#15349: fixST is a bit wrong -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: bug | Status: patch Priority: normal | Milestone: 8.6.1 Component: Core Libraries | Version: 8.5 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4948 Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): I've put up a differential to fix ''strict'' `ST`. Unfortunately, all my attempts thus far to fix ''lazy'' `ST` have been extremely fragile. I don't really understand what's going on well enough to see exactly what the trouble is, let alone how to fix it. My lazy `ST` test case: {{{#!hs foo :: ST s Int foo = do ref <- strictToLazyST (newSTRef True) fixST $ \res -> strictToLazyST $ do x <- readSTRef ref if x then do writeSTRef ref False return $! (res + 5) else return 10 main = print $ runST foo }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15349#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler