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source: branches/f4grobner/term.lisp@ 412

Last change on this file since 412 was 410, checked in by Marek Rychlik, 9 years ago

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1;;; -*- Mode: Lisp; Package: Maxima; Syntax: Common-Lisp; Base: 10 -*-
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 :monomial :ring)
24 (:export
25 "MAKE-TERM"
26 "MAKE-TERM-VARIABLE"
27 "TERM-MUL"
28 "TERM-SUGAR"))
29
30
31(defun make-term-variable (ring nvars pos
32 &optional
33 (power 1)
34 (coeff (funcall (ring-unit ring)))
35 &aux
36 (monom (make-monom nvars :initial-element 0)))
37 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
38over the ring RING which represents a single variable. It assumes
39number of variables NVARS and the variable is at position
40POS. Optionally, the variable may appear raised to power POWER.
41Optionally, the term may appear with an arbitrary coefficient, which
42defaults to the unit of the RING."
43 (declare (fixnum nvars pos power))
44 (incf (monom-elt monom pos) power)
45 (make-term monom coeff))
46
47(defstruct (term
48 (:constructor make-term (monom coeff))
49 ;;(:constructor make-term-variable)
50 ;;(:type list)
51 )
52 (monom (make-monom 0) :type monom)
53 (coeff nil))
54
55(defun term-mul (ring term1 term2)
56 "Returns the product of the terms TERM1 and TERM2,
57or NIL when the product is 0. This definition takes care of divisors of 0
58in the coefficient ring."
59 (let ((c (funcall (ring-mul ring) (term-coeff term1) (term-coeff term2))))
60 (unless (funcall (ring-zerop ring) c)
61 (make-term (monom-mul (term-monom term1) (term-monom term2)) c))))
62
63(defun term-sugar (term)
64 (monom-sugar (term-monom term)))
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