Is "speed x" at least a somewhat universal term for the number of list elements that get operated on per iteration? It works really well.

I was also wondering about what you just pointed out: if there's a nice way to form (what I now know to call) speed >1 functions. Your form looks a lot nicer than some of the stranger things I've been coming up with.

On Thu, Jan 12, 2012 at 1:37 AM, Stephen Tetley <stephen.tetley@gmail.com> wrote:
Direct recursion is almost always clearer if you are traversing the
list at a "different speed". The usual list functionals (map, filter,
folds) are all speed 1 - traversing one element at a time. Here we
want pairwise traversal:

unscan :: (a -> a -> b) -> [a] -> [b]
unscan f (a:b:bs) = f a b : unscan f b bs
unscan _ _        = []