diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2006-2010
+Copyright (c) 2006-2012
         The President and Fellows of Harvard College.
 
 Redistribution and use in source and binary forms, with or without
diff --git a/Text/PrettyPrint/Mainland.hs b/Text/PrettyPrint/Mainland.hs
--- a/Text/PrettyPrint/Mainland.hs
+++ b/Text/PrettyPrint/Mainland.hs
@@ -1,10 +1,12 @@
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE OverlappingInstances #-}
 {-# LANGUAGE TypeSynonymInstances #-}
 {-# LANGUAGE UndecidableInstances #-}
 
--- Copyright (c) 2006-2010
+-- Copyright (c) 2006-2012
 --         The President and Fellows of Harvard College.
 --
 -- Redistribution and use in source and binary forms, with or without
@@ -34,7 +36,7 @@
 --------------------------------------------------------------------------------
 -- |
 -- Module      :  Text.PrettyPrint.Mainland
--- Copyright   :  (c) Harvard University 2006-2010
+-- Copyright   :  (c) Harvard University 2006-2012
 -- License     :  BSD-style
 -- Maintainer  :  mainland@eecs.harvard.edu
 --
@@ -97,20 +99,20 @@
   ) where
 
 import Data.Int
-import qualified Data.Map as Map
-import qualified Data.Set as Set
-import Data.Word
-
 import Data.Loc (L(..),
                  Loc(..),
                  Located(..),
                  Pos(..),
                  posFile,
                  posLine)
+import qualified Data.Map as Map
+import Data.Monoid
+import qualified Data.Set as Set
 import Data.Symbol
+import Data.Word
 
 infixr 5 </>, <+/>, <//>
-infixr 6 <>, <+>
+infixr 6 <+>
 
 data Doc = Empty                -- ^ The empty document
          | Char Char            -- ^ A single character
@@ -189,9 +191,6 @@
 flatten (Column f)   = Column (flatten . f)
 flatten (Nesting f)  = Nesting (flatten . f)
 
-(<>) :: Doc -> Doc -> Doc
-x <> y = x `Cat` y
-
 (<+>) :: Doc -> Doc -> Doc
 x <+> y = x <> space <> y
 
@@ -438,18 +437,20 @@
 renderCompact :: Doc -> RDoc
 renderCompact doc = scan 0 [doc]
   where
-    scan _ []     = REmpty
-    scan k (d:ds) = case d of
-                      Empty     -> scan k ds
-                      Char c    -> let k' = k+1 in k' `seq` RChar c (scan k' ds)
-                      Text l s  -> let k' = k+l in k' `seq` RText l s (scan k' ds)
-                      Line      -> RLine 0 (scan 0 ds)
-                      Nest _ x  -> scan k (x:ds)
-                      SrcLoc _  -> scan k ds
-                      Cat x y   -> scan k (x:y:ds)
-                      Alt x _   -> scan k (x:ds)
-                      Column f  -> scan k (f k:ds)
-                      Nesting f -> scan k (f 0:ds)
+    scan :: Int -> [Doc] -> RDoc
+    scan !_ []     = REmpty
+    scan !k (d:ds) =
+        case d of
+          Empty     -> scan k ds
+          Char c    -> RChar c (scan (k+1) ds)
+          Text l s  -> RText l s (scan (k+l) ds)
+          Line      -> RLine 0 (scan 0 ds)
+          Nest _ x  -> scan k (x:ds)
+          SrcLoc _  -> scan k ds
+          Cat x y   -> scan k (x:y:ds)
+          Alt x _   -> scan k (x:ds)
+          Column f  -> scan k (f k:ds)
+          Nesting f -> scan k (f 0:ds)
 
 -- | Display a rendered document.
 displayS :: RDoc -> ShowS
@@ -530,7 +531,7 @@
           | Cons !Int Doc Docs -- ^ Indentation, document and tail
 
 best :: Int -> Int -> Doc -> RDoc
-best w k x = be Nothing Nothing k id (Cons 0 x Nil)
+best !w k x = be Nothing Nothing k id (Cons 0 x Nil)
   where
     be :: Maybe Pos -- ^ Previous source position
        -> Maybe Pos -- ^ Current source position
@@ -538,18 +539,15 @@
        -> RDocS
        -> Docs
        -> RDoc
-    be  _ _  _  f Nil           = f REmpty
-    be  p p' k  f (Cons i d ds) =
+    be  _ _  !_  f Nil           = f REmpty
+    be  p p' !k  f (Cons i d ds) =
         case d of
           Empty      -> be p p' k f ds
-          Char c     -> let k' = k + 1 in
-                        k' `seq` be p p' k' (f . RChar c) ds
-          Text l s   -> let k' = k + l in
-                        k' `seq` be p p' k' (f . RText l s) ds
+          Char c     -> be p p' (k+1) (f . RChar c) ds
+          Text l s   -> be p p' (k+l) (f . RText l s) ds
           Line       -> (f . pragma . RLine i) (be p'' Nothing i id ds)
           x `Cat` y  -> be p p' k f (Cons i x (Cons i y ds))
-          Nest j x   -> let j' = i + j in
-                        j' `seq` be p p' k f (Cons j' x ds)
+          Nest j x   -> be p p' k f (Cons (i+j) x ds)
           x `Alt` y  -> better k f (be p p' k id (Cons i x ds))
                                    (be p p' k id (Cons i y ds))
           SrcLoc loc -> be p (merge p' loc) k f ds
@@ -559,16 +557,28 @@
         (p'', pragma) = lineloc p p'
 
     better :: Int -> RDocS -> RDoc -> RDoc -> RDoc
-    better k f x y | fits (w - k) x = f x
-                   | otherwise      = f y
+    better !k f x y | fits (w - k) x = f x
+                    | otherwise      = f y
 
     fits :: Int -> RDoc -> Bool
-    fits  w  _        | w < 0 = False
-    fits  _  REmpty           = True
-    fits  w  (RChar _ x)      = fits (w - 1) x
-    fits  w  (RText l _ x)    = fits (w - l) x
-    fits  w  (RPos _ x)       = fits w x
-    fits  _  (RLine _ _)      = True
+    fits  !w  _        | w < 0 = False
+    fits  !_  REmpty           = True
+    fits  !w  (RChar _ x)      = fits (w - 1) x
+    fits  !w  (RText l _ x)    = fits (w - l) x
+    fits  !w  (RPos _ x)       = fits w x
+    fits  !_  (RLine _ _)      = True
+
+#if MIN_VERSION_base(4,5,0)
+#else
+infixr 6 <>
+
+(<>) :: Doc -> Doc -> Doc
+x <> y = x `Cat` y
+#endif
+
+instance Monoid Doc where
+    mempty  = empty
+    mappend = Cat
 
 class Pretty a where
     ppr     :: a -> Doc
diff --git a/mainland-pretty.cabal b/mainland-pretty.cabal
--- a/mainland-pretty.cabal
+++ b/mainland-pretty.cabal
@@ -1,9 +1,9 @@
 name:           mainland-pretty
-version:        0.1.1.1
+version:        0.1.2.0
 cabal-version:  >= 1.6
 license:        BSD3
 license-file:   LICENSE
-copyright:      (c) 2006-2010 Harvard University
+copyright:      (c) 2006-2012 Harvard University
 author:         Geoffrey Mainland <mainland@eecs.harvard.edu>
 maintainer:     mainland@eecs.harvard.edu
 stability:      alpha