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source: branches/f4grobner/term.lisp@ 3199

Last change on this file since 3199 was 3199, 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 0 :exponents '() :coeff 1)
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 print-object ((self term) stream)
48 (print-unreadable-object (self stream :type t :identity t)
49 (format stream "DIMENSION=~A EXPONENTS=~A COEFF=~A"
50 (slot-value self 'dimension)
51 (slot-value self 'exponents)
52 (slot-value self 'coeff))))
53
54
55(defmethod r-equalp ((term1 term) (term2 term))
56 (and (r-equalp (scalar-coeff term1) (scalar-coeff term2))
57 (= (monom-dimension term1) (monom-dimension term2))
58 (equalp (monom-exponents term1) (monom-exponents term2))))
59
60
61#|
62(defmethod shared-initialize ((self term) slot-names
63 &rest
64 initargs
65 &key
66 coeff
67 &allow-other-keys)
68 (declare (ignore initargs))
69 (if (eq slot-names t) (setf slot-names '(coeff)))
70 (dolist (slot-name slot-names)
71 (case slot-name
72 (coeff
73 (setf (slot-value self 'coeff) coeff)))))
74|#
75
76(defmethod update-instance-for-different-class :after ((old monom) (new scalar) &key)
77 (setf (scalar-coeff new) 1))
78
79#|
80(defun make-term-variable (nvars pos
81 &optional
82 (power 1)
83 (coeff 1))
84 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
85over the ring RING which represents a single variable. It assumes
86number of variables NVARS and the variable is at position
87POS. Optionally, the variable may appear raised to power POWER.
88Optionally, the term may appear with an arbitrary coefficient, which
89defaults to the unit of the RING."
90 (declare (type fixnum nvars pos))
91 (make-term :monom (make-monom-variable nvars pos power)
92 :coeff coeff))
93
94|#
95
96(defmethod multiply-by :before ((self term) (other term))
97 "Destructively multiply terms SELF and OTHER and store the result into SELF.
98It returns SELF."
99 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other))))
100
101(defmethod left-tensor-product-by ((self term) (other term))
102 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
103 (call-next-method))
104
105(defmethod right-tensor-product-by ((self term) (other term))
106 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
107 (call-next-method))
108
109(defmethod left-tensor-product-by ((self term) (other monom))
110 (call-next-method))
111
112(defmethod right-tensor-product-by ((self term) (other monom))
113 (call-next-method))
114
115(defmethod divide-by ((self term) (other term))
116 "Destructively divide term SELF by OTHER and store the result into SELF.
117It returns SELF."
118 (setf (scalar-coeff self) (divide-by (scalar-coeff self) (scalar-coeff other)))
119 (call-next-method))
120
121(defmethod unary-minus ((self term))
122 (setf (scalar-coeff self) (unary-minus (scalar-coeff self)))
123 self)
124
125(defmethod r* ((term1 term) (term2 term))
126 "Non-destructively multiply TERM1 by TERM2."
127 (multiply-by (copy-instance term1) (copy-instance term2)))
128
129(defmethod r-zerop ((self term))
130 (r-zerop (scalar-coeff self)))
131
132#|
133
134(defun term->cons (term)
135 "A human-readable representation of a term as a cons (MONOM . COEFF)."
136 (declare (type term term))
137 (cons (monom->list (term-monom term)) (scalar-coeff term)))
138
139|#
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