source: CGBLisp/src/monom.lisp@ 1

#|
        $Id: monom.lisp,v 1.3 2009/01/22 04:04:31 marek Exp $   
  *--------------------------------------------------------------------------*
  |  Copyright (C) 1994, Marek Rychlik (e-mail: rychlik@math.arizona.edu)    |
  |    Department of Mathematics, University of Arizona, Tucson, AZ 85721    |
  |                                                                          |
  | Everyone is permitted to copy, distribute and modify the code in this    |
  | directory, as long as this copyright note is preserved verbatim.         |
  *--------------------------------------------------------------------------*
|#
(defpackage "MONOM"
  (:use "COMMON-LISP")
  (:export monom-equal monom-divides-p monom-divisible-by-p monom-rel-prime
           monom* nmonom* monom/ 
           monom-lcm monom-gcd))

(in-package "MONOM")

#+debug(proclaim '(optimize (speed 0) (debug 3)))
#-debug(proclaim '(optimize (speed 3) (debug 0)))

;;----------------------------------------------------------------
;; This package implements BASIC OPERATIONS ON MONOMIALS
;;----------------------------------------------------------------
;; DATA STRUCTURES: Monomials are represented as lists:
;;
;;      monom:  (n1 n2 ... nk) where ni are non-negative integers
;;
;;----------------------------------------------------------------
;; EXAMPLES: Suppose that variables are x and y. Then
;;
;;      Monom x*y^2 ---> (1 2)
;;
;;----------------------------------------------------------------

(defun monom/ (m1 m2)
  "Divide monomial M1 by monomial M2."
  (mapcar #'- m1 m2))

(defun monom* (m1 m2)
  "Multiply monomial M1 by monomial M2."
  (mapcar #'+ m1 m2))

(defun nmonom* (m1 m2)
  "Multiply monomials M1 and M2 - destructive version.
  M1 is destructively modified, M2 is not modified."
  (mapl #'(lambda (x y) (incf (car x) (car y))) m1 m2))

(defun monom-divides-p (m1 m2)
  "Returns T if monomial M1 divides monomial M2, NIL otherwise."
   (every #'<= m1 m2))

(defun monom-divisible-by-p (m1 m2)
  "Returns T if monomial M1 is divisible by monomial M2, NIL otherwise."
   (every #'>= m1 m2))

(defun monom-rel-prime (m1 m2)
  "Returns T if two monomials M1 and M2 are relatively prime (disjoint)."
  (every #'(lambda (x y) (zerop (min x y))) m1 m2))

(defun monom-equal (m1 m2)
  "Returns T if two monomials M1 and M2 are equal."
   (every #'= m1 m2))

(defun monom-lcm (m1 m2)
  "Returns least common multiple of monomials M1 and M2."
  (mapcar #'max m1 m2))

(defun monom-gcd (m1 m2)
  "Returns greatest common divisor of monomials M1 and M2."
  (mapcar #'min m1 m2))