Problem with 'write(format()) ' wrapper

["Chris Percival" <cpercival@...>]

I have added a function Printf to my script using the following code:

int PrintfCmd(lua_State *L)
	{
	lua_getglobal(L,"format");
	lua_insert(L,1);
	lua_call(L,lua_gettop(L)-1,LUA_MULTRET);
	lua_getglobal(L,"_PRINT");
	lua_insert(L,1);
	lua_call(L,lua_gettop(L)-1,LUA_MULTRET);
	return lua_gettop(L);
	}

_PRINT is my own function that displays text.  If I call the Printf function
in the script with something like Printf(undeclared), then my _PRINTF
function gets NULL as a string.  However if I call format(undeclared), then
I get the following error:

bad argument #1 to `format' (string expected, got nil)

I can't explain why this happens, is it anything to do with the above code,
or is there somthing else wrong?  How could I fix it?

Thanks.

Chris Percival
Software Engineer
DDI: +44 (0)1249 700072
www.interaxis.co.uk