//=======================================================================

 // Copyright 2002 Indiana University.

 // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek

 //

 // Distributed under the Boost Software License, Version 1.0. (See

 // accompanying file LICENSE_1_0.txt or copy at

 // http://www.boost.org/LICENSE_1_0.txt)

 //=======================================================================

 #ifndef BOOST_GRAPH_EXCEPTION_HPP

 #define BOOST_GRAPH_EXCEPTION_HPP

 #include <stdexcept>

 #include <string>

 namespace boost {

   struct bad_graph : public std::invalid_argument {

     bad_graph(const std::string& what_arg)

       : std::invalid_argument(what_arg) { }

   };

   struct not_a_dag : public bad_graph {

     not_a_dag()

         : bad_graph("The graph must be a DAG.") { } 

   };

   struct negative_edge : public bad_graph {

     negative_edge()

       : bad_graph("The graph may not contain an edge with negative weight."){ }

   };

   struct negative_cycle : public bad_graph {

     negative_cycle()

       : bad_graph("The graph may not contain negative cycles.") { }

   };

   struct not_connected : public bad_graph {

     not_connected()

       : bad_graph("The graph must be connected.") { }

   };

 } // namespace boost

 #endif // BOOST_GRAPH_EXCEPTION_HPP