RhodeCode

        IncEdgeIt(const Graph&, const Edge&) { }

        /// Next incident arc

        /// Assign the iterator to the next incident arc

        /// of the corresponding node.

        IncEdgeIt& operator++() { return *this; }

      };

      /// The directed arc type.

      /// The directed arc type. It can be converted to the

      /// edge or it should be inherited from the undirected

      public:

        /// Default constructor

        /// @warning The default constructor sets the iterator

        /// to an undefined value.

        Arc() { }

        /// Copy constructor.

        /// Copy constructor.

        ///

        /// Initialize the iterator to be invalid.

        /// Initialize the iterator to be invalid.

        ///

        Arc(Invalid) { }

        /// Equality operator

        /// Two iterators are equal if and only if they point to the

        /// same object or both are invalid.

        bool operator==(Arc) const { return true; }

        /// Inequality operator

        bool operator!=(Arc) const { return true; }

        /// Artificial ordering operator.

        /// To allow the use of graph descriptors as key type in std::map or

        /// similar associative container we require this.

        ///

        /// \note This operator only have to define some strict ordering of

        /// the items; this order has nothing to do with the iteration

        /// ordering of the items.

        bool operator<(Arc) const { return false; }

      };

      /// This iterator goes through each directed arc.

      /// This iterator goes through each arc of a graph.

      /// Its usage is quite simple, for example you can count the number

      /// of arcs in a graph \c g of type \c Graph as follows:

      ///\code

      /// int count=0;

      /// for(Graph::ArcIt e(g); e!=INVALID; ++e) ++count;

      ///\endcode

      class ArcIt : public Arc {

      public: