#lang racket

(struct pony (race name alist))

(define (unicorn name)

  (pony 'unicorn name '()))

(define (pegasus name)

  (pony 'pegasus name '()))

(define (earth-pony name)

  (pony 'earth-pony name '()))

(define ponies

  (list (unicorn "Twilight Sparkle")

        (unicorn "Rarity")

        (pegasus "Rainbow Dash")

        (pegasus "Fluttershy")

        (earth-pony "Pinkie Pie")

        (earth-pony "Applejack")

        (pony 'unicorn "Moon Dancer" '((best? . #t)))))

(define (is-multiword-name name)

  (>= (length (string-split name " ")) 2))

(define pony-names

  (map (lambda (x) (pony-name x)) ponies))

(define multiword-pony-names

  (filter (lambda (x) (is-multiword-name x)) pony-names))

(define (best-pony? pony)

  (if (assq 'best? (pony-alist pony))

      #t

      #f))

(define best-pony (car (memf best-pony? ponies)))