source: branches/f4grobner/priority-queue.lisp@ 3990

;;; -*-  Mode: Lisp -*- 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;                                                                              
;;;  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.                                         
;;;                                                                              
;;;  This program is distributed in the hope that it will be useful,             
;;;  but WITHOUT ANY WARRANTY; without even the implied warranty of              
;;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               
;;;  GNU General Public License for more details.                                
;;;                                                                              
;;;  You should have received a copy of the GNU General Public License           
;;;  along with this program; if not, write to the Free Software                 
;;;  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
;;;                                                                              
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; A conventional implementation of priority queues based on heaps
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(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))))

(defgeneric dequeue (self)
  (:method ((self priority-queue))
    (with-slots (heap test)
        self
      (heap-remove heap test))))

(defgeneric queue-empty-p (self)
  (:method ((self priority-queue))
    (with-slots (heap)
        self
      (heap-empty-p heap))))

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