Method add

Structural/Flyweight/flyweight.cpp:56–67

  static int seed;

  static key add(const string& s)
  {
    auto it = names.right.find(s);
    if (it == names.right.end())
    {
      // add it
      key id = ++seed;
      names.insert({seed, s});
      return id;
    }
    return it->second;
  }
  key first_name, last_name;
};