asclass ILCCompactIndex {
  S its(int idx) { ret itemToString(idx); }
  abstract S itemToString(int idx);
  abstract int[] getLeftPairs(int symbol);
  abstract int[] getRightPairs(int symbol);
  abstract int getProdLength(int idx);
  abstract int getOccurrences(int idx);
  abstract int lookupLiteral(char c);
  int pairLeft(int idx) { ret firstIntFromLong(getPair(idx)); }
  int pairRight(int idx) { ret secondIntFromLong(getPair(idx)); }
  abstract long getPair(int idx);
  abstract IntegerIterator getRightPairsStartingWith(int symbol, S from, S to);
  abstract IntegerIterator getLeftPairsEndingWith(int symbol, S from, S to);
  abstract L<Int> symbolToFiles(int symbol);
  abstract S symbolToProtocol(int symbol);
}