On 16 Oct 2009, at 02:10, Thomas Klimpel wrote:
So I'm left with the impression that there might be quite some good reasons not to implement move-assignment as swap, but no really conclusive counter examples against it. On the other hand, as long as the absence of conclusive counter examples can't be "proved", ruling that move-assignment may generally be implemented as swap will be risky or worse.
Just as one point of information, which I've previously seen used in favour of using swap as move. While it is true that a move which doesn't swap on (for example) vector<T> is O(n) rather than O(1), due to the need to destruct all the elements, I found in experiments that sorting a range of vector<T> is actually very slightly faster when move-assignment is NOT implemented as swap, so performance isn't even really an argument in it's favour. Chris