+% -----------------------------------------------------------------------------
+% $Id: PrelArr.lhs,v 1.26 2001/03/25 09:57:24 qrczak Exp $
%
-% (c) The AQUA Project, Glasgow University, 1994-1996
+% (c) The University of Glasgow, 1994-2000
%
+
\section[PrelArr]{Module @PrelArr@}
Array implementation, @PrelArr@ exports the basic array
types and operations.
+For byte-arrays see @PrelByteArr@.
+
\begin{code}
{-# OPTIONS -fno-implicit-prelude #-}
module PrelArr where
import {-# SOURCE #-} PrelErr ( error )
-import Ix
-import PrelList (foldl)
+import PrelEnum
+import PrelNum
import PrelST
import PrelBase
-import PrelCCall
-import PrelAddr
-import PrelUnsafeST ( runST )
-import PrelGHC
+import PrelShow
infixl 9 !, //
+
+default ()
\end{code}
+
+%*********************************************************
+%* *
+\subsection{The @Ix@ class}
+%* *
+%*********************************************************
+
\begin{code}
-{-# GENERATE_SPECS array a{~,Int,IPr} b{} #-}
-array :: (Ix a) => (a,a) -> [(a,b)] -> Array a b
+class (Ord a) => Ix a where
+ range :: (a,a) -> [a]
+ index, unsafeIndex :: (a,a) -> a -> Int
+ inRange :: (a,a) -> a -> Bool
+
+ -- 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
+\end{code}
-{-# GENERATE_SPECS (!) a{~,Int,IPr} b{} #-}
-(!) :: (Ix a) => Array a b -> a -> b
-bounds :: (Ix a) => Array a b -> (a,a)
+%*********************************************************
+%* *
+\subsection{Instances of @Ix@}
+%* *
+%*********************************************************
-{-# GENERATE_SPECS (//) a{~,Int,IPr} b{} #-}
-(//) :: (Ix a) => Array a b -> [(a,b)] -> Array a b
+\begin{code}
+-- abstract these errors from the relevant index functions so that
+-- the guts of the function will be small enough to inline.
-{-# GENERATE_SPECS accum a{~,Int,IPr} b{} c{} #-}
-accum :: (Ix a) => (b -> c -> b) -> Array a b -> [(a,c)] -> Array a b
+{-# NOINLINE indexError #-}
+indexError :: Show a => (a,a) -> a -> String -> b
+indexError rng i tp
+ = error (showString "Ix{" . showString tp . showString "}.index: Index " .
+ showParen True (showsPrec 0 i) .
+ showString " out of range " $
+ showParen True (showsPrec 0 rng) "")
-{-# GENERATE_SPECS accumArray a{~,Int,IPr} b{} c{} #-}
-accumArray :: (Ix a) => (b -> c -> b) -> b -> (a,a) -> [(a,c)] -> Array a b
+----------------------------------------------------------------------
+instance Ix Char where
+ {-# INLINE range #-}
+ range (m,n) = [m..n]
+
+ {-# INLINE unsafeIndex #-}
+ unsafeIndex (m,_n) i = fromEnum i - fromEnum m
+
+ index b i | inRange b i = unsafeIndex b i
+ | otherwise = indexError b i "Char"
+
+ inRange (m,n) i = m <= i && i <= n
+
+----------------------------------------------------------------------
+instance Ix Int where
+ {-# INLINE range #-}
+ -- The INLINE stops the build in the RHS from getting inlined,
+ -- so that callers can fuse with the result of range
+ range (m,n) = [m..n]
+
+ {-# INLINE unsafeIndex #-}
+ unsafeIndex (m,_n) i = i - m
+
+ index b i | inRange b i = unsafeIndex b i
+ | otherwise = indexError b i "Int"
+
+ {-# INLINE inRange #-}
+ inRange (I# m,I# n) (I# i) = m <=# i && i <=# n
+
+----------------------------------------------------------------------
+instance Ix Integer where
+ {-# INLINE range #-}
+ range (m,n) = [m..n]
+
+ {-# INLINE unsafeIndex #-}
+ unsafeIndex (m,_n) i = fromInteger (i - m)
+
+ index b i | inRange b i = unsafeIndex b i
+ | otherwise = indexError b i "Integer"
+
+ inRange (m,n) i = m <= i && i <= n
+
+
+----------------------------------------------------------------------
+instance Ix Bool where -- as derived
+ {-# INLINE range #-}
+ range (m,n) = [m..n]
+
+ {-# INLINE unsafeIndex #-}
+ unsafeIndex (l,_) i = fromEnum i - fromEnum l
+
+ index b i | inRange b i = unsafeIndex b i
+ | otherwise = indexError b i "Bool"
+
+ inRange (l,u) i = fromEnum i >= fromEnum l && fromEnum i <= fromEnum u
+
+----------------------------------------------------------------------
+instance Ix Ordering where -- as derived
+ {-# INLINE range #-}
