Any particular reason why 'is_trivially_default_constructible' was not provided as just the functionally-equivalent of 'has_trivial_default_constructor'?

Ummm, that would be because I forgot about those :/ There are a few traits like that which have changed name between TR1 and C++11, and I guess we should provide the new names as aliases. When I get a chance I'll deal with it. John.