Changing Roles

    void person::become(actor* p) { role[Person] = p; } 
 permanent


  
    void person::become(Role r) {
     require( Person <= r && r <= Final );
     if (exists()) self()->become(r);
     else {
       _role = r;
       if ( role [role] == this ) {
        switch (_role) {
          case Person:  break;                  
 nothing changes


          case Student: role [role] = new student; break;
          case Employer: role [role] = new employer; break;
          case Final: role [role] = new actor; break;
          };
       }
     }
    }