+ range (m,n) = [m..n]
+
+ {-# INLINE unsafeIndex #-}
+ unsafeIndex (l,_) i = fromEnum i - fromEnum l
+
+ index b i | inRange b i = unsafeIndex b i
+ | otherwise = indexError b i "Ordering"
+
+ inRange (l,u) i = fromEnum i >= fromEnum l && fromEnum i <= fromEnum u
+
+----------------------------------------------------------------------
+instance Ix () where
+ {-# INLINE range #-}
+ range ((), ()) = [()]
+ {-# INLINE unsafeIndex #-}
+ unsafeIndex ((), ()) () = 0
+ {-# INLINE inRange #-}
+ inRange ((), ()) () = True
+ {-# INLINE index #-}
+ index b i = unsafeIndex b i
+
+
+----------------------------------------------------------------------
+instance (Ix a, Ix b) => Ix (a, b) where -- as derived
+ {-# SPECIALISE instance Ix (Int,Int) #-}
+
+ {- INLINE range #-}
+ range ((l1,l2),(u1,u2)) =
+ [ (i1,i2) | i1 <- range (l1,u1), i2 <- range (l2,u2) ]
+
+ {- INLINE unsafeIndex #-}
+ unsafeIndex ((l1,l2),(u1,u2)) (i1,i2) =
+ unsafeIndex (l1,u1) i1 * unsafeRangeSize (l2,u2) + unsafeIndex (l2,u2) i2
+
+ {- INLINE inRange #-}
+ inRange ((l1,l2),(u1,u2)) (i1,i2) =
+ inRange (l1,u1) i1 && inRange (l2,u2) i2
+
+ -- Default method for index
+
+----------------------------------------------------------------------
+instance (Ix a1, Ix a2, Ix a3) => Ix (a1,a2,a3) where
+ {-# SPECIALISE instance Ix (Int,Int,Int) #-}
+
+ range ((l1,l2,l3),(u1,u2,u3)) =
+ [(i1,i2,i3) | i1 <- range (l1,u1),
+ i2 <- range (l2,u2),
+ i3 <- range (l3,u3)]
+
+ unsafeIndex ((l1,l2,l3),(u1,u2,u3)) (i1,i2,i3) =
+ unsafeIndex (l3,u3) i3 + unsafeRangeSize (l3,u3) * (
+ unsafeIndex (l2,u2) i2 + unsafeRangeSize (l2,u2) * (
+ unsafeIndex (l1,u1) i1))
+
+ inRange ((l1,l2,l3),(u1,u2,u3)) (i1,i2,i3) =
+ inRange (l1,u1) i1 && inRange (l2,u2) i2 &&
+ inRange (l3,u3) i3
+
+ -- Default method for index
+
+----------------------------------------------------------------------
+instance (Ix a1, Ix a2, Ix a3, Ix a4) => Ix (a1,a2,a3,a4) where
+ range ((l1,l2,l3,l4),(u1,u2,u3,u4)) =
+ [(i1,i2,i3,i4) | i1 <- range (l1,u1),
+ i2 <- range (l2,u2),
+ i3 <- range (l3,u3),
+ i4 <- range (l4,u4)]
+
+ unsafeIndex ((l1,l2,l3,l4),(u1,u2,u3,u4)) (i1,i2,i3,i4) =
+ unsafeIndex (l4,u4) i4 + unsafeRangeSize (l4,u4) * (
+ unsafeIndex (l3,u3) i3 + unsafeRangeSize (l3,u3) * (
+ unsafeIndex (l2,u2) i2 + unsafeRangeSize (l2,u2) * (
+ unsafeIndex (l1,u1) i1)))
+
+ inRange ((l1,l2,l3,l4),(u1,u2,u3,u4)) (i1,i2,i3,i4) =
+ inRange (l1,u1) i1 && inRange (l2,u2) i2 &&
+ inRange (l3,u3) i3 && inRange (l4,u4) i4
+
+ -- Default method for index
+
+instance (Ix a1, Ix a2, Ix a3, Ix a4, Ix a5) => Ix (a1,a2,a3,a4,a5) where
+ range ((l1,l2,l3,l4,l5),(u1,u2,u3,u4,u5)) =
+ [(i1,i2,i3,i4,i5) | i1 <- range (l1,u1),
+ i2 <- range (l2,u2),
+ i3 <- range (l3,u3),
+ i4 <- range (l4,u4),
+ i5 <- range (l5,u5)]
+
+ unsafeIndex ((l1,l2,l3,l4,l5),(u1,u2,u3,u4,u5)) (i1,i2,i3,i4,i5) =
+ unsafeIndex (l5,u5) i5 + unsafeRangeSize (l5,u5) * (
+ unsafeIndex (l4,u4) i4 + unsafeRangeSize (l4,u4) * (
+ unsafeIndex (l3,u3) i3 + unsafeRangeSize (l3,u3) * (
+ unsafeIndex (l2,u2) i2 + unsafeRangeSize (l2,u2) * (
+ unsafeIndex (l1,u1) i1))))
+
+ inRange ((l1,l2,l3,l4,l5),(u1,u2,u3,u4,u5)) (i1,i2,i3,i4,i5) =
+ inRange (l1,u1) i1 && inRange (l2,u2) i2 &&
+ inRange (l3,u3) i3 && inRange (l4,u4) i4 &&
+ inRange (l5,u5) i5
+
+ -- Default method for index
\end{code}
+%********************************************************
+%* *
+\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
+\end{code}
+
+
+
%*********************************************************
%* *
\subsection{The @Array@ types}
\begin{code}
type IPr = (Int, Int)
-data Ix ix => Array ix elt = Array (ix,ix) (Array# elt)
-data Ix ix => ByteArray ix = ByteArray (ix,ix) ByteArray#
-data Ix ix => MutableArray s ix elt = MutableArray (ix,ix) (MutableArray# s elt)
-data Ix ix => MutableByteArray s ix = MutableByteArray (ix,ix) (MutableByteArray# s)
+data Ix ix => Array ix elt = Array ix ix (Array# elt)
+data Ix ix => STArray s ix elt = STArray ix ix (MutableArray# s elt)
+
+-- Mutterings about dependent types... ignore!
