On 8/24/2011 07:23 Frederic Bron wrote:

Please give your preference between A, B and C before Sept. 5th.

Of these three choices, I think C is easiest to live with. However, if you're going to have has_unary_plus I think the symmetry of has_unary_minus is preferable to has_negate, and I continue to believe that an additional has_operator<Tag, TypeA, TypeB> (or can_call_operator<>) should be provided for use in more generic code (e.g. forwarding ETs from a higher level without caring exactly which operators are involved.) Brent