!752

// A vessel is a list of strings (sentences).

sclass Vessel {

  new L<S> data;

  int index;

  *() {}

  *(L<S> *data, int *index) {}

  void add(S s) {

    data.add(simplify(s));

  }

  bool consume(S s) {

    if (end()) ret false;

    s = simplify(s);

    /*if (same(next(), s)) {

      ++index;

      ret true;

    }

    ret false;*/

    //++index;

    if (!same(next(), s)) {

      --index;

      ret false;

    }

    ret true;

  }

  void restart() {

    index = 0;

  }

  // may be null if index after end

  S next() {

    ret end() ? null : get(data, index++);

  }

  bool end() {

    ret index >= l(data);

  }

  public Vessel clone() {

    ret new Vessel(cloneList(data), index);

  }

}

static S simplify(S s) {

  ret s.trim().toUpperCase();

}

static bool same(S a, S b) {

  ret eq(a, b);

}

p {

  new Vessel v;

  v.add("hello");

  v.add("world");

  print("HELLO");

  assertTrue(v.consume("HELLO"));

  assertEquals(1, v.index);

  print("world? " + v.next());

  print("end? " + v.end());

}