+-- Array :: ix -> ix -> Array# elt -> Array
+-- Array :: forall { l::int, h::int, l<=h } Int(l) -> Int(h) -> Array#(h-l+1) -> Array(l,h)
+-- Array :: forall { l1,l2::int, h1,h2::int, l1<=h1+1,l2<=h2+1 }
+-- (Int(l1),Int(l2)) -> (Int(h1),Int(h2)) -> Array#((h1-l1+1)*(h2-l2+1)) -> Array(l1,h1,l2,h2)
-instance CCallable (MutableByteArray s ix)
-instance CCallable (MutableByteArray# s)
-instance CCallable (ByteArray ix)
-instance CCallable ByteArray#
+data STRef s a = STRef (MutVar# s a)
--- A one-element mutable array:
-type MutableVar s a = MutableArray s Int a
+instance Eq (STRef s a) where
+ STRef v1# == STRef v2#
+ = sameMutVar# v1# v2#
-- just pointer equality on arrays:
-instance Eq (MutableArray s ix elt) where
- MutableArray _ arr1# == MutableArray _ arr2#
+instance Eq (STArray s ix elt) where
+ STArray _ _ arr1# == STArray _ _ arr2#
= sameMutableArray# arr1# arr2#
-
-instance Eq (MutableByteArray s ix) where
- MutableByteArray _ arr1# == MutableByteArray _ arr2#
- = sameMutableByteArray# arr1# arr2#
\end{code}
%*********************************************************
%*********************************************************
\begin{code}
-newVar :: a -> ST s (MutableVar s a)
-readVar :: MutableVar s a -> ST s a
-writeVar :: MutableVar s a -> a -> ST s ()
+newSTRef :: a -> ST s (STRef s a)
+readSTRef :: STRef s a -> ST s a
+writeSTRef :: STRef s a -> a -> ST s ()
-newVar init = ST $ \ s# ->
- case (newArray# 1# init s#) of { StateAndMutableArray# s2# arr# ->
- STret s2# (MutableArray vAR_IXS arr#) }
- where
- vAR_IXS = error "newVar: Shouldn't access `bounds' of a MutableVar\n"
+newSTRef init = ST $ \ s# ->
+ case (newMutVar# init s#) of { (# s2#, var# #) ->
+ (# s2#, STRef var# #) }
-readVar (MutableArray _ var#) = ST $ \ s# ->
- case readArray# var# 0# s# of { StateAndPtr# s2# r ->
- STret s2# r }
+readSTRef (STRef var#) = ST $ \ s# -> readMutVar# var# s#
-writeVar (MutableArray _ var#) val = ST $ \ s# ->
- case writeArray# var# 0# val s# of { s2# ->
- STret s2# () }
+writeSTRef (STRef var#) val = ST $ \ s# ->
+ case writeMutVar# var# val s# of { s2# ->
+ (# s2#, () #) }
\end{code}
%*********************************************************
"array", "!" and "bounds" are basic; the rest can be defined in terms of them
\begin{code}
-bounds (Array b _) = b
+bounds :: (Ix a) => Array a b -> (a,a)
+{-# INLINE bounds #-}
+bounds (Array l u _) = (l,u)
+
+assocs :: (Ix a) => Array a b -> [(a,b)]
+{-# INLINE assocs #-} -- Want to fuse the list comprehension
+assocs a = [(i, a!i) | i <- indices a]
+
+indices :: (Ix a) => Array a b -> [a]
+{-# INLINE indices #-}
+indices = range . bounds
-(Array bounds arr#) ! i
- = let n# = case (index bounds i) of { I# x -> x } -- index fails if out of range
+{-# SPECIALISE amap :: (b -> c) -> Array Int b -> Array Int c #-}
+amap :: (Ix a) => (b -> c) -> Array a b -> Array a c
+amap f a = array b [(i, f (a!i)) | i <- range b]
+ where b = bounds a
+
+{-# SPECIALISE (!) :: Array Int b -> Int -> b #-}
+(!) :: (Ix a) => Array a b -> a -> b
+(Array l u arr#) ! i
+ = let n# = case (index (l,u) i) of { I# x -> x } -- index fails if out of range
in
case (indexArray# arr# n#) of
- Lift v -> v
+ (# v #) -> v
-#ifdef USE_FOLDR_BUILD
-{-# INLINE array #-}
-#endif
-array ixs@(ix_start, ix_end) ivs =
- runST ( ST $ \ s ->
- case (newArray ixs arrEleBottom) of { ST new_array_thing ->
- case (new_array_thing s) of { STret s# arr@(MutableArray _ arr#) ->
- let
- fill_in s# [] = s#
- fill_in s# ((i,v):ivs) =
- case (index ixs i) of { I# n# ->
- case writeArray# arr# n# v s# of { s2# ->
- fill_in s2# ivs }}
- in
-
- case (fill_in s# ivs) of { s# ->
- case (freezeArray arr) of { ST freeze_array_thing ->
- freeze_array_thing s# }}}})
+array :: (Ix a) => (a,a) -> [(a,b)] -> Array a b
+{-# INLINE array #-}
+array ixs ivs
+ = case rangeSize ixs of { I# n ->
+ runST ( ST $ \ s1 ->
+ case newArray# n arrEleBottom s1 of { (# s2, marr #) ->
+ foldr (fill ixs marr) (done ixs marr) ivs s2
+ })}
+
+fill :: Ix ix => (ix,ix) -> MutableArray# s elt
+ -> (ix,elt) -> STRep s a -> STRep s a
+{-# INLINE fill #-}
+fill ixs marr (i,v) next = \s1 -> case index ixs i of { I# n ->
+ case writeArray# marr n v s1 of { s2 ->
+ next s2 }}
+
+done :: Ix ix => (ix,ix) -> MutableArray# s elt
+ -> STRep s (Array ix elt)
+{-# INLINE done #-}
+done (l,u) marr = \s1 ->
+ case unsafeFreezeArray# marr s1 of { (# s2, arr #) ->
+ (# s2, Array l u arr #) }
+
+arrEleBottom :: a
arrEleBottom = error "(Array.!): undefined array element"
-fill_it_in :: Ix ix => MutableArray s ix elt -> [(ix, elt)] -> ST s ()
-fill_it_in arr lst
- = foldr fill_one_in (return ()) lst
- where -- **** STRICT **** (but that's OK...)
