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{-# LANGUAGE CPP,PatternGuards #-}
module ImmList where
import Control.Concurrent
import Data.IORef
import qualified Data.Sequence as S
import Data.Sequence (Seq, (|>), (<|), (><), ViewL(..))
import Data.Maybe
import Data.Foldable
#if 0
newtype ListHandle a = ListHandle (IORef (Seq a))
newList :: IO (ListHandle a)
newList = do
r <- newIORef S.empty
return (ListHandle r)
addToTail :: Eq a => ListHandle a -> a -> IO ()
addToTail (ListHandle r) x =
atomicModifyIORef r $ \s -> (s |> x, ())
find :: Eq a => ListHandle a -> a -> IO Bool
find (ListHandle r) x = do
s <- readIORef r
return (isJust (S.elemIndexL x s))
delete :: Eq a => ListHandle a -> a -> IO Bool
delete (ListHandle r) x = atomicModifyIORef r $ \s ->
case S.breakl (== x) s of
(xs, ys) | c :< zs <- S.viewl ys, c == x -> (xs >< zs, True)
| otherwise -> (xs >< ys, False)
printList :: Show a => ListHandle a -> IO ()
printList (ListHandle r) = do
s <- readIORef r
print (toList s)
cntList :: Show a => ListHandle a -> IO Int
cntList (ListHandle r) = readIORef r >>= return . S.length
#else
newtype ListHandle a = ListHandle (IORef [a])
newList :: IO (ListHandle a)
newList = do
r <- newIORef []
return (ListHandle r)
addToTail :: Eq a => ListHandle a -> a -> IO ()
addToTail (ListHandle r) x =
atomicModifyIORef r $ \s -> (s ++ [x], ())
find :: Eq a => ListHandle a -> a -> IO Bool
find (ListHandle r) x = do
s <- readIORef r
return (x `Prelude.elem` s)
delete :: Eq a => ListHandle a -> a -> IO Bool
delete (ListHandle r) x = atomicModifyIORef r $ \s ->
case break (== x) s of
(xs, ys) | (c:zs) <- ys, c == x -> (xs ++ zs, True)
| otherwise -> (xs ++ ys, False)
printList :: Show a => ListHandle a -> IO ()
printList (ListHandle r) = do
s <- readIORef r
print s
cntList :: Show a => ListHandle a -> IO Int
cntList (ListHandle r) = readIORef r >>= return . length
#endif
|
