> I am unconvinded that this is any more wrong than using a for > loop in an imperative language. Remember that the lists are > lazy, so it’s misleading to say “convert the array to a list” > since what happens most of the time is that elements are taken > out of the array and passed to the processing function and then > thrown away before the next element is processed.
I don't think it's misleading to say "convert to a list". Without the presence of some fusion-esque optimization, the entire list is created and destroyed. It's nice if it can be done incrementally, but that's still a lot of garbage. And for a concrete example, consider concatenating a bunch of arrays. Unless it gets deforested, you have to copy each element a couple of times, since there is intermediate list concatenation. And then this kind of API is incompatible with unboxing... if you later decide to unbox the data type then I don't think you could ever get the intermediate list approach to work, since it's boxed by nature. > I’m not familiar with Repa or NumPy, but what can they do that > cannot be done with judicious use of ixmap, which is a very > powerful mechanism. I spent hours messing with ixmap before getting something that seemed to work right. Maybe I just have more trouble than most with it, but though it may be powerful it's certainly not easy to use! After spending too much time on it I learned to just convert to a list and back. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
