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source: branches/f4grobner/priority-queue.lisp@ 4330

Last change on this file since 4330 was 4157, checked in by Marek Rychlik, 8 years ago

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1;;; -*- Mode: Lisp -*-
2;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
3;;;
4;;; Copyright (C) 1999, 2002, 2009, 2015 Marek Rychlik <rychlik@u.arizona.edu>
5;;;
6;;; This program is free software; you can redistribute it and/or modify
7;;; it under the terms of the GNU General Public License as published by
8;;; the Free Software Foundation; either version 2 of the License, or
9;;; (at your option) any later version.
10;;;
11;;; This program is distributed in the hope that it will be useful,
12;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14;;; GNU General Public License for more details.
15;;;
16;;; You should have received a copy of the GNU General Public License
17;;; along with this program; if not, write to the Free Software
18;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19;;;
20;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
21
22(defpackage "PRIORITY-QUEUE"
23 (:use :cl :heap)
24 (:export "PRIORITY-QUEUE"
25 "PRIORITY-QUEUE-ELEMENT-TYPE"
26 "PRIORITY-QUEUE-TEST"
27 "ENQUEUE"
28 "DEQUEUE"
29 "QUEUE-EMPTY-P"
30 "QUEUE-SIZE"
31 )
32 (:documentation "Implements a priority queue."))
33
34(in-package :priority-queue)
35
36(defclass priority-queue ()
37 ((element-type :initarg :element-type
38 :initform 'fixnum
39 :accessor priority-queue-element-type
40 :type symbol
41 :documentation "Element type stored in this queue.")
42 (test :initarg :test
43 :accessor priority-queue-test
44 :documentation "The partial order used in element comparison.")
45 (heap :documentation "A private slot holding the heap."))
46 (:documentation "Represents a priority queue based on heaps. Slots
47HEAP and TEST are read-only after they are initialized. The slot
48ELEMENT-TYPE can be overriden in subclasses, by initializing it in
49a :BEFORE or an :AFTER method."))
50
51
52(defmethod initialize-instance :around ((self priority-queue)
53 &key
54 (test #'<=)
55 (element-key #'identity))
56 "Fill in the HEAP slot with an instance of a heap. NOTE: This has to
57be an :AROUND method, so that the slot ELEMENT-TYPE can be initialized
58in a :BEFORE or :AFTER method of a subclass of PRIORITY-QUEUE."
59 (with-slots (heap (test-x test) element-type)
60 (call-next-method)
61 (setf heap (make-heap :element-type element-type)
62 test-x #'(lambda (x y)
63 (funcall test
64 (funcall element-key y)
65 (funcall element-key x)))))
66 self)
67
68(defgeneric enqueue (self item)
69 (:method ((self priority-queue) (item t))
70 (with-slots (heap test)
71 self
72 (heap-insert heap item test))
73 self))
74
75(defgeneric dequeue (self)
76 (:method ((self priority-queue))
77 (with-slots (heap test)
78 self
79 (heap-remove heap test))))
80
81(defgeneric queue-empty-p (self)
82 (:method ((self priority-queue))
83 (with-slots (heap)
84 self
85 (heap-empty-p heap))))
86
87(defgeneric queue-size (self)
88 (:method ((self priority-queue))
89 (with-slots (heap)
90 self
91 (heap-size heap))))
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