bc_quarry_prep

-- Put bricks in slot 1, landmark in slot 2

turtle_pos = vector.new(0, 0, 0)
  turtle_pos.x = 0
  turtle_pos.y = 0
  turtle_pos.z = 0
square_size = vector.new(0, 0, 0)

function place_corner()
  -- Move down 1 square.
  while not turtle.down() do
    turtle.digDown()
    os.sleep(1)
  end

  -- Decrement turtle's Z
  turtle_pos.z = turtle_pos.z - 1

  -- If no block is present, place block.
  if not turtle.detectDown() then
    turtle.select(1)
    turtle.placeDown()
  end

  -- Move up 1 level.
  while not turtle.up() do
    if turtle.detectUp() then turtle.digUp() end
    os.sleep(1)
  end

  -- Increment turtle's Z coordinate because it 1 block above where the quarry will be placed.
  turtle_pos.z = turtle_pos.z + 1

  -- Place landmark.
  turtle.select(2)
  turtle.placeDown()
end

-- Go through following code and convert to functions as needed.

-- Get input
-- Prompt for length and width.

function mark_quarry()
  print("How long?")
  square_size.x = tonumber(read()) - 1
  print("How wide?")
  square_size.y = tonumber(read()) - 1

  -- Place bricks in slot 1, landmark in slot 2
  -- Turtle starts in lower left corner. Place block beneath turtle if no block there.
  if not turtle.detectDown() then
    turtle.select(1)
    turtle.placeDown()
  end

  while not turtle.up() do
    turtle.digUp()
    os.sleep(2)
  end

  -- Increment turtle's Z coordinate because it 1 block above where the quarry will be placed.
  turtle_pos.z = 1

  -- Place the lower left landmark.
  turtle.select(2)
  turtle.placeDown()

  -- Move to upper left corner:
  repeat
    while not turtle.forward() do
      if turtle.detect() then turtle.dig() end
      os.sleep(1)
    end
    turtle_pos.y = turtle_pos.y +1
  until turtle_pos.y >= square_size.y

  -- Place upper left landmark
  print("Placing upper left beacon")
  place_corner()

  -- Move to upper right.
  turtle.turnRight()
  repeat
    while not turtle.forward() do
      if turtle.detect() then turtle.dig() end
      os.sleep(1)
    end
    turtle_pos.x = turtle_pos.x + 1
  until turtle_pos.x >= square_size.x

  -- Place upper right
  print("Placing upper right beacon")
  place_corner()

  -- Move to lower right
  turtle.turnRight()
  repeat
    while not turtle.forward() do
      if turtle.detect() then turtle.dig() end
      os.sleep(1)
    end
    turtle_pos.y = turtle_pos.y - 1
  until turtle_pos.y <= 0

  -- Place lower right
  print("Place lower right beacon")
  place_corner()

  -- Return to just above point of origin.
  turtle.turnRight()
  repeat
    while not turtle.forward() do
      if turtle.detect() then turtle.dig() end
      os.sleep(1)
    end
    turtle_pos.x = turtle_pos.x - 1
  until turtle_pos.x <= 0
end

mark_quarry()