- fill_one_in (i, v) rst
- = writeArray arr i v >> rst
-----------------------------------------------------------------------
--- these also go better with magic: (//), accum, accumArray
+-- These also go better with magic: (//), accum, accumArray
+-- *** NB *** We INLINE them all so that their foldr's get to the call site
+(//) :: (Ix a) => Array a b -> [(a,b)] -> Array a b
+{-# INLINE (//) #-}
old_array // ivs
= runST (do
-- copy the old array:
- arr <- thawArray old_array
+ arr <- thawSTArray old_array
-- now write the new elements into the new array:
- fill_it_in arr ivs
- freezeArray arr
+ foldr (fill_one_in arr) (unsafeFreezeSTArray arr) ivs
)
- where
- bottom = error "(Array.//): error in copying old array\n"
-zap_with_f :: Ix ix => (elt -> elt2 -> elt) -> MutableArray s ix elt -> [(ix,elt2)] -> ST s ()
+{-# INLINE fill_one_in #-}
+fill_one_in :: Ix ix => STArray s ix e -> (ix, e) -> ST s a -> ST s a
+fill_one_in arr (i, v) next = writeSTArray arr i v >> next
+
+zap_with_f :: Ix ix => (elt -> elt2 -> elt) -> STArray s ix elt -> [(ix,elt2)] -> ST s ()
-- zap_with_f: reads an elem out first, then uses "f" on that and the new value
+{-# INLINE zap_with_f #-}
zap_with_f f arr lst
- = foldr zap_one (return ()) lst
- where
- zap_one (i, new_v) rst = do
- old_v <- readArray arr i
- writeArray arr i (f old_v new_v)
+ = foldr (zap_one f arr) (return ()) lst
+
+zap_one f arr (i, new_v) rst = do
+ old_v <- readSTArray arr i
+ writeSTArray arr i (f old_v new_v)
rst
+accum :: (Ix a) => (b -> c -> b) -> Array a b -> [(a,c)] -> Array a b
+{-# INLINE accum #-}
accum f old_array ivs
= runST (do
-- copy the old array:
- arr <- thawArray old_array
+ arr <- thawSTArray old_array
-- now zap the elements in question with "f":
zap_with_f f arr ivs
- freezeArray arr
+ unsafeFreezeSTArray arr
)
- where
- bottom = error "Array.accum: error in copying old array\n"
+
+accumArray :: (Ix a) => (b -> c -> b) -> b -> (a,a) -> [(a,c)] -> Array a b
+{-# INLINE accumArray #-}
accumArray f zero ixs ivs
= runST (do
- arr# <- newArray ixs zero
- zap_with_f f arr# ivs
- freezeArray arr#
+ arr <- newSTArray ixs zero
+ zap_with_f f arr ivs
+ unsafeFreezeSTArray arr
)
\end{code}
%*********************************************************
%* *
+\subsection{Array instances}
+%* *
+%*********************************************************
+
+
+\begin{code}
+instance Ix a => Functor (Array a) where
+ fmap = amap
+
+instance (Ix a, Eq b) => Eq (Array a b) where
+ a == a' = assocs a == assocs a'
+ a /= a' = assocs a /= assocs a'
+
+instance (Ix a, Ord b) => Ord (Array a b) where
+ compare a b = compare (assocs a) (assocs b)
+
+instance (Ix a, Show a, Show b) => Show (Array a b) where
+ showsPrec p a = showParen (p > 9) (
+ showString "array " .
+ shows (bounds a) . showChar ' ' .
+ shows (assocs a) )
+
+{-
+instance (Ix a, Read a, Read b) => Read (Array a b) where
+ readsPrec p = readParen (p > 9)
+ (\r -> [(array b as, u) | ("array",s) <- lex r,
+ (b,t) <- reads s,
+ (as,u) <- reads t ])
+-}
+\end{code}
+
+
+%*********************************************************
+%* *
\subsection{Operations on mutable arrays}
%* *
%*********************************************************
Idle ADR question: What's the tradeoff here between flattening these
-datatypes into @MutableArray ix ix (MutableArray# s elt)@ and using
+datatypes into @STArray ix ix (MutableArray# s elt)@ and using
it as is? As I see it, the former uses slightly less heap and
provides faster access to the individual parts of the bounds while the
code used has the benefit of providing a ready-made @(lo, hi)@ pair as
might be different, though.
\begin{code}
-newArray :: Ix ix => (ix,ix) -> elt -> ST s (MutableArray s ix elt)
-newCharArray, newIntArray, newAddrArray, newFloatArray, newDoubleArray
- :: Ix ix => (ix,ix) -> ST s (MutableByteArray s ix)
+newSTArray :: Ix ix => (ix,ix) -> elt -> ST s (STArray s ix elt)
-{-# SPECIALIZE newArray :: IPr -> elt -> ST s (MutableArray s Int elt),
- (IPr,IPr) -> elt -> ST s (MutableArray s IPr elt)
+{-# SPECIALIZE newSTArray :: IPr -> elt -> ST s (STArray s Int elt),
+ (IPr,IPr) -> elt -> ST s (STArray s IPr elt)
#-}
-{-# SPECIALIZE newCharArray :: IPr -> ST s (MutableByteArray s Int) #-}
-{-# SPECIALIZE newIntArray :: IPr -> ST s (MutableByteArray s Int) #-}
-{-# SPECIALIZE newAddrArray :: IPr -> ST s (MutableByteArray s Int) #-}
-{-# SPECIALIZE newFloatArray :: IPr -> ST s (MutableByteArray s Int) #-}
-{-# SPECIALIZE newDoubleArray :: IPr -> ST s (MutableByteArray s Int) #-}
-
-newArray ixs init = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case (newArray# n# init s#) of { StateAndMutableArray# s2# arr# ->
- STret s2# (MutableArray ixs arr#) }}
-
-newCharArray ixs = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case (newCharArray# n# s#) of { StateAndMutableByteArray# s2# barr# ->
- STret s2# (MutableByteArray ixs barr#) }}
-
-newIntArray ixs = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case (newIntArray# n# s#) of { StateAndMutableByteArray# s2# barr# ->
