Computercraft Turtle Movement Wrapper

-- Turtle Self-tracking System created by Arclight306

local xPos, yPos, zPos = nil
local face = nil
local cal = false

function gpsLocation(facing) -- get gps using other computers
   xPos, yPos, zPos = gps.locate()
   if xPos == nil then
      cal = false
      return false
   else
      if facing == "north" or facing == "east" or facing == "south" or facing == "west" then
         face = facing
         cal = true
         return true
      else
         cal=false
         assert(false, "Facing must be north, south, east or west")
      end
      return false
   end
end

function manSetLocation(x, y, z, facing) -- manually set location

   assert(type(x) == "number", "x must be a number")
   assert(type(y) == "number", "y must be a number")
   assert(type(z) == "number", "z must be a number")

   if facing == "north" or facing == "east" or facing == "south" or facing == "west" then
      face = facing
      cal = true
   else
      cal=false
      assert(false, "Facing must be north, south, east or west")
   end

   xPos = x
   yPos = y
   zPos = z
   face = facing
end

function getLocation() -- return the location
   if xPos ~= nil then
      return xPos, yPos, zPos, face
   elseif xPos == nil then
      return nil
   end
end

function turnLeft() -- turn left
   if(turtle.turnLeft()) then
      if face == "north" then
         face = "west"
      elseif face == "west" then
         face = "south"
      elseif face == "south" then
         face = "east"
      elseif face == "east" then
         face = "north"
      end
      return true
   end
   return false
end

function turnRight() -- turn right
   if(turtle.turnRight()) then
      if face == "north" then
         face = "east"
      elseif face == "east" then
         face = "south"
      elseif face == "south" then
         face = "west"
      elseif face == "west" then
         face = "north"
      end
      return true
   end
   return false
end

function forward() -- go forward

   if(turtle.forward()) then
      if cal == true then
         if face == "north" then
            zPos = zPos - 1
         elseif face == "west" then
            xPos = xPos - 1
         elseif face == "south" then
            zPos = zPos + 1
         elseif face == "east" then
            xPos = xPos + 1
         end
      else
         print("Not Calibrated.")
      end
      return true
   end
   return false
end

function back() -- go back

   if(turtle.back()) then
      if cal == true then
         if face == "north" then
            zPos = zPos + 1
         elseif face == "west" then
            xPos = xPos + 1
         elseif face == "south" then
            zPos = zPos - 1
         elseif face == "east" then
            xPos = xPos - 1
         end
      else
         print("Not Calibrated.")
      end
      return true
   else
      return false
   end
end

function up() -- go up
   if(turtle.up()) then
      if cal == true then
         yPos = yPos + 1
      else
         print("Not Calibrated.")
      end
      return true
   else
      return false
   end
end

function down() -- go down
   if(turtle.down()) then
      if cal == true then
         yPos = yPos - 1
      else
         print("Not Calibrated.")
      end
      return true
   else
      return false
   end
end