Re: [Boost-Users] Re: Q: Graphs. Sorting edges. Possible? How to?

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2002-06-19 09:32:28

On Wed, 19 Jun 2002, stas_fomin wrote:
stas_f> > By using a custom container (use a std::set with your custom
stas_f> comparison
stas_f> > function) for the EdgeList type, you can get the out-edges of each
stas_f> vertex
stas_f> > sorted, but there currently is not a way to get the entire edge list
stas_f> > sorted.
stas_f> Ok... But BGL docs is less understandable (in comparison with
stas_f> LEDAbook) for me (I know I am stupid).

Have you tried reading the BGL book?

stas_f> So, please, show me small example of declaration
stas_f> of some graph with out_edges sorted according to some function...

Here you go. Also, this example is checked into the libs/graph/example/
directory.

#include <boost/config.hpp>
#include <iostream>
#include <functional>
#include <string>

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/properties.hpp>

/*
  Sample output:

  0  --chandler--> 1   --joe--> 1
  1  --chandler--> 0   --joe--> 0   --curly--> 2   --dick--> 3   --dick-->
3
  2  --curly--> 1   --tom--> 4
  3  --dick--> 1   --dick--> 1   --harry--> 4
  4  --tom--> 2   --harry--> 3

  name(0,1) = chandler

  name(0,1) = chandler
  name(0,1) = joe

 */

template <class StoredEdge>
struct order_by_name
  : public std::binary_function<StoredEdge,StoredEdge,bool>
{
  bool operator()(const StoredEdge& e1, const StoredEdge& e2) const {
    // Order by target vertex, then by name.
    // std::pair's operator< does a nice job of implementing
    // lexicographical compare on tuples.
    return std::make_pair(e1.get_target(), boost::get(boost::edge_name,
e1))
      < std::make_pair(e2.get_target(), boost::get(boost::edge_name, e2));
  }
};
struct ordered_set_by_nameS { };

#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
namespace boost {
  template <class ValueType>
  struct container_gen<ordered_set_by_nameS, ValueType> {
    typedef std::multiset<ValueType, order_by_name<ValueType> > type;
  };
  template <>
  struct parallel_edge_traits<ordered_set_by_nameS> {
    typedef allow_parallel_edge_tag type;
  };
}
#endif
int
main()
{
#ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  std::cout << "This program requires partial specialization" <<
std::endl;
#else
  using namespace boost;
  typedef property<edge_name_t, std::string> EdgeProperty;
  typedef adjacency_list<ordered_set_by_nameS, vecS, undirectedS,
    no_property, EdgeProperty> graph_type;
  graph_type g;

  add_edge(0, 1, EdgeProperty("joe"), g);
  add_edge(1, 2, EdgeProperty("curly"), g);
  add_edge(1, 3, EdgeProperty("dick"), g);
  add_edge(1, 3, EdgeProperty("dick"), g);
  add_edge(2, 4, EdgeProperty("tom"), g);
  add_edge(3, 4, EdgeProperty("harry"), g);
  add_edge(0, 1, EdgeProperty("chandler"), g);

  property_map<graph_type, vertex_index_t>::type id = get(vertex_index,
g);
  property_map<graph_type, edge_name_t>::type name = get(edge_name, g);

  graph_traits<graph_type>::vertex_iterator i, end;
  graph_traits<graph_type>::out_edge_iterator ei, edge_end;
  for (boost::tie(i, end) = vertices(g); i != end; ++i) {
    std::cout << id[*i] << " ";
    for (boost::tie(ei, edge_end) = out_edges(*i, g); ei != edge_end;
++ei)
      std::cout << " --" << name[*ei] << "--> " << id[target(*ei, g)] << "
";
    std::cout << std::endl;
  }
  std::cout << std::endl;

  bool found;
  typedef graph_traits<graph_type> Traits;
  Traits::edge_descriptor e;
  Traits::out_edge_iterator e_first, e_last;

  tie(e, found) = edge(0, 1, g);
  if (found)
    std::cout << "name(0,1) = " << name[e] << std::endl;
  else
    std::cout << "not found" << std::endl;
  std::cout << std::endl;

  tie(e_first, e_last) = edge_range(0, 1, g);
  while (e_first != e_last)
    std::cout << "name(0,1) = " << name[*e_first++] << std::endl;
#endif
  return 0;
}

----------------------------------------------------------------------
 Jeremy Siek                          http://php.indiana.edu/~jsiek/
 Ph.D. Student, Indiana Univ. B'ton   email: jsiek_at_[hidden]
 C++ Booster (http://www.boost.org)   office phone: [phone]
----------------------------------------------------------------------