Haskell: Deriving Show for custom type

Question

I have this type definition:

data Operace = Op (Int->Int->Int) String (Int->Int->Int) deriving Show

I want to print this type into

Answer 1

The instance declaration you made is the correct way to go. It seems you forgot to remove that faulty deriving clause from the original data declaration.

data Operace = Op (Int->Int->Int) String (Int->Int->Int)

instance Show Operace where
   show (Op op str inv) = show str

Answer 2

You can derive Show, just import Text.Show.Functions first.