new Graph subclass edge_iterator

graph.h

@@ -15,6 +15,7 @@ class Graph {
 
 private:
   class Vertex;
+  class EdgeTo;
 
 public:
 
@@ -42,6 +43,8 @@ public:
     pointer m_destination;
     float m_weight;
   };
+  typedef Edge* edge_pointer;
+  typedef Edge& edge_reference;
 
 
   Graph();
@@ -62,6 +65,8 @@ public:
   bool contains(const_reference data) const;
   std::vector<pointer> vertices() const;
   std::vector<pointer> neighboursOf(const_reference data) const;
+
+  /// @todo come up with a more clear name
   std::vector<float> edgesBetween(const_reference source, const_reference destination) const;
   std::vector<Edge> edges() const;
 
@@ -98,8 +103,50 @@ public:
     typename std::vector<Vertex>::iterator m_it;
   };
 
-  vertex_iterator begin() { return vertex_iterator(m_vertices.begin()); }
-  vertex_iterator end() { return vertex_iterator(m_vertices.begin()); }
+  vertex_iterator vertex_begin() { return vertex_iterator(m_vertices.begin()); }
+  vertex_iterator vertex_end() { return vertex_iterator(m_vertices.end()); }
+
+  class edge_iterator : public std::iterator<std::forward_iterator_tag,
+                                             Edge,
+                                             difference_type,
+                                             edge_pointer,
+                                             edge_reference>
+  {
+  public:
+    typedef edge_iterator self_type;
+    typedef edge_iterator& reference_self_type;
+    typedef const edge_iterator& const_reference_self_type;
+
+    edge_iterator() : m_vertex_it(), m_edge_it(), m_edge(0) {}
+    edge_iterator(typename std::vector<Vertex>::iterator vertex_it,
+                  typename std::list<EdgeTo>::iterator edge_it)
+      : m_vertex_it(vertex_it), m_edge_it(edge_it) {}
+    ~edge_iterator() { if (m_edge) delete m_edge; }
+
+    edge_iterator(const_reference_self_type o)
+      : m_vertex_it(o.m_vertex_it), m_edge_it(o.m_edge_it) {}
+    reference_self_type operator=(const_reference_self_type o)
+      { if (this != &o) { m_vertex_it = o.m_vertex_it; m_edge_it = o.m_edge_it; } return *this; }
+
+    edge_reference operator*() { if (!m_edge) { m_edge = new Edge(*m_vertex_it, (*m_edge_it).m_destination, (*m_edge_it).m_weight); } return *m_edge; }
+    edge_pointer operator->() { if (!m_edge) { m_edge = new Edge(*m_vertex_it, (*m_edge_it).m_destination, (*m_edge_it).m_weight); } return m_edge; }
+
+    /// @todo implement: delete m_edge & step;
+//     self_type &operator++() { ++m_it; return *this; }
+//     self_type operator++(int) { self_type tmp(*this); ++(*this); return tmp; }
+//     self_type operator+(difference_type n) { self_type tmp(*this); tmp.pos_ += n; return tmp; }
+//     self_type &operator+=(difference_type n) {  m_it += n; return *this; }
+    bool operator==(const_reference_self_type o) { return m_vertex_it == o.m_vertex_it && m_edge_it == o.m_edge_it; }
+    bool operator!=(const_reference_self_type o) { return !(*this == o); }
+
+  private:
+    typename std::vector<Vertex>::iterator m_vertex_it;
+    typename std::list<EdgeTo>::iterator m_edge_it;
+    edge_pointer m_edge;
+  };
+
+  edge_iterator edge_begin() { return edge_iterator(m_vertices.begin()); }
+  edge_iterator edge_end() { return edge_iterator(m_vertices.end()); }
 
 
 private:

main.cpp

@@ -63,8 +63,8 @@ int main()
   std::vector<int> v(vertices_array, vertices_array + sizeof(vertices_array) / sizeof(int) );
   Graph<int>::vertex_iterator g_it;
   std::vector<int>::iterator v_it;
-  for (g_it = g.begin(), v_it = v.begin();
-       g_it != g.end();
+  for (g_it = g.vertex_begin(), v_it = v.begin();
+       g_it != g.vertex_end();
        g_it++, v_it++)
     assert(*g_it == *v_it);
 
@@ -79,8 +79,8 @@ int main()
 
   int vertices_array2[] = {1, 2, 3, 4};
   std::vector<int> v2(vertices_array2, vertices_array2 + sizeof(vertices_array2) / sizeof(int) );
-  for (g_it = g2.begin(), v_it = v2.begin();
-       g_it != g2.end();
+  for (g_it = g2.vertex_begin(), v_it = v2.begin();
+       g_it != g2.vertex_end();
        g_it++, v_it++)
     assert(*g_it == *v_it);