diff --git a/pointless-lenses.cabal b/pointless-lenses.cabal
--- a/pointless-lenses.cabal
+++ b/pointless-lenses.cabal
@@ -1,5 +1,5 @@
 Name:            pointless-lenses
-Version:         0.0.1
+Version:         0.0.2
 License:         BSD3
 License-file:    LICENSE
 Author:          Alcino Cunha <alcino@di.uminho.pt>, Hugo Pacheco <hpacheco@di.uminho.pt>
diff --git a/src/Generics/Pointless/Lenses/Combinators.hs b/src/Generics/Pointless/Lenses/Combinators.hs
--- a/src/Generics/Pointless/Lenses/Combinators.hs
+++ b/src/Generics/Pointless/Lenses/Combinators.hs
@@ -19,9 +19,26 @@
 
 import Generics.Pointless.Lenses
 import Generics.Pointless.Combinators
+import Generics.Pointless.Functors
 
 -- * Point-free lens combinators
 
+-- | Function application is a lens.
+ap_lns :: Eq a => a -> Lens ((a -> b),a) b
+ap_lns a = Lens get' put' create'
+    where get' = app
+          put' (b,(f,a)) = (\x -> if x==a then b else f x,a)
+          create' = const /\ const a
+
+-- | Predicate application is a lens.
+infix 0 ?<
+(?<) :: Eq a => Lens (a -> Bool,a) (Either a a)
+(?<) = Lens get' put' create'
+    where get' = (snd -|- snd) . distl . (out . app /\ snd)
+          put' = ((orf \/ andf) . distl . (eqneq >< fst)) /\ ((id \/ id) . fst)
+          create' = (curry eq /\ id) \/ (const (inn . inr . bang) /\ id)
+          eqneq = curry eq -|- curry neq
+
 -- | The right exponentiation combinator as a lens.
 -- Applies a lens to the domain of a function.
 rexp_lns :: Lens b c -> Lens (a -> b) (a -> c)
@@ -178,4 +195,3 @@
 -- | The @coassocr@ point-free combinator.
 coassocr_lns :: Lens (Either (Either a b) c) (Either a (Either b c))
 coassocr_lns = Lens coassocr (coassocl . fst) coassocl
-
diff --git a/src/Generics/Pointless/Lenses/Examples/Examples.hs b/src/Generics/Pointless/Lenses/Examples/Examples.hs
--- a/src/Generics/Pointless/Lenses/Examples/Examples.hs
+++ b/src/Generics/Pointless/Lenses/Examples/Examples.hs
@@ -42,6 +42,33 @@
 filter_lns :: Lens [Either a b] [a]
 filter_lns = cata_lns _L ((inn_lns .\/< snd_lns _L) .< coassocl_lns .< (id_lns -|-< distl_lns))
 
+-- | Binary list concatenation.
+cat_lns :: Lens ([a],[a]) [a]
+cat_lns = Lens get' put' create'
+    where get' = uncurry (++)
+          put' (l,(e,d)) = splitAt (length e) l
+          create' l = splitAt (length l `div` 2) l
+
+data Tree a = Empty | Node a (Tree a) (Tree a) deriving (Eq,Show)
+
+type instance BF Tree = BConst One :+| (BPar :*| (BId :*| BId))
+
+type instance PF (Tree a) = Const One :+: (Const a :*: (Id :*: Id))
+
+instance Mu (Tree a) where
+   inn (Left _) = Empty
+   inn (Right (a,(b,c))) = Node a b c
+   out Empty = Left _L
+   out (Node a b c) = Right (a,(b,c))
+
+-- | Flatten a tree.
+flatten_lns :: Lens (Tree a) [a]
+flatten_lns = cata_lns _L (inn_lns .< (id_lns -|-< id_lns ><< cat_lns))
+
+-- | List concatenation.
+concat_lns :: Lens [[a]] [a]
+concat_lns = cata_lns _L (inn_lns .< (((id_lns .\/< id_lns) -|-< id_lns) .< coassocl_lns .< (id_lns -|-< out_lns .< cat_lns)))
+
 -- | List mapping lens.
 map_lns :: Lens c a -> Lens [c] [a]
 map_lns f = nat_lns _L (\x -> id_lns -|-< f ><< id_lns)
diff --git a/src/Generics/Pointless/Lenses/RecursionPatterns.hs b/src/Generics/Pointless/Lenses/RecursionPatterns.hs
--- a/src/Generics/Pointless/Lenses/RecursionPatterns.hs
+++ b/src/Generics/Pointless/Lenses/RecursionPatterns.hs
@@ -28,9 +28,11 @@
 import Generics.Pointless.Lenses
 import Generics.Pointless.Lenses.Combinators
 
+-- | The @inn@ point-free combinator.
 inn_lns :: Mu a => Lens (F a a) a
 inn_lns = Lens inn (out . fst) out
 
+-- | The @out@ point-free combinator.
 out_lns :: Mu a => Lens a (F a a)
 out_lns = Lens out (inn . fst) inn