public static Batch <Recreation> audienceFor(Boardable venue, Performance p) {
    final Batch <Recreation> audience = new Batch <Recreation> () ;
    for (Mobile m : venue.inside()) if (m instanceof Actor) {
      final Actor a = (Actor) m ;
      for (Behaviour b : a.mind.agenda()) if (b instanceof Recreation) {
        final Recreation r = (Recreation) b ;
        if (p.matches(r)) { audience.add(r) ; break ; }
      }
    }
    return audience ;
  }