text: //
  //=======================================================================
  // 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
  // http://www.boost.org/LICENSE_1_0.txt)
  //=======================================================================
  //
  #ifndef BOOST_MUTABLE_QUEUE_HPP
  #define BOOST_MUTABLE_QUEUE_HPP
  
  #include <vector>
  #include <algorithm>
  #include <functional>
  #include <boost/property_map/property_map.hpp>
  #include <boost/pending/mutable_heap.hpp>
  #include <boost/pending/is_heap.hpp>
  #include <boost/graph/detail/array_binary_tree.hpp>
  #include <iterator>
  
  namespace boost {
  
    // The mutable queue whose elements are indexed
    //
    // This adaptor provides a special kind of priority queue that has
    // and update operation. This allows the ordering of the items to
    // change. After the ordering criteria for item x changes, one must
    // call the Q.update(x)
    //
    // In order to efficiently find x in the queue, a functor must be
    // provided to map value_type to a unique ID, which the
    // mutable_queue will then use to map to the location of the
    // item. The ID's generated must be between 0 and N, where N is the
    // value passed to the constructor of mutable_queue
  
    template <class IndexedType,
              class RandomAccessContainer = std::vector<IndexedType>,
              class Comp = std::less<typename RandomAccessContainer::value_type>,
              class ID = identity_property_map >
    class mutable_queue {
    public:
      typedef IndexedType value_type;
      typedef typename RandomAccessContainer::size_type size_type;
    protected:
      typedef typename RandomAccessContainer::iterator iterator;
  #if !defined BOOST_NO_STD_ITERATOR_TRAITS
      typedef array_binary_tree_node<iterator, ID> Node;
  #else
      typedef array_binary_tree_node<iterator, value_type, ID> Node;
  #endif
      typedef compare_array_node<RandomAccessContainer,Comp> Compare;
      typedef std::vector<size_type> IndexArray;
    public:
      typedef Compare value_compare;
      typedef ID id_generator;
  
      mutable_queue(size_type n, const Comp& x, const ID& _id)
        : index_array(n), comp(x), id(_id) {
        c.reserve(n);
      }
      template <class ForwardIterator>
      mutable_queue(ForwardIterator first, ForwardIterator last,
                    const Comp& x, const ID& _id)
        : index_array(std::distance(first, last)), comp(x), id(_id)
      {
        while( first != last ) {
          push(*first);
          ++first;
        }
      }
  
      bool empty() const { return c.empty(); }
  
      void pop() {
        value_type tmp = c.back();
        c.back() = c.front();
        c.front() = tmp;
  
        size_type id_f = get(id, c.back());
        size_type id_b = get(id, tmp);
        size_type i = index_array[ id_b ];
        index_array[ id_b ] = index_array[ id_f ];
        index_array[ id_f ] = i;
  
        c.pop_back();
        Node node(c.begin(), c.end(), c.begin(), id);
        down_heap(node, comp, index_array);
      }
      void push(const IndexedType& x) {
        c.push_back(x);
        /*set index-array*/
        index_array[ get(id, x) ] = c.size()-1;
        Node node(c.begin(), c.end(), c.end() - 1, id);
        up_heap(node, comp, index_array);
      }
  
      void update(const IndexedType& x) {
        size_type current_pos = index_array[ get(id, x) ];
        c[current_pos] = x;
  
        Node node(c.begin(), c.end(), c.begin()+current_pos, id);
        update_heap(node, comp, index_array);
      }
  
      value_type& front() { return c.front(); }
      value_type& top() { return c.front(); }
  
      const value_type& front() const { return c.front(); }
      const value_type& top() const { return c.front(); }
  
      size_type size() const { return c.size(); }
  
      void clear() { c.clear(); }
  
  #if 0
          // dwa 2003/7/11 - I don't know what compiler is supposed to
          // be able to compile this, but is_heap is not standard!!
      bool test() {
        return std::is_heap(c.begin(), c.end(), Comp());
      }
  #endif
  
     protected:
      IndexArray index_array;
      Compare comp;
      RandomAccessContainer c;
      ID id;
    };
  
  
  }
  
  #endif // BOOST_MUTABLE_QUEUE_HPP
  