!752

//static new Set<S> things;
static new L<S> sentences;
static Map<S, L<S>> rewrites = new TreeMap; // thing -> cluster

p {
  addRewrite("john", "johnnie");
  addRewrite("klaus", "klausi");
  assertTrue(isThing("john"));
  assertTrue(isThing("klausi"));
  assertFalse(isThing("jack"));
  print("all ok");
}

static void addThing(S a) {
  addRewrite(a, a);
}

static void addRewrite(S a, S b) {
  if (eq(a, b)) {
    L<S> cluster = rewrites.get(a);
    if (cluster == null)
      rewrites.put(a, litlist(a));
    ret;
  }
  
  L<S> clusterA = rewrites.get(a);
  L<S> clusterB = rewrites.get(b);
  if (clusterA == null && clusterB == null) {
    L<S> cluster = litlist(a, b);
    rewrites.put(a, cluster);
    rewrites.put(b, cluster);
  } else if (clusterA == null) {
    clusterB.add(a);
    rewrites.put(a, clusterB);
  } else if (clusterB == null) {
    clusterA.add(b);
    rewrites.put(b, clusterA);
  } else if (clusterA != clusterB)
    mergeClusters(clusterA, clusterB);
}

static void mergeClusters(L<S> a, L<S> b) {
  for (S x : b) {
    a.add(x);
    rewrites.put(x, a);
  }
}

static boolean isThing(S a) {
  ret rewrites.containsKey(a);
}