# HG changeset patch
# User Peter Kovacs <kpeter@inf.elte.hu>
# Date 1255347675 -7200
# Node ID 41bdb4d6c8c32c29a1eaebc3eef9bef7ef1f9862
# Parent  32fb28fc9d4298c95033cd2d41e634757d6952b4
Fix in pathSource() and pathTarget() (#250)
and extend the doc.

diff -r 32fb28fc9d42 -r 41bdb4d6c8c3 lemon/path.h
--- a/lemon/path.h	Tue Apr 28 18:45:29 2009 +0100
+++ b/lemon/path.h	Mon Oct 12 13:41:15 2009 +0200
@@ -1015,18 +1015,20 @@
 
   /// \brief The source of a path
   ///
-  /// This function returns the source of the given path.
+  /// This function returns the source node of the given path.
+  /// If the path is empty, then it returns \c INVALID.
   template <typename Digraph, typename Path>
   typename Digraph::Node pathSource(const Digraph& digraph, const Path& path) {
-    return digraph.source(path.front());
+    return path.empty() ? INVALID : digraph.source(path.front());
   }
 
   /// \brief The target of a path
   ///
-  /// This function returns the target of the given path.
+  /// This function returns the target node of the given path.
+  /// If the path is empty, then it returns \c INVALID.
   template <typename Digraph, typename Path>
   typename Digraph::Node pathTarget(const Digraph& digraph, const Path& path) {
-    return digraph.target(path.back());
+    return path.empty() ? INVALID : digraph.target(path.back());
   }
 
   /// \brief Class which helps to iterate through the nodes of a path