Turtle Swarm Turtle Lib

facing = 0
xPos = 0
yPos = 0
zPos = 0


local oldForward = turtle.forward
function forward()
    if oldForward() then
        if facing == 0 then
            xPos = xPos + 1
        elseif facing == 1 then
            zPos = zPos + 1
        elseif facing == 2 then
            xPos = xPos - 1
        else
            zPos = zPos - 1
        end
        return true
    else
        return false
    end
end


local oldLeft = turtle.turnLeft
function turnLeft()
    oldLeft()
    facing = facing + 1
    facing = facing % 4
end

local oldRight = turtle.turnRight
function turnRight()
    oldRight()
    facing = facing - 1
    facing = facing % 4
end

local oldBack = turtle.back
function back()
    if oldBack() then
        if facing == 0 then
            xPos = xPos - 1
        elseif facing == 1 then
            zPos = zPos - 1
        elseif facing == 2 then
            xPos = xPos + 1
        else
            zPos = zPos + 1
        end
        return true
    else
        return false
    end
end

local oldDown = turtle.down
function down()
    if oldDown() then
        yPos = yPos - 1
        return true
    else
        return false
    end
end

local oldUp = turtle.up
function up()
    if oldUp() then
        yPos = yPos + 1
        return true
    else
        return false
    end
end