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source: branches/f4grobner/term.lisp@ 2851

Last change on this file since 2851 was 2851, 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 "TERM-EQUALP"
26 "TERM-CLONE"
27 "MAKE-TERM-VARIABLE"
28 )
29 (:documentation "This package implements class TERM. A term is a
30product of a scalar and powers of some variables, such as
315*X^2*Y^3. The part of the term without the coefficient is a monomial
32X^2*Y^3, which is represented by class MONOM, provided by the :MONOM
33package. In this implementation, a TERM specializes MONOL. Also, a
34monomial can be considered a TERM whose coefficient is the unit
35element (1) of the underlying ring. The generic method CHANGE-CLASS
36can be used to convert between a MONOM and a TERM, observing this
37convention."))
38
39(in-package :term)
40
41(proclaim '(optimize (speed 3) (space 0) (safety 0) (debug 0)))
42
43(defclass term (monom)
44 ((coeff :initarg :coeff :accessor term-coeff
45 :documentation "The coefficient."))
46 (:default-initargs :dimension nil :exponents nil :coeff nil)
47 (:documentation "Implements a term, i.e. a product of a ring element
48and powers of some variables, such as 5*X^2*Y^3."))
49
50(defmethod r-coeff ((self term))
51 (term-coeff self))
52
53(defmethod (setf r-coeff) (new-value (self term))
54 (setf (term-coeff self) new-value))
55
56(defmethod r-equalp ((term1 term) (term2 term))
57 (and (r-equalp (term-coeff term1) (term-coeff term2))
58 (call-next-method)))
59
60(defmethod r-equalp ((term1 term) (term2 term))
61 (term-equalp term1 term2))
62
63(defmethod print-object ((self term) stream)
64 (format stream "#<TERM DIMENSION=~A EXPONENTS=~A COEFF=~A>"
65 (r-dimension self)
66 (r-exponents self)
67 (r-coeff self)))
68
69(defmethod shared-initialize ((self term) slot-names
70 &rest
71 initargs
72 &key
73 coeff
74 &allow-other-keys)
75 (declare (ignore initargs))
76 (if (eq slot-names t) (setf slot-names '(coeff)))
77 (dolist (slot-name slot-names)
78 (case slot-name
79 (coeff
80 (setf (slot-value self 'coeff) coeff)))))
81
82(defmethod update-instance-for-different-class :after ((old monom)
83 (new term)
84 &key)
85 ;; Changing an instance of class MONOM to class TERM may also
86 ;; happen when OLD is an instance of TERM, in which case the
87 ;; value of the coefficient should be preserved.
88 ;; This implementation calls R-COEFF, which satisfies
89 ;; this requirement.
90 (setf (slot-value new 'coeff) (r-coeff old)))
91
92
93#|
94(defun make-term-variable (nvars pos
95 &optional
96 (power 1)
97 (coeff 1))
98 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
99over the ring RING which represents a single variable. It assumes
100number of variables NVARS and the variable is at position
101POS. Optionally, the variable may appear raised to power POWER.
102Optionally, the term may appear with an arbitrary coefficient, which
103defaults to the unit of the RING."
104 (declare (type fixnum nvars pos))
105 (make-term :monom (make-monom-variable nvars pos power)
106 :coeff coeff))
107
108|#
109
110(defmethod multiply-by ((self term) (other term))
111 "Destructively multiply terms SELF and OTHER and store the result into SELF.
112It returns SELF."
113 (setf (r-coeff self) (multiply-by (r-coeff self) (r-coeff other)))
114 (call-next-method))
115
116(defmethod divide-by ((self term) (other term))
117 "Destructively divide term SELF by OTHER and store the result into SELF.
118It returns SELF."
119 (setf (r-coeff self) (divide-by (r-coeff self) (r-coeff other)))
120 (call-next-method))
121
122(defmethod unary-minus ((self term))
123 (setf (term-coeff self) (unary-minus (term-coeff self)))
124 self)
125
126#|
127
128(defun term->cons (term)
129 "A human-readable representation of a term as a cons (MONOM . COEFF)."
130 (declare (type term term))
131 (cons (monom->list (term-monom term)) (term-coeff term)))
132
133|#
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