Re: [boost] Formal review: Optional library

From: Joel de Guzman (djowel_at_[hidden])
Date: 2002-12-10 16:47:24

----- Original Message ----- 
From: "Fernando Cacciola" <fernando_cacciola_at_[hidden]>

> ----- Original Message -----
> From: "Joel de Guzman" <djowel_at_[hidden]>

> > Hi,
> >
> > Probably a dumb question but allow me to ask anyway:
> >
> > Wouldn't a more generic variant<T0, T1...TN> class do what the
> > optional is trying to do? I feel that optional<T> is just a variant<T,
> nil_t>
> > in disguise. Correct me if I'm wrong.
> >
> The difference is that optional<> *explicitly* deals with the possibility of
> being
> uninitialized, while variant<T,nil_t> doesn't. (for the later, nil_t is just
> another possible value).
> 
> In this regard optional<> is more handy for its intended usage.

Hmmm, I'm not sure if I agree with this. T can very well be
uninitialized in the variant when nil_t is in effect. Then
nil_t can just be struct nil_t {}; which costs nothing to initialize.
Why is optional "more handy" in this regard?

Joel de Guzman
joel_at_[hidden]
http://www.boost-consulting.com