Joe Fredette
Consider the set of all rationals with 1 as a numerator, and positive denominator, eg:
S = {1/n, n : Nat}
this is bounded, enumerable, but infinite.
Isn't making this an instance of Enum something of an abuse? How would you use enumFromThenTo (or equivalently, [x0,x1..xn]) for these fractions? I think the intuition is that you can use 'enumFromTo minBound maxBound' to exhaustively list the values in a type. E.g. Ashley's own:
allValues :: (Bounded a,Enum a) => [a] allValues = enumFrom minBound
But this doesn't work for Double (or rational), either, so it's abuse with some precedent. Another practical consideration is that checking a function taking a simple Int parameter for equality would mean 2^65 function evaluations. I think function equality would be too much of a black hole to be worth it. -k -- If I haven't seen further, it is by standing in the footprints of giants