Meldable priority queues in Clojure, based on Okasaki's maxiphobic heaps.
See Okasaki, "Alternatives to Two Classic Data Structures".
There is a single public namespace called maxiphobe.core:
(require '[maxiphobe.core :as pq])There are four factory functions:
;; return a priority queue containing the contents of the input collection
(pq/pq [0 -1 3 4 2])
;= (-1 0 2 3 4)
;; as above, but with a custom comparator
(pq/pq-by > [0 -1 3 4 2])
;= (4 3 2 0 -1)
;; return a priority queue containing the given items
(pq/pqueue 0 -1 3 4 2)
;= (-1 0 2 3 4)
;; as above, but with a custom comparator
(pq/pqueue-by > 0 -1 3 4 2)
;= (4 3 2 0 -1)Priority queues can be melded:
(pq/meld (pq/pq [0 -1 3 4 2]) (pq/pq [8 -3 10 2 4 2]))
;= (-3 -1 0 2 2 2 3 4 4 8 10)peek and pop can be used to retrieve and to remove the minimum element:
(peek (pq/pq [0 -1 3 4 2]))
;= -1
(pop (pq/pq [0 -1 3 4 2]))
;= (0 2 3 4)Items can be added using conj:
(conj (pq/pq [0 -1 8 7]) 5)
;= (-1 0 5 7 8)Additionally, priority queues are seqs and support first (equivalent to
peek) and next (equivalent to pop) directly.
Elements can be tied on priority (that is, they can compare equal), in which case they will be returned in arbitrary order.
This is an experimental library. Alpha releases are available from Clojars. Follow the link above to discover the current release number.
Leiningen dependency information:
[maxiphobe "${version}"]
Maven dependency information:
<dependency>
<groupId>maxiphobe</groupId>
<artifactId>maxiphobe</artifactId>
<version>${version}</version>
</dependency>
Gradle dependency information:
compile "maxiphobe:maxiphobe:${version}"
The implementation of the static class MaxiphobicHeap.EmptyMaxiphobicHeap is
adapted from the implementation of the analogous PersistentList.EmptyList
class in Clojure.
The Clojure source files containing the relevant code carry the following copyright notice:
Copyright (c) Rich Hickey. All rights reserved.
The use and distribution terms for this software are covered by the
Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
which can be found in the file epl-v10.html at the root of this distribution.
By using this software in any fashion, you are agreeing to be bound by
the terms of this license.
You must not remove this notice, or any other, from this software.
Copyright © 2016 Michał Marczyk
Distributed under the Eclipse Public License version 1.0.