#lang racket
(define (rev lst)
  (match lst
    ['() '()]
    [(list a) (list a)]
    [(cons h t)
      (append
        (rev t)
        (list h))]))

(define (annihilate lst pred)
  (match lst
    ['() '()]
    [(list a) (if (pred a) '() (list a))]
    [(cons h t)
      (let ([nt (annihilate t pred)])
        (if (pred h)
          nt
          (cons h nt)))]))

(displayln (annihilate '(1 2 3 4 5 6 7 8 9 10) (λ (n) (odd? n))))
(displayln (rev '(1 2 3 4 5 6)))