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|
module BoundedSet
( new
, readBound
, readSize
, read
, clear
, insert
, spaceAvail
, rmSuch
, rmSuchN
, BoundedSet
, iterateSet
) where
import LazyST
import Prelude hiding (read)
import List
new :: Int -> ST s (BoundedSet s a)
readBound :: BoundedSet s a -> ST s Int
readSize :: BoundedSet s a -> ST s Int
read :: BoundedSet s a -> ST s [a]
clear :: BoundedSet s a -> ST s [a]
insert :: BoundedSet s a -> [a] -> ST s ()
spaceAvail :: BoundedSet s a -> ST s Int
rmSuch :: BoundedSet s a -> (a -> Bool) -> ST s [a]
rmSuchN :: BoundedSet s a -> Int -> (a -> Bool) -> ST s [a]
iterateSet :: BoundedSet s a -> (a -> a) -> ST s ()
-- Implementation ----------------------------------------------------
type BoundedSet s a = (STRef s [a],Int)
iterateSet s f =
do { set <- read s
; write s (map f set)
}
read (s,n) = readSTRef s
rmSuch s f
= do { set <- read s
; let (yes,no) = partition f set
; write s no
; return yes
}
rmSuchN s n f
= do { such <- rmSuch s f
; let (big,small) = splitAt n such
; insert s small
; return big
}
write :: BoundedSet s a -> [a] -> ST s ()
write (s,n) x = writeSTRef s x
readBound (s,n) = return n
new n
= do { set <- newSTRef []
; return (set,n)
}
clear s =
do { set <- read s
; write s []
; return set
}
readSize s =
do { set <- read s
; return ( length set)
}
spaceAvail s
= do { bnd <- readBound s
; sz <- readSize s
; return (bnd - sz)
}
insert s l
= do { set <- read s
; n <- readBound s
; write s $ take n (set ++ l)
}
|
