;; Predicates

(define title
  (lambda (recipe)
    (car (recipe))))

(define ingredients
  (lambda (recipe)
    (car (cdr recipe))))

(define steps
  (lambda (recipe)
    (car (cdr (cdr recipe)))))

(define ingredient-name
  (lambda (ingredient)
    (if (= (length ingredient) 2)
        (car (cdr ingredient))
        (car (cddr ingredient)))))

(define ingredient-amount
  (lambda (ingredient)
    (car ingredient)))


;;

(define ingredient-ref
  (lambda (ingredients n)
    (if (= n 0)
        (car ingredients)
        (ingredient-ref (cdr ingredients) (- n 1)))))

(define ingredient-by-name
  (lambda (ingredients search-name)
    (let ((ingredient (car ingredients)))
      (cond [(equal? (ingredient-name ingredient)
                     search-name)
             ingredient]
            [(null? (cdr ingredients)) #f]
            [else (ingredient-by-name (cdr ingredients)
                                      search-name)]))))

(define contains-ingredient?
  (lambda (recipe ingredient)
    (let ((ingredients (ingredients recipe)))
      (ingredient-by-name ingredients ingredient))))