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source: branches/f4grobner/term.lisp@ 3208

Last change on this file since 3208 was 3205, 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 "MAKE-TERM-VARIABLE"
26 )
27 (:documentation "This package implements class TERM. A term is a
28product of a scalar and powers of some variables, such as
295*X^2*Y^3. The part of the term without the coefficient is a monomial
30X^2*Y^3, which is represented by class MONOM, provided by the :MONOM
31package. In this implementation, a TERM specializes MONOL. Also, a
32monomial can be considered a TERM whose coefficient is the unit
33element (1) of the underlying ring. The generic method CHANGE-CLASS
34can be used to convert between a MONOM and a TERM, observing this
35convention."))
36
37(in-package :term)
38
39(proclaim '(optimize (speed 3) (space 0) (safety 0) (debug 0)))
40
41(defclass term (monom scalar)
42 ()
43 (:default-initargs :dimension nil :exponents nil :coeff nil)
44 (:documentation "Implements a term, i.e. a product of a scalar
45and powers of some variables, such as 5*X^2*Y^3."))
46
47(defmethod r-equalp ((term1 term) (term2 term))
48 (and (r-equalp (scalar-coeff term1) (scalar-coeff term2))
49 (= (monom-dimension term1) (monom-dimension term2))
50 (equalp (monom-exponents term1) (monom-exponents term2))))
51
52#|
53(defmethod shared-initialize ((self term) slot-names
54 &rest
55 initargs
56 &key
57 coeff
58 &allow-other-keys)
59 (declare (ignore initargs))
60 (if (eq slot-names t) (setf slot-names '(coeff)))
61 (dolist (slot-name slot-names)
62 (case slot-name
63 (coeff
64 (setf (slot-value self 'coeff) coeff)))))
65|#
66
67(defmethod update-instance-for-different-class :after ((old monom) (new scalar) &key)
68 (setf (scalar-coeff new) 1))
69
70#|
71(defun make-term-variable (nvars pos
72 &optional
73 (power 1)
74 (coeff 1))
75 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
76over the ring RING which represents a single variable. It assumes
77number of variables NVARS and the variable is at position
78POS. Optionally, the variable may appear raised to power POWER.
79Optionally, the term may appear with an arbitrary coefficient, which
80defaults to the unit of the RING."
81 (declare (type fixnum nvars pos))
82 (make-term :monom (make-monom-variable nvars pos power)
83 :coeff coeff))
84
85|#
86
87(defmethod multiply-by :before ((self term) (other term))
88 "Destructively multiply terms SELF and OTHER and store the result into SELF.
89It returns SELF."
90 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other))))
91
92(defmethod left-tensor-product-by ((self term) (other term))
93 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
94 (call-next-method))
95
96(defmethod right-tensor-product-by ((self term) (other term))
97 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
98 (call-next-method))
99
100(defmethod left-tensor-product-by ((self term) (other monom))
101 (call-next-method))
102
103(defmethod right-tensor-product-by ((self term) (other monom))
104 (call-next-method))
105
106(defmethod divide-by ((self term) (other term))
107 "Destructively divide term SELF by OTHER and store the result into SELF.
108It returns SELF."
109 (setf (scalar-coeff self) (divide-by (scalar-coeff self) (scalar-coeff other)))
110 (call-next-method))
111
112(defmethod unary-minus ((self term))
113 (setf (scalar-coeff self) (unary-minus (scalar-coeff self)))
114 self)
115
116(defmethod r* ((term1 term) (term2 term))
117 "Non-destructively multiply TERM1 by TERM2."
118 (multiply-by (copy-instance term1) (copy-instance term2)))
119
120(defmethod r-zerop ((self term))
121 (r-zerop (scalar-coeff self)))
122
123#|
124
125(defun term->cons (term)
126 "A human-readable representation of a term as a cons (MONOM . COEFF)."
127 (declare (type term term))
128 (cons (monom->list (term-monom term)) (scalar-coeff term)))
129
130|#
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