On Thu, 2006-01-26 at 17:31 +0000, Simon Peyton-Jones wrote:
I agree that if (n+k) patterns go, then so should k patterns. Both are overloaded, and that's the root of their complexity.
I have to say that we use 'k' patterns in teaching all the time, though we do not teach n+k patterns. There are lots of cases where it's convenient to say: foo 0 = ... foo n = ... Intuitively it seems reasonable to me that 1 is a constructor for the Int type just as 'c' is a constructor for type Char, and since it's a constructor we can pattern patch on it. To be honest, the difficulty of the internal translation needed for tools seems less important to me than the convenience for users. I don't think the difference that character constants are not overloaded where as numeric constants are overloaded causes any difficult in understanding for users. Duncan