if (index >= args.length || args[index] instanceof vNull) { return dflt;
if (index >= args.length) { iRuntime.error(101); return 0;
static long argVal(vDescriptor[] args, int index, int dflt)	// optional arg{    if (index >= args.length || args[index] instanceof vNull) {	return dflt;    } else {	return args[index].mkInteger().value;    }}