;;; KEEPAFT.CAL
;;;
;;; A CAL program to "thin" channel aftertouch data.
;;; 
;;; Keeps every N'th channel aftertouch event, and those whose pressure value
;;; is 0, 64, or 127.
;;;
;;;

;;; Prolog
(do
  (int N 4)   ; thin every N'th event
  (int i 0)   ; index for moving through

  (getInt N "Keep every Nth ChanAft event:" 1 100)
)

;;; Body
(do
  (if (== Event.Kind CHANAFT)
    (do
      (switch ChanAft.Val
        ;; Don't delete if value is 0, 64, or 127....
        0     
          NIL
        64
          NIL
        127
          NIL

        ChanAft.Val   ; Default -- anything else...
          (if (== 0 (% i N))  ; is it the N'th event?
            NIL
            (delete)
          )
      )
      (++ i)          ; this counts
    )
    NIL
  )
)

;; Epilog
NIL