[Haskell-cafe] shortest paths, prioritiy queues

Hello. I am looking for a single-source shortest-path implementation (Dijkstra's algorithm, cf. Chapter 25 in Cormen,Leiserson,Rivest). An efficient implementation would use Binomial or Fibonacci heaps (Chap.s 20 + 21). The problem seems to be "(fib-)heap-decrease-key" which assumes that we have, with the key, a pointer to its position in the heap, because that is where there will be a destructive update. How is this dealt with in Okasaki's book + library? - Thanks, J.W.