n implementation of priority queues. Priority
      queues are queue data structures, that order their elements by a priority.
      The STL provides a single template class <code class="literal">std::priority_queue</code>,
      which only provides a limited functionality. To overcome these limitations,
      <code class="literal">boost.heap</code> implements <a class="link" href="heap/data_structures.html" title="Data Structures">data
      structures</a> with more functionality and different performance 