Extend Foldable (foldl', null, length) (#223)

* extend Foldable (foldl', null, length)

* ghc 7.8.4 Foldable compat

Data/HashMap/Base.hs

@@ -197,7 +197,16 @@ instance Functor (HashMap k) where
     fmap = map
 
 instance Foldable.Foldable (HashMap k) where
-    foldr f = foldrWithKey (const f)
+    foldr = Data.HashMap.Base.foldr
+    {-# INLINE foldr #-}
+    foldl' = Data.HashMap.Base.foldl'
+    {-# INLINE foldl' #-}
+#if MIN_VERSION_base(4,8,0)
+    null = Data.HashMap.Base.null
+    {-# INLINE null #-}
+    length = Data.HashMap.Base.size
+    {-# INLINE length #-}
+#endif
 
 #if __GLASGOW_HASKELL__ >= 711
 instance (Eq k, Hashable k) => Semigroup (HashMap k v) where
@@ -1530,7 +1539,7 @@ intersectionWithKey f a b = foldlWithKey' go empty a
 -- | /O(n)/ Reduce this map by applying a binary operator to all
 -- elements, using the given starting value (typically the
 -- left-identity of the operator).  Each application of the operator
--- is evaluated before using the result in the next application. 
+-- is evaluated before using the result in the next application.
 -- This function is strict in the starting value.
 foldl' :: (a -> v -> a) -> a -> HashMap k v -> a
 foldl' f = foldlWithKey' (\ z _ v -> f z v)
@@ -1539,7 +1548,7 @@ foldl' f = foldlWithKey' (\ z _ v -> f z v)
 -- | /O(n)/ Reduce this map by applying a binary operator to all
 -- elements, using the given starting value (typically the
 -- left-identity of the operator).  Each application of the operator
--- is evaluated before using the result in the next application.  
+-- is evaluated before using the result in the next application.
 -- This function is strict in the starting value.
 foldlWithKey' :: (a -> k -> v -> a) -> a -> HashMap k v -> a
 foldlWithKey' f = go

Data/HashSet/Base.hs

@@ -140,6 +140,16 @@ instance Ord1 HashSet where
 instance Foldable.Foldable HashSet where
     foldr = Data.HashSet.Base.foldr
     {-# INLINE foldr #-}
+    foldl' = Data.HashSet.Base.foldl'
+    {-# INLINE foldl' #-}
+#if MIN_VERSION_base(4,8,0)
+    toList = Data.HashSet.Base.toList
+    {-# INLINE toList #-}
+    null = Data.HashSet.Base.null
+    {-# INLINE null #-}
+    length = Data.HashSet.Base.size
+    {-# INLINE length #-}
+#endif
 
 #if __GLASGOW_HASKELL__ >= 711
 instance (Hashable a, Eq a) => Semigroup (HashSet a) where