diff --git a/deferred-folds.cabal b/deferred-folds.cabal
--- a/deferred-folds.cabal
+++ b/deferred-folds.cabal
@@ -1,5 +1,5 @@
 name: deferred-folds
-version: 0.9.15
+version: 0.9.16
 category: Folding
 synopsis: Abstractions over deferred folds
 description:
diff --git a/library/DeferredFolds/Defs/Unfoldr.hs b/library/DeferredFolds/Defs/Unfoldr.hs
--- a/library/DeferredFolds/Defs/Unfoldr.hs
+++ b/library/DeferredFolds/Defs/Unfoldr.hs
@@ -5,6 +5,7 @@
 import DeferredFolds.Types
 import qualified Data.Map.Strict as Map
 import qualified Data.IntMap.Strict as IntMap
+import qualified Data.IntSet as IntSet
 import qualified Data.HashMap.Strict as HashMap
 import qualified Data.ByteString as ByteString
 import qualified Data.ByteString.Short.Internal as ShortByteString
@@ -65,7 +66,8 @@
 {-| Apply a Gonzalez fold -}
 {-# INLINE fold #-}
 fold :: Fold input output -> Unfoldr input -> output
-fold (Fold step init extract) = extract . foldl' step init
+fold (Fold step init extract) (Unfoldr run) =
+  run (\ input next state -> next $! step state input) extract init
 
 {-| Apply a monadic Gonzalez fold -}
 {-# INLINE foldM #-}
@@ -73,10 +75,20 @@
 foldM (FoldM step init extract) (Unfoldr unfoldr) =
   init >>= unfoldr (\ input next state -> step state input >>= next) return >>= extract
 
+{-| Construct from any value by supplying a definition of foldr -}
+{-# INLINE foldrAndContainer #-}
+foldrAndContainer :: (forall x. (elem -> x -> x) -> x -> container -> x) -> container -> Unfoldr elem
+foldrAndContainer foldr a = Unfoldr (\ step init -> foldr step init a)
+
 {-| Construct from any foldable -}
 {-# INLINE foldable #-}
 foldable :: Foldable foldable => foldable a -> Unfoldr a
-foldable foldable = Unfoldr (\ step init -> foldr step init foldable)
+foldable = foldrAndContainer foldr
+
+{-| Elements of IntSet. -}
+{-# INLINE intSet #-}
+intSet :: IntSet -> Unfoldr Int
+intSet = foldrAndContainer IntSet.foldr
 
 {-| Filter the values given a predicate -}
 {-# INLINE filter #-}
diff --git a/library/DeferredFolds/Unfoldr.hs b/library/DeferredFolds/Unfoldr.hs
--- a/library/DeferredFolds/Unfoldr.hs
+++ b/library/DeferredFolds/Unfoldr.hs
@@ -5,4 +5,4 @@
 where
 
 import DeferredFolds.Types as Exports (Unfoldr(..))
-import DeferredFolds.Defs.Unfoldr as Exports
+import DeferredFolds.Defs.Unfoldr as Exports hiding (foldrAndContainer)