A quick follow up after discussing this some with Alex, he agrees with my points but also noticed a discrepancy. Item 5 is striving to establish the relationship between the algebraic operators and operator <. We would also like the following to hold: a < b => a + c < b + c A lexicographical compare for std::complex would violate this. So I need to refine item 5 to specify the algebraic relations that should hold and std::complex is no longer a counter example to 4. But std::less<> should be defined for complex under the rules of 4a. Sean