static O analyzeBitMap_idToText; // func(long) -> S

// Looks only at the values

static void analyzeBitMap(MultiMap<Long, Long> bitMap) {

  analyzeBitMap(values(bitMap.data));

}

static void analyzeBitMap(Collection<L<Long>> bitMap) {

  if (bitMap.isEmpty()) ret;

  new HashSet<Long> allSeen;

  for (L<Long> l : bitMap)

    allSeen.addAll(l);

  printStruct(+allSeen);

  MultiMap<Long, Long> implies = fullSelfMap(allSeen);

  MultiMap<Long, Long> eq = fullSelfMap(allSeen);

  for (L<Long> l : bitMap) {

    HashSet<Long> set = new HashSet(l);

    for (Long a : cloneList(implies.keySet())) {

      bool ax = set.contains(a);

      for (Long b : cloneList(implies.get(a))) {

        bool bx = set.contains(b);

        if (ax && !bx)

          implies.remove(a, b);

      }

    }

    for (Long a : cloneList(eq.keySet())) {

      bool ax = set.contains(a);

      for (Long b : cloneList(eq.get(a))) {

        bool bx = set.contains(b);

        if (ax != bx)

          eq.remove(a, b);

      }

    }

  }

  printStruct(+implies);

  //printStruct(+eq);

  L<L<Long>> clusters = multiMapToClusters(eq);

  for i over clusters:

    print("Cluster \* i+1 */: " + struct(mapIfFunctionNotNull(analyzeBitMap_idToText, clusters.get(i))));

}

static MultiMap<Long, Long> fullSelfMap(Collection<Long> l) {

  new MultiMap<Long, Long> mm;

  for (Long x : l) mm.putAll(x, l);

  ret mm;

}

static L<L<Long>> multiMapToClusters(MultiMap<Long, Long> mm) {

  // a cluster is a list of concepts.

  // first, make trivial clusters (one per item).

  Map<Long, L<Long>> clusters = new TreeMap<Long, L<Long>>();

  for (Long a : mm.keySet()) {

    if (!clusters.containsKey(a))

      clusters.put(a, ll(a));

  }

  // then, merge the clusters.

  for (Long a : mm.keySet())

    for (Long b : mm.get(a)) {

      L<Long> c1 = clusters.get(a);

      L<Long> c2 = clusters.get(b);

      if (c1 != c2) // different clusters, need to merge!

        mergeClusters(clusters, c1, c2);

    }

  ret asList(new HashSet<L<Long>>(clusters.values()));

}

static void mergeClusters(Map<Long, L<Long>> clusters, L<Long> c1, L<Long> c2) {

  for (Long x : c2) {

    clusters.put(x, c1);

    c1.add(x);

  }

}