[project @ 1996-01-08 20:28:12 by partain]

[ghc-hetmet.git] / ghc / compiler / tests / typecheck / should_fail / tcfail068.hs

diff --git a/ghc/compiler/tests/typecheck/should_fail/tcfail068.hs b/ghc/compiler/tests/typecheck/should_fail/tcfail068.hs
new file mode 100644 (file)
index 0000000..2b17bce
--- /dev/null
+++ b/ghc/compiler/tests/typecheck/should_fail/tcfail068.hs
@@ -0,0 +1,92 @@
+--!! Make sure that state threads don't escape
+--!! (example from Neil Ashton at York)
+--
+module IndTree(IndTree(..), itgen, itiap, itrap, itrapstate) where
+
+--partain: import Auxiliary
+import PreludeGlaST
+
+type IndTree s t = _MutableArray s (Int,Int) t
+
+itgen :: Constructed a => (Int,Int) -> a -> IndTree s a
+itgen n x = 
+       _runST (
+       newArray ((1,1),n) x)
+
+itiap :: Constructed a => (Int,Int) -> (a->a) -> IndTree s a -> IndTree s a
+itiap i f arr =
+       _runST (
+       readArray arr i `thenStrictlyST` \val ->
+       writeArray arr i (f val) `seqStrictlyST`
+       returnStrictlyST arr)
+
+itrap :: Constructed a => ((Int,Int),(Int,Int)) -> (a->a) -> IndTree s a -> IndTree s a
+itrap ((i,k),(j,l)) f arr = _runST(itrap' i k)
+       where
+       itrap' i k = if k > l then returnStrictlyST arr
+                    else (itrapsnd i k `seqStrictlyST`
+                       itrap' i (k+1))
+       itrapsnd i k = if i > j then returnStrictlyST arr
+                     else (readArray arr (i,k) `thenStrictlyST` \val ->
+                       writeArray arr (i,k) (f val) `seqStrictlyST`
+                       itrapsnd (i+1) k)
+
+itrapstate :: Constructed b => ((Int,Int),(Int,Int)) -> (a->b->(a,b)) -> ((Int,Int)->c->a) ->
+               (a->c) -> c -> IndTree s b -> (c, IndTree s b)
+itrapstate ((i,k),(j,l)) f c d s arr = _runST(itrapstate' i k s)
+       where
+       itrapstate' i k s = if k > l then returnStrictlyST (s,arr)
+                           else (itrapstatesnd i k s `thenStrictlyST` \(s,arr) ->
+                               itrapstate' i (k+1) s)
+       itrapstatesnd i k s = if i > j then returnStrictlyST (s,arr)
+                            else (readArray arr (i,k) `thenStrictlyST` \val ->
+                              let (newstate, newval) = f (c (i,k) s) val
+                              in writeArray arr (i,k) newval `seqStrictlyST`
+                              itrapstatesnd (i+1) k (d newstate))
+
+-- stuff from Auxiliary: copied here (partain)
+
+sap :: (a->b) -> (c,a) -> (c,b)
+sap f (x,y) = (x, f y)
+
+fap :: (a->b) -> (a,c) -> (b,c)
+fap f (x,y) = (f x, y)
+
+nonempty :: [a] -> Bool
+nonempty []    = False
+nonempty (_:_) = True
+
+-- const :: a -> b -> a
+-- const k x = k
+
+-- id :: a -> a
+-- id x = x
+
+compose :: [a->a] -> a -> a
+compose = foldr (.) id
+
+data Maybe t = Just t | Nothing
+
+class Constructed a where
+   normal :: a -> Bool
+
+instance Constructed Bool where
+   normal True = True
+   normal False = True
+
+instance Constructed Int where
+   normal 0 = True
+   normal n = True
+
+instance (Constructed a, Constructed b) => Constructed (a,b) where
+   normal (x,y) = normal x && normal y
+
+-- pair :: (Constructed a, Constructed b) => a -> b -> (a,b)
+-- pair x y | normal x && normal y = (x,y)
+
+instance Constructed (Maybe a) where
+   normal Nothing = True
+   normal (Just _) = True
+
+just :: Constructed a => a -> Maybe a
+just x | normal x = Just x