[Boost-users] Using a binomial_heap with indirect_cmp

Subject: [Boost-users] Using a binomial_heap with indirect_cmp
From: David Doria (daviddoria_at_[hidden])
Date: 2012-09-05 15:27:30

I am trying to keep a heap sorted by values in a property map. I tried
the code below, but the compiler does not like my arguments to the
heap constructor (PriorityQueueType pq(indirectComparison);).
According to the documentation
(http://www.boost.org/doc/libs/1_51_0/doc/html/boost/heap/binomial_heap.html),
there is a constructor:

  explicit binomial_heap(value_compare const & = value_compare());

that takes a value_compare, which I was thinking would of type
IndirectComparisonType that I provided (I don't really understand the
optional template arguments and the base_maker::compare_argument type
of things)?

Here is the indirect_cmp doc for reference:
http://www.boost.org/doc/libs/1_51_0/boost/pending/indirect_cmp.hpp

#include <boost/heap/binomial_heap.hpp>
#include <boost/pending/indirect_cmp.hpp>
#include <boost/array.hpp>
#include <boost/graph/grid_graph.hpp>
#include <iostream>

int main(int, char*[])
{
  // Construct a graph
  boost::array<std::size_t, 2> lengths = { { 2,2 } };
  typedef boost::grid_graph<2> GraphType;
  GraphType graph(lengths);
  typedef boost::graph_traits<GraphType>::vertex_descriptor Vertex;
  typedef boost::property_map<GraphType,
boost::vertex_index_t>::const_type GridIndexMapType;
  GridIndexMapType gridIndexMap(get(boost::vertex_index, graph));

  // Construct a property map
  typedef boost::vector_property_map<float, GridIndexMapType> PriorityMapType;
  PriorityMapType priorityMap(gridIndexMap);

  // Construct the indirect comparison functor
  typedef boost::indirect_cmp<PriorityMapType, std::less<float> >
IndirectComparisonType;
  IndirectComparisonType indirectComparison(priorityMap);

  // Construct the queue
  typedef int ValueType;
  typedef boost::heap::binomial_heap<ValueType,
boost::heap::stable<false>, IndirectComparisonType> PriorityQueueType;
  PriorityQueueType pq(indirectComparison);

  return 0;
}

Does anyone know how to provide this indirect comparison functor to
the queue properly?

Thanks,

David