On 17 Sep 2009, at 15:21, José Pedro Magalhães wrote:
E.g. here's a type Bar with three constructors:
data Bar = X | Y | Z deriving (Show) instance Enumerated Bar where constructors = [X, Y, Z]
(This is certainly ugly. Any suggestions?)
|constructors| is expressible in SYB: Wow.
What about
data Bar = X | Y | Z deriving (Show, Eq, Ord, Enum, Bounded)
instance Enumerated Bar where constructors = [minBound .. maxBound]
?
Oh yes, that will certainly work for this very simple datatype. However, one cannot automatically derive instances of |Bounded| for datatypes with non-nullary constructors.
That would be OK in this instance, I think; I'm already dealing with some of those cases by hand, but there were enough purely nullary ones that this seemed worth doing. I don't know if that will work any better with Foo/convert, though... :-) Thanks though Daniel - it's good to meet Enum and Bounded. -Andy