Remove all blocks ComputerCraft Script

blocks = {
    'redwood'
}
x = 0
y = 0
z = 0
xv = 1
yv = 0
todo = {{0,0,0}}
nodes = {['0,0,0']=1}
explored = {}
function digForward()
    while not turtle.forward() do
        turtle.dig()
    end
    x = x+xv
    y = y +yv
end

function digDown()
    while not turtle.down() do
        turtle.digDown()
    end
    z = z - 1
end

function digUp()
    while not turtle.up() do
        turtle.digUp()
    end
    z = z + 1
end

function turnRight()
    turtle.turnRight()
    if xv == 1 then
        xv, yv = 0, 1
    elseif xv == -1 then
        xv, yv = 0, -1
    elseif yv == 1 then
        yv, xv = 0, -1
    elseif yv == -1 then
        yv, xv = 0, 1
    end
end

function check(name)
    local a = false
    for k, pat in pairs(blocks) do
        a = a or name:find(pat)
    end
    return a
end

function newBlock(a, block, x,y,z)
    if a and check(block.name) then
        local newPoint = string.format('%i,%i,%i',x,y,z)
        if nodes[newPoint] then
            print('n: '..nodes[newPoint])
            todo[nodes[newPoint]] = nil
        end
        table.insert(todo, {x,y,z})
        print(#todo)
        nodes[newPoint] = #todo
    end
end

function newNode()
    local point = string.format('%i,%i,%i',x,y,z)
    if nodes[point] then
        todo[nodes[point]] = nil
    end
    explored[point] = true
    for i = 1, 4 do
        turnRight()
        local a, block = turtle.inspect()
        newBlock(a, block, x+xv,y+yv,z)
    end
    local a, block = turtle.inspectUp()
    newBlock(a, block, x,y,z+1)
    local a, block = turtle.inspectDown()
    newBlock(a, block, x,y,z-1)
    --goto first node on todo list
end

function sign(n)
    return (n > 0) and 1 or  -1
end

function goto(gx,gy,gz)
    --print(string.format('cords: %i, %i, %i', x, y, z))
    --print(string.format('goals: %i, %i, %i', gx, gy, gz))
    --print(string.format('velocity: %i, %i', xv, yv))
    --print('Todo: '..tostring(#todo))
    if gx ~= x then
        while sign(gx-x) ~= xv do
            turnRight()
        end
        while x ~= gx do
            digForward()
            --newNode()
        end
    elseif gy ~= y then
        while sign(gy-y) ~= yv do
            turnRight()
        end
        --while y ~= gy do
            digForward()
            --newNode()
        --end
    elseif z ~= gz then
        if gz > z then
            digUp()
            --newNode()
        else
            digDown()
        end
    else return end
    newNode()
    goto(gx,gy,gz)
end

newNode()
while #todo > 0 do
    if not todo[#todo] then table.remove(todo, #todo) print "table error" end
    goto(unpack(todo[#todo]))
end