On 2005-07-12 12:22, "TSa (Thomas Sandlaß)" <[EMAIL PROTECTED]> wrote: > I am also interested in the rationale behind the approach to manage MMD > my means of a metric instead of a partial order on the types. > Metric is a geometric concept which in my eyes doesn't fit type > theory.
The geometric interpretation does bring us into somewhat philosophical territory. Not that that's anything new on this list. :) Let me try a concrete example. Suppose that class Answer has subclasses Animal, Vegetable, and Mineral, with respective subclasses Dog, Potato, and Diamond. There are two methods named foo in scope, neither overriding the other. One is declared to take (Animal, Vegetable, Mineral), the other (Dog, Potato, Answer). Assuming the obvious memberships, which method should foo(Snoopy, Mr_PotatoHead, HopeDiamond) call? And more importantly, why do you feel that is the right answer? According to Damian's metric, we have distances of 0+0+2=2 and 1+1+1=3, so (Dog, Potato, Answer) is "closer" and would get called.
