[boost] Re: is_base_and_derived question

From: Gennaro Prota (gennaro_prota_at_[hidden])
Date: 2003-02-02 06:30:44

On Sat, 1 Feb 2003 20:01:15 -0800, "Eric Niebler" <neric_at_[hidden]>
wrote:

>"Gennaro Prota" <gennaro_prota_at_[hidden]> wrote
>>
>> Well, then I imagine you would prefer the old semantics. Was there
>> anybody complaining that being not enough?
>>
>
>Yes, I was.  A while back, I pointed out to Rani that is_base_and_derived
>was insufficient to implement is_com_ptr, a trait I needed.  In COM
>programming, every interface inherits from IUnknown, and many COM objects
>implement multiple interfaces.  So is_base_and_derived<IUnknown,
>MyCOMObject> was almost always ambiguous.
>
>I was content to gripe, but Rani actually did something about it.  The new
>behavior of is_base_and_derived is very welcome, IMO.

Yes, Rani pointed out the usage for COM interfaces too, and that's a
good one. I'm only a little perplexed about inaccessible bases,
because the relevant example looks a little artificial; that doesn't
mean that there aren't better examples, or that it is a good example
but I have not understood it. As I said in another post, let's see how
will this behave in practice. After all, boost is (also) a sort of
test-bed for C++ libraries.

Genny.