public static <T extends DC> Equality getPhiEqu(Set<Pair<T,T>> done)
  { if(done!=null)
    { if(done.next!=null)
      { return new Equality(done.a.fst().delta(done.a.snd()).equa().getValue()&&getPhiEqu(done.next).getValue());
      }
      else
      { return new Equality(done.a.fst().delta(done.a.snd()).equa().getValue());
      }  
    }
    else
    { return new Equality(false);
    }  
  }