# HG changeset patch
# User deba
# Date 1121699248 0
# Node ID 96244ea562a3e1007c215b61b018eb4ee5066a78
# Parent  16d316199cf661358f13c876613f2b5367ccda03
Improve findEdge interface
ConEdgeIt is a high level replacement of findEdge

diff -r 16d316199cf6 -r 96244ea562a3 lemon/graph_utils.h
--- a/lemon/graph_utils.h	Mon Jul 18 15:05:50 2005 +0000
+++ b/lemon/graph_utils.h	Mon Jul 18 15:07:28 2005 +0000
@@ -160,8 +160,35 @@
   }
 
 
-  /// Finds an edge between two nodes of a graph.
+  template <typename Graph>
+  inline
+  typename enable_if<typename Graph::FindEdgeTag, typename Graph::Edge>::type 
+  _findEdge(const Graph &g,
+	    typename Graph::Node u, typename Graph::Node v,
+	    typename Graph::Edge prev = INVALID) {
+    return g.findEdge(u, v, prev);
+  }
 
+  template <typename Graph>
+  inline typename Graph::Edge 
+  _findEdge(Wrap<Graph> w,
+	    typename Graph::Node u, 
+	    typename Graph::Node v,
+	    typename Graph::Edge prev = INVALID) {
+    const Graph& g = w.value;
+    if (prev == INVALID) {
+      typename Graph::OutEdgeIt e(g, u);
+      while (e != INVALID && g.target(e) != v) ++e;
+      return e;
+    } else {
+      typename Graph::OutEdgeIt e(g, prev); ++e;
+      while (e != INVALID && g.target(e) != v) ++e;
+      return e;
+    }
+  }
+
+  /// \brief Finds an edge between two nodes of a graph.
+  ///
   /// Finds an edge from node \c u to node \c v in graph \c g.
   ///
   /// If \c prev is \ref INVALID (this is the default value), then
@@ -175,22 +202,65 @@
   ///   ...
   /// }
   /// \endcode
-  /// \todo We may want to use the "GraphBase"
-  /// interface here...
-  /// \bug Untested ...
+  // /// \todo We may want to use the "GraphBase" 
+  // /// interface here...
+  // /// It would not work with the undirected graphs.
   template <typename Graph>
-  typename Graph::Edge findEdge(const Graph &g,
-				typename Graph::Node u, typename Graph::Node v,
-				typename Graph::Edge prev = INVALID) 
-  {
-    typename Graph::OutEdgeIt e(g,prev);
-    //    if(prev==INVALID) g.first(e,u);
-    if(prev==INVALID) e=typename Graph::OutEdgeIt(g,u);
-    else ++e;
-    while(e!=INVALID && g.target(e)!=v) ++e;
-    return e;
+  inline typename Graph::Edge findEdge(const Graph &g,
+				       typename Graph::Node u, 
+				       typename Graph::Node v,
+				       typename Graph::Edge prev = INVALID) {
+    return _findEdge<Graph>(g, u, v, prev);
   }
 
+  /// \brief Iterator for iterating on edges connected the same nodes.
+  ///
+  /// Iterator for iterating on edges connected the same nodes. It is 
+  /// higher level interface for the findEdge() function. You can
+  /// use it the next way:
+  /// \code
+  /// for (ConEdgeIt<Graph> it(g, src, trg); it != INVALID; ++it) {
+  ///   ...
+  /// }
+  /// \endcode
+  ///
+  /// \author Balazs Dezso 
+  template <typename _Graph>
+  class ConEdgeIt : public _Graph::Edge {
+  public:
+
+    typedef _Graph Graph;
+    typedef typename Graph::Edge Parent;
+
+    typedef typename Graph::Edge Edge;
+    typedef typename Graph::Node Node;
+
+    /// \brief Constructor.
+    ///
+    /// Construct a new ConEdgeIt iterating on the edges which
+    /// connects the \c u and \c v node.
+    ConEdgeIt(const Graph& g, Node u, Node v) : graph(g) {
+      Parent::operator=(findEdge(graph, u, v));
+    }
+
+    /// \brief Constructor.
+    ///
+    /// Construct a new ConEdgeIt which continues the iterating from 
+    /// the \c e edge.
+    ConEdgeIt(const Graph& g, Edge e) : Parent(e), graph(g) {}
+    
+    /// \brief Increment operator.
+    ///
+    /// It increments the iterator and gives back the next edge.
+    ConEdgeIt& operator++() {
+      Parent::operator=(findEdge(graph, graph.source(*this), 
+				 graph.target(*this), *this));
+      return *this;
+    }
+  private:
+    const Graph& graph;
+  };
+
   /// \brief Copy a map.
   ///
   /// This function copies the \c source map to the \c target map. It uses the