(* General function that checks if an int list is sorted *)
fun issorted [] = true  |
        issorted [x] = true |
        issorted (x::y::t) = x <= y andalso issorted(y::t);

(* Function that does the bubbling *)
fun bubble [] = [] |
    bubble [x] = [x] |
    bubble (x::y::t) = if (x > y) then y::(bubble (x::t))
                       else x::(bubble (y::t));

(* Call bubble on list until it is sorted *)
fun bubbleSort [] = [] |
    bubbleSort l = if (issorted l) then l else bubbleSort (bubble l);