therefore mapException is equally buggy!
mapException :: (Exception e1, Exception e2) => (e1 -> e2) -> a -> a mapException f v = unsafePerformIO (catch (evaluate v) (\x -> throw (f x)))
If it maps an asynchronous exception.. and it's re-thrown as synchronous... the same non-resumability happens! mapException is a particular culprit because of the unsafePerformIO (so you had a good reason to expect resumability, since it's for a pure computation, not in IO) - does anyone use mapException? - is there some reason that we don't have all "throw"s (synch. or asynch.) "patch up" the thunks? (memory leaks or serious inefficiency or something?) if "yes", I don't think mapException can currently be implemented; we'd need some way in its "catch" to detect whether the thrown exception was asynchronous, and *iff* so, throw the new exception asynchronously (if synchronous, rethrow synchronously). Or some equivalent. Or maybe some add some magic to unsafePerformIO (probably a bad idea). -Isaac