1 ;;; 8sync --- Asynchronous programming for Guile
2 ;;; Copyright (C) 2015, 2016 Christopher Allan Webber <cwebber@dustycloud.org>
4 ;;; This file is part of 8sync.
6 ;;; 8sync is free software: you can redistribute it and/or modify it
7 ;;; under the terms of the GNU Lesser General Public License as
8 ;;; published by the Free Software Foundation, either version 3 of the
9 ;;; License, or (at your option) any later version.
11 ;;; 8sync is distributed in the hope that it will be useful,
12 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ;;; GNU Lesser General Public License for more details.
16 ;;; You should have received a copy of the GNU Lesser General Public
17 ;;; License along with 8sync. If not, see <http://www.gnu.org/licenses/>.
19 (define-module (8sync agenda)
20 #:use-module (srfi srfi-1)
21 #:use-module (srfi srfi-9)
22 #:use-module (srfi srfi-9 gnu)
23 #:use-module (ice-9 q)
24 #:use-module (ice-9 match)
25 #:use-module (ice-9 receive)
28 agenda-queue agenda-prompt-tag
29 agenda-read-port-map agenda-write-port-map agenda-except-port-map
37 make-time-segment time-segment?
38 time-segment-time time-segment-queue
40 time< time= time<= time-delta+
44 make-time-delta tdelta time-delta?
45 time-delta-sec time-delta-usec
48 make-schedule schedule?
49 schedule-add! schedule-empty?
53 schedule-segments-split schedule-extract-until!
54 add-segments-contents-to-queue!
57 make-run-request run-request?
58 run-request-proc run-request-when
61 make-port-request port-request port-request?
63 port-request-read port-request-write port-request-except
66 make-port-remove-request port-remove-request port-remove-request?
67 port-remove-request-port
69 run-it wrap wrap-apply run run-at run-delay
72 8sync-run 8sync-run-at 8sync-run-delay
73 8sync-port 8sync-port-remove
78 ;; used for introspecting the error, but a method for making
81 wrapped-exception-key wrapped-exception-args
82 wrapped-exception-stacks
84 print-error-and-continue
89 start-agenda agenda-run-once))
91 ;; @@: Using immutable agendas here, so wouldn't it make sense to
92 ;; replace this queue stuff with using pfds based immutable queues?
98 ;;; The agenda consists of:
99 ;;; - a queue of immediate items to handle
100 ;;; - sheduled future events to be added to a future queue
101 ;;; - a tag by which running processes can escape for some asynchronous
102 ;;; operation (from which they can be returned later)
103 ;;; - a mapping of ports to various handler procedures
105 ;;; The goal, eventually, is for this all to be immutable and functional.
106 ;;; However, we aren't there yet. Some tricky things:
107 ;;; - The schedule needs to be immutable, yet reasonably efficient.
108 ;;; - Need to use immutable queues (ijp's pfds library?)
109 ;;; - Modeling reading from ports as something repeatable,
110 ;;; and with reasonable separation from functional components?
112 (define-immutable-record-type <agenda>
113 (make-agenda-intern queue prompt-tag
114 read-port-map write-port-map except-port-map
115 schedule time catch-handler pre-unwind-handler)
118 (prompt-tag agenda-prompt-tag)
119 (read-port-map agenda-read-port-map)
120 (write-port-map agenda-write-port-map)
121 (except-port-map agenda-except-port-map)
122 (schedule agenda-schedule)
124 (catch-handler agenda-catch-handler)
125 (pre-unwind-handler agenda-pre-unwind-handler))
127 (define (make-async-prompt-tag)
128 "Make an async prompt tag for an agenda.
130 Generally done automatically for the user through (make-agenda)."
131 (make-prompt-tag "prompt"))
133 (define* (make-agenda #:key
135 (prompt (make-prompt-tag))
136 (read-port-map (make-hash-table))
137 (write-port-map (make-hash-table))
138 (except-port-map (make-hash-table))
139 (schedule (make-schedule))
140 (time (gettimeofday))
142 (pre-unwind-handler print-error-and-continue))
143 ;; TODO: document arguments
144 "Make a fresh agenda."
145 (make-agenda-intern queue prompt
146 read-port-map write-port-map except-port-map
148 catch-handler pre-unwind-handler))
150 (define (current-agenda-prompt)
151 "Get the prompt for the current agenda; signal an error if there isn't one."
152 (let ((current-agenda (%current-agenda)))
153 (if (not current-agenda)
156 "Can't get current agenda prompt if there's no current agenda!")
