[boost] Re: Variant Library: copy constructible requirements

From: Eric Friedman (ebf_at_[hidden])
Date: 2003-04-02 21:14:44

Gennadiy Rozental wrote:
> > > 3. Copy Constructible/Assignable requirements on bounded types
> > > This only need to be required if variant should have appropriate
> > > feature.
> >
> > I disagree. As-is, every variant object requires CopyConstructible
> > bounded types, as it is the only way to construct its content.
> >
> > Some notes, however. I may be able to eliminate the Assignable
> > requirement altogether by modifying the implementation of
> > variant::swap. As well, there has been some discussion about in-place
> > construction, which could eliminate the CopyConstructible requirement
> > except in cases of actual variant copying. (This conversation occurred
> > with regard to optional, but could work with equal applicability to
> > variant.)
>
>  I think it's the way to go. This implementation issue shouldn't affect
> overall design. It would be a pity if we couldn't use variant for
> noncopyable types.

OK, I'll certainly work to eliminate the Assignable requirement altogether.
As well, I will discuss with Fernando his progress on in-place construction,
which will make CopyConstructible an optional requirement.

Let me know if there are further issues to be considered in this regard.

Thanks,
Eric