Re: [boost] review request: addition to type_traits library of is_less_comparable<T, U> and others

What immediately comes to my mind are expression templates (e.g., Boost.Proto).  This is also a case where the return type is not necessarily convertible to bool.  I don't think this library should decide whether it's appropriate for a client of this library to test operator< for such types; leave that decision for the client.

I did not think about expression templates but do you see any reason for asking if the expression template is comparable? Normally the user do not bother about expression templates (which is an implementation detail) but only about the result type which is a "normal" type? I may be wrong as I only know expression templates in the frame of uBlas. Frédéric