This is a program for ComputerCraft, it tells the turtle to build a one wide bridge

bridge.lua

function refuel()
    local fueled = false
    
    for i=12,16 do
        turtle.select(i)
        fueled = turtle.refuel()
    end
    
    return fueled
end

function select_slot()
    for i=1,16 do
        if turtle.getItemCount(i) > 0 then
            turtle.select(i)
            return true
        end
    end
    
    return false
end

function bridge()
    if select_slot() then
        turtle.placeDown()
        
        if not turtle.forward() then
            turtle.dig()
            turtle.forward()
            turtle.digUp()
        end
        
        return true
    end
    
    term.write("Need Blocks!")
    return false
end
    
local tArgs = { ... }

function main()
    if not refuel() and turtle.getFuelLevel() <= 10 then
        term.write("No fuel!")
        return
    end
    
    local length = tonumber(tArgs[1])
    length = length or -1
    
    local let_turtle_return = true
    if tArgs[2] == "false" then
        let_turtle_return = false
    end
    
    local moved = -1
    
    while bridge() do
        moved = moved + 1
        
        if length > 0 and moved > length then
            term.write("I am done!")
            break
        end
        
        if moved >= turtle.getFuelLevel() and let_turtle_return then
            term.write("Need Fuel!")
            break
        end
    end
    
    if let_turtle_return then
        for i=0,moved do
            turtle.back()
        end
    end
end

main()