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Section: 23.6 [container.adaptors] Status: C++11 Submitter: Pablo Halpern Opened: 2009-08-26 Last modified: 2016-01-28
Priority: Not Prioritized
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Discussion:
Under 23.6 [container.adaptors] of
N2914
the member function of swap of queue and stack call:
swap(c, q.c);
But under 23.6 [container.adaptors] of N2723 these members are specified to call:
c.swap(q.c);
Neither draft specifies the semantics of member swap for
priority_queue though it is declared.
Although the distinction between member swap and non-member
swap is not important when these adaptors are adapting standard
containers, it may be important for user-defined containers.
We (Pablo and Howard) feel that
it is more likely for a user-defined container to support a namespace scope
swap than a member swap, and therefore these adaptors
should use the container's namespace scope swap.
[ 2009-09-30 Daniel adds: ]
The outcome of this issue should be considered with the outcome of 774(i) both in style and in content (e.g. 774(i) bullet 9 suggests to define the semantic of
void priority_queue::swap(priority_queue&)in terms of the memberswapof the container).
[ 2010-03-28 Daniel update to diff against N3092. ]
[ 2010 Rapperswil: ]
Preference to move the wording into normative text, rather than inline function definitions in the class synopsis. Move to Tenatively Ready.
[ Adopted at 2010-11 Batavia ]
Proposed resolution:
Change 23.6.3.1 [queue.defn]:
template <class T, class Container = deque<T> >
class queue {
...
void swap(queue& q) { using std::swap;
c.swap(c, q.c); }
...
};
Change 23.6.4 [priority.queue]:
template <class T, class Container = vector<T>,
class Compare = less<typename Container::value_type> >
class priority_queue {
...
void swap(priority_queue& q); { using std::swap;
swap(c, q.c);
swap(comp, q.comp); }
...
};
Change 23.6.6.2 [stack.defn]:
template <class T, class Container = deque<T> >
class stack {
...
void swap(stack& s) { using std::swap;
c.swap(c, s.c); }
...
};