module Relations where
import Sets

type Relation a b = Set (a,b)

composeRelations :: (Eq a, Eq b, Eq c) => 
                    Relation a b -> Relation b c -> Relation a c 
isReflexive :: Eq a => Set a -> Relation a a -> Bool
isSymmetric :: Eq a => Relation a a -> Bool
isTransitive :: Eq a => Relation a a -> Bool
isEquivalence :: Eq a => Set a -> Relation a a -> Bool