- STret s2# (MutableByteArray ixs barr#) }}
-
-newAddrArray ixs = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case (newAddrArray# n# s#) of { StateAndMutableByteArray# s2# barr# ->
- STret s2# (MutableByteArray ixs barr#) }}
-
-newFloatArray ixs = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case (newFloatArray# n# s#) of { StateAndMutableByteArray# s2# barr# ->
- STret s2# (MutableByteArray ixs barr#) }}
-
-newDoubleArray ixs = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case (newDoubleArray# n# s#) of { StateAndMutableByteArray# s2# barr# ->
- STret s2# (MutableByteArray ixs barr#) }}
-
-boundsOfArray :: Ix ix => MutableArray s ix elt -> (ix, ix)
-boundsOfByteArray :: Ix ix => MutableByteArray s ix -> (ix, ix)
-
-{-# SPECIALIZE boundsOfArray :: MutableArray s Int elt -> IPr #-}
-{-# SPECIALIZE boundsOfByteArray :: MutableByteArray s Int -> IPr #-}
-
-boundsOfArray (MutableArray ixs _) = ixs
-boundsOfByteArray (MutableByteArray ixs _) = ixs
-
-readArray :: Ix ix => MutableArray s ix elt -> ix -> ST s elt
-
-readCharArray :: Ix ix => MutableByteArray s ix -> ix -> ST s Char
-readIntArray :: Ix ix => MutableByteArray s ix -> ix -> ST s Int
-readAddrArray :: Ix ix => MutableByteArray s ix -> ix -> ST s Addr
-readFloatArray :: Ix ix => MutableByteArray s ix -> ix -> ST s Float
-readDoubleArray :: Ix ix => MutableByteArray s ix -> ix -> ST s Double
-
-{-# SPECIALIZE readArray :: MutableArray s Int elt -> Int -> ST s elt,
- MutableArray s IPr elt -> IPr -> ST s elt
+newSTArray (l,u) init = ST $ \ s# ->
+ case rangeSize (l,u) of { I# n# ->
+ case (newArray# n# init s#) of { (# s2#, arr# #) ->
+ (# s2#, STArray l u arr# #) }}
+
+
+
+boundsSTArray :: Ix ix => STArray s ix elt -> (ix, ix)
+{-# SPECIALIZE boundsSTArray :: STArray s Int elt -> IPr #-}
+boundsSTArray (STArray l u _) = (l,u)
+
+readSTArray :: Ix ix => STArray s ix elt -> ix -> ST s elt
+{-# SPECIALIZE readSTArray :: STArray s Int elt -> Int -> ST s elt,
+ STArray s IPr elt -> IPr -> ST s elt
#-}
-{-# SPECIALIZE readCharArray :: MutableByteArray s Int -> Int -> ST s Char #-}
-{-# SPECIALIZE readIntArray :: MutableByteArray s Int -> Int -> ST s Int #-}
-{-# SPECIALIZE readAddrArray :: MutableByteArray s Int -> Int -> ST s Addr #-}
---NO:{-# SPECIALIZE readFloatArray :: MutableByteArray s Int -> Int -> ST s Float #-}
-{-# SPECIALIZE readDoubleArray :: MutableByteArray s Int -> Int -> ST s Double #-}
-
-readArray (MutableArray ixs arr#) n = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case readArray# arr# n# s# of { StateAndPtr# s2# r ->
- STret s2# r }}
-
-readCharArray (MutableByteArray ixs barr#) n = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case readCharArray# barr# n# s# of { StateAndChar# s2# r# ->
- STret s2# (C# r#) }}
-
-readIntArray (MutableByteArray ixs barr#) n = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case readIntArray# barr# n# s# of { StateAndInt# s2# r# ->
- STret s2# (I# r#) }}
-
-readAddrArray (MutableByteArray ixs barr#) n = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case readAddrArray# barr# n# s# of { StateAndAddr# s2# r# ->
- STret s2# (A# r#) }}
-
-readFloatArray (MutableByteArray ixs barr#) n = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case readFloatArray# barr# n# s# of { StateAndFloat# s2# r# ->
- STret s2# (F# r#) }}
-
-readDoubleArray (MutableByteArray ixs barr#) n = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case readDoubleArray# barr# n# s# of { StateAndDouble# s2# r# ->
- STret s2# (D# r#) }}
-
---Indexing of ordinary @Arrays@ is standard Haskell and isn't defined here.
-indexCharArray :: Ix ix => ByteArray ix -> ix -> Char
-indexIntArray :: Ix ix => ByteArray ix -> ix -> Int
-indexAddrArray :: Ix ix => ByteArray ix -> ix -> Addr
-indexFloatArray :: Ix ix => ByteArray ix -> ix -> Float
-indexDoubleArray :: Ix ix => ByteArray ix -> ix -> Double
-
-{-# SPECIALIZE indexCharArray :: ByteArray Int -> Int -> Char #-}
-{-# SPECIALIZE indexIntArray :: ByteArray Int -> Int -> Int #-}
-{-# SPECIALIZE indexAddrArray :: ByteArray Int -> Int -> Addr #-}
---NO:{-# SPECIALIZE indexFloatArray :: ByteArray Int -> Int -> Float #-}
-{-# SPECIALIZE indexDoubleArray :: ByteArray Int -> Int -> Double #-}
-
-indexCharArray (ByteArray ixs barr#) n
- = case (index ixs n) of { I# n# ->
- case indexCharArray# barr# n# of { r# ->
- (C# r#)}}
-
-indexIntArray (ByteArray ixs barr#) n
- = case (index ixs n) of { I# n# ->
- case indexIntArray# barr# n# of { r# ->
- (I# r#)}}
-
-indexAddrArray (ByteArray ixs barr#) n
- = case (index ixs n) of { I# n# ->
- case indexAddrArray# barr# n# of { r# ->
- (A# r#)}}
-
-indexFloatArray (ByteArray ixs barr#) n
- = case (index ixs n) of { I# n# ->
- case indexFloatArray# barr# n# of { r# ->
- (F# r#)}}
-
-indexDoubleArray (ByteArray ixs barr#) n
- = case (index ixs n) of { I# n# ->
- case indexDoubleArray# barr# n# of { r# ->
- (D# r#)}}
-
---Indexing off @Addrs@ is similar, and therefore given here.
