CPE 123 11.15.13.rkt

;; Nancy Truong, Mitchell Salles, Dan Stone
;; CPE 123 (3:00 P - 5:00 P) 

(define (s sec) (* 44100 sec))

;; a note is (make-note midi-num frames frames)
(define-struct note (pitch time dur))


;; note -> boolean
(define (check-if-first-ten n)
  (if (<= (+ (note-time n) (note-dur n)) (s 10)) true false))

; list-of-notes -> list-of-notes
;; returns alist of notes that end in the first 10 seconds
(define (first-ten lon)
  (cond [(empty? lon) empty]
        [else
         (if (check-if-first-ten (first lon))
             (cons (first lon)
               (first-ten (rest lon)))
              (first-ten (rest lon)))]))

(check-expect (first-ten (cons (make-note 40 0 (s 2))
                               (cons (make-note 50 (s 3) (s 2))
                               (cons (make-note 40 (s 5) (s 4))
                               (cons (make-note 40 (s 10) (s 2)) empty)))))
                         (cons (make-note 40 0 (s 2))
                               (cons (make-note 50 (s 3) (s 2))
                               (cons (make-note 40 (s 5) (s 4)) empty))))

(check-expect (first-ten (cons (make-note 40 (s 9) (s 2))
                               (cons (make-note 50 (s 11) (s 2))
                               (cons (make-note 40 (s 13) (s 4))
                               (cons (make-note 40 (s 3) (s 2)) empty)))))
              (cons (make-note 40 (s 3) (s 2)) empty))