Torcher

depth = 64

function down()
  while not turtle.down() do
    turtle.digDown()
  end
end

function up()
  while not turtle.up() do
    turtle.digUp()
  end
end

function forward()
  while not turtle.forward() do
    turtle.dig()
  end
end

function back()
  while not turtle.back() do
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.dig()
    turtle.turnLeft()
    turtle.turnLeft()
  end
end

function dig()
  turtle.dig()
end

function downColumn()
  for i=1,depth do
    down()
    dig()
  end
end

function upColumn()
  for i=1,depth do
    dig()
    up()
  end
end

function left()
  turtle.turnLeft()
end

function right()
  turtle.turnRight()
end

function setup()
  for i=1,4 do
    downColumn()
    forward()
    left()
    upColumn()
    right()
    forward()
    right()
  end
end

function centre()
  forward()
  right()
  downColumn()
  forward()
  turtle.select(1)
  for i=1,depth do
    up()
    turtle.placeDown()
  end
end

function placeTorch()
  back()
  back()
  for i=1,depth do
    down()
    turtle.place()
  end
  for i=1,depth do
    up()
  end
  forward()
  forward()
end


left()
forward()
left()
forward()
left()
left()
setup()
centre()

for i=2,5 do
  turtle.select(i)
  placeTorch()
  left()
end
left()