Re: [boost] Re: [repost][interfaces] would the following work?

From: JOAQUIN LOPEZ MU?Z (joaquin_at_[hidden])
Date: 2005-05-12 16:25:37

----- Mensaje original -----
De: Jonathan Turkanis <technews_at_[hidden]>
Fecha: Jueves, Mayo 12, 2005 10:15 pm
Asunto: [boost] Re: [repost][interfaces] would the following work?

> JOAQUIN LOPEZ MU?Z wrote:
> 
> [Sorry I didn't answer sooner; I'm reviewing a long manuscript]
> 
> > Allow me to repost this, since given the current traffic in
> > the list it could well have passed unnoticed.
> >
> > Is (the proposed) Boost.Interfaces lib able to handle the following
> > scenario?
> >
> >
> > template<typename T>
> > interface IIterator
> > {
> >   T& operator*()const;
> >   ...
> > };
> >
> >
> > template<typename T>
> > interface IContainer
> > {
> >   IIterator<T> begin();
> >   IIterator<T> end();
> >   ...
> > };
> 
> > It is not the issue of specifying an operator as part of the 
> interface> IIterator (this'll be taken care of in the future 
> according to the
> > docs), but the fact that IContainer::begin is required to return an
> > object implicitly convertible to IIterator<T>. Can Boost.Interfaces
> > do that?
> 
> This is one of the main motivating examples for introducing 
> operator overloading
> and self-referential interfaces. Unfortunately, it's not done yet, 
> but it's the
> first or second thing on my list. The implicit conversion from an 
> iterator of
> the underlying container shouldn't be difficult. Iterators with 
> operatorsreturning proxies may be a problem. Another issue is that 
> IIterator<T> must
> clone the underlying iterator; otherwise you will often end up 
> with pointers to
> deallocated objects.
> 
> I'm thinking of using the following syntax for polymorphic 
> container wrappers
> (stealing from Andrei):
> 
>    sequence              - sequence of anything
>    sequence::of<T>   - sequence of T's
>    iterator                 - any iterator (more or less)
>    iterator::over<T>  (or of<T>) - any iterator over T's

Is this container wrapper stuff further elaborated somewhere
I can take a look at?

> 
> This allows sequence and iterator to be typedefs for template 
> specializationsinvolving allocator policies.
> 
> > Joaquín M López Muñoz
> > Telefónica, Investigación y Desarrollo
> >
> > PS: Just for motivation, I' think this idiom could be taken 
> advantage> of in a possible implementation of a dynamic multi-
> index container.
> 
> Sounds great!
> 

The rationale is, in a multi-index container where indices
are added at run-time, some sort of dynamic polymorphism
is called for when retrieveing and using the indices, much in
the vein of the poly container wrappers.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo