gistfile1.lua

-- run by calling: f=fs.open("excavate","w");f.write(http.get("https://raw.github.com/gist/4299979").readAll());f.close();dofile("excavate")
-- orientation: 0 = N, 1 = E, 2 = S, 3 = W

x_pos = 0
y_pos = 0
z_pos = 0
orientation = 0
current_slot = 1

function orient_to(target_orientation)
    delta_orientation = ((target_orientation % 4) - orientation) % 4

    if delta_orientation == 3 then
        delta_orientation = -1
    end

    if delta_orientation == -3 then
        delta_orientation = 1
    end

    while delta_orientation > 0 do
        turtle.turnRight()
        delta_orientation = delta_orientation - 1
    end

    while delta_orientation < 0 do
        turtle.turnLeft()
        delta_orientation = delta_orientation + 1
    end

    orientation = target_orientation
end


function move_up()
    turtle.digUp()
    turtle.attackUp()
    turtle.suckUp()

    r = turtle.up()
    if r then
        y_pos = y_pos + 1
    end

    return r
end


function move_down()
    turtle.digDown()
    turtle.attackDown()
    turtle.suckDown()

    r = turtle.down()
    if r then
        y_pos = y_pos - 1
    end

    return r
end

function move_forward()
    turtle.dig()
    turtle.attack()
    turtle.suck()

    r = turtle.forward()
    if r then
        if orientation == 0 then
            z_pos = z_pos + 1
        elseif orientation == 1 then
            x_pos = x_pos + 1
        elseif orientation == 2 then
            z_pos = z_pos - 1
        elseif orientation == 3 then
            x_pos = x_pos - 1
        end
    end

    return r
end


function move_to_pos_step(target_x, target_z, target_y)
    -- prioritize y over x over z

    -- we're under the target point
    if y_pos < target_y then
        move_up()
    end

    -- we're above the target point
    if y_pos > target_y then
        move_down()
    end

    -- we're to the west of the target point
    if x_pos < target_x then
        orient_to(1)
        move_forward()
    end

    -- we're to the east of the target point
    if x_pos > target_x then
        orient_to(3)
        move_forward()
    end

    -- we're to the south of the target point
    if z_pos < target_z then
        orient_to(0)
        move_forward()
    end

    -- we're to the north of the target point
    if z_pos > target_z then
        orient_to(2)
        move_forward()
    end

    if x_pos == target_x and y_pos == target_y and z_pos == target_z then
        return true
    else
        return false
    end
end

function move_to_pos(target_x, target_y, target_z)
    while not move_to_pos_step(target_x, target_y, target_z) do

    end
end

function inventory_has_empty_slot()
    for i = 1, 16 do
        if turtle.getItemCount(i) == 0 then
            return true
        end
    end

    return false
end

function iterate_point(x, y, limit)
  z1 = 0
  z2 = 0
  c1 = x
  c2 = y
  for i=0, limit do
    a = z1*z1 - z2*z2 + c1
    b = 2*z1*z2 + c2
    z1 = a
    z2 = b
    if (z1*z1 + z2*z2 > 4) then
      return i
    else
      return -1
    end
  end
end

function draw(width, length, height)
  move_to_pos(0, 0, height+1)
  for z=0, width do
    move_to_pos(z, 0, height+1)
    orient_to(0)
    y_math = 4*(z/width) - 2
    for x=0, length do
      x_math = 4*(x/length) - 2
      if (iterate_point(x_math, y_math, 200) == -1) then
        if (turtle.getItemCount(current_slot) == 0) then
          current_slot = current_slot+1
          turtle.select(current_slot)
        end
        turtle.placeDown()
      end
      move_forward()
    end
  end
  move_to_pos(0, 0, height+1)
  move_to_pos(0, 0, 0)
end

function main()
    turtle.select(current_slot)
    term.clear()
    term.setCursorPos(1, 1)
    print("----- Excavate program -----")
    print("")
    print("What dimensions?")
    print("")
    term.write("Width (to the right of the turtle): ")
    z = math.abs(tonumber(io.read()))

    term.write("Length (in front of the turtle): ")
    x = math.abs(tonumber(io.read()))
     
    term.write("Height: ")
    y = math.abs(tonumber(io.read()))

    print("Excavating...")
    draw(z, x, y)
    print("Done!")
end

main()