map2zero.fs

let map2zero (f: float -> float -> 'a) (s1: float list) (s2: float list) =
  let rec take xs ys result =
    match xs, ys with
        | [], []         -> result
        | x::xs', []     -> (f x 0.0) :: take xs' [] result
        | [], y::ys'     -> (f 0.0 y) :: take [] ys' result
        | x::xs', y::ys' -> (f x y)   :: take xs' ys' result
        
  take s1 s2 []
  
let a = [4.0;3.0;6.0;1.5]
let b = [1.2;2.9]
let floats = map2zero (fun x y -> x - y) a b