The error is here: At 2001-06-29 00:42, Michael Ackerman wrote:

toEnum n = if n > 0 then 1 + toEnum n

^^^^^^^^^^^^ (toEnum n) :: Nat, so you can't do (+) on it unless (Num Nat), because (+) is a member of the Num class. Obviously you want -- toEnum n = if n > 0 then Succ (toEnum n) else error "bah" -- -- Ashley Yakeley