-indexCharOffAddr :: Addr -> Int -> Char
-indexIntOffAddr :: Addr -> Int -> Int
-indexAddrOffAddr :: Addr -> Int -> Addr
-indexFloatOffAddr :: Addr -> Int -> Float
-indexDoubleOffAddr :: Addr -> Int -> Double
-
-indexCharOffAddr (A# addr#) n
- = case n of { I# n# ->
- case indexCharOffAddr# addr# n# of { r# ->
- (C# r#)}}
-
-indexIntOffAddr (A# addr#) n
- = case n of { I# n# ->
- case indexIntOffAddr# addr# n# of { r# ->
- (I# r#)}}
-
-indexAddrOffAddr (A# addr#) n
- = case n of { I# n# ->
- case indexAddrOffAddr# addr# n# of { r# ->
- (A# r#)}}
-
-indexFloatOffAddr (A# addr#) n
- = case n of { I# n# ->
- case indexFloatOffAddr# addr# n# of { r# ->
- (F# r#)}}
-
-indexDoubleOffAddr (A# addr#) n
- = case n of { I# n# ->
- case indexDoubleOffAddr# addr# n# of { r# ->
- (D# r#)}}
-
-writeArray :: Ix ix => MutableArray s ix elt -> ix -> elt -> ST s ()
-writeCharArray :: Ix ix => MutableByteArray s ix -> ix -> Char -> ST s ()
-writeIntArray :: Ix ix => MutableByteArray s ix -> ix -> Int -> ST s ()
-writeAddrArray :: Ix ix => MutableByteArray s ix -> ix -> Addr -> ST s ()
-writeFloatArray :: Ix ix => MutableByteArray s ix -> ix -> Float -> ST s ()
-writeDoubleArray :: Ix ix => MutableByteArray s ix -> ix -> Double -> ST s ()
-
-{-# SPECIALIZE writeArray :: MutableArray s Int elt -> Int -> elt -> ST s (),
- MutableArray s IPr elt -> IPr -> elt -> ST s ()
+
+readSTArray (STArray l u arr#) n = ST $ \ s# ->
+ case (index (l,u) n) of { I# n# ->
+ case readArray# arr# n# s# of { (# s2#, r #) ->
+ (# s2#, r #) }}
+
+writeSTArray :: Ix ix => STArray s ix elt -> ix -> elt -> ST s ()
+{-# SPECIALIZE writeSTArray :: STArray s Int elt -> Int -> elt -> ST s (),
+ STArray s IPr elt -> IPr -> elt -> ST s ()
#-}
-{-# SPECIALIZE writeCharArray :: MutableByteArray s Int -> Int -> Char -> ST s () #-}
-{-# SPECIALIZE writeIntArray :: MutableByteArray s Int -> Int -> Int -> ST s () #-}
-{-# SPECIALIZE writeAddrArray :: MutableByteArray s Int -> Int -> Addr -> ST s () #-}
---NO:{-# SPECIALIZE writeFloatArray :: MutableByteArray s Int -> Int -> Float -> ST s () #-}
-{-# SPECIALIZE writeDoubleArray :: MutableByteArray s Int -> Int -> Double -> ST s () #-}
-
-writeArray (MutableArray ixs arr#) n ele = ST $ \ s# ->
- case index ixs n of { I# n# ->
- case writeArray# arr# n# ele s# of { s2# ->
- STret s2# () }}
-
-writeCharArray (MutableByteArray ixs barr#) n (C# ele) = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case writeCharArray# barr# n# ele s# of { s2# ->
- STret s2# () }}
-
-writeIntArray (MutableByteArray ixs barr#) n (I# ele) = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case writeIntArray# barr# n# ele s# of { s2# ->
- STret s2# () }}
-
-writeAddrArray (MutableByteArray ixs barr#) n (A# ele) = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case writeAddrArray# barr# n# ele s# of { s2# ->
- STret s2# () }}
-
-writeFloatArray (MutableByteArray ixs barr#) n (F# ele) = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case writeFloatArray# barr# n# ele s# of { s2# ->
- STret s2# () }}
-
-writeDoubleArray (MutableByteArray ixs barr#) n (D# ele) = ST $ \ s# ->
- case (index ixs n) of { I# n# ->
- case writeDoubleArray# barr# n# ele s# of { s2# ->
- STret s2# () }}
+
+writeSTArray (STArray l u arr#) n ele = ST $ \ s# ->
+ case index (l,u) n of { I# n# ->
+ case writeArray# arr# n# ele s# of { s2# ->
+ (# s2#, () #) }}
\end{code}
%*********************************************************
\begin{code}
-freezeArray :: Ix ix => MutableArray s ix elt -> ST s (Array ix elt)
-freezeCharArray :: Ix ix => MutableByteArray s ix -> ST s (ByteArray ix)
-freezeIntArray :: Ix ix => MutableByteArray s ix -> ST s (ByteArray ix)
-freezeAddrArray :: Ix ix => MutableByteArray s ix -> ST s (ByteArray ix)
-freezeFloatArray :: Ix ix => MutableByteArray s ix -> ST s (ByteArray ix)
-freezeDoubleArray :: Ix ix => MutableByteArray s ix -> ST s (ByteArray ix)
-
-{-# SPECIALISE freezeArray :: MutableArray s Int elt -> ST s (Array Int elt),
- MutableArray s IPr elt -> ST s (Array IPr elt)
+freezeSTArray :: Ix ix => STArray s ix elt -> ST s (Array ix elt)
+{-# SPECIALISE freezeSTArray :: STArray s Int elt -> ST s (Array Int elt),
+ STArray s IPr elt -> ST s (Array IPr elt)
#-}
-{-# SPECIALISE freezeCharArray :: MutableByteArray s Int -> ST s (ByteArray Int) #-}
-freezeArray (MutableArray ixs arr#) = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case freeze arr# n# s# of { StateAndArray# s2# frozen# ->
- STret s2# (Array ixs frozen#) }}
- where
- freeze :: MutableArray# s ele -- the thing
- -> Int# -- size of thing to be frozen
- -> State# s -- the Universe and everything
- -> StateAndArray# s ele
-
- freeze arr# n# s#
- = case newArray# n# init s# of { StateAndMutableArray# s2# newarr1# ->
- case copy 0# n# arr# newarr1# s2# of { StateAndMutableArray# s3# newarr2# ->
- unsafeFreezeArray# newarr2# s3#
- }}
- where
