/usr/share/scheme48-1.9/cml/time.scm is in scheme48 1.9-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 | ; Part of Scheme 48 1.9.  See file COPYING for notices and license.
; Authors: Mike Sperber
;; Rendezvous that happen at a specified time
(define (at-real-time-rv time)
  (make-time-rv (lambda () time)))
(define (after-time-rv time-difference)
  (make-time-rv (lambda () (+ (real-time) time-difference))))
(define (make-time-rv compute-time)
  (make-base
   (lambda ()
     (let ((time (compute-time)))
       (if (> (real-time) time)
	   (make-enabled 0
			 (lambda (queue)
			   (unspecific)))
	   (make-blocked
	    (lambda (trans-id cleanup-proc wrap-proc)
	      (register-dozer!
	       time
	       ;; alive?
	       (lambda ()
		 (not (trans-id-cancelled? trans-id)))
	       ;; wakeup
	       ;; It doesn't matter if this is repeated due to a
	       ;; failed commit or due to a race.  A stillborn commit
	       ;; will result in a no-op, and trans-ids can deal with
	       ;; a premature set.
	       (lambda ()
		 (with-new-proposal (lose)
		   (let ((thread-queue (make-queue)))
		     (cleanup-proc thread-queue)
		     (trans-id-set-value! trans-id
					  (cons (unspecific)
						wrap-proc))
		     (enqueue! thread-queue
			       (trans-id-thread-cell trans-id))
		     ;; we can't lose because we're running in the
		     ;; root scheduler
		     (maybe-commit-and-make-ready thread-queue))))))))))))
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