Subject: Re: [boost] [move][container] Review Request (new versions of Boost.Move and Boost.Container in sandbox and vault)
From: Christopher Jefferson (chris_at_[hidden])
Date: 2009-10-17 04:39:26
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