Castle Wall Merlon Block Placer For Turtle in ComputerCraft

-- This is a block placement program for a turtle that will place a block then move 2 blocks and place another one until it reaches the given length.
-- Useful for the tops of castle walls or any other situation where you need blocks spaced out.

-- Written by Richard Reigens 10/12/2013
-- Version 1.3

-- Make sure turtle has building blocks and is fueled up.
-- The program will detect whether there is a block under the turtle or not and start alternating the pattern based on that.
-- Place your turtle facing the direction you want the line made.
-- Useage is: merlon <length>


local tArgs = {...}
local length = tonumber(tArgs[1])
local slot = 1
local space = true

if turtle.detectDown() == true then
    space = false

    end

turtle.select(slot)

putIt = function ()
    if turtle.getItemCount(slot) == 0 then
      slot = slot + 1
      turtle.select(slot)
      turtle.placeDown()

    else
      turtle.placeDown()

    end
end

checkSpace = function ()
    if space == true then
        turtle.forward()
        putIt()
        space = false

    else turtle.forward()
        space = true

    end
end

for i = 1, length, 1 do

    if i < length then
        checkSpace()

        end
end

print("Complete")