#lang racket
(define (parity x . l)
  (define (check-parity y)
    (not (xor (= (remainder x 2) 0)
             (= (remainder y 2) 0))))
  (cond ((null? l) '())
        ((check-parity (car l))
         (cons (car l) (apply parity x (cdr l))))
        (else (apply parity x (cdr l)))))

(parity 1 2 3 4 5 6 7 8 9)