fun robPoint () =
    let
        val maxX = ref ~1
        val maxY = ref ~1
        val x = ref ~1
        val y = ref ~1

        fun move(i,j) =
            (
            x := !x + i;
            y := !y + j;
            if !x <= !maxX andalso !y <= !maxY andalso !x >= 0 andalso !y >= 0 then
                (i,j)
            else raise RobolOutOfGrid
            )

        fun start(i,j) =
            (x := i ; y := j;(i,j))

        fun get(i,j) =
            (!x,!y)

        fun setMax(i,j) =
            (maxX := i ; maxY := j;(i,j))

        fun dispatch("move") = move
        |   dispatch("start") = start
        |   dispatch("setMax") = setMax
        |   dispatch(_) = get

    in
        dispatch
    end;

val robolPoint = robPoint();