157 (agenda-prompt-tag current-agenda))))
159 ;; helper for making queues for an agenda
160 (define (list->q lst)
161 "Makes a queue composed of LST items"
169 (define (make-q* . args)
170 "Makes a queue and populates it with this invocation's ARGS"
177 ;;; This is where we handle timed events for the future
179 ;; This section totally borrows from the ideas in SICP
182 ;; NOTE: time is a cons of (seconds . microseconds)
184 (define-record-type <time-segment>
185 (make-time-segment-intern time queue)
187 (time time-segment-time)
188 (queue time-segment-queue))
190 ;; @@: This seems to be the same as srfi-18's seconds->time procedure?
191 ;; Maybe double check and switch to that? (Thanks amz3!)
193 (define (time-from-float-or-fraction time)
194 "Produce a (sec . usec) pair from TIME, a float or fraction"
195 (let* ((mixed-whole (floor time))
196 (mixed-rest (- time mixed-whole)) ; float or fraction component
198 (usec (floor (* 1000000 mixed-rest))))
199 (cons (inexact->exact sec) (inexact->exact usec))))
201 (define (time-segment-right-format time)
202 "Ensure TIME is in the right format.
204 The right format means (second . microsecond).
205 If an integer, will convert appropriately."
206 ;; TODO: add floating point / rational number support.
208 ;; time is already a cons of second and microsecnd
209 (((? integer? s) . (? integer? u)) time)
210 ;; time was just an integer (just the second)
211 ((? integer? _) (cons time 0))
212 ((or (? rational? _) (? inexact? _))
213 (time-from-float-or-fraction time))
214 (_ (throw 'invalid-time "Invalid time" time))))
216 (define* (make-time-segment time #:optional (queue (make-q)))
217 "Make a time segment of TIME and QUEUE
219 No automatic conversion is done, so you might have to
220 run (time-segment-right-format) first."
221 (make-time-segment-intern time queue))
223 (define (time< time1 time2)
224 "Check if TIME1 is less than TIME2"
225 (cond ((< (car time1)
235 (define (time= time1 time2)
236 "Check whether TIME1 and TIME2 are equivalent"
237 (and (= (car time1) (car time2))
238 (= (cdr time1) (cdr time2))))
240 (define (time<= time1 time2)
241 "Check if TIME1 is less than or equal to TIME2"
242 (or (time< time1 time2)
243 (time= time1 time2)))
246 (define-record-type <time-delta>
247 (make-time-delta-intern sec usec)
250 (usec time-delta-usec))
252 (define* (make-time-delta time)
253 "Make a <time-delta> of SEC seconds and USEC microseconds.
255 This is used primarily so the agenda can recognize RUN-REQUEST objects
256 which are meant to delay computation"
257 (match (time-segment-right-format time)
259 (make-time-delta-intern sec usec))))
261 (define tdelta make-time-delta)
263 (define (time-carry-correct time)
264 "Corrects/handles time microsecond carry.
265 Will produce (0 . 0) instead of a negative number, if needed."
266 (cond ((>= (cdr time) 1000000)
269 (- (cdr time) 1000000)))
275 (+ (cdr time) 1000000))))
278 (define (time-delta+ time time-delta)
279 "Increment a TIME by the value of TIME-DELTA"
281 (cons (+ (car time) (time-delta-sec time-delta))
282 (+ (cdr time) (time-delta-usec time-delta)))))
284 (define (time-minus time1 time2)
285 "Subtract TIME2 from TIME1"
287 (cons (- (car time1) (car time2))
288 (- (cdr time1) (cdr time2)))))
290 (define (time-plus time1 time2)
291 "Add TIME1 and TIME2"
293 (cons (+ (car time1) (car time2))
294 (+ (cdr time1) (cdr time2)))))
297 (define-record-type <schedule>
298 (make-schedule-intern segments)
300 (segments schedule-segments set-schedule-segments!))
302 (define* (make-schedule #:optional segments)
303 "Make a schedule, optionally pre-composed of SEGMENTS"
304 (make-schedule-intern (or segments '())))
306 (define (schedule-soonest-time schedule)
307 "Return a cons of (sec . usec) for next time segement, or #f if none"
308 (let ((segments (schedule-segments schedule)))
309 (if (eq? segments '())
311 (time-segment-time (car segments)))))
313 ;; TODO: This code is reasonably easy to read but it
314 ;; mutates AND is worst case of O(n) in both space and time :(
315 ;; but at least it'll be reasonably easy to refactor to
316 ;; a more functional setup?
317 (define (schedule-add! schedule time proc)
318 "Mutate SCHEDULE, adding PROC at an appropriate time segment for TIME"
319 (let ((time (time-segment-right-format time)))
320 (define (new-time-segment)
322 (make-time-segment time)))
323 (enq! (time-segment-queue new-segment) proc)
325 (define (loop segments)
326 (define (segment-equals-time? segment)
327 (time= time (time-segment-time segment)))
329 (define (segment-more-than-time? segment)
330 (time< time (time-segment-time segment)))
332 ;; We could switch this out to be more mutate'y
333 ;; and avoid the O(n) of space... is that over-optimizing?
