diff --git a/Text/Parsec/Pos.hs b/Text/Parsec/Pos.hs
--- a/Text/Parsec/Pos.hs
+++ b/Text/Parsec/Pos.hs
@@ -22,6 +22,8 @@
     , updatePosChar, updatePosString
     ) where
 
+import Data.Generics
+
 -- < Source positions: a file name, a line and a column
 -- upper left is (1,1)
 
@@ -35,7 +37,7 @@
 -- 'Ord' class. 
 
 data SourcePos  = SourcePos SourceName !Line !Column
-    deriving ( Eq, Ord )
+    deriving ( Eq, Ord, Data, Typeable)
 
 -- | Create a new 'SourcePos' with the given source name,
 -- line number and column number.
diff --git a/Text/Parsec/Prim.hs b/Text/Parsec/Prim.hs
--- a/Text/Parsec/Prim.hs
+++ b/Text/Parsec/Prim.hs
@@ -52,7 +52,9 @@
 -- | ParserT monad transformer and Parser type
 
 -- | @ParsecT s u m a@ is a parser with stream type @s@, user state type @u@,
--- underlying monad @m@ and return type @a@
+-- underlying monad @m@ and return type @a@.  Parsec is strict in the user state.
+-- If this is undesirable, simply used a data type like @data Box a = Box a@ and
+-- the state type @Box YourStateType@ to add a level of indirection.
 
 data ParsecT s u m a
     = ParsecT { runParsecT :: State s u -> m (Consumed (m (Reply s u a))) }
@@ -62,7 +64,7 @@
 data Consumed a  = Consumed a
                  | Empty !a
 
-data Reply s u a = Ok !a !(State s u) ParseError
+data Reply s u a = Ok a !(State s u) ParseError
                  | Error ParseError
 
 data State s u = State {
diff --git a/Text/ParserCombinators/Parsec/Expr.hs b/Text/ParserCombinators/Parsec/Expr.hs
--- a/Text/ParserCombinators/Parsec/Expr.hs
+++ b/Text/ParserCombinators/Parsec/Expr.hs
@@ -27,12 +27,14 @@
 
 data Operator tok st a   = Infix  (GenParser tok st (a -> a -> a)) Assoc
                          | Prefix (GenParser tok st (a -> a))
+                         | Postfix (GenParser tok st (a -> a))
 
 type OperatorTable tok st a = [[Operator tok st a]]
 
 convert :: Operator tok st a -> N.Operator [tok] st Identity a
 convert (Infix p a) = N.Infix p a
 convert (Prefix p)  = N.Prefix p
+convert (Postfix p)  = N.Postfix p
 
 buildExpressionParser :: OperatorTable tok st a
                       -> GenParser tok st a
diff --git a/parsec.cabal b/parsec.cabal
--- a/parsec.cabal
+++ b/parsec.cabal
@@ -1,6 +1,6 @@
 name:		parsec
-version:	3.0.0
-cabal-version: >= 1.2
+version:	3.0.1
+cabal-version: >= 1.2.3
 license:	BSD3
 license-file:	LICENSE
 author:		Daan Leijen <daan@cs.uu.nl>, Paolo Martini <paolo@nemail.it>
@@ -17,6 +17,10 @@
 	stacked on arbitrary monads, and it is also parametric in the
 	input stream type.
 
+flag base4
+    Description: Use base-4.*
+    Default:    True
+
 library    
     exposed-modules:
         Text.Parsec,
@@ -42,7 +46,11 @@
         Text.ParserCombinators.Parsec.Pos,
         Text.ParserCombinators.Parsec.Prim,
         Text.ParserCombinators.Parsec.Token
-    build-depends:	base, mtl, bytestring
-    extensions:	ExistentialQuantification, PolymorphicComponents, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts
+    if flag(base4)
+        build-depends: base >= 4 && < 5, syb
+    else
+        build-depends: base >= 3.0.3 && < 4
+    build-depends: mtl, bytestring
+    extensions:	ExistentialQuantification, PolymorphicComponents, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, DeriveDataTypeable
     ghc-options:	-O2
     ghc-prof-options:	-auto-all