----- Original Message -----
From: "Fernando Cacciola" <[EMAIL PROTECTED]>
> > > optional captures the zero/one distinction, which, as its analogy to
> > > pointers makes clear, is a very useful one. A type which can contain
> > > any number of different types would have a much more complicated
> > > interface. Maybe it's just a different library?
> >
> > Or perhaps, optional is just a limited add-on API over the variant?
> > The low-level implementation mechanism in place seems to be very
> > similar and having 2 separate libraries will be redundant, I think.
> >
> Not so...
> The low-level implementation is like a variant ONLY is the wrapped object is
> not a POD.
> When you have, say, optional<int>, the implementation uses: struct { int
> m_value ; bool m_initialized }
> As a result, value access, via operator*() is more efficient since it
> doesn't dereference a pointer.
That depends on how the variant is implemented. Which variant
implementation are you referring to? I'm sorry. I'm confused with
what you are saying. I can't see why it is more efficient. Neither do
I see a dereference in any case.
Joel de Guzman
[EMAIL PROTECTED]
http://www.boost-consulting.com
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