diff --git a/data-function-meld.cabal b/data-function-meld.cabal
--- a/data-function-meld.cabal
+++ b/data-function-meld.cabal
@@ -1,5 +1,5 @@
 name:                data-function-meld
-version:             0.1.0.0
+version:             0.1.1.0
 synopsis:            Map the arguments and return value of functions.
 description:         Map the arguments and return value of functions.   
 homepage:            https://github.com/erisco/data-function-meld
@@ -16,8 +16,17 @@
 
   exposed-modules:     Data.Function.Meld
   
-  build-depends:       base >=4.7 && <4.8
+  build-depends:       base >=4.0 && <999
   
   hs-source-dirs:      src
   
   default-language:    Haskell2010
+
+source-repository head
+  type:     git
+  location: https://github.com/erisco/data-function-meld
+
+source-repository this
+  type:     git
+  location: https://github.com/erisco/data-function-meld
+  tag:      v0.1.1.0
diff --git a/src/Data/Function/Meld.hs b/src/Data/Function/Meld.hs
--- a/src/Data/Function/Meld.hs
+++ b/src/Data/Function/Meld.hs
@@ -1,8 +1,8 @@
-{-| Map the arguments and return value of functions. 
+{-| Map the arguments and return value of functions. 
 
 General use:
 
-  - @f $* g1 $$ g2 … $$ gn *$ h = \x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
+  - @f $* g1 $$ g2 … $$ gn *$ h = \\x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
 
 Examples:
 
@@ -10,7 +10,22 @@
   - @comparing f = compare $* f $$ f *$ id@
   - @f . g = f $* g *$ id@
 
-Work based on <http://conal.net/blog/posts/semantic-editor-combinators Semantic Editor Combinators> (Conal Elliot, 2016/05/19).
+Related work:
+
+  - <http://conal.net/blog/posts/semantic-editor-combinators Semantic Editor Combinators> 
+    (Conal Elliott, 2008\/11\/24). Introduces composable editors for 
+    function arguments and return values.
+  - <http://matt.immute.net/content/pointless-fun Pointless Fun> (Matt 
+    Hellige, 2008\/12\/03). Derives a similar operator named @~>@. This
+    operator composes an editor which can then be applied to the subject
+    to edit. This better agrees with Conal's concept of Semantic Editor 
+    Combinators. In contrast, @$*@ includes the subject as part of the 
+    editor, though you can write @($* g1 $$ g2 … $$ gn *$ h)@ for an 
+    editor independent of the subject. Also, @~>@ is right-associative 
+    whereas @$*@ and @$$@ are left-associative.
+  - <http://hackage.haskell.org/package/TypeCompose-0.9.11/docs/Control-Compose.html TypeCompose version 0.9.11>
+    (Conal Elliott, 2016\/01\/15). Package including an implementation of
+    @~>@.
 -}
 module Data.Function.Meld
 ( ($*)
@@ -18,33 +33,42 @@
 , (*$)
 ) where
 
-import Prelude (flip, (.), ($))
+import Prelude (flip)
+import Control.Category (Category, (.), id)
 
 -- | Map a function argument.
-arg :: (a' -> a) -> (a -> b) -> a' -> b
+arg :: Category cat => cat a' a -> cat a b -> cat a' b
 arg = flip (.)
 
 -- | Map a function return value.
-ret :: (b -> c) -> (a -> b) -> a -> c
+ret :: Category cat => cat b c -> cat a b -> cat a c
 ret = (.)
 
 -- | Begin melding.
 --
--- @f $* g1 $$ g2 … $$ gn *$ h = \x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
-($*) :: (b -> c) -> (a -> b) -> (c -> d) -> a -> d
+-- @f $* g1 $$ g2 … $$ gn *$ h = \\x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
+($*) :: Category cat =>
+           cat b c
+        -> cat a b
+        -> cat c d
+        -> cat a d
 ($*) x f g = ret g (arg f x)
 infixl 8 $*
 
 -- | Continue melding.
 --
--- @f $* g1 $$ g2 … $$ gn *$ h = \x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
-($$) :: (((b -> c) -> a -> d) -> e) -> (a -> b) -> (c -> d) -> e
+-- @f $* g1 $$ g2 … $$ gn *$ h = \\x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
+($$) :: Category cat =>
+           ((cat b c -> cat a d) -> e)
+        -> cat a b 
+        -> cat c d
+        -> e
 ($$) f g h = f (ret h . arg g)
 infixl 7 $$
 
 -- | Finish melding.
 --
--- @f $* g1 $$ g2 … $$ gn *$ h = \x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
-(*$) :: (a -> b) -> a -> b
-(*$) = ($)
+-- @f $* g1 $$ g2 … $$ gn *$ h = \\x1 … xn -> h (f (g1 x1) (g2 x2) … (gn xn))@
+(*$) :: Category cat => cat a b -> cat a b
+(*$) = id
 infixl 6 *$