miner

MAXSTEPS=50

-- Digs forward, one up and one down
function dig()
    while turtle.detect() do
        turtle.dig()
        sleep(1)
    end
    turtle.forward()
    turtle.digUp()
    turtle.digDown()
end

-- Returns a table {found: true, slot: 7} or {found: false}
-- itemName is expected to be what turtle.getItemDetail returns
-- for instance minecraft:torch
function find(itemName)
    report =  {["found"] = false}

    for slot=1,16 do
        item = turtle.getItemDetail(slot)

        if (item ~= nil and item.name == itemName) then
            report["found"] = true
             report["slot"] = slot
            return report
        end
    end

    return report
end

-- Try to place a torch if it can
function placeTorch()
    torch = find("minecraft:torch")
    if (torch.found) then
        turtle.select(torch.slot)
        turtle.turnLeft()
        turtle.dig()
        turtle.place()
        turtle.turnRight()
    end
end

for steps=1,MAXSTEPS do
    dig()
    if (steps%6 == 0) then
        placeTorch()
    end
end

turtle.turnRight()
dig()
turtle.turnRight()

for steps=1,MAXSTEPS do
    dig() -- no need to place torches
end