Optional Arguments

rednet.send(message, id, [protocol]

function foo(bar,...)
local notRiggedArgs = {...}
if notRiggedArgs[1] ~= nil then
print("OPTIONAL ARGUMENT!!!!one")
else
print("no optional argument awww")
end
end

function send( nRecipient, message, sProtocol )
    -- Generate a (probably) unique message ID
    -- We could do other things to guarantee uniqueness, but we really don't need to
    -- Store it to ensure we don't get our own messages back
    local nMessageID = math.random( 1, 2147483647 )
    tReceivedMessages[ nMessageID ] = true
    tReceivedMessageTimeouts[ os.startTimer( 30 ) ] = nMessageID

    -- Create the message
    local nReplyChannel = os.getComputerID()
    local tMessage = {
        nMessageID = nMessageID,
        nRecipient = nRecipient,
        message = message,
        sProtocol = sProtocol,
    }

    if nRecipient == os.getComputerID() then
        -- Loopback to ourselves
        os.queueEvent( "rednet_message", nReplyChannel, message, sProtocol )

    else
        -- Send on all open modems, to the target and to repeaters
        local sent = false
        for n,sModem in ipairs( peripheral.getNames() ) do
            if isOpen( sModem ) then
                peripheral.call( sModem, "transmit", nRecipient, nReplyChannel, tMessage );
                peripheral.call( sModem, "transmit", CHANNEL_REPEAT, nReplyChannel, tMessage );
                sent = true
            end
        end
    end
end

local function printSomeText(text1, text2)
   print(text1 or "") --# Pass text1 to print, or an empty string (will still make a new line) if text1 is nil.
   print(text2 or "") --# Same as above but with text2.
end

printSomeText("hello", "world") --# Prints
                                        --# hello
                                        --# world
printSomeText("hello") --# Prints hello and an empty line.
printSomeText() --# Prints two empty lines.