009-10 Santa Cruz: ]

NAD EditorialResolved. Addressed by N2997.

Proposed resolution:

1. In 32.10.6 [futures.promise], before p.1, immediately after class template promise add:

   
   template <class R>
   void swap(promise<R>& x, promise<R>& y);
   
   

2. Change 32.10.6 [futures.promise]/10 as indicated (to fix a circular definition):

   -10- Effects: swap(*this, other)Swaps the associated state of *this and other

   Throws: Nothing.

3. After the last paragraph in 32.10.6 [futures.promise] add the following prototype description:

   
   template <class R>
   void swap(promise<R>& x, promise<R>& y);
   

   Effects: x.swap(y)

   Throws: Nothing.