This is a ClojureScript port of Mark Engelberg's clojure.data.priority-map for Clojure.
A priority map is very similar to a sorted map, but whereas a sorted map produces a sequence of the entries sorted by key, a priority map produces the entries sorted by value.
Artifacts are published on Clojars.
[tailrecursion/cljs-priority-map "1.2.1"]<dependency>
<groupId>tailrecursion</groupId>
<artifactId>cljs-priority-map</artifactId>
<version>1.2.1</version>
</dependency>;; Require or use tailrecursion.priority-map in your namespace.
(ns your-ns
(:require [tailrecursion.priority-map :refer [priority-map priority-map-by]])))
;; The standard way to construct a priority map is with priority-map:
(def p (priority-map :a 2 :b 1 :c 3 :d 5 :e 4 :f 3))
p ;=> {:b 1, :a 2, :c 3, :f 3, :e 4, :d 5}
;; So :b has priority 1, :a has priority 2, and so on. Notice how the
;; priority map prints in an order sorted by its priorities (i.e., the
;; map's values)
;; We can use assoc to assign a priority to a new item:
(assoc p :g 1) ;=> {:b 1, :g 1, :a 2, :c 3, :f 3, :e 4, :d 5}
;; or to assign a new priority to an extant item:
(assoc p :c 4) ;=> {:b 1, :a 2, :f 3, :c 4, :e 4, :d 5}
;; We can remove an item from the priority map:
(dissoc p :e) ;=> {:b 1, :a 2, :c 3, :f 3, :d 5}
;; An alternative way to add to the priority map is to conj a [item priority] pair:
(conj p [:g 0]) ;=> {:g 0, :b 1, :a 2, :c 3, :f 3, :e 4, :d 5}
(into p [[:g 0] [:h 1] [:i 2]]) ;=> {:g 0, :b 1, :h 1, :a 2, :i 2, :c 3, :f 3, :e 4, :d 5}
;; Priority maps are countable:
(count p) ;=> 6
;; Like other maps, equivalence is based not on type, but on contents.
;; In other words, just as a sorted-map can be equal to a hash-map, so
;; can a priority-map.
(= p {:b 1, :a 2, :c 3, :f 3, :e 4, :d 5}) ;=> true
;; You can test them for emptiness:
(empty? (priority-map)) ;=> true
(empty? p) ;=> false
;; You can test whether an item is in the priority map:
(contains? p :a) ;=> true
(contains? p :g) ;=> false
;; It is easy to look up the priority of a given item, using any of
;; the standard map mechanisms:
(get p :a) ;=> 2
(get p :g 10) ;=> 10
(p :a) ;=> 2
(:a p) ;=> 2
;; Priority maps derive much of their utility by providing priority-based
;; seq. Note that no guarantees are made about the order in which items
;; of the same priority appear.
(seq p) ;=> ([:b 1] [:a 2] [:c 3] [:f 3] [:e 4] [:d 5])
;; Because no guarantees are made about the order of same-priority items,
;; note that rseq might not be an exact reverse of the seq. It is only
;; guaranteed to be in descending order.
(rseq p) ;=> ([:d 5] [:e 4] [:c 3] [:f 3] [:a 2] [:b 1])
;; This means first/rest/next/for/map/etc. All operate in priority order.
(first p) ;=> [:b 1]
(rest p) ;=> ([:a 2] [:c 3] [:f 3] [:e 4] [:d 5])
;; This implementation supports subseq for obtaining sorted seqs of
;; entries for which one or two predicates are true.
;; seq of entries of priority > 3:
(subseq p > 3) ;=> ([:e 4] [:d 5])
;; seq of entries of priority >= 3 but < 5:
(subseq p >= 3 < 5) ;=> ([:c 3] [:f 3] [:e 4])
;; Priority maps support metadata:
(meta (with-meta p {:extra :info})) ;=> {:extra :info}
;; But perhaps most importantly, priority maps can also function as
;; priority queues. peek, like first, gives you the first
;; [item priority] pair in the collection. pop removes the first
;; [item priority] from the collection. (Note that unlike rest, which
;; returns a seq, pop returns a priority map).
(peek p) ;=> [:b 1]
(pop p) ;=> {:a 2, :c 3, :f 3, :e 4, :d 5}
;; It is also possible to use a custom comparator:
(priority-map-by > :a 1 :b 2 :c 3) ;=> {:c 3, :b 2, :a 1}PhantomJS is used for unit testing. With it installed, you can run the tests like so:
lein cljsbuild test
Copyright © 2013 Alan Dipert
Distributed under the Eclipse Public License, the same as Clojure.