+freezeSTArray (STArray l u arr#) = ST $ \ s# ->
+ case rangeSize (l,u) of { I# n# ->
+ case freeze arr# n# s# of { (# s2#, frozen# #) ->
+ (# s2#, Array l u frozen# #) }}
+
+freeze :: MutableArray# s ele -- the thing
+ -> Int# -- size of thing to be frozen
+ -> State# s -- the Universe and everything
+ -> (# State# s, Array# ele #)
+freeze m_arr# n# s#
+ = case newArray# n# init s# of { (# s2#, newarr1# #) ->
+ case copy 0# n# m_arr# newarr1# s2# of { (# s3#, newarr2# #) ->
+ unsafeFreezeArray# newarr2# s3#
+ }}
+ where
init = error "freezeArray: element not copied"
copy :: Int# -> Int#
- -> MutableArray# s ele -> MutableArray# s ele
+ -> MutableArray# s ele
+ -> MutableArray# s ele
-> State# s
- -> StateAndMutableArray# s ele
+ -> (# State# s, MutableArray# s ele #)
- copy cur# end# from# to# s#
+ copy cur# end# from# to# st#
| cur# ==# end#
- = StateAndMutableArray# s# to#
+ = (# st#, to# #)
| otherwise
- = case readArray# from# cur# s# of { StateAndPtr# s1# ele ->
+ = case readArray# from# cur# st# of { (# s1#, ele #) ->
case writeArray# to# cur# ele s1# of { s2# ->
copy (cur# +# 1#) end# from# to# s2#
}}
-freezeCharArray (MutableByteArray ixs arr#) = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case freeze arr# n# s# of { StateAndByteArray# s2# frozen# ->
- STret s2# (ByteArray ixs frozen#) }}
- where
- freeze :: MutableByteArray# s -- the thing
- -> Int# -- size of thing to be frozen
- -> State# s -- the Universe and everything
- -> StateAndByteArray# s
-
- freeze arr# n# s#
- = case (newCharArray# n# s#) of { StateAndMutableByteArray# s2# newarr1# ->
- case copy 0# n# arr# newarr1# s2# of { StateAndMutableByteArray# s3# newarr2# ->
- unsafeFreezeByteArray# newarr2# s3#
- }}
- where
- copy :: Int# -> Int#
- -> MutableByteArray# s -> MutableByteArray# s
- -> State# s
- -> StateAndMutableByteArray# s
-
- copy cur# end# from# to# s#
- | cur# ==# end#
- = StateAndMutableByteArray# s# to#
- | otherwise
- = case (readCharArray# from# cur# s#) of { StateAndChar# s1# ele ->
- case (writeCharArray# to# cur# ele s1#) of { s2# ->
- copy (cur# +# 1#) end# from# to# s2#
- }}
-
-freezeIntArray (MutableByteArray ixs arr#) = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case freeze arr# n# s# of { StateAndByteArray# s2# frozen# ->
- STret s2# (ByteArray ixs frozen#) }}
- where
- freeze :: MutableByteArray# s -- the thing
- -> Int# -- size of thing to be frozen
- -> State# s -- the Universe and everything
- -> StateAndByteArray# s
-
- freeze arr# n# s#
- = case (newIntArray# n# s#) of { StateAndMutableByteArray# s2# newarr1# ->
- case copy 0# n# arr# newarr1# s2# of { StateAndMutableByteArray# s3# newarr2# ->
- unsafeFreezeByteArray# newarr2# s3#
- }}
- where
- copy :: Int# -> Int#
- -> MutableByteArray# s -> MutableByteArray# s
- -> State# s
- -> StateAndMutableByteArray# s
-
- copy cur# end# from# to# s#
- | cur# ==# end#
- = StateAndMutableByteArray# s# to#
- | otherwise
- = case (readIntArray# from# cur# s#) of { StateAndInt# s1# ele ->
- case (writeIntArray# to# cur# ele s1#) of { s2# ->
- copy (cur# +# 1#) end# from# to# s2#
- }}
-
-freezeAddrArray (MutableByteArray ixs arr#) = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case freeze arr# n# s# of { StateAndByteArray# s2# frozen# ->
- STret s2# (ByteArray ixs frozen#) }}
- where
- freeze :: MutableByteArray# s -- the thing
- -> Int# -- size of thing to be frozen
- -> State# s -- the Universe and everything
- -> StateAndByteArray# s
-
- freeze arr# n# s#
- = case (newAddrArray# n# s#) of { StateAndMutableByteArray# s2# newarr1# ->
- case copy 0# n# arr# newarr1# s2# of { StateAndMutableByteArray# s3# newarr2# ->
- unsafeFreezeByteArray# newarr2# s3#
- }}
- where
- copy :: Int# -> Int#
- -> MutableByteArray# s -> MutableByteArray# s
- -> State# s
- -> StateAndMutableByteArray# s
-
- copy cur# end# from# to# s#
- | cur# ==# end#
- = StateAndMutableByteArray# s# to#
- | otherwise
- = case (readAddrArray# from# cur# s#) of { StateAndAddr# s1# ele ->
- case (writeAddrArray# to# cur# ele s1#) of { s2# ->
- copy (cur# +# 1#) end# from# to# s2#
- }}
-
-freezeFloatArray (MutableByteArray ixs arr#) = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case freeze arr# n# s# of { StateAndByteArray# s2# frozen# ->
- STret s2# (ByteArray ixs frozen#) }}
- where
- freeze :: MutableByteArray# s -- the thing
- -> Int# -- size of thing to be frozen
- -> State# s -- the Universe and everything
- -> StateAndByteArray# s
-
- freeze arr# end# s#
- = case (newFloatArray# end# s#) of { StateAndMutableByteArray# s2# newarr1# ->
- case copy 0# arr# newarr1# s2# of { StateAndMutableByteArray# s3# newarr2# ->
- unsafeFreezeByteArray# newarr2# s3#
- }}
- where
- copy :: Int#
- -> MutableByteArray# s -> MutableByteArray# s
- -> State# s
- -> StateAndMutableByteArray# s
-
- copy cur# from# to# s#
- | cur# ==# end#
- = StateAndMutableByteArray# s# to#
- | otherwise
