window.hs

window :: Int -> [a] -> [[a]]
--base case
window sz [] = []

-- the "@" sign lets you alias the destructed variable as in "whole@(head:tail)"
-- "take N list" gives you the first N elements of list
window sz lst@(h:tl)= [take sz lst] ++ window sz tl

main = do
        let seq = window 2 [1..25]
        print "here's a 2-item sliding window"
        print $ seq 
        
        print "summing over the window"
        --sum is just "foldl (+) 0"
        print $ map sum seq 
        
        --scanl doesn't make sense over a list of lists
        --but maybe you want the intermediate values as you accumulate a total?
        print "scanning over the window sums"
        print $ scanl (+) 0  $ map sum seq