diff --git a/functor-combo.cabal b/functor-combo.cabal
--- a/functor-combo.cabal
+++ b/functor-combo.cabal
@@ -1,6 +1,6 @@
 Name:                functor-combo
-Version:             0.2.1
-Cabal-Version:       >= 1.2
+Version:             0.3
+Cabal-Version:       >= 1.6
 Synopsis:            Functor combinators with tries & zippers
 Category:            Data
 Description:
@@ -9,20 +9,15 @@
   .
 Author:              Conal Elliott
 Maintainer:          conal@conal.net
-Homepage:            http://haskell.org/haskellwiki/functor-combo
 Copyright:           (c) 2010-2012 by Conal Elliott
 License:             BSD3
 License-File:        COPYING
 Stability:           experimental
 build-type:          Simple
 
-Package-Url:         http://code.haskell.org/~conal/code/functor-combo
--- Wait until Cabal 1.6 is more wide-spread and then add the following
--- in place of the Package-Url field and bump Cabal-Version to >= 1.6.
--- 
--- Source-Repository head
---     type:         darcs
---     location:     http://code.haskell.org/~conal/code/functor-combo
+source-repository head
+  type:     git
+  location: git://github.com/conal/functor-combo.git
 
 Library
   hs-Source-Dirs:      src
diff --git a/src/FunctorCombo/StrictMemo.hs b/src/FunctorCombo/StrictMemo.hs
--- a/src/FunctorCombo/StrictMemo.hs
+++ b/src/FunctorCombo/StrictMemo.hs
@@ -18,7 +18,8 @@
 
 module FunctorCombo.StrictMemo
   (
-    HasTrie(..),(:->:),memo,memo2,memo3
+    HasTrie(..),(:->:),memo,memo2,memo3,idTrie
+  , onUntrie, onUntrie2
   ) where
 
 import Control.Arrow (first)
@@ -30,7 +31,7 @@
 import qualified Data.IntTrie as IT  -- data-inttrie
 import Data.Tree
 
-import Control.Compose (result)  -- TypeCompose
+import Control.Compose (result,(<~))  -- TypeCompose
 
 -- import FunctorCombo.Strict
 import FunctorCombo.Functor
@@ -48,7 +49,7 @@
 type k :->: v = Trie k v
 
 
--- #define FunctorSuperClass
+#define FunctorSuperClass
 
 #ifdef FunctorSuperClass
 
@@ -451,3 +452,17 @@
   type PF (Tree a) = Const a :*: []
   unwrap (Node a ts) = Const a :*: ts
   wrap (Const a :*: ts) = Node a ts
+
+{--------------------------------------------------------------------
+    Acting on function
+--------------------------------------------------------------------}
+
+onUntrie :: (HasTrie a, HasTrie b) =>
+            ((a  ->  a') -> (b  ->  b'))
+         -> ((a :->: a') -> (b :->: b'))
+onUntrie = trie <~ untrie
+
+onUntrie2  :: (HasTrie a, HasTrie b, HasTrie c) =>
+             ((a  ->  a') -> (b  ->  b') -> (c  ->  c'))
+          -> ((a :->: a') -> (b :->: b') -> (c :->: c'))
+onUntrie2 = onUntrie <~ untrie