2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
4 \section[module_ST]{The State Transformer Monad, @ST@}
7 {-# OPTIONS -fno-implicit-prelude #-}
13 runST, -- :: (All s => ST s a) -> a
14 fixST, -- :: (a -> ST s a) -> ST s a
18 -- ST is one, so you'll likely need some Monad bits
22 newSTRef, readSTRef, writeSTRef,
25 newSTArray, readSTArray, writeSTArray, Ix
30 import Unsafe ( unsafeInterleaveST )
32 import PrelBase ( Eq(..), Int, Bool, ($), ()(..) )
38 %*********************************************************
40 \subsection{Variables}
42 %*********************************************************
45 newtype STRef s a = STRef (MutableVar s a)
48 newSTRef :: a -> ST s (STRef s a)
49 newSTRef v = newVar v >>= \ var -> return (STRef var)
51 readSTRef :: STRef s a -> ST s a
52 readSTRef (STRef var) = readVar var
54 writeSTRef :: STRef s a -> a -> ST s ()
55 writeSTRef (STRef var) v = writeVar var v
58 %*********************************************************
62 %*********************************************************
65 newtype STArray s ix elt = STArray (MutableArray s ix elt)
68 newSTArray :: Ix ix => (ix,ix) -> elt -> ST s (STArray s ix elt)
69 writeSTArray :: Ix ix => STArray s ix elt -> ix -> elt -> ST s ()
70 readSTArray :: Ix ix => STArray s ix elt -> ix -> ST s elt
71 boundsSTArray :: Ix ix => STArray s ix elt -> (ix, ix)
72 thawSTArray :: Ix ix => Array ix elt -> ST s (STArray s ix elt)
73 freezeSTArray :: Ix ix => STArray s ix elt -> ST s (Array ix elt)
74 unsafeFreezeSTArray :: Ix ix => STArray s ix elt -> ST s (Array ix elt)
77 newArray ixs elt >>= \arr ->
80 boundsSTArray (STArray arr) = boundsOfArray arr
82 readSTArray (STArray arr) ix = readArray arr ix
84 writeSTArray (STArray arr) ix elt = writeArray arr ix elt
86 thawSTArray arr = thawArray arr >>= \starr -> return (STArray starr)
88 freezeSTArray (STArray arr) = freezeArray arr
90 unsafeFreezeSTArray (STArray arr) = unsafeFreezeArray arr