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source: branches/f4grobner/term.lisp@ 3436

Last change on this file since 3436 was 3436, checked in by Marek Rychlik, 9 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 "TERM"
23 (:use :cl :monom :ring)
24 (:export "TERM")
25 (:documentation "This package implements class TERM. A term is a
26product of a scalar and powers of some variables, such as
275*X^2*Y^3. The part of the term without the coefficient is a monomial
28X^2*Y^3, which is represented by class MONOM, provided by the :MONOM
29package. In this implementation, a TERM specializes MONOL. Also, a
30monomial can be considered a TERM whose coefficient is the unit
31element (1) of the underlying ring. The generic method CHANGE-CLASS
32can be used to convert between a MONOM and a TERM, observing this
33convention."))
34
35(in-package :term)
36
37(proclaim '(optimize (speed 3) (space 0) (safety 0) (debug 0)))
38
39;; NOTE: Since term does not have slots of its own,
40;; INITIALIZE-INSTANCE is not called by MAKE-INSTANCE.
41(defclass term (monom scalar)
42 ()
43 (:documentation "Implements a term, i.e. a product of a scalar
44and powers of some variables, such as 5*X^2*Y^3."))
45
46(defmethod print-object ((self term) stream)
47 (print-unreadable-object (self stream :type t :identity t)
48 (with-accessors ((exponents monom-exponents)
49 (coeff scalar-coeff))
50 self
51 (format stream "EXPONENTS=~A COEFF=~A"
52 exponents coeff))))
53
54
55(defmethod r-equalp ((term1 term) (term2 term))
56 (when (r-equalp (scalar-coeff term1) (scalar-coeff term2))
57 (call-next-method)))
58
59(defmethod update-instance-for-different-class :after ((old monom) (new scalar) &key)
60 (setf (scalar-coeff new) 1))
61
62(defmethod multiply-by :before ((self term) (other term))
63 "Destructively multiply terms SELF and OTHER and store the result into SELF.
64It returns SELF."
65 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other))))
66
67(defmethod left-tensor-product-by ((self term) (other term))
68 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
69 (call-next-method))
70
71(defmethod right-tensor-product-by ((self term) (other term))
72 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
73 (call-next-method))
74
75(defmethod left-tensor-product-by ((self term) (other monom))
76 (call-next-method))
77
78(defmethod right-tensor-product-by ((self term) (other monom))
79 (call-next-method))
80
81(defmethod divide-by ((self term) (other term))
82 "Destructively divide term SELF by OTHER and store the result into SELF.
83It returns SELF."
84 (setf (scalar-coeff self) (divide-by (scalar-coeff self) (scalar-coeff other)))
85 (call-next-method))
86
87(defmethod unary-minus ((self term))
88 (setf (scalar-coeff self) (unary-minus (scalar-coeff self)))
89 self)
90
91(defmethod r* ((term1 term) (term2 term))
92 "Non-destructively multiply TERM1 by TERM2."
93 (multiply-by (copy-instance term1) (copy-instance term2)))
94
95(defmethod r* ((term1 number) (term2 monom))
96 "Non-destructively multiply TERM1 by TERM2."
97 (r* term1 (change-class (copy-instance term2) 'term)))
98
99(defmethod r* ((term1 number) (term2 term))
100 "Non-destructively multiply TERM1 by TERM2."
101 (setf (scalar-coeff term2)
102 (r* term1 (scalar-coeff term2)))
103 term2)
104
105(defmethod r-zerop ((self term))
106 (r-zerop (scalar-coeff self)))
107
108#|
109
110(defun term->cons (term)
111 "A human-readable representation of a term as a cons (MONOM . COEFF)."
112 (declare (type term term))
113 (cons (monom->list (term-monom term)) (scalar-coeff term)))
114
115|#
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