partition sml
fun parition f xs =
let
fun split x (xs,ys) =
if f x
then (x::xs,ys)
else (xs, x::ys)
val (trueList, falseList) = List.foldl (fn (x,y) => split x y)
([],[]) xs
in
(List.rev trueList, List.rev falseList)
end