[project @ 2001-12-21 15:07:20 by simonmar]

[ghc-base.git] / GHC / Arr.lhs

diff --git a/GHC/Arr.lhs b/GHC/Arr.lhs
index 940b603..bc8b809 100644 (file)
--- a/GHC/Arr.lhs
+++ b/GHC/Arr.lhs
@@ -1,5 +1,5 @@
 % -----------------------------------------------------------------------------
-% $Id: Arr.lhs,v 1.1 2001/06/28 14:15:03 simonmar Exp $
+% $Id: Arr.lhs,v 1.2 2001/12/21 15:07:22 simonmar Exp $
 %
 % (c) The University of Glasgow, 1994-2000
 %
@@ -37,17 +37,38 @@ default ()
 %*********************************************************
 
 \begin{code}
-class  (Ord a) => Ix a  where
+class (Ord a) => Ix a where
     range              :: (a,a) -> [a]
     index, unsafeIndex :: (a,a) -> a -> Int
     inRange            :: (a,a) -> a -> Bool
+    rangeSize          :: (a,a) -> Int
+    unsafeRangeSize     :: (a,a) -> Int
 
        -- Must specify one of index, unsafeIndex
     index b i | inRange b i = unsafeIndex b i
              | otherwise   = error "Error in array index"
     unsafeIndex b i = index b i
+
+       -- As long as you don't override the default rangeSize, 
+       -- you can specify unsafeRangeSize as follows, to speed up
+       -- some operations:
+       --
+       --    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+       --
+    rangeSize b@(_l,h) | inRange b h = unsafeIndex b h + 1
+                      | otherwise   = 0
+    unsafeRangeSize b = rangeSize b
 \end{code}
 
+Note that the following is NOT right
+       rangeSize (l,h) | l <= h    = index b h + 1
+                       | otherwise = 0
+
+Because it might be the case that l<h, but the range
+is nevertheless empty.  Consider
+       ((1,2),(2,1))
+Here l<h, but the second index ranges from 2..1 and
+hence is empty
 
 %*********************************************************
 %*                                                     *
@@ -80,6 +101,8 @@ instance  Ix Char  where
 
     inRange (m,n) i    =  m <= i && i <= n
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+
 ----------------------------------------------------------------------
 instance  Ix Int  where
     {-# INLINE range #-}
@@ -96,6 +119,8 @@ instance  Ix Int  where
     {-# INLINE inRange #-}
     inRange (I# m,I# n) (I# i) =  m <=# i && i <=# n
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+
 ----------------------------------------------------------------------
 instance  Ix Integer  where
     {-# INLINE range #-}
@@ -109,6 +134,7 @@ instance  Ix Integer  where
 
     inRange (m,n) i    =  m <= i && i <= n
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
 
 ----------------------------------------------------------------------
 instance Ix Bool where -- as derived
@@ -123,6 +149,8 @@ instance Ix Bool where -- as derived
 
     inRange (l,u) i = fromEnum i >= fromEnum l && fromEnum i <= fromEnum u
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+
 ----------------------------------------------------------------------
 instance Ix Ordering where -- as derived
     {-# INLINE range #-}
@@ -136,6 +164,8 @@ instance Ix Ordering where -- as derived
 
     inRange (l,u) i = fromEnum i >= fromEnum l && fromEnum i <= fromEnum u
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+
 ----------------------------------------------------------------------
 instance Ix () where
     {-# INLINE range #-}
@@ -147,6 +177,7 @@ instance Ix () where
     {-# INLINE index #-}
     index b i = unsafeIndex b i
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
 
 ----------------------------------------------------------------------
 instance (Ix a, Ix b) => Ix (a, b) where -- as derived
@@ -164,6 +195,8 @@ instance (Ix a, Ix b) => Ix (a, b) where -- as derived
     inRange ((l1,l2),(u1,u2)) (i1,i2) =
       inRange (l1,u1) i1 && inRange (l2,u2) i2
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+
     -- Default method for index
 
 ----------------------------------------------------------------------
@@ -184,6 +217,8 @@ instance  (Ix a1, Ix a2, Ix a3) => Ix (a1,a2,a3)  where
       inRange (l1,u1) i1 && inRange (l2,u2) i2 &&
       inRange (l3,u3) i3
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+
     -- Default method for index
 
 ----------------------------------------------------------------------
@@ -204,6 +239,8 @@ instance  (Ix a1, Ix a2, Ix a3, Ix a4) => Ix (a1,a2,a3,a4)  where
       inRange (l1,u1) i1 && inRange (l2,u2) i2 &&
       inRange (l3,u3) i3 && inRange (l4,u4) i4
 
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
+
     -- Default method for index
 
 instance  (Ix a1, Ix a2, Ix a3, Ix a4, Ix a5) => Ix (a1,a2,a3,a4,a5)  where
@@ -226,40 +263,9 @@ instance  (Ix a1, Ix a2, Ix a3, Ix a4, Ix a5) => Ix (a1,a2,a3,a4,a5)  where
       inRange (l3,u3) i3 && inRange (l4,u4) i4 && 
       inRange (l5,u5) i5
 
-    -- Default method for index
-\end{code}
-
+    unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
 
-%********************************************************
-%*                                                     *
-\subsection{Size of @Ix@ interval}
-%*                                                     *
-%********************************************************
-
-The @rangeSize@ operator returns the number of elements
-in the range for an @Ix@ pair.
-
-\begin{code}
-{-# SPECIALISE unsafeRangeSize :: (Int,Int) -> Int #-}
-{-# SPECIALISE unsafeRangeSize :: ((Int,Int),(Int,Int)) -> Int #-}
-unsafeRangeSize :: (Ix a) => (a,a) -> Int
-unsafeRangeSize b@(_l,h) = unsafeIndex b h + 1
-
-{-# SPECIALISE rangeSize :: (Int,Int) -> Int #-}
-{-# SPECIALISE rangeSize :: ((Int,Int),(Int,Int)) -> Int #-}
-rangeSize :: (Ix a) => (a,a) -> Int
-rangeSize b@(_l,h) | inRange b h = unsafeIndex b h + 1
-                  | otherwise   = 0
-
--- Note that the following is NOT right
---     rangeSize (l,h) | l <= h    = index b h + 1
---                     | otherwise = 0
---
--- Because it might be the case that l<h, but the range
--- is nevertheless empty.  Consider
---     ((1,2),(2,1))
--- Here l<h, but the second index ranges from 2..1 and
--- hence is empty
+    -- Default method for index
 \end{code}
 
 %*********************************************************