variables.rkt

#lang racket/base

;;;; This file has been changed from its original dharmatech/mpl version.

(provide variables) 

(require (only-in srfi/1 lset-union)
        "misc.rkt")

(define (union . lists)
  (apply lset-union (cons equal? lists)))

(define (VAR-1 u)
  (and (number? u) '()))

(define (VAR-2 u)
  (and (power? u) ;; VAR-2
       (let ((n (list-ref u 2)))
         (and (integer? n)
              (> n 1)))
       (list (list-ref u 1))))

(define (VAR-3 u)
  (and (sum? u)
       (apply union
              (map
               (lambda (operand)
                 (or (VAR-1 operand)
                     (VAR-2 operand)
                     (VAR-4 operand)
                     (VAR-5 operand)))
               (cdr u)))))

(define (VAR-4 u)
  (and (product? u)
       (apply union
              (map 
               (lambda (operand)
                 (or (VAR-1 operand)
                     (VAR-2 operand)
                     (and (sum? operand) (list operand))
                     (VAR-5 operand)))
               (cdr u)))))

(define (VAR-5 u)
  (list u))

;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(define (variables u)
  (or (VAR-1 u)
      (VAR-2 u)
      (VAR-3 u)
      (VAR-4 u)
      (VAR-5 u)))

;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;