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source: branches/f4grobner/term.lisp@ 798

Last change on this file since 798 was 798, 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 "TERM"
25 "TERM-EXPONENTS"
26 "TERM-COEFF"
27 "MAKE-TERM"
28 "MAKE-TERM-VARIABLE"
29 "TERM-MUL"
30 "TERM-SUGAR"))
31
32
33(in-package :term)
34
35(defstruct (term
36 (:include monom)
37 ;; BOA constructor. TODO: avoid code duplication with MONOM?
38 (:constructor make-term (monom &key (coeff nil coeff-supplied-p)
39 (ring *ring-of-integers* ring-supplied-p)
40 &aux
41 (coeff (cond
42 (coeff-supplied-p coeff)
43 (ring-supplied-p (funcall (ring-unit ring)))
44 (t
45 (error "Coefficient or ring must be supplied."))))
46 (exponents (monom-exponents monom))))
47 ;;(:constructor make-term-variable)
48 ;;(:type list)
49 )
50 (coeff nil))
51
52
53(defun make-term-variable (ring nvars pos
54 &optional
55 (power 1)
56 (coeff (funcall (ring-unit ring))))
57 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
58over the ring RING which represents a single variable. It assumes
59number of variables NVARS and the variable is at position
60POS. Optionally, the variable may appear raised to power POWER.
61Optionally, the term may appear with an arbitrary coefficient, which
62defaults to the unit of the RING."
63 (declare (fixnum nvars pos power))
64 (let ((result (make-term (make-monom nvars) :coeff coeff)))
65 (setf (monom-elt result pos) power)
66 result))
67
68(defun term-mul (ring term1 term2)
69 "Returns the product of the terms TERM1 and TERM2,
70or NIL when the product is 0. This definition takes care of divisors of 0
71in the coefficient ring."
72 (let ((c (funcall (ring-mul ring) (term-coeff term1) (term-coeff term2))))
73 (unless (funcall (ring-zerop ring) c)
74 (make-term (monom-mul term1 term2) :coeff c))))
75
76(defun term-sugar (term)
77 (monom-sugar term))
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