Re: [boost] [TypeErasure] references

Subject: Re: [boost] [TypeErasure] references
From: Felipe Magno de Almeida (felipe.m.almeida_at_[hidden])
Date: 2013-05-09 20:32:50

On Wed, May 1, 2013 at 6:18 PM, Steven Watanabe <watanabesj_at_[hidden]>wrote:

> AMDG
>
> On 05/01/2013 08:15 AM, Felipe Magno de Almeida wrote:
>

[snip]

>  > Your argument about any_iterator is valid because a forward iterator
> that
> > doesn't save its position is not a forward iterator at all, but that's
> not
> > true for all concepts. And using boost::ref by the user and implementing
> a
> > non-ForwardIterator directly is no different. And creating specific
> > wrappers will be a pain for these concepts that allow the implementation
> to
> > use pointer/references. Using the _self& is no use for these concepts,
> > since the whole point is to type erase, having multiple types to
> implement
> > the same concept with a type-erased interface won't scale at all.
> >
> > Support for smart pointers and naked pointers would be a great plus as
> well.
>

using boost::ref is safe iff. boost::reference_wrapper<T>
> can be considered a model of the concept.
>

Yes.

> Therefore the correct way to handle this is to design
> your concepts in such a way that they accept
> boost::reference_wrapper, pointers, etc.
>

Do you mean algorithms in such a way that they accept
boost::reference_wrapper, pointers, etc? If so, that's how I already do it
for these concepts where I want to use boost::ref with type_erasure. But if
I use type_erasure, my algorithms won't receive boost::reference_wrapper or
pointers because it will use type_erasure::any. What I need is to be able
to use type_erasure::any the same way as generic algorithms that accept
boost::reference_wrapper, but I can't do it with type_erasure::any as is.
Only by creating a specific model with the same semantics as
reference_wrapper as a proxy to the real implementation and use this proxy
to construct the type_erasure::any, which is not great because I wanted the
user to decide how it should be handled and automatically convertible to
type_erasure::any.

> In Christ,
> Steven Watanabe
>

Regards,
-- 
Felipe Magno de Almeida