;; circular.scm - (c) rohan drape, 2005-2006

;; The fmod() function computes the remainder of dividing x by y.  The
;; return value is x - n * y, where n is the quotient of x / y,
;; rounded towards zero to an integer.

(define (fmod x y)
  (let ((n (quotient x y)))
    (- x (* n y))))

(define (takt->pulse cycle pulse takt)
  (let* ((m (fmod pulse cycle))
	 (i (- takt m))
	 (p (if (negative? i) (+ i cycle) i)))
    (+ p pulse)))

;; 'p' and the value reported to 'f' are cyclic in [0, 'cycle').

(define (tschedule-at%! T cycle p f)
  (tschedule-at! T
		 (takt->pulse cycle
			      (utc->pulse T (utc))
			      p)
		 (lambda (pulse utc)
		   (f (fmod pulse cycle) utc))))