Merge pull request #21 from zudov/foldable-instance

Added Foldable instance

Author: paf31

src/Data/Set.purs

@@ -28,7 +28,7 @@ import Data.Int ()
 import Data.Maybe 
 import Data.Monoid
 import Data.Tuple
-import Data.Foldable (foldl) 
+import Data.Foldable (Foldable, foldMap, foldl, foldr)
 
 import Data.List (List(..))
 
@@ -50,6 +50,11 @@ instance monoidSet :: (Ord a) => Monoid (Set a) where
 instance monoidSemigroup :: (Ord a) => Semigroup (Set a) where
   append = union
 
+instance foldableSet :: Foldable Set where
+  foldMap f = foldMap f <<< toList
+  foldl f x = foldl f x <<< toList
+  foldr f x = foldr f x <<< toList
+
 -- | An empty set
 empty :: forall a. Set a
 empty = Set M.empty