Hi, I want to do something like: | main = do | monstrousDataStructure <- monstrousComputation | hPutStr stderr "success!" | ... The important point is that I want to make sure that the computation has terminated and not failed before I go to `...'. I have tried | x <- x `seq` x and | x <- id $! x which should be equivalent anyway, but they both did not have any effect. Then, I remember that there was something called strict, but I can't find it any more. I am afraid I am missing something basic here. If you can't help me, I will come back with a more precise example, I just haven't found one so far (only the original code, but you don't want to read 1843 LOC on this list, do you?... :) thanks a lot, Matthias -- Matthias Fischmann | Research Engineer | +358 (9) 8565 7474 fis@ssh.fi | SSH Communication Security Corp | +358 (40) 752 5291