source: branches/f4grobner/priority-queue.lisp@ 3989

;;; -*-  Mode: Lisp -*- 
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;;;  Copyright (C) 1999, 2002, 2009, 2015 Marek Rychlik <rychlik@u.arizona.edu>          
;;;                                                                              
;;;  This program is free software; you can redistribute it and/or modify        
;;;  it under the terms of the GNU General Public License as published by        
;;;  the Free Software Foundation; either version 2 of the License, or           
;;;  (at your option) any later version.                                         
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;;
;; A conventional implementation of priority queues based on heaps
;;
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(defpackage "PRIORITY-QUEUE"
  (:use :cl :heap)
  (:export "PRIORITY-QUEUE"
           "MAKE-PRIORITY-QUEUE"
           "PRIORITY-QUEUE-INSERT"
           "PRIORITY-QUEUE-REMOVE"
           "PRIORITY-QUEUE-EMPTY-P"
           "PRIORITY-QUEUE-SIZE"
           ))

(in-package :priority-queue)

(defclass priority-queue ()
  ((heap :initarg :heap :accessor priority-queue-heap)
   (test :initarg :ters :accessor priority-queue-test))
  (:documentation "Representa a priority queue."))

(defmethod initialize-instance ((self priority-queue) 
                                &key 
                                  (element-type 'fixnum)
                                  (test #'<=)
                                  (element-key #'identity))
  (with-slots (heap test)
      self
    (setf heap (make-heap :element-type element-type)
          test #'(lambda (x y) (funcall test (funcall element-key y) (funcall element-key x))))))
  
(defgeneric enqueue (self item)
  (:method ((self priority-queue) (item t))
    (with-slots (heap test)
        self
    (heap-insert heap item test))))

(defun priority-queue-remove (pq)
  (heap-remove (priority-queue-heap pq) (priority-queue-test pq)))

(defun priority-queue-empty-p (pq)
  (heap-empty-p (priority-queue-heap pq)))

(defun priority-queue-size (pq)
  (fill-pointer (priority-queue-heap pq)))