Re: [boost] [mp_math] a multi precision signed integer library

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
>  ALWAYS.
>  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.

-- 
gpd