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Subject: Re: [boost] [TypeErasure] references
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2013-05-01 14:18:36


On 05/01/2013 08:15 AM, Felipe Magno de Almeida wrote:
> I also need something like this. I don't see much difference from using
> boost::ref and defining my copying and value semantics to not take the
> attributes into account as my documented semantics
> So I really don't see what the problem is. While algorithms might get
> confused, this is directly related to the semantics given, which might be
> different from type to type that is erased. That is no difference, to me,
> from creating a specific wrapper with different copying semantics.

The difference is that you're asking me to handle
boost::ref in Boost.TypeErasure, regardless of
whether it's correct or not. There is no way for
me to determine automatically whether handling
boost::ref is safe.

> 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.

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

In Christ,
Steven Watanabe

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