Re: [Haskell-cafe] Stream-fusion without the lists

On Tue, May 12, 2009 at 1:39 PM, Roman Leshchinskiy wrote:

let xs = map f ys in (sum xs, product xs)

the elements of xs will be computed once if it is a list but twice if it is a stream.

If you're using lists for loops rather than data, that's what you want (what you probably really want is cfoldl' ((,) <$> sumF <*> productF) xs, in terms of combinable folds).

Roman

--Max