On Wed, Feb 20, 2008 at 5:53 PM, Roman Leshchinskiy
In general, I don't see why programming directly with streams is something that should be avoided. You do have to be quite careful, though, if you want to get good performance (but GHC's simplifier is becoming increasingly robust in this respect).
Hmm. I was taking the approach of getting something working, given what is currently exported from Data.Stream. How would you deal with this? Should there be a Data.Stream.Internal or something that exports streams and unlifted types? If I'm understanding this correctly, these things were not exported in the first place because this fusion framework provides an approximation, but not an isomorphism, so partial bottoms don't always behave nicely. I was hoping to get around this by programming instead to Step and then hoping rules could be constructed to translate to Streams. Do you think there's a better way around it?
extract ns xs == [xs !! n | n <- ns]
Note that in contrast to your function, this doesn't assume that ns is sorted and hence, there is no way to implement this without producing an intermediate list.
Oh yes, good point. It's so easy to forget about assumptions like that. Chad