public static String yieldGensymName(String prefix, int counter) {
    { String suffix = Native.integerToString(((long)(counter)));
      int maskend = 4 - suffix.length();

      if (maskend < 1) {
        maskend = 1;
      }
      return (prefix + Native.string_subsequence(Stella.$GENSYM_MASK$, 0, maskend) + suffix);
    }
  }