RhodeCode

        if (arc != INVALID) return direct(arc, false);

      }

      return INVALID;

    }

    Edge findEdge(Node s, Node t, Edge p = INVALID) const {

      if (s != t) {

        if (p == INVALID) {

          Edge arc = Parent::findArc(s, t);

          if (arc != INVALID) return arc;

          arc = Parent::findArc(t, s);

          if (arc != INVALID) return arc;

        } else if (Parent::s(p) == s) {

          Edge arc = Parent::findArc(s, t, p);

          if (arc != INVALID) return arc;

          arc = Parent::findArc(t, s);

          if (arc != INVALID) return arc;

        } else {

          Edge arc = Parent::findArc(t, s, p);

          if (arc != INVALID) return arc;

        }

      } else {

        return Parent::findArc(s, t, p);

      }

      return INVALID;

    }

  };

  template <typename Base>

  class BidirBpGraphExtender : public Base {

  public:

    typedef Base Parent;

    typedef BidirBpGraphExtender Digraph;

    typedef typename Parent::Node Node;

    typedef typename Parent::Edge Edge;

    using Parent::first;

    using Parent::next;

    using Parent::id;

    class Red : public Node {

      friend class BidirBpGraphExtender;

    public:

      Red() {}

      Red(const Node& node) : Node(node) {

      }

      Red& operator=(const Node& node) {

        Node::operator=(node);

        return *this;

      }

      Red(Invalid) : Node(INVALID) {}

      Red& operator=(Invalid) {

        Node::operator=(INVALID);

        return *this;

      }

    };

    void first(Red& node) const {

      Parent::firstRed(static_cast<Node&>(node));

    }

    void next(Red& node) const {

      Parent::nextRed(static_cast<Node&>(node));

    }

    int id(const Red& node) const {

      return Parent::redId(node);

    }

    class Blue : public Node {

      friend class BidirBpGraphExtender;

    public:

      Blue() {}

      Blue(const Node& node) : Node(node) {

      }

      Blue& operator=(const Node& node) {

        Node::operator=(node);

        return *this;

      }

      Blue(Invalid) : Node(INVALID) {}

      Blue& operator=(Invalid) {

        Node::operator=(INVALID);

        return *this;

      }

    };

    void first(Blue& node) const {

      Parent::firstBlue(static_cast<Node&>(node));

    }

    void next(Blue& node) const {

      Parent::nextBlue(static_cast<Node&>(node));

    }

    int id(const Blue& node) const {

      return Parent::redId(node);

    }

    Node source(const Edge& arc) const {

      return red(arc);

    }

    Node target(const Edge& arc) const {

      return blue(arc);

    }

    void firstInc(Edge& arc, bool& dir, const Node& node) const {

      if (Parent::red(node)) {

        Parent::firstFromRed(arc, node);

        dir = true;

      } else {

        Parent::firstFromBlue(arc, node);

        dir = static_cast<Edge&>(arc) == INVALID;

      }

    }

    void nextInc(Edge& arc, bool& dir) const {

      if (dir) {

        Parent::nextFromRed(arc);

      } else {

        Parent::nextFromBlue(arc);

        if (arc == INVALID) dir = true;

      }

    }

    class Arc : public Edge {

      friend class BidirBpGraphExtender;