To take care of operators involving *only* builtin types, I dispatch to another metafunction, which might be preferable to listing out all the special cases of combinations of builtin types.
Could you give an example? I do not understand clearly what you mean. Problem here is that for example (double % double) yields a compile time error and that it is not possible to overload operator%(built-in type, built-in type). So if you have a solution that replaces a long list of template specialization by much fewer lines, please propose.
Actually, I'm not entirely sure how you cover builtin types. I see in has_operator_bit_and.hpp that you list combinations of builtin types that *don't* have the bitand operator is this list suppose to be exhaustive?
Yes it is supposed to be exhaustive.
I still think one should be able to pass a metafunction to an operator trait to be invoked on the actual result type of the operation, but that's more of a feature request than an implementation comment.
I will first try to comply to all other request, i.e. (i) extension to all operators (already done <<, >> and op=), (ii) use existing is_convertible<T>. Then, maybe you could add your proposal as a later addition. Frédéric