Is there some way to define an Enum in haskell that wraps around?

Question

Consider I was designing a Monopoly game:

data Board = GO | A1 | CC1 | A2 | T1 | R1 | B1 | CH1 | B2 | B3 | 
  JAIL | C1 | U1 | C2 | C3 | R2 | D1 | CC2 | D2 |         


        

Answer 1

I know this is an old question but I just had this problem and I solved it this way.

data SomeEnum = E0 | E1 | E2 | E3
               deriving (Enum, Bounded, Eq)

-- | a `succ` that wraps 
succB :: (Bounded a, Enum a, Eq a) => a -> a 
succB en | en == maxBound = minBound
         | otherwise = succ en

-- | a `pred` that wraps
predB :: (Bounded a, Enum a, Eq a) => a -> a
predB en | en == minBound = maxBound
         | otherwise = pred en  

The solution derives both Enum and Bounded but avoids abusing pred and succ as suggested.

Incidently, I found that having

allSomeEnum = [minBound..maxBound] :: [SomeEnum] 

can be useful. That requires Bounded.