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source: branches/f4grobner/term.lisp@ 2547

Last change on this file since 2547 was 2490, 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" "MAKE-TERM-VARIABLE"))
25
26(in-package :term)
27
28(proclaim '(optimize (speed 3) (space 0) (safety 0) (debug 0)))
29
30(defclass term (monom)
31 ((coeff :initarg :coeff :accessor r-coeff))
32 (:default-initargs :dimension nil :exponents nil :coeff nil))
33
34(defmethod print-object ((self term) stream)
35 (format stream "#<TERM DIMENSION=~A EXPONENTS=~A COEFF=~A>"
36 (r-dimension self)
37 (r-exponents self)
38 (r-coeff self)))
39
40(defmethod shared-initialize ((self term) slot-names
41 &rest
42 initargs
43 &key
44 coeff
45 &allow-other-keys)
46 (declare (ignore initargs))
47 (if (eq slot-names t) (setf slot-names '(coeff)))
48 (dolist (slot-name slot-names)
49 (case slot-name
50 (coeff
51 (setf (slot-value self 'coeff) coeff)))))
52
53(defmethod update-instance-for-different-class :after ((old monom)
54 (new term)
55 &key)
56 ;; Changing an instance of class MONOM to class TERM may also
57 ;; happen when OLD is an instance of TERM, in which case the
58 ;; value of the coefficient should be preserved.
59 ;; This implementation calls R-COEFF, which satisfies
60 ;; this requirement.
61 (setf (slot-value new 'coeff) (r-coeff old)))
62
63
64#|
65(defun make-term-variable (nvars pos
66 &optional
67 (power 1)
68 (coeff 1))
69 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
70over the ring RING which represents a single variable. It assumes
71number of variables NVARS and the variable is at position
72POS. Optionally, the variable may appear raised to power POWER.
73Optionally, the term may appear with an arbitrary coefficient, which
74defaults to the unit of the RING."
75 (declare (type fixnum nvars pos))
76 (make-term :monom (make-monom-variable nvars pos power)
77 :coeff coeff))
78
79|#
80
81(defmethod r* :around ((term1 term) (term2 term))
82 "Returns the product of the terms TERM1 and TERM2,
83or NIL when the product is 0. This definition takes care of divisors of 0
84in the coefficient ring."
85 (let ((result (change-class (call-next-method) 'term)))
86 (setf (r-coeff result) (r* (r-coeff term1) (r-coeff term2)))
87 result))
88
89(defmethod multiply-by ((self term) (other monom))
90 "Returns the product of the terms TERM1 and TERM2,
91or NIL when the product is 0. This definition takes care of divisors of 0
92in the coefficient ring."
93 (setf (r-coeff self) (multiply-by (r-coeff self) (r-coeff other)))
94 self)
95
96(defmethod multiply-by ((self term) (other scalar))
97 "Returns the product of the terms TERM1 and TERM2,
98or NIL when the product is 0. This definition takes care of divisors of 0
99in the coefficient ring."
100 (setf (r-coeff self) (multiply-by (r-coeff self) other))
101 self)
102
103#|
104
105(defun term->cons (term)
106 "A human-readable representation of a term as a cons (MONOM . COEFF)."
107 (declare (type term term))
108 (cons (monom->list (term-monom term)) (term-coeff term)))
109
110|#
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