A ComputerCraft program to dig a hole of your desired dimensions and place ladders along the way

dig_a_hole.lua

-- Hole Digger by dillmo --
--[[
      This program will dig a hole of your description and place ladders for
      you. To begin with, place your mining turtle in the bottom left corner of
      your hole. Be sure to place ladders in slot one of your turtle's
      inventory and specify configuration variables before beginning.
--]]

-- Configuration --
local current_height = 70 -- The current y value of your turtle. This should be
                          -- the y value of your feet, not your head.

local desired_height = 67 -- The y value you want to dig down to.

local length = 4          -- The length of your hole. Your turtle is facing
                          -- this way.

local width = 5           -- The width of your hole. This should be
                          -- perpendicular to the direction your turtle is
                          -- facing.

-- Function Definitions --
local function turnAround()
  turtle.turnRight()
  turtle.turnRight()
end

-- Program --
for i = desired_height, current_height - 1 do
  if width % 2 == 0 then
    middle_of_width = width / 2
  else
    middle_of_width = width / 2 + 0.5
  end
  turtle.digDown()
  turtle.down()
  for i2 = 1, width do
    if i2 == middle_of_width then
      for i3 = 2, length do
        turtle.dig()
        turtle.forward()
      end
      turnAround()
      for i3 = 3, length do
        turtle.forward()
      end
      turtle.select(1)
      turtle.place()
      turtle.turnLeft()
      turtle.dig()
      turtle.forward()
      turtle.turnRight()
      turtle.dig()
      turtle.forward()
      turnAround()
    else
      for i3 = 2, length do
        turtle.dig()
        turtle.forward()
      end
      turnAround()
      for i3 = 2, length do
        turtle.forward()
      end
      turnAround()
      if i2 < width then
        turtle.turnRight()
        turtle.dig()
        turtle.forward()
        turtle.turnLeft()
      end
    end
    if i2 == width then
      turtle.forward()
      turtle.turnLeft()
      for i3 = 2, width do
        turtle.forward()
      end
      turtle.turnLeft()
      turtle.forward()
      turnAround()
    end
  end
end