;;; -*-  Mode: Lisp -*- 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;                                                                              
;;;  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 		 
;;;  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.	 
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(defpackage "INTEGER-RING"
  (:use :cl :copy :ring :rational-field)
  (:shadowing-import-from "RATIONAL-FIELD" value)
  (:export "INTEGER-RING"
	   "INTEGER-RING-VALUE"
	   "ADD-TO"
	   "SUBTRACT-FROM"
	   "MULTIPLY-BY"
	   "DIVIDE-BY"
	   "UNARY-MINUS"
	   "UNARY-INVERSE"
	   "UNIVERSAL-GCD"
	   "UNIVERSAL-EZGCD"
	   "UNIVERSAL-EQUALP"
	   "UNIVERSAL-ZEROP"
	   "->SEXP")
  (:documentation "Wraps integers into an object."))

(in-package "INTEGER-RING")

(defclass integer-ring (rational-field)
  ((value :initarg :value :initform 0 :accessor integer-ring-value :type integer))
  (:documentation "An object representing an integer.")
  )
	   
(defmethod print-object ((self integer-ring) stream)
  (print-unreadable-object (self stream :type t :identity t)
    (with-accessors ((value integer-ring-value))
	self
      (format stream "VALUE=~A" value))))

(defmethod unary-inverse ((self integer-ring))
  (with-slots (value)
      self
    (case value
      (1 self)
      (-1 self)
      (otherwise 
       (unary-inverse (change-class self 'rational-field))))))

(defmethod universal-gcd ((self integer-ring) (other integer-ring))
  (with-slots (value)
      self
    (with-slots ((other-value value))
	other
      (make-instance 'integer-ring :value (gcd value other-value)))))

(defmethod universal-ezgcd ((object integer-ring) (other integer-ring))
  (with-slots (value)
      object
    (with-slots ((other-value value))
	other
      (let ((c (gcd value other-value)))
	(values (make-instance 'integer-ring :value c)
		(make-instance 'integer-ring :value (/ value c))
		(make-instance 'integer-ring :value (/ other-value c)))))))