Re: [Haskell-cafe] Enum instantiation

R J writes:

I'd like to make "Day" an instance of class "Enum," but the definition of toEnum below seems to be completely wrong, because integers seem not permit pattern matching. How is toEnum defined? Thanks.

You could try using guards:

toEnum x | x == 0 = Sunday | x == 1 = Monday | x == 2 = Tuesday | x == 3 = Wednesday | x == 4 = Thursday | x == 5 = Friday | x == 6 = Saturday | otherwise = error "bad enum"

BTW if none of your constructors have fields you can just add Enum to the "deriving (...)" list for your type, and the compiler will write basically the same instance for you. G. -- Gregory Collins