335 ;; If we're at the end of the list, time to make a new
337 ('() (cons (new-time-segment) '()))
338 ;; If the segment's time is exactly our time, good news
339 ;; everyone! Let's append our stuff to its queue
340 (((? segment-equals-time? first) rest ...)
341 (enq! (time-segment-queue first) proc)
343 ;; If the first segment is more than our time,
344 ;; ours belongs before this one, so add it and
345 ;; start consing our way back
346 (((? segment-more-than-time? first) rest ...)
347 (cons (new-time-segment) segments))
348 ;; Otherwise, build up recursive result
350 (cons first (loop rest)))))
351 (set-schedule-segments!
353 (loop (schedule-segments schedule)))))
355 (define (schedule-empty? schedule)
356 "Check if the SCHEDULE is currently empty"
357 (eq? (schedule-segments schedule) '()))
359 (define (schedule-segments-split schedule time)
360 "Does a multiple value return of time segments before/at and after TIME"
361 (let ((time (time-segment-right-format time)))
362 (define (segment-is-now? segment)
363 (time= (time-segment-time segment) time))
364 (define (segment-is-before-now? segment)
365 (time< (time-segment-time segment) time))
367 (let loop ((segments-before '())
368 (segments-left (schedule-segments schedule)))
370 ;; end of the line, return
372 (values (reverse segments-before) '()))
374 ;; It's right now, so time to stop, but include this one in before
375 ;; but otherwise return
376 (((? segment-is-now? first) rest ...)
377 (values (reverse (cons first segments-before)) rest))
379 ;; This is prior or at now, so add it and keep going
380 (((? segment-is-before-now? first) rest ...)
381 (loop (cons first segments-before) rest))
383 ;; Otherwise it's past now, just return what we have
385 (values segments-before segments-after))))))
387 (define (schedule-extract-until! schedule time)
388 "Extract all segments until TIME from SCHEDULE, and pop old segments off"
389 (receive (segments-before segments-after)
390 (schedule-segments-split schedule time)
391 (set-schedule-segments! schedule segments-after)
394 (define (add-segments-contents-to-queue! segments queue)
397 (let ((seg-queue (time-segment-queue segment)))
398 (while (not (q-empty? seg-queue))
399 (enq! queue (deq! seg-queue)))))
404 ;;; Request to run stuff
405 ;;; ====================
407 (define-record-type <run-request>
408 (make-run-request proc when)
410 (proc run-request-proc)
411 (when run-request-when))
413 (define* (run-it proc #:optional when)
414 "Make a request to run PROC (possibly at WHEN)"
415 (make-run-request proc when))
417 (define-syntax-rule (wrap body ...)
418 "Wrap contents in a procedure"
422 (define-syntax-rule (wrap-apply body)
423 "Wrap possibly multi-value function in a procedure, applies all arguments"
428 ;; @@: Do we really want `body ...' here?
429 ;; what about just `body'?
430 (define-syntax-rule (run body ...)
431 "Run everything in BODY but wrap in a convenient procedure"
432 (make-run-request (wrap body ...) #f))
434 (define-syntax-rule (run-at body ... when)
436 (make-run-request (wrap body ...) when))
438 ;; @@: Is it okay to overload the term "delay" like this?
439 ;; Would `run-in' be better?
440 (define-syntax-rule (run-delay body ... delay-time)
441 "Run BODY at DELAY-TIME time from now"
442 (make-run-request (wrap body ...) (tdelta delay-time)))
445 ;; A request to set up a port with at least one of read, write, except
446 ;; handling processes
448 (define-record-type <port-request>
449 (make-port-request-intern port read write except)
451 (port port-request-port)
452 (read port-request-read)
453 (write port-request-write)
454 (except port-request-except))
456 (define* (make-port-request port #:key read write except)
457 (if (not (or read write except))
458 (throw 'no-port-handler-given "No port handler given.\n"))
459 (make-port-request-intern port read write except))
461 (define port-request make-port-request)
463 (define-record-type <port-remove-request>
464 (make-port-remove-request port)
466 (port port-remove-request-port))
468 (define port-remove-request make-port-remove-request)
472 ;;; Asynchronous escape to run things
473 ;;; =================================
475 (define-syntax-rule (8sync-abort-to-prompt async-request)
476 (abort-to-prompt (current-agenda-prompt)
479 ;; Async port request and run-request meta-requests
480 (define (make-async-request proc)
481 "Wrap PROC in an async-request
483 The purpose of this is to make sure that users don't accidentally
484 return the wrong thing via (8sync) and trip themselves up."
