Turtlescripts Fence Builder Command

--[[
Source: http://adf.ly/mQGKM
Authors: Lyqyd, Zaflis, Kreezxil
Ripped by: Kreezxil
Notes: Until now this code sat freely in forum, its still free, but now its encapsulated in a program that can be run and given arguments as well as loaded with 'pastebin get'
Changelog:
2/22/14 - Requested Concept by Narny123 - http://adf.ly/mQFxT
2/22/14 - Original Code by Lyqyd - http://adf.ly/mQG5h
2/28/14 - Modified Code by Zaflis - http://adf.ly/mQGD2
- now supports digging through gravel, and digs high enough tunnel for player to follow through
- added code to allow fence removal
5/10/14 - Modified Code by Kreezxil
- rearranged and encapsulated with function declarations parts of code to allow it to be in a program much easier
- added arguments for variable sized fence building and removing
- added help when arguments fail to match or nothing slot 1
--]]

local index = 1
turtle.select(1)

function place()
  while turtle.detectUp() do
    turtle.digUp()
  end
  turtle.digDown()
  turtle.placeDown()
  if turtle.getItemCount(index) == 0 then
    index = index + 1
  end
  if index > 16 then
      index = 1
  end
  turtle.select(index)
end

function removeFence(length,width)
    turtle.digDown()
	for i = 1, 4 do
      if i==1 or i==3 then
          side=length
      else
          side=width
      end
	  for j = 1, side-1 do
		turtle.dig()
		turtle.forward()
		turtle.digDown()
	  end
	  turtle.turnRight()
	end
end

function buildFence(length,width)
	place()
	for i = 1, 4 do
      if i==1 or i==3 then
          side=length
      else
          side=width
      end
	  for j = 1, side-1 do
		while turtle.detect() do
		  turtle.dig()
		end
		turtle.forward()
		place()
	  end
	  turtle.turnRight() -- Goes clockwise
	end
end

function myName()
	fullName = shell.getRunningProgram()
	return fs.getName(fullName)
end

function mats()
  count=0
  for i=1,16 do
	count = count + turtle.getItemCount(i)
  end
  return count
end

function needed(length,width)
   return (length*2)+(width*2)
end

args = {...}

if #args < 3 then
  print("Usage:")
  print(" "..myName().." <length> <width> <remove|build>")
  print(" Turtle should also contain materials to be used as fences, preferably fences.")
  return
end

if tonumber(args[1])==nil or tonumber(args[2])==nil then
    print("Dimensions must be numerical.")
    return
end

if tonumber(args[1]) < 1 or tonumber(args[2]) < 1 then
  print("A dimension may not be less than 1")
  return
end

if mats() < needed(tonumber(args[1]),tonumber(args[2])) then
  print("Not enough materials in turtle to build fence, please add more materials.")
  return
end

if args[3]== "remove" then
  removeFence(tonumber(args[1]),tonumber(args[2]))
elseif args[3]=="build" then
  buildFence(tonumber(args[1]),tonumber(args[2]))
else
  print("The third option must be either 'remove' or 'build'")
end