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source: branches/f4grobner/term.lisp@ 784

Last change on this file since 784 was 782, 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 (dimension
39 &key
40 (initial-exponents #() initial-exponents-supplied-p)
41 (initial-exponent #() initial-exponent-supplied-p)
42 (exponents (cond
43 ;; when exponents are supplied
44 (initial-exponents-supplied-p
45 (make-array (list dimension) :initial-contents initial-exponents
46 :element-type 'exponent))
47 ;; when all exponents are to be identical
48 (initial-exponent-supplied-p
49 (make-array (list dimension) :initial-element initial-exponent
50 :element-type 'exponent))
51 ;; otherwise, all exponents are zero
52 (t (make-array (list dimension) :element-type 'exponent :initial-element 0))))
53 (ring *ring-of-integers*)
54 (coeff (funcall (ring-unit ring)))))
55 ;;(:constructor make-term-variable)
56 ;;(:type list)
57 )
58 (coeff nil))
59
60
61(defun make-term-variable (ring nvars pos
62 &optional
63 (power 1)
64 (coeff (funcall (ring-unit ring))))
65 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
66over the ring RING which represents a single variable. It assumes
67number of variables NVARS and the variable is at position
68POS. Optionally, the variable may appear raised to power POWER.
69Optionally, the term may appear with an arbitrary coefficient, which
70defaults to the unit of the RING."
71 (declare (fixnum nvars pos power))
72 (let ((result (make-term nvars :coeff coeff)))
73 (setf (monom-elt result pos) power)
74 result))
75
76(defun term-mul (ring term1 term2)
77 "Returns the product of the terms TERM1 and TERM2,
78or NIL when the product is 0. This definition takes care of divisors of 0
79in the coefficient ring."
80 (let ((c (funcall (ring-mul ring) (term-coeff term1) (term-coeff term2))))
81 (unless (funcall (ring-zerop ring) c)
82 (make-term (monom-dimension term1)
83 :initial-exponents (monom-exponents (monom-mul term1 term2))
84 :coeff c))))
85
86(defun term-sugar (term)
87 (monom-sugar term))
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