On Feb 2, 2008, at 18:41 , I wrote:

No instance for (Bounded a)

arising from use of `maxBound' at Hbot.hs:6:34-41

(...)

My (clearly flawed) understanding of the signature I've specified

The

*not* extend to

for 'turn' means *exactly* that a is Bounded. Brandon Allbery replied: problem is that the scope of a is the type signature; it does the definition.

You

can enable

can try omitting the type on maxBound and minBound, or you the scoped type variables extension Thank you. This compiles fine with the Glasgow extensions turned on as long as the type in the function signature is universally quantified: turn :: forall a. (Enum a, Bounded a) => Int -> a -> a turn n e = toEnum (add (fromEnum (maxBound::a) + 1) (fromEnum e) n) where add mod x y = (x + y + mod) `rem` mod