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From: Giovanni Piero Deretta (gpderetta_at_[hidden])
Date: 2008-03-31 17:01:44

On Mon, Mar 31, 2008 at 9:22 PM, Maarten Kronenburg
<M.Kronenburg_at_[hidden]> wrote:
> > >
> > > Probably you would use conversion operators.
> >
> > Not necessarily, you just make your operators templated on the policy.
> > No need to do any conversions.
> >
> > > But runtime polymorphism allows
> > > basetype pointers to derived type objects, and still it works (through
> the
> > > vtable). So runtime polymorphism can never be fully replaced by
> something
> > > else.
> >
> > Of couse you need runtime indirection if you need dynamic indirection
> > :). But 99.9% of the times you do not need it. When you need it is
> > easy to add.
> >
> I'm not so sure it will be 0.01%. This integer will be used by MANY users,
> and you try to explain to a user that it does not work once you use a base
> pointer to a derived object.

Uh? Users do not expect to have a base class for integers, why should
they expect it for multiprecision integers?
It is a value type, why would you expect to treat it polymorphically?

> This will be one of the most important classes of C++, and I want it to work
> Therefore in my opinion in this case there is no alternative for runtime
> polymorphism.

I'm still far from convinced. But anyways, I'm not the one
implementing it, so I have little say :)
At most I'll be able to voice my concerns at review time.


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