Joaquín Mª López Muñoz wrote:
David Abrahams ha escrito:
It seems to me that true is the appropriate safe default for is_abstract. Am I missing something?
So that generic code won't try to instantiate an abstract type? Is this your rationale?
Yes.
Well, maybe. In the case of Boost.Serialization, however, I think that the appropriate default is false, since serializating (types derived from) an abstract type is more difficult than the non-abstract case.
But serialization can always check the macro. The standard practice for type traits that need some compiler support is to degrade gracefully (code still compiles) and safely (only the most conservative assumptions are made). Why shouldn't we do that in this case?
Either way, if we have a BOOST_NO_IS_ABSTRACT (for instance) macro, the programmer can choose whether to rely on is_abstract's default of not.
Yes, but that's a different issue. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com