notefilter

(require rsound)

;a note is
;(make-note number number number)
(define-struct note (pitch time duration))

;a list-of-notes is one of:
;-empty, or
;-(cons note list-nof-notes)

;list-of-notes -> list-of-notes
;takes in a list of notes and produces a list of notes containing only those that end in the first 10 seconds
(define (note-filter lon)
  (cond[(empty? lon) empty]
       [else (if (> (* 10 44100) (+ (note-duration (first lon)) (note-time (first lon)))) 
                 (cons (first lon) (note-filter (rest lon)))
                 (note-filter (rest lon)))]))



(check-expect (note-filter (cons (make-note 100 10000 44100)(cons (make-note 100 10000 (* 11 44100)) (cons (make-note 100 441001 44100) empty))))
              (cons (make-note 100 10000 44100) empty))

(check-expect (note-filter (cons (make-note 100 10000 44100)(cons (make-note 100 10000 (* 9 44100)) (cons (make-note 100 441001 44100) empty))))
              (cons (make-note 100 10000 44100) (cons (make-note 100 10000 (* 9 44100)) empty)))