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// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// 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

#include <boost/config.hpp>
#include <boost/property_map/property_map.hpp>
#include <boost/graph/depth_first_search.hpp>
#include <boost/graph/visitors.hpp>
#include <boost/graph/exception.hpp>
#include <boost/throw_exception.hpp>

namespace boost

// Topological sort visitor
// This visitor merely writes the linear ordering into an
// OutputIterator. The OutputIterator could be something like an
// ostream_iterator, or it could be a back/front_insert_iterator.
// Note that if it is a back_insert_iterator, the recorded order is
// the reverse topological order. On the other hand, if it is a
// front_insert_iterator, the recorded order is the topological
// order.
template < typename OutputIterator >
struct topo_sort_visitor : public dfs_visitor<>
    topo_sort_visitor(OutputIterator _iter) : m_iter(_iter) {}

    template < typename Edge, typename Graph >
    void back_edge(const Edge&, Graph&)

    template < typename Vertex, typename Graph >
    void finish_vertex(const Vertex& u, Graph&)
        *m_iter++ = u;

    OutputIterator m_iter;

// Topological Sort
// The topological sort algorithm creates a linear ordering
// of the vertices such that if edge (u,v) appears in the graph,
// then u comes before v in the ordering. The graph must
// be a directed acyclic graph (DAG). The implementation
// consists mainly of a call to depth-first search.

template < typename VertexListGraph, typename OutputIterator, typename P,
    typename T, typename R >
void topological_sort(VertexListGraph& g, OutputIterator result,
    const bgl_named_params< P, T, R >& params)
    typedef topo_sort_visitor< OutputIterator > TopoVisitor;
    depth_first_search(g, params.visitor(TopoVisitor(result)));

template < typename VertexListGraph, typename OutputIterator >
void topological_sort(VertexListGraph& g, OutputIterator result)
        g, result, bgl_named_params< int, buffer_param_t >(0)); // bogus

} // namespace boost