Hi,
The short answer: use
runST (long expression)
rather than
runST $ long expression
when it comes to higher-ranked functions such as runST.
I suppose the same holds for runSTUArray, right? But this still gives
me that same error, about being less polymorphic than expected.
(+=) x y = let updateX i = do xi <- readArray x i
writeArray x i (xi + y!i)
in sequence_ . map updateX $ indices x
sumArrays [] = error "Can't apply sumArrays to an empty list"
sumArrays (x:xs) = runSTUArray result
where
result = do x0 <- thaw x
mapM_ (x0 +=) xs
x0
--
Chad Scherrer
"Time flies like an arrow; fruit flies like a banana" -- Groucho Marx
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
