| 1 | ;;; -*- Mode: Lisp -*-
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| 2 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| 3 | ;;;
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| 4 | ;;; Copyright (C) 1999, 2002, 2009, 2015 Marek Rychlik <rychlik@u.arizona.edu>
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| 5 | ;;;
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| 6 | ;;; This program is free software; you can redistribute it and/or modify
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| 7 | ;;; it under the terms of the GNU General Public License as published by
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| 8 | ;;; the Free Software Foundation; either version 2 of the License, or
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| 9 | ;;; (at your option) any later version.
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| 10 | ;;;
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| 11 | ;;; This program is distributed in the hope that it will be useful,
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| 12 | ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 13 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 14 | ;;; GNU General Public License for more details.
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| 15 | ;;;
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| 16 | ;;; You should have received a copy of the GNU General Public License
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| 17 | ;;; along with this program; if not, write to the Free Software
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| 18 | ;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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| 19 | ;;;
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| 20 | ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| 21 |
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| 22 | (defpackage "TERM"
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| 23 | (:use :cl :monom :ring)
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| 24 | (:export "TERM"
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| 25 | "TERM-EXPONENTS"
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| 26 | "TERM-MONOM"
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| 27 | "TERM-COEFF"
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| 28 | "MAKE-TERM"
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| 29 | "MAKE-TERM-VARIABLE"
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| 30 | "TERM-MUL"
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| 31 | "TERM-SUGAR"
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| 32 | "TERM-DEPENDS-P"
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| 33 | "TERM->CONS"))
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| 34 |
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| 35 |
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| 36 | (in-package :term)
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| 37 |
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| 38 | (defstruct (term
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| 39 | ;; A simple BOA constructor
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| 40 | ;;(:constructor make-term (monom coeff))
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| 41 | ;;(:constructor make-term-variable)
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| 42 | ;;(:type list)
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| 43 | )
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| 44 | (monom nil :type monom)
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| 45 | (coeff nil))
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| 46 |
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| 47 |
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| 48 | (defun make-term-variable (ring nvars pos
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| 49 | &optional
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| 50 | (power 1)
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| 51 | (coeff (funcall (ring-unit ring))))
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| 52 | "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
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| 53 | over the ring RING which represents a single variable. It assumes
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| 54 | number of variables NVARS and the variable is at position
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| 55 | POS. Optionally, the variable may appear raised to power POWER.
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| 56 | Optionally, the term may appear with an arbitrary coefficient, which
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| 57 | defaults to the unit of the RING."
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| 58 | (make-term :monom (make-monom-variable nvars pos power) :coeff coeff))
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| 59 |
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| 60 | (defun term-mul (ring term1 term2)
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| 61 | "Returns the product of the terms TERM1 and TERM2,
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| 62 | or NIL when the product is 0. This definition takes care of divisors of 0
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| 63 | in the coefficient ring."
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| 64 | (let ((c (funcall (ring-mul ring) (term-coeff term1) (term-coeff term2))))
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| 65 | (unless (funcall (ring-zerop ring) c)
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| 66 | (make-term (monom-mul (term-monom term1) (term-monom term2)) c))))
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| 67 |
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| 68 | (defun term-sugar (term)
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| 69 | (monom-sugar (term-monom term)))
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| 70 |
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| 71 | ;; Does the term depend on variable K?
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| 72 | (defun term-depends-p (term k)
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| 73 | "Return T if the term TERM depends on variable number K."
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| 74 | (monom-depends-p (term-monom term) k))
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| 75 |
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| 76 | (defun term->cons (term)
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| 77 | "A human-readable representation of a term as a cons (MONOM . COEFF)."
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| 78 | (cons (monom->list (term-monom term)) (term-coeff term)))
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| 79 |
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