H.
Jon Fairbairn
writes: The idea in Haskell is not to think of stepping through the array. Look at accumArray and ixmap.
Thanks for your answer.
But I can't really see how the calc-function can be written more efficiently with accumArray or ixmap, perhaps you can write it as an example?
Well, for your example, neither is needed since you could write something like: upb = 10000 listArray (1,upb) (repeat False) //map (\n->(2^n,True)) [1..floor (logBase 2 $ fromIntegral upb)] or a = listArray (1,upb) (repeat False) b = a//map (\n->(2^n,not (a!(2^n)))) [1..floor (logBase 2 $ fromIntegral upb)] but the first one is obviously better, so it depends on what you really want to do. -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2007-05-07)