Re: [Haskell-cafe] do you have to use fix with forkio?

On Sat, 2009-03-07 at 23:12 +0100, Martijn van Steenbergen wrote:

Derek Elkins wrote:

...

Both are poorish style.

reader <- forkIO $ forever $ do (nr', line) <- readChan; when (nr /= nr') $ putStrLn hdl line

This is fine assuming you always want to re-enter the loop. If you want to loop conditionally (which is most often the case), forever isn't going to work, unless you use exceptions.

If you are doing something else, use something else. This makes it clear that you -aren't- going to break out (non-exceptionally), i.e. the control flow is more obvious in this code than in the other versions. By your logic 'map' would be bad because not everything is a map, of course, this is precisely why using map, when applicable, is good.