Stephen Hicks
Magnus Therning wrote:
Martijn van Steenbergen wrote:
Otherwise, you can use unsafeInterleaveIO: no unsafePerformIO or seq needed, but there's still "unsafe" in that name there. This works for me:
... Thanks, that does indeed work, but it still requires that "unsafe" there so I'm hesitant replacing the call to threadDelay with something more complicated, where it isn't obviously safe.
Sorry for the late reply, but I'd like to piggy-back on this. It's my understanding that unsafeInterleaveIO is only unsafe insofar as it makes the IO lazy and so the IO may be performed later or never at all (if its return value is never wanted) and is therefore no less safe than, say, generating a list of IO actions as was suggested by an earlier reply. It seems to me that its unsafeness is of a completely different nature than unsafePerformIO... am I missing something?
There are two issues with unsafePerformIO: The laziness makes evaluation unpredictable to some extent, but that's intentional. But for example what if the IO computation throws an exception? There is no well-defined behaviour, not even a well-known convention. For example, hGetContents simply aborts, which makes errors undetectable. All in all, unsafeInterleaveIO is a handy tool, but you need to be careful about its side effects. Greets, Ertugrul. -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://blog.ertes.de/