x, y = ...

direction = 1
xPos = 0
yPos = 0

function turnLeft(x)
    for i=1, x do
        turtle.turnLeft()

        if direction == 1 then
            direction = 4
        else
            direction = direction - 1
        end
    end
end

function turnRight(x)
    for i=1, x do
        turtle.turnRight()

        if direction == 4 then
            direction = 1
        else
            direction = direction + 1
        end
    end
end

function setDirection(x)
    delta = x - xPos

    if x < 0 then
        turnLeft(-x)
    else
        turnRight(x)
    end
end

function forward(x)
    for i=1, x do
        turtle.forward()

        if direction == 1 then
            yPos = yPos + 1
        elseif direction == 2 then
            xPos = xPos + 1
        elseif direction == 3 then
            yPos = yPos - 1
        else
            xPos = xPos - 1
        end
    end
end

function back(x)
    for i=1, x do
        turtle.back()

        if direction == 1 then
            yPos = yPos - 1
        elseif direction == 2 then
            xPos = xPos - 1
        elseif direction == 3 then
            yPos = yPos + 1
        else
            xPos = xPos + 1
        end
    end
end

function navigate(x, y)
    dx = x - xPos
    dy = y - yPos

    if dx < 0 then
        setDirection(4)
        forward(-dx)
    else
        setDirection(2)
        forward(dx)
    end

    if dy < 0 then
        setDirection(3)
        forward(-dy)
    else
        setDirection(1)
        forward(dy)
    end

    print xPos + ", " + yPos
end

navigate(x, y)