Re: [boost] [optional] problems with swap()

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-04-10 16:53:40

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Thursday 10 April 2008 16:02 pm, Thorsten Ottosen wrote:
> > Your approach requires the T to be default constructible which is not
> > always the case.
>
> Why is this better than the far more expensive copy-construction?

The documentation indicates optional<T> requires T to be copy constructible.  
It explicitly does not require T to be default constructible.

> > Besides, to my mind, the current implementation is more
> > obvious for the user.
>
> No user expects swap to throw or invalidate iterators or references like
> the current implementation does.

Personally, I consider any preservation of iterators/references/pointers to 
the internals of a swapped object to be purely a side-effect of a swap 
specialization, whose raise d'etre is as a speed optimization.

- -- 
Frank
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)

iD8DBQFH/n5V5vihyNWuA4URAr9RAJ4q7fodOLKbArYSBzTbosEwQHKWvACcDs8d
AukOjKNmV5bJ70lp6ozcp8g=
=zPA9
-----END PGP SIGNATURE-----