On Thu, Mar 3, 2011 at 8:00 PM, Paul Sujkov
Hi, you can always check the types using GHCi prompt: *Prelude> :i (,) data (,) a b = (,) a b -- Defined in GHC.Tuple instance (Bounded a, Bounded b) => Bounded (a, b) -- Defined in GHC.Enum instance (Eq a, Eq b) => Eq (a, b) -- Defined in Data.Tuple instance Functor ((,) a) -- Defined in Control.Monad.Instances instance (Ord a, Ord b) => Ord (a, b) -- Defined in Data.Tuple instance (Read a, Read b) => Read (a, b) -- Defined in GHC.Read instance (Show a, Show b) => Show (a, b) -- Defined in GHC.Show that's for a tuple. You can see that tuple has an instance for the Ord class. *Prelude> :i () data () = () -- Defined in GHC.Unit instance Bounded () -- Defined in GHC.Enum instance Enum () -- Defined in GHC.Enum instance Eq () -- Defined in Data.Tuple instance Ord () -- Defined in Data.Tuple instance Read () -- Defined in GHC.Read instance Show () -- Defined in GHC.Show and that's for a unit type. [snip] Ah, thanks! I didn't know about :i, tried only :t () which didn't give very interesting information.