- = case (readFloatArray# from# cur# s#) of { StateAndFloat# s1# ele ->
- case (writeFloatArray# to# cur# ele s1#) of { s2# ->
- copy (cur# +# 1#) from# to# s2#
- }}
-
-freezeDoubleArray (MutableByteArray ixs arr#) = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case freeze arr# n# s# of { StateAndByteArray# s2# frozen# ->
- STret s2# (ByteArray ixs frozen#) }}
- where
- freeze :: MutableByteArray# s -- the thing
- -> Int# -- size of thing to be frozen
- -> State# s -- the Universe and everything
- -> StateAndByteArray# s
-
- freeze arr# n# s#
- = case (newDoubleArray# n# s#) of { StateAndMutableByteArray# s2# newarr1# ->
- case copy 0# n# arr# newarr1# s2# of { StateAndMutableByteArray# s3# newarr2# ->
- unsafeFreezeByteArray# newarr2# s3#
- }}
- where
- copy :: Int# -> Int#
- -> MutableByteArray# s -> MutableByteArray# s
- -> State# s
- -> StateAndMutableByteArray# s
-
- copy cur# end# from# to# s#
- | cur# ==# end#
- = StateAndMutableByteArray# s# to#
- | otherwise
- = case (readDoubleArray# from# cur# s#) of { StateAndDouble# s1# ele ->
- case (writeDoubleArray# to# cur# ele s1#) of { s2# ->
- copy (cur# +# 1#) end# from# to# s2#
- }}
-
-unsafeFreezeArray :: Ix ix => MutableArray s ix elt -> ST s (Array ix elt)
-unsafeFreezeByteArray :: Ix ix => MutableByteArray s ix -> ST s (ByteArray ix)
-
-{-# SPECIALIZE unsafeFreezeByteArray :: MutableByteArray s Int -> ST s (ByteArray Int)
- #-}
-
-unsafeFreezeArray (MutableArray ixs arr#) = ST $ \ s# ->
- case unsafeFreezeArray# arr# s# of { StateAndArray# s2# frozen# ->
- STret s2# (Array ixs frozen#) }
-
-unsafeFreezeByteArray (MutableByteArray ixs arr#) = ST $ \ s# ->
- case unsafeFreezeByteArray# arr# s# of { StateAndByteArray# s2# frozen# ->
- STret s2# (ByteArray ixs frozen#) }
-
+unsafeFreezeSTArray :: Ix ix => STArray s ix elt -> ST s (Array ix elt)
+unsafeFreezeSTArray (STArray l u arr#) = ST $ \ s# ->
+ case unsafeFreezeArray# arr# s# of { (# s2#, frozen# #) ->
+ (# s2#, Array l u frozen# #) }
--This takes a immutable array, and copies it into a mutable array, in a
--hurry.
-{-# SPECIALISE thawArray :: Array Int elt -> ST s (MutableArray s Int elt),
- Array IPr elt -> ST s (MutableArray s IPr elt)
+thawSTArray :: Ix ix => Array ix elt -> ST s (STArray s ix elt)
+{-# SPECIALISE thawSTArray :: Array Int elt -> ST s (STArray s Int elt),
+ Array IPr elt -> ST s (STArray s IPr elt)
#-}
-thawArray :: Ix ix => Array ix elt -> ST s (MutableArray s ix elt)
-thawArray (Array ixs arr#) = ST $ \ s# ->
- case rangeSize ixs of { I# n# ->
- case thaw arr# n# s# of { StateAndMutableArray# s2# thawed# ->
- STret s2# (MutableArray ixs thawed#)}}
- where
- thaw :: Array# ele -- the thing
- -> Int# -- size of thing to be thawed
- -> State# s -- the Universe and everything
- -> StateAndMutableArray# s ele
+thawSTArray (Array l u arr#) = ST $ \ s# ->
+ case rangeSize (l,u) of { I# n# ->
+ case thaw arr# n# s# of { (# s2#, thawed# #) ->
+ (# s2#, STArray l u thawed# #)}}
+
+thaw :: Array# ele -- the thing
+ -> Int# -- size of thing to be thawed
+ -> State# s -- the Universe and everything
+ -> (# State# s, MutableArray# s ele #)
- thaw arr# n# s#
- = case newArray# n# init s# of { StateAndMutableArray# s2# newarr1# ->
- copy 0# n# arr# newarr1# s2# }
- where
- init = error "thawArray: element not copied"
+thaw arr1# n# s#
+ = case newArray# n# init s# of { (# s2#, newarr1# #) ->
+ copy 0# n# arr1# newarr1# s2# }
+ where
+ init = error "thawSTArray: element not copied"
copy :: Int# -> Int#
-> Array# ele
-> MutableArray# s ele
-> State# s
- -> StateAndMutableArray# s ele
+ -> (# State# s, MutableArray# s ele #)
- copy cur# end# from# to# s#
+ copy cur# end# from# to# st#
| cur# ==# end#
- = StateAndMutableArray# s# to#
+ = (# st#, to# #)
| otherwise
- = case indexArray# from# cur# of { Lift ele ->
- case writeArray# to# cur# ele s# of { s1# ->
+ = case indexArray# from# cur# of { (# ele #) ->
+ case writeArray# to# cur# ele st# of { s1# ->
copy (cur# +# 1#) end# from# to# s1#
}}
-\end{code}
-
-%*********************************************************
-%* *
-\subsection{Ghastly return types}
-%* *
-%*********************************************************
-\begin{code}
-data StateAndArray# s elt = StateAndArray# (State# s) (Array# elt)
-data StateAndMutableArray# s elt = StateAndMutableArray# (State# s) (MutableArray# s elt)
-data StateAndByteArray# s = StateAndByteArray# (State# s) ByteArray#
-data StateAndMutableByteArray# s = StateAndMutableByteArray# (State# s) (MutableByteArray# s)
+-- this is a quicker version of the above, just flipping the type
+-- (& representation) of an immutable array. And placing a
+-- proof obligation on the programmer.
+unsafeThawSTArray :: Ix ix => Array ix elt -> ST s (STArray s ix elt)
+unsafeThawSTArray (Array l u arr#) = ST $ \ s# ->
+ case unsafeThawArray# arr# s# of
+ (# s2#, marr# #) -> (# s2#, STArray l u marr# #)
\end{code}