I particularily like that one : "I expect type names will ordinarily be symbols, but they don't have to be. Either argument can be of any type. I can't imagine why users would want to have type labels other than symbols, but I also can't see any reason to prevent it."
You know, the first thing I thought when I read that x years ago was "You could pass around a load of functions as the type to do polymorphism"! I wonder if everyone has the same thought.
