Re: [boost] variant invariant

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-08-04 17:57:54

AMDG

Emil Dotchevski wrote:
> This still doesn't mean that it is desirable for operator= to be
> allowed to change the type of the stored object.
>   

In other words, you /are/ advocating the strong guarantee.

> If you list boost::blank as a valid variant, then there's nothing
> unusual about this state. The difference in meaning is subtle but
> nevertheless important: it's similar to a pointer that may legally be
> null, requiring the user to deal with this possibility, vs. a pointer
> which can never be null, allowing the user to assert when it is.
>   

I don't follow.  IMO, unless you are making the exact variant type
part of your class' public interface, it is irrelevant how you represent
an empty variant.  The only difference with adding boost::blank vs.
creating some empty state, is that the presence of the empty state is
explicit.

In Christ,
Steven Watanabe