if (index >= args.length || args[index] instanceof vNull) { return dflt;
if (index >= args.length) { iRuntime.error(102); return 0.0;
static double argVal(vDescriptor[] args, int index, double dflt) // optional arg{    if (index >= args.length || args[index] instanceof vNull) {	return dflt;    } else {	return args[index].mkReal().value;    }}