485 (cons '*async-request* proc))
487 (define (setup-async-request resume-kont async-request)
488 "Complete an async request for agenda-run-once's continuation handling"
490 (('*async-request* . async-setup-proc)
491 (async-setup-proc resume-kont))
492 ;; TODO: deliver more helpful errors depending on what the user
494 (_ (throw 'invalid-async-request
495 "Invalid request passed back via an (8sync) procedure."
498 (define-record-type <wrapped-exception>
499 (make-wrapped-exception key args stacks)
501 (key wrapped-exception-key)
502 (args wrapped-exception-args)
503 (stacks wrapped-exception-stacks))
505 (define-syntax-rule (propagate-%async-exceptions body)
506 (let ((body-result body))
507 (if (wrapped-exception? body-result)
508 (throw '8sync-caught-error
509 (wrapped-exception-key body-result)
510 (wrapped-exception-args body-result)
511 (wrapped-exception-stacks body-result))
516 "Run BODY asynchronously (8synchronously?) at a prompt, then return.
518 Possibly specify WHEN as the second argument."
522 (8sync-run-at body when))))
524 (define-syntax-rule (8sync-run body ...)
525 (8sync-run-at body ... #f))
527 (define-syntax-rule (8sync-run-at body ... when)
528 (propagate-%async-exceptions
529 (8sync-abort-to-prompt
530 ;; Send an asynchronous request to apply a continuation to the
531 ;; following function, then handle that as a request to the agenda
534 ;; We're making a run request
536 ;; Wrapping the following execution to run...
538 ;; Once we get the result from the inner part, we'll resume
539 ;; this continuation, but first
540 ;; @@: Is this running immediately, or queueing the result
541 ;; after evaluation for the next agenda tick? It looks
542 ;; like evaluating immediately. Is that what we want?
544 ;; Any unhandled errors are caught
545 (let ((exception-stack #f))
547 ;; Run the actual code the user requested
550 ;; If something bad happened and we didn't catch it,
551 ;; we'll wrap it up in such a way that the continuation
555 ((eq? key '8sync-caught-error)
557 ((orig-key orig-args orig-stacks)
558 (make-wrapped-exception
560 (cons exception-stack orig-stacks)))))
562 (make-wrapped-exception key args
563 (list exception-stack)))))
565 (set! exception-stack (make-stack #t 1 0)))))))
568 (define-syntax-rule (8sync-run-delay body ... delay-time)
569 (8sync-run-at body ... (tdelta delay-time)))
571 (define-syntax-rule (8sync-delay args ...)
572 (8sync-run-delay args ...))
574 (define-syntax-rule (8sync-port port port-request-args ...)
575 (8sync-abort-to-prompt
578 (list (make-port-request port port-request-args ...)
580 ;; What's with returning #f to kont?
581 ;; Otherwise we sometimes get errors like
582 ;; "Zero values returned to single-valued continuation""
583 (wrap (kont #f)) #f))))))
585 (define-syntax-rule (8sync-port-remove port)
586 (8sync-abort-to-prompt
589 (list (make-port-remove-request port)
591 ;; See comment in 8sync-port
592 (wrap (kont #f)) #f))))))
595 ;; TODO: Write (%run-immediately)
597 (define-syntax-rule (8sync-nowait body)
598 "Run body asynchronously but ignore its result...
599 forge ahead in our current function!"
600 (8sync-abort-to-prompt
603 (list (make-run-request
604 ;; See comment in 8sync-port
606 (make-run-request (lambda () body) #f))))))
608 (define-syntax-rule (catch-8sync exp (handler-key handler) ...)
609 (catch '8sync-caught-error
612 (lambda (_ orig-key orig-args orig-stacks)
614 ((or (eq? handler-key #t)
615 (eq? orig-key handler-key))
616 (apply handler orig-stacks orig-args)) ...
617 (else (raise '8sync-caught-error
618 orig-key orig-args orig-stacks))))))
622 ;;; Execution of agenda, and current agenda
623 ;;; =======================================
625 (define %current-agenda (make-parameter #f))
627 (define (update-agenda-from-select! agenda)
628 "Potentially (select) on ports specified in agenda, adding items to queue.
630 Also handles sleeping when all we have to do is wait on the schedule."
631 (define (hash-keys hash)
632 (hash-map->list (lambda (k v) k) hash))
633 (define (get-wait-time)
634 ;; TODO: we need to figure this out based on whether there's anything
635 ;; in the queue, and if not, how long till the next scheduled item
636 (let ((soonest-time (schedule-soonest-time (agenda-schedule agenda))))
638 ((not (q-empty? (agenda-queue agenda)))
640 (soonest-time ; ie, the agenda is non-empty
641 (let* ((current-time (agenda-time agenda)))
642 (if (time<= soonest-time current-time)
643 ;; Well there's something due so let's select
644 ;; (this avoids a (possible?) race condition chance)
646 (time-minus soonest-time current-time))))
650 ;; TODO: support usecond wait time too
651 (