How do I get elements from boost::fibonacci_heap by handle?

Question

I am using the boost::fibonacci_heap class from Boost 1.53.0 to maintain an updateable priority queue.

When I want to update an element I need to compare the element in the heap with the new element that I want to replace it with. I only want to replace elements in the heap with "smaller" versions so I want to compare them before I update.

When I insert elements I store their handle (boost::fibonacci_heap::handle_type). All the functions I have seen in the documentation for fibonacci_heap that take a handle type only provide some sort of write access (update(), decrease(), increase() etc.) and don't allow me to inspect the element identified by the handle before I update it.

Is there some way to look at an element in a fibonacci_heap by using its handle only?

Answer 1

You should be able to dereference the handle. An example of this is provided here: http://www.boost.org/doc/libs/1_50_0/doc/html/heap/concepts.html

Example from site

fibonacci_heap<heap_data> heap;
heap_data f;
fibonacci_heap<heap_data>::handle_type handle = heap.push(f);
(*handle).handle = handle; // store handle in node

So simply call

(*handle)

to get the reference to your class stored in the heap.