[boost] is_base_and_derived

From: David Abrahams (dave_at_[hidden])
Date: 2003-10-26 20:52:32

I'd like to make a small plea to consider usefulness over technical
accuracy.  I find myself consciously avoiding is_base_and_derived ever
since we decided it should return false the case where the two types
are actually the same.  This is partly because I nearly always want to
treat the case where the two types are the same in the same way as
when they are actually base and derived classes (or else it's a case
where I don't care about the outcome of that case), and partly because
I know it costs extra compile time resources to rule that case out.  I
know I can get the effect I want with

    is_convertible<D*,B*>

but it's far less clear than writing is_base_and_derived<B,D>.  I
honestly can't imagine a case where I'd want the semantics as they're
currently defined.  I think we should either change the semantics back
(possibly changing the name to something more appropriate if people
are more comfortable with that) or simply remove is_base_and_derived,
unless someone can come up with a compelling case for keeping it.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com