let rec partition f = function
  | [] -> ([], [])
  | x::xs -> 
    let (ys, zs) = partition f xs
    match f x with
    | true  -> (x::ys, zs)
    | false -> (ys, x::zs)

[1..8] |> partition (fun x -> x%2 = 1) |> printfn "%A"