"Cale Gibbard"
Another thing to note is that all the natural literals are not, as one might initially think, plain values, but actually represent the embedding of that natural number into the ring (instance of Num), by way of 0 and 1.
I wasn't sure where to add this, so here will have to do: I think the present design is wrong because we don't have a type for naturals. So in my view, “-1” should be “negate (fromNatural 1)” -- whatever names we use for those two functions. I can't remember right now why the early versions of Haskell didn't have a Natural type, or what makes it difficult to change to now (and I think this is something we really should do), but even given that, I think the present special casing of “-” is a reasonable compromise. Given a built in Natural type, it makes no sense to have “-” as part of the syntax for literals, since Natural literals don't have it and there's no way to add more constructors (ie negative literals) onto an existing type to get Integer, but having a symbol for negate does it in a straightforward way. * ** * For my own taste, I would have “-” as a character that can appear in identifiers and operators (but special in that if it appears at the beginning it cannot be followed by anything? Otherwise -1 would just be an identifier!) and define
- n = negate n a +- b = a + (- b)
but I think that most people would baulk at having to use “+-” for infix minus. People would similarly baulk at the opposite tack of making “-” solely infix and using something else for negate (as in ML), although finding a different token (such as “__”) for "don't care" and using “_” for unary minus doesn't seem too bad to me. -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk