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(defpackage "RING"
  (:use :cl)
  (:export "R-PARSE"
	   "UNIT-ELEMENT"
	   "R-ZEROP"
	   "R+"
	   "R-"
	   "R*"
	   "R+"
	   "R/"
	   "R-EXPT"
	   "R-LCM"
	   "R-EZGCD"
	   "R-GCD"
	   "R-TOTAL-DEGREE"
	   "R-DIMENSION"
	   "R-EXPONENTS"
	   "R-COEFF"
	   "R-SUGAR"
	   "R-DIVIDES-P"   
	   "R-DIVIDES-LCM-P"
	   "R-LCM-DIVIDES-LCM-P"
	   "R-LCM-EQUAL-LCM-P"
	   "R-REL-PRIME-P"    
	   "R-EQUALP"	       
	   "R-ELT"
	   "R->LIST"
	   "R-DIVISIBLE-BY-P"	
	   "R-REL-PRIME-P"	
	   "R-DEPENDS-P"	
	   "R-TENSOR-PRODUCT"
	   "R-CONTRACT"      
	   "R-LENGTH"
	   "MULTIPLY-BY"
	   "ADD-TO"
	   "SUBTRACT-FROM"
	   "UNARY-MINUS"
	   "SCALAR"
	   "INSERT-ITEM"
	   "APPEND-ITEM")
  (:documentation
   "Implements ring operations.  These are all operations that are
performed on the coefficients by the package, and thus the coefficient
ring can be changed by merely redefining these operations."))

(in-package :ring)

(defclass scalar () 
  ((value :initarg :value :accessor value))
  (:documentation "Wraps objects suitable as scalars/polynomial coefficients"))

(defgeneric unit-element (class))

(defgeneric r-zerop (object)
  (:method ((self number)) (zerop self)))

(defgeneric r+ (x y)
  (:method ((x number) (y number)) (+ x y))) 

(defgeneric r- (x y)
  (:method ((x number) (y number)) (- x y))) 

(defgeneric r* (x y)
  (:method ((x number) (y number)) (* x y))) 

(defgeneric r-tensor-product (x y))

(defgeneric r/ (x y)
  (:method ((x number) (y number)) (/ x y))) 

(defgeneric r-lcm (x y)
  (:method ((x integer) (y integer)) (lcm x y))) 

(defgeneric r-expt (x y)
  (:method ((x integer) (y integer)) (expt x y))) 

(defgeneric r-ezgcd (x y)
  (:method ((x integer) (y integer)
	    &aux (c (gcd x y)))
    (values c (/ x c) (/ y c))))

(defgeneric r-gcd (x y)
  (:method ((x integer) (y integer))
    (gcd x y)))

(defgeneric r-dimension (object))
(defgeneric r-exponents (object))

(defgeneric r-coeff (object))
(defgeneric (setf r-coeff) (new-value object))

(defgeneric r-total-degree (object &optional start end))

(defgeneric r-divides-p (object1 object2)
  (:method ((object1 integer) (object2 integer))
    (zerop (rem object2 object1)))
  (:documentation "Returns T if OBJECT1 divides OBJECT2"))

(defgeneric r-divides-lcm-p (object1 object2 object3)
  (:documentation "Returns T if OBJECT divides LCM(OBJECT2, OBJECT3), NIL otherwise."))

(defgeneric r-lcm-divides-lcm-p (object1 object2 object3 object4)
  (:documentation "Returns T if LCM(OBJECT1,OBJECT2) divides LCM(OBJECT3,OBJECT4), NIL otherwise."))

(defgeneric r-lcm-equal-lcm-p (object1 object2 object3 object4)
  (:documentation "Returns T if object LCM(OBJECT1,OBJECT2) equals LCM(OBJECT3,OBJECT4), NIL otherwise."))

(defgeneric r-equalp (object1 object2)
  (:method ((object1 t) (object2 t)) (equalp object1 object2))
  (:documentation "Equality using deep comparison of object slots."))

(defgeneric r-elt (object index))

(defgeneric (setf r-elt) (new-value object index))

(defgeneric r-length (object))

(defgeneric r->list (object))
(defgeneric r-sugar (object))
(defgeneric r-rel-prime-p (object1 object2))
(defgeneric r-contract (object k))
(defgeneric r-divisible-by-p (object1 object2))
(defgeneric r-depends-p (object k))

(defgeneric multiply-by (self other)
  (:method (self other) (r* self other)))

(defgeneric add-to (self other)
  (:documentation "Add to object SELF another object OTHER.  For
complex objects, it may destructively modify SELF and destructively
modify/invalidate object OTHER.  The result is an object which is EQ
to SELF. NOTE: For built-in classes, such as NUMBER, the returned
object may not be EQ to the original, but it will be EQL to it.")
  (:method (self other) (r+ self other)))

(defgeneric subtract-from (self other)
  (:method (self other) (r- self other)))

(defgeneric unary-minus (self)
  (:method ((x number)) (- x)))

(defgeneric insert-item (self item))
(defgeneric append-item (self item))