>All arguments can be type checked in advance. Define "advance"? Yes, it is typechecked before the decision is made. The exact sequence of said operations is implementation dependent. That's why I said we are talking about different definition of time. My point was that the policy document MAY be tested and accepted INDEPENDENT of context data type verification. In implementation that is concerned about efficiency that may be a key distinction. >The theory of type systems and polymorphic functions allows complete >typing of every element of an expression. The practice of implementation of said systems cause a great deal of PITA for extension API development, that being the reason of such language being rather unpopular. D;