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source: branches/f4grobner/term.lisp@ 2212

Last change on this file since 2212 was 2192, checked in by Marek Rychlik, 9 years ago

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File size: 3.3 KB
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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 "TERM-EXPONENTS"
26 "TERM-MONOM"
27 "TERM-COEFF"
28 "MAKE-TERM"
29 "MAKE-TERM-VARIABLE"
30 "TERM-MUL"
31 "TERM-SUGAR"
32 "TERM-DEPENDS-P"
33 "TERM->CONS"))
34
35
36(in-package :term)
37
38(proclaim '(optimize (speed 3) (space 0) (safety 0) (debug 0)))
39
40(defclass term (monom)
41 ((coeff :initarg :coeff :accessor term-coeff)))
42
43(defun make-term (&key
44 (exponents nil exponents-supplied-p)
45 (monom nil monom-supplied-p)
46 coeff
47 &aux
48 (exponents
49 (cond (monom-supplied-p (monom-coefficients monom))
50 (exponents-supplied-p exponents)
51 (t (error "Either COEFFICIENTS or MONOM must be supplied.")))))
52 (make-instance 'term :exponents exponents :coeff coeff))
53
54(defun make-term-variable (nvars pos
55 &optional
56 (power 1)
57 (coeff 1))
58 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
59over the ring RING which represents a single variable. It assumes
60number of variables NVARS and the variable is at position
61POS. Optionally, the variable may appear raised to power POWER.
62Optionally, the term may appear with an arbitrary coefficient, which
63defaults to the unit of the RING."
64 (declare (type fixnum nvars pos))
65 (make-term :monom (make-monom-variable nvars pos power)
66 :coeff coeff))
67
68(defmethod ring-mul ((term1 term) (term2 term))
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 (ring-mul (term-coeff term1) (term-coeff term2))))
73 (unless (ring-zerop c)
74 (make-term :monom (monom-mul (term-monom term1) (term-monom term2))
75 :coeff c))))
76
77(defun term-sugar (term)
78 (declare (type term term))
79 (monom-sugar (term-monom term)))
80
81;; Does the term depend on variable K?
82(defun term-depends-p (term k)
83 "Return T if the term TERM depends on variable number K."
84 (declare (type term term) (type fixnum k))
85 (monom-depends-p (term-monom term) k))
86
87(defun term->cons (term)
88 "A human-readable representation of a term as a cons (MONOM . COEFF)."
89 (declare (type term term))
90 (cons (monom->list (term-monom term)) (term-coeff term)))
91
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