Square Mine (Computer Craft)

function driver(n) -- Drives whole program
    for i = 1,3 do
        tunnel(n)
    end
    tunnelLastWall(n)
    if(n >= 6) then
        for i = 1,3 do
            tunnelFor()
        end
    end
end

function tunnel(n) -- Dig a tunnel straight out
    for i = 1,n-1 do
        tunnelFor()
    end
    turtle.turnRight()
end

function tunnelLastWall(n) -- Dig fourth tunnel (shorter than normal tunnel)
    for i = 1,n-4 do
        tunnelFor()
    end
    turtle.turnRight()
end

function tunnelFor() -- Tunnel forward
    gravelDig()
    turtle.forward()
    turtle.digUp()
    count = count + 1
    if count % 7 == 0 then
        torch()
    end
    checkWalls()
end

function checkWalls() -- Fill in walls to avoid water/lave problems
    turtle.select(2)
    if(turtle.detectDown() == false) then
        turtle.placeDown()
    end
    turtle.turnLeft()
    detectAndPlace()
    turnAround()
    detectAndPlace()
    gravelDigUp()
    turtle.up()
    if(turtle.detectUp() == false) then
        turtle.placeUp()
    end
    detectAndPlace()
    turnAround()
    detectAndPlace()
    turtle.turnRight()
    turtle.down()
end

function torch() -- Place torch every 7 spots
    turtle.select(1)
    turtle.turnLeft()
    gravelDig()
    turtle.place()
    turtle.turnRight()
end

function turnAround() -- 180 degree turn
    turtle.turnRight()
    turtle.turnRight()
end

function detectAndPlace() -- Place block if nothing there
    if(turtle.detect() == false) then
        turtle.place()
    end
end

function gravelDig() -- Dig forward, check for gravel/sand
    while(turtle.detect()) do
        turtle.dig()
    end
end

function gravelDigUp() -- Dig up, checking for gravel/sand
    while(turtle.detectUp()) do
        turtle.digUp()
    end
end

local n
count = 0
print("Torches in slot 1. Cobblestone in slot 2.");
print("Enter size of square mine.");
n = tonumber(read())

while(n >= 0) do
    driver(n)
    n = n - 6
end