private int stringChar(LuaCallFrame callFrame, int nArguments) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < nArguments; i++) {
            int num = getDoubleArg(callFrame, i + 1, names[CHAR]).intValue();
            sb.append((char) num);
        }
        return callFrame.push(sb.toString());
    }
Only works with non-negative numbers
main/src/main/java/cgeo/geocaching/wherigo/kahlua/stdlib/StringLib.java