diff --git a/Control/Arrow/Reader/Class.hs b/Control/Arrow/Reader/Class.hs
--- a/Control/Arrow/Reader/Class.hs
+++ b/Control/Arrow/Reader/Class.hs
@@ -11,4 +11,7 @@
 };
 
 asks :: (ArrowReader r s) => (r -> a) -> s () a;
-asks x = ask >>> arr x;
+asks = asksA . arr;
+
+asksA :: (ArrowReader r s) => s r a -> s () a;
+asksA x = ask >>> x;
diff --git a/Control/Arrow/State.hs b/Control/Arrow/State.hs
--- a/Control/Arrow/State.hs
+++ b/Control/Arrow/State.hs
@@ -6,6 +6,7 @@
 import Control.Arrow.Transformer;
 import Control.Arrow.State.Class;
 import Control.Category;
+import Util;
 
 newtype StateT s r a b = StateT { runStateT :: r (a, s) (b, s) };
 
@@ -18,9 +19,6 @@
   id = StateT id;
   StateT x . StateT y = StateT (x . y);
 };
-
-swap_snds_A :: Arrow r => r ((a, b), c) ((a, c), b);
-swap_snds_A = arr $ \ ((x, y), z) -> ((x, z), y);
 
 instance (Arrow r) => Arrow (StateT s r) where {
   arr = StateT . arr . (*** id);
diff --git a/Control/Arrow/Writer.hs b/Control/Arrow/Writer.hs
new file mode 100644
--- /dev/null
+++ b/Control/Arrow/Writer.hs
@@ -0,0 +1,46 @@
+{-# LANGUAGE KindSignatures, ScopedTypeVariables #-}
+
+module Control.Arrow.Writer (module Control.Arrow.Writer.Class, WriterT (..)) where
+
+import Prelude hiding ((.), id);
+
+import Control.Arrow;
+import Control.Arrow.Transformer;
+import Control.Arrow.Writer.Class;
+import Control.Category;
+import Data.Monoid;
+import Util;
+
+newtype WriterT w r a b = WriterT { runWriterT :: r a (b, w) };
+
+instance Monoid w => ArrowTransformer (WriterT w) where {
+  lift = WriterT . (&&& arr (const mempty));
+  tmap f = WriterT . f . runWriterT;
+};
+
+instance (Monoid w, Arrow r) => Category (WriterT w r) where {
+  id = lift id;
+  WriterT x . WriterT y = WriterT $
+                          arr (\ ((v, w2), w1) -> (v, w1 `mappend` w2)) <<< x *** id <<< y;
+};
+
+instance (Monoid w, Arrow r) => Arrow (WriterT w r) where {
+  arr = WriterT . arr . (&&& const mempty);
+  first = WriterT . (.) swap_snds_A . first . runWriterT;
+};
+
+instance (Monoid w, ArrowApply r) => ArrowApply (WriterT w r) where {
+  app = WriterT $ arr runWriterT *** id >>> app;
+};
+
+instance (Monoid w, Arrow r) => ArrowWriter w (WriterT w r) where {
+  tell = WriterT $ constA () &&& id;
+  look = lift (runWriterT id);
+  censor = withWriterT;
+};
+
+withWriterTA :: (Arrow r) => r x w -> WriterT x r a b -> WriterT w r a b;
+withWriterTA a = WriterT . (>>> id *** a) . runWriterT;
+
+withWriterT :: (Arrow r) => (x -> w) -> WriterT x r a b -> WriterT w r a b;
+withWriterT = withWriterTA . arr;
diff --git a/Control/Arrow/Writer/Class.hs b/Control/Arrow/Writer/Class.hs
new file mode 100644
--- /dev/null
+++ b/Control/Arrow/Writer/Class.hs
@@ -0,0 +1,20 @@
+{-# LANGUAGE FunctionalDependencies #-}
+
+module Control.Arrow.Writer.Class where
+
+import Prelude hiding ((.), id);
+
+import Control.Arrow;
+import Control.Category;
+
+class Arrow r => ArrowWriter w r | r -> w where {
+  tell :: r w ();
+  look :: r a (a, w);
+  censor :: (w -> w) -> r a b -> r a b;
+};
+
+looksA :: ArrowWriter w r => r w b -> r a (a, b);
+looksA x = look >>> id *** x;
+
+looks :: ArrowWriter w r => (w -> b) -> r a (a, b);
+looks = looksA . arr;
diff --git a/atl.cabal b/atl.cabal
--- a/atl.cabal
+++ b/atl.cabal
@@ -1,5 +1,5 @@
 Name:atl
-Version:15320.1
+Version:15321.1
 Description:Arrow Transformer Library
 License:LGPL
 License-File:license.txt
@@ -13,5 +13,5 @@
 Library {
   Build-Depends: base >= 4 && < 5
   Extensions: UnicodeSyntax, RankNTypes, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts
-  Exposed-Modules: Control.Arrow.Transformer, Control.Arrow.Reader, Control.Arrow.Reader.Class, Control.Arrow.List.Class, Control.Arrow.Abort, Control.Arrow.Abort.Class, Control.Arrow.State, Control.Arrow.State.Class
+  Exposed-Modules: Control.Arrow.Transformer, Control.Arrow.Reader, Control.Arrow.Reader.Class, Control.Arrow.List.Class, Control.Arrow.Abort, Control.Arrow.Abort.Class, Control.Arrow.State, Control.Arrow.State.Class, Control.Arrow.Writer, Control.Arrow.Writer.Class
 }