[Haskell-cafe] Re: Something like scan1
lemming at henning-thielemann.de
Wed Jun 18 11:06:13 EDT 2008
On Wed, 18 Jun 2008, Achim Schneider wrote:
> Henning Thielemann <lemming at henning-thielemann.de> wrote:
>> On Wed, 18 Jun 2008, Achim Schneider wrote:
>>> Is there a generalisation of scan1, such that eg.
>>> foo (+) [0,1] (1,2) = [0,1,1,2,3,5,8,13,...]
>> What is the (1,2) for?
> Specifying the relative indexes an element depends on. Ideally, it
> should be generalised for n-ary functions.
foo f prefix (n,m) =
let k = length prefix
xs = prefix ++ zipWith f (xss!!(k-n)) (xss!!(k-m))
xss = List.tails xs
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