Include Graph.reindex_edges() and Graph.max_edge_index

These functions/properties provide more information and control about
edge indexing, which might be useful.

src/graph/graph_bind.cc

@@ -367,6 +367,7 @@ BOOST_PYTHON_MODULE(libgraph_tool_core)
         .def("GetVertexIndex", &GraphInterface::GetVertexIndex)
         .def("GetEdgeIndex", &GraphInterface::GetEdgeIndex)
         .def("GetMaxEdgeIndex", &GraphInterface::GetMaxEdgeIndex)
+        .def("ReIndexEdges", &GraphInterface::ReIndexEdges)
         .def("GetGraphIndex", &GraphInterface::GetGraphIndex)
         .def("CopyVertexProperty", &GraphInterface::CopyVertexProperty)
         .def("CopyEdgeProperty", &GraphInterface::CopyEdgeProperty);

src/graph/graph_filtering.cc

@@ -210,11 +210,9 @@ bool GraphInterface::IsEdgeFilterActive() const
 void GraphInterface::ReIndexEdges()
 {
     size_t index = 0;
-    graph_traits<multigraph_t>::vertex_iterator v, v_end;
-    graph_traits<multigraph_t>::out_edge_iterator e, e_end;
-    for (tie(v, v_end) = vertices(_mg); v != v_end; ++v)
-        for (tie(e, e_end) = out_edges(*v, _mg); e != e_end; ++e)
-            _edge_index[*e] = index++;
+    graph_traits<multigraph_t>::edge_iterator e, e_end;
+    for (tie(e, e_end) = edges( _mg); e != e_end; ++e)
+        _edge_index[*e] = index++;
     _max_edge_index =  (index > 0) ? index - 1 : 0;
     _nedges = index;
     _free_indexes.clear();

src/graph_tool/core.py

@@ -696,6 +696,26 @@ class Graph(object):
         return self.__edge_index
     edge_index = property(_get_edge_index, doc="Edge index map.")
 
+    def _get_max_edge_index(self):
+        return self.__graph.GetMaxEdgeIndex()
+    max_edge_index = property(_get_max_edge_index,
+                              doc="The maximum value of the edge index map.")
+
+    def reindex_edges(self):
+        """
+        Reset the edge indexes so that they lie in the [0, :meth:`~graph_tool.Graph.num_edges` - 1]
+        range. The index ordering will be compatible with the sequence returned
+        by the :meth:`~graph_tool.Graph.edges` function.
+
+        .. WARNING::
+
+           Calling this function will invalidate all existing edge property
+           maps, if the index ordering is modified! The property maps will still
+           be usable, but their contents will still be tied to the old indices,
+           and thus may be scrambled.
+        """
+        self.__graph.ReIndexEdges()
+
     # Property map creation
 
     def new_property(self, key_type, value_type):