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diff --git a/GHC/PArr.hs b/GHC/PArr.hs
index d385d84..bb031c0 100644
--- a/GHC/PArr.hs
+++ b/GHC/PArr.hs
@@ -1,11 +1,17 @@
---  $Id: PArr.hs,v 1.1 2002/02/11 17:11:12 simonmar Exp $
---
---  Copyright (c) [2001..2002] Manuel M T Chakravarty & Gabriele Keller
+{-# OPTIONS_GHC -fparr #-}
+
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  GHC.PArr
+-- Copyright   :  (c) 2001-2002 Manuel M T Chakravarty & Gabriele Keller
+-- License     :  see libraries/base/LICENSE
+-- 
+-- Maintainer  :  Manuel M. T. Chakravarty <chak@cse.unsw.edu.au>
+-- Stability   :  internal
+-- Portability :  non-portable (GHC Extensions)
 --
 --  Basic implementation of Parallel Arrays.
 --
---- DESCRIPTION ---------------------------------------------------------------
---
 --  This module has two functions: (1) It defines the interface to the
 --  parallel array extension of the Prelude and (2) it provides a vanilla
 --  implementation of parallel arrays that does not require to flatten the
@@ -65,10 +71,8 @@
 --  * We might want to add bounds checks that can be deactivated.
 --
 
-{-# OPTIONS -fno-implicit-prelude #-}
-
 module GHC.PArr (
-  [::],			-- abstract
+  -- [::],		-- Built-in syntax
 
   mapP,			-- :: (a -> b) -> [:a:] -> [:b:]
   (+:+),		-- :: [:a:] -> [:a:] -> [:a:]
@@ -136,11 +140,11 @@ module GHC.PArr (
   indexOfP		-- :: (a -> Bool) -> [:a:] -> [:Int:]
 ) where
 
-import PrelBase
-import PrelST   (ST(..), STRep, runST)
-import PrelList
-import PrelShow
-import PrelRead
+import Prelude
+
+import GHC.ST   ( ST(..), STRep, runST )
+import GHC.Exts	( Int#, Array#, Int(I#), MutableArray#, newArray#,
+		  unsafeFreezeArray#, indexArray#, writeArray# )
 
 infixl 9  !:
 infixr 5  +:+
@@ -212,7 +216,7 @@ scanlP     :: (a -> b -> a) -> a -> [:b:] -> [:a:]
 scanlP f z  = fst . loop (scanEFL (flip f)) z
 
 scanl1P        :: (a -> a -> a) -> [:a:] -> [:a:]
-acanl1P f [::]  = error "Prelude.scanl1P: empty array"
+scanl1P f [::]  = error "Prelude.scanl1P: empty array"
 scanl1P f a     = fst $ loopFromTo 1 (lengthP a - 1) (scanEFL f) (a!:0) a
 
 foldrP :: (a -> b -> b) -> b -> [:a:] -> b
@@ -293,7 +297,7 @@ sumP :: (Num a) => [:a:] -> a
 sumP  = foldP (+) 0
 
 productP :: (Num a) => [:a:] -> a
-productP  = foldP (*) 0
+productP  = foldP (*) 1
 
 maximumP      :: (Ord a) => [:a:] -> a
 maximumP [::]  = error "Prelude.maximumP: empty parallel array"
@@ -398,7 +402,7 @@ instance Read a => Read [:a:]  where
 -- Ideally, we would like `enumFromToP' and `enumFromThenToP' to be members of
 -- `Enum'.  On the other hand, we really do not want to change `Enum'.  Thus,
 -- for the moment, we hope that the compiler is sufficiently clever to
--- properly fuse the following definition.
+-- properly fuse the following definitions.
 
 enumFromToP	:: Enum a => a -> a -> [:a:]
 enumFromToP x y  = mapP toEnum (eftInt (fromEnum x) (fromEnum y))
@@ -410,7 +414,7 @@ enumFromThenToP x y z  =
   mapP toEnum (efttInt (fromEnum x) (fromEnum y) (fromEnum z))
   where
     efttInt x y z = scanlP (+) x $ 
-		      replicateP ((z - x + 1) `div` delta - 1) delta
+		      replicateP (abs (z - x) `div` abs delta + 1) delta
       where
        delta = y - x
 
@@ -566,7 +570,7 @@ loopFromTo from to mf start arr = runST (do
 	     -- unlike standard Haskell arrays, this value represents an
 	     -- internal error
 
--- actually loop body of `loop'
+-- actual loop body of `loop'
 --
 -- * for this to be really efficient, it has to be translated with the
 --   constructor specialisation phase "SpecConstr" switched on; as of GHC 5.03