On Saturday 28 October 2006 09:15, Larry Wall wrote: > My initial inclination is to say that "where" clauses in a signature > are only there for pattern matching, and do not modify the official > type of the parameter within the function body. However, on a "subset" > the "where" clause is there precisely to contribute to the typing, > so if you want the extra constraints to apply to all uses of the > parameter variable within the body, you'd need to declare a subset > type that enforces it.
Right; it's awfully difficult to have nominal typing in a room full of blank "Hello my name is" tags. > On the other hand, I can imagine that an alternative would be to say > that a "where" clause will always "subsetize" the official type; > that would imply that we'd need to add a "when" clause for mere > pattern matching. Something to be said for making such a distinction, > if it can be taught. -- c
