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source: branches/f4grobner/term.lisp@ 3134

Last change on this file since 3134 was 3134, checked in by Marek Rychlik, 9 years ago

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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 "MAKE-TERM-VARIABLE"
26 )
27 (:documentation "This package implements class TERM. A term is a
28product of a scalar and powers of some variables, such as
295*X^2*Y^3. The part of the term without the coefficient is a monomial
30X^2*Y^3, which is represented by class MONOM, provided by the :MONOM
31package. In this implementation, a TERM specializes MONOL. Also, a
32monomial can be considered a TERM whose coefficient is the unit
33element (1) of the underlying ring. The generic method CHANGE-CLASS
34can be used to convert between a MONOM and a TERM, observing this
35convention."))
36
37(in-package :term)
38
39(proclaim '(optimize (speed 3) (space 0) (safety 0) (debug 0)))
40
41(defclass term (monom scalar)
42 (:default-initargs :dimension nil :exponents nil :coeff nil)
43 (:documentation "Implements a term, i.e. a product of a ring element
44and powers of some variables, such as 5*X^2*Y^3."))
45
46(defmethod print-object ((self term) stream)
47 (format stream "#<TERM DIMENSION=~A EXPONENTS=~A VALUE=~A>"
48 (monom-dimension self)
49 (monom-exponents self)
50 (scalar-value self)))
51
52(defmethod shared-initialize ((self term) slot-names
53 &rest
54 initargs
55 &key
56 coeff
57 &allow-other-keys)
58 (declare (ignore initargs))
59 (if (eq slot-names t) (setf slot-names '(coeff)))
60 (dolist (slot-name slot-names)
61 (case slot-name
62 (coeff
63 (setf (slot-value self 'coeff) coeff)))))
64
65(defmethod update-instance-for-different-class :around ((old monom) (new term) &key)
66 ;; Changing an instance of class MONOM to class TERM may also
67 ;; happen when OLD is an instance of TERM, in which case the
68 ;; value of the coefficient should be preserved.
69 (unless (slot-boundp new 'coeff)
70 (setf (term-coeff new) 1))
71 new)
72
73#|
74(defun make-term-variable (nvars pos
75 &optional
76 (power 1)
77 (coeff 1))
78 "Construct a term in the polynomial ring RING[X[0],X[1],X[2],...X[NVARS-1]]
79over the ring RING which represents a single variable. It assumes
80number of variables NVARS and the variable is at position
81POS. Optionally, the variable may appear raised to power POWER.
82Optionally, the term may appear with an arbitrary coefficient, which
83defaults to the unit of the RING."
84 (declare (type fixnum nvars pos))
85 (make-term :monom (make-monom-variable nvars pos power)
86 :coeff coeff))
87
88|#
89
90(defmethod multiply-by :before ((self term) (other term))
91 "Destructively multiply terms SELF and OTHER and store the result into SELF.
92It returns SELF."
93 (setf (r-coeff self) (multiply-by (r-coeff self) (r-coeff other))))
94
95(defmethod left-tensor-product-by ((self term) (other term))
96 (setf (r-coeff self) (multiply-by (r-coeff self) (r-coeff other)))
97 (call-next-method))
98
99(defmethod right-tensor-product-by ((self term) (other term))
100 (setf (r-coeff self) (multiply-by (r-coeff self) (r-coeff other)))
101 (call-next-method))
102
103(defmethod left-tensor-product-by ((self term) (other monom))
104 (call-next-method))
105
106(defmethod right-tensor-product-by ((self term) (other monom))
107 (call-next-method))
108
109(defmethod divide-by ((self term) (other term))
110 "Destructively divide term SELF by OTHER and store the result into SELF.
111It returns SELF."
112 (setf (r-coeff self) (divide-by (r-coeff self) (r-coeff other)))
113 (call-next-method))
114
115(defmethod unary-minus ((self term))
116 (setf (term-coeff self) (unary-minus (term-coeff self)))
117 self)
118
119(defmethod r* ((term1 term) (term2 term))
120 "Non-destructively multiply TERM1 by TERM2."
121 (multiply-by (copy-instance term1) (copy-instance term2)))
122
123(defmethod r-zerop ((self term))
124 (r-zerop (term-coeff self)))
125
126#|
127
128(defun term->cons (term)
129 "A human-readable representation of a term as a cons (MONOM . COEFF)."
130 (declare (type term term))
131 (cons (monom->list (term-monom term)) (term-coeff term)))
132
133|#
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