# HG changeset patch
# User alpar
# Date 1132147564 0
# Node ID 5f2f3d982eba1a2c867c199bc252ad3ff6a73426
# Parent  1530c115580fc2c0c8d5d59213f270e4333d1b5c
Empty graph is (strongly) connected.

diff -r 1530c115580f -r 5f2f3d982eba lemon/topology.h
--- a/lemon/topology.h	Wed Nov 16 13:21:57 2005 +0000
+++ b/lemon/topology.h	Wed Nov 16 13:26:04 2005 +0000
@@ -48,12 +48,12 @@
   /// Check that the given undirected graph connected.
   /// \param graph The undirected graph.
   /// \return %True when there is path between any two nodes in the graph.
-  /// \warning The empty graph is not connected.
+  /// \note By definition, the empty graph is connected.
   template <typename UndirGraph>
   bool connected(const UndirGraph& graph) {
     checkConcept<concept::UndirGraph, UndirGraph>();
     typedef typename UndirGraph::NodeIt NodeIt;
-    if (NodeIt(graph) == INVALID) return false;
+    if (NodeIt(graph) == INVALID) return true;
     Dfs<UndirGraph> dfs(graph);
     dfs.run(NodeIt(graph));
     for (NodeIt it(graph); it != INVALID; ++it) {
@@ -72,6 +72,8 @@
   ///
   /// \param graph The graph. It should be undirected.
   /// \return The number of components
+  /// \note By definition, the empty graph consists
+  /// of zero connected components.
   template <typename UndirGraph>
   int countConnectedComponents(const UndirGraph &graph) {
     checkConcept<concept::UndirGraph, UndirGraph>();
@@ -237,11 +239,11 @@
   /// \return %False when the graph is not strongly connected.
   /// \see connected
   ///
-  /// \warning Empty graph is not strongly connected.
+  /// \note By definition, the empty graph is strongly connected.
   template <typename Graph>
   bool stronglyConnected(const Graph& graph) {
     checkConcept<concept::StaticGraph, Graph>();
-    if (NodeIt(graph) == INVALID) return false;
+    if (NodeIt(graph) == INVALID) return true;
 
     typedef typename Graph::Node Node;
     typedef typename Graph::NodeIt NodeIt;
@@ -293,6 +295,8 @@
   ///
   /// \param graph The graph.
   /// \return The number of components
+  /// \note By definition, the empty graph has zero
+  /// strongly connected components.
   template <typename Graph>
   int countStronglyConnectedComponents(const Graph& graph) {
     checkConcept<concept::StaticGraph, Graph>();
@@ -356,10 +360,6 @@
   /// \image latex strongly_connected_components.eps "Strongly connected components" width=\textwidth
   ///
   /// \param graph The graph.
-  /// \param compMap A writable node map. The values will be set from 0 to
-  /// the number of the connected components minus one. Each values of the map
-  /// will be set exactly once, the values of a certain component will be
-  /// set continuously.
   /// \retval compMap A writable node map. The values will be set from 0 to
   /// the number of the strongly connected components minus one. Each values 
   /// of the map will be set exactly once, the values of a certain component