source: branches/f4grobner/ring.lisp@ 4322

;;; -*-  Mode: Lisp -*- 
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;;;                                                                              
;;;  Copyright (C) 1999, 2002, 2009, 2015 Marek Rychlik <rychlik@u.arizona.edu>          
;;;                                                                              
;;;  This program is free software; you can redistribute it and/or modify        
;;;  it under the terms of the GNU General Public License as published by        
;;;  the Free Software Foundation; either version 2 of the License, or           
;;;  (at your option) any later version.                                         
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;;;  This program is distributed in the hope that it will be useful,             
;;;  but WITHOUT ANY WARRANTY; without even the implied warranty of              
;;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               
;;;  GNU General Public License for more details.                                
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;;;  You should have received a copy of the GNU General Public License           
;;;  along with this program; if not, write to the Free Software                 
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(defpackage "RING"
  (:use :cl)
  (:export "RING"
           "ADD-TO"
           "SUBTRACT-FROM"
           "MULTIPLY-BY"
           "DIVIDE-BY"
           "UNARY-MINUS"
           "UNARY-INVERSE"
           "UNIVERSAL-GCD"
           "UNIVERSAL-EZGCD"
           "UNIVERSAL-EQUALP"
           "UNIVERSAL-ZEROP"
           "MAKE-ZERO-FOR"
           "MAKE-UNIT-FOR"
           "->SEXP")
  (:documentation "Defines an abstract ring class and ring operations."))

(in-package "RING")

(defclass ring () () (:documentation "An abstract ring."))
           
(defgeneric multiply-by (self other)
  (:documentation "Multiply SELF by OTHER."))

(defgeneric divide-by (self other)
  (:documentation "Divide SELF by OTHER."))

(defgeneric add-to (self other)
  (:documentation "Add OTHER to SELF."))

(defgeneric subtract-from (self other)
  (:documentation "Subtract OTHER from SELF."))

(defgeneric unary-minus (self)
  (:documentation "Changes SELF to its negative."))

(defgeneric unary-inverse (self)
  (:documentation "Changes SELF to the unary inverse of SELF."))

(defgeneric universal-gcd (object other)
  (:documentation "Returns GCD(OBJECT, OTHER)"))

(defgeneric universal-ezgcd (x y)
  (:documentation "Solves the diophantine system: X=C*X1, Y=C*X2,
C=GCD(X,Y).  It returns three values: C, X1 and Y1. The result may be obtained by
the Euclidean algorithm."))

(defgeneric universal-equalp (self other)
  (:documentation "Return T if objects SELF and OTHER are equal, NIL otherwise.")
  (:method ((object1 cons) (object2 cons)) (every #'universal-equalp object1 object2))
  (:method ((self number) (other number)) (= self other)))

(defgeneric universal-zerop (self)
  (:documentation "Return T if SELF is a zero in the ring it belongs to."))

(defgeneric ->sexp (self &optional vars)
  (:documentation "Convert SELF to an S-expression."))

(defgeneric make-zero-for (self)
  (:documentation "Create a zero in the ring of SELF. A fresh instance
should be returned upon every call."))

(defgeneric make-unit-for (self)
  (:documentation "Create a unit in the ring of SELF. A fresh instance
should be returned upon every call."))