diff --git a/Control/Lens.hs b/Control/Lens.hs
--- a/Control/Lens.hs
+++ b/Control/Lens.hs
@@ -1,7 +1,7 @@
 module Control.Lens (Lens, Refractor, Traversal,
                      lens, iso,
-                     get, set, modify,
-                     fstL, sndL, swapL, unitL) where
+                     get, set, modify, mapping,
+                     fstL, sndL, swapL, unitL, bitL) where
 
 import Prelude hiding (id)
 
@@ -12,6 +12,7 @@
 import Data.Bits (Bits (..))
 import Data.Bool (bool)
 import Data.Functor.Identity
+import Data.Profunctor
 import Data.Tuple (swap)
 
 type Refractor c d α β a b = ∀ p f . (d f, c p) ⇒ p a (f b) → p α (f β)
@@ -20,11 +21,13 @@
 
 type Traversal α β a b = Refractor ((~) (→)) Applicative α β a b
 
+type Iso α β a b = Refractor Profunctor Functor α β a b
+
 lens :: (α → a) → (b → α → β) → Lens α β a b
 lens get set ret = liftA2 fmap (flip set) (ret ∘ get)
 
-iso :: (α → a) → (b → β) → Lens α β a b
-iso f g = (fmap g ∘) ∘ (∘ f)
+iso :: (α → a) → (b → β) → Iso α β a b
+iso f g = dimap f (fmap g)
 
 get :: ((a → Const a b) → α → Const a β) → α → a
 get l = getConst ∘ l Const
@@ -35,13 +38,25 @@
 modify :: ((a → Identity b) → α → Identity β) → (a → b) → α → β
 modify l f = runIdentity ∘ l (Identity ∘ f)
 
+mapping :: (Functor f, Functor g) => AnIso α β a b -> Iso (f α) (g β) (f a) (g b)
+mapping = (`withIso` \ f g -> iso (fmap f) (fmap g))
+
+withIso :: AnIso α β a b -> ((α -> a) -> (b -> β) -> c) -> c
+withIso x = case x (Xchg id Identity) of Xchg φ φ' -> \ f -> f φ (runIdentity ∘ φ')
+
+type AnIso α β a b = Xchg a b a (Identity b) -> Xchg a b α (Identity β)
+
+data Xchg a b α β = Xchg (α -> a) (b -> β) deriving (Functor)
+
+instance Profunctor (Xchg a b) where dimap f g (Xchg φ φ') = Xchg (φ ∘ f) (g ∘ φ')
+
 fstL :: Lens (a, c) (b, c) a b
 fstL = swapL ∘ sndL
 
 sndL :: Lens (a, b) (a, c) b c
 sndL f = id *** f >>> uncurry (fmap ∘ (,))
 
-swapL :: Lens (a, b) (c, d) (b, a) (d, c)
+swapL :: Iso (a, b) (c, d) (b, a) (d, c)
 swapL = iso swap swap
 
 unitL :: Lens α α () ()
diff --git a/LICENSE b/LICENSE
deleted file mode 100644
--- a/LICENSE
+++ /dev/null
@@ -1,5 +0,0 @@
-© Unix year 44 (Strake = M Farkas-Dyck)
-
-Leave to use, copy, modify, and distribute this work for any purpose is hereby granted if the above copyright notice and this license are included.
-
-THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
diff --git a/lenz.cabal b/lenz.cabal
--- a/lenz.cabal
+++ b/lenz.cabal
@@ -1,9 +1,9 @@
 name:           lenz
-version:        0.2.0.0
+version:        0.2.1.0
 synopsis:       Van Laarhoven lenses
-license:        OtherLicense
-license-file:   LICENSE
+license:        BSD3
 author:	        M Farkas-Dyck
+copyright:      © Unix year 47 M Farkas-Dyck
 maintainer:     strake888@gmail.com
 category:       Data, Lenses
 build-type:     Simple
@@ -14,5 +14,9 @@
 
 library
   exposed-modules:      Control.Lens
-  build-depends:        base >= 4.8 && <5, base-unicode-symbols >= 0.1 && <0.3, transformers >=0.2 && <0.6
-  extensions:           UnicodeSyntax, RankNTypes, ConstraintKinds, GADTs
+  build-depends:        base >= 4.8 && <5
+                      , base-unicode-symbols >= 0.1 && <0.3
+                      , profunctors >=5.2.1 && <5.3
+                      , transformers >=0.2 && <0.6
+  extensions:           UnicodeSyntax, RankNTypes, ConstraintKinds, GADTs, DeriveFunctor
+  ghc-options:          -Wall -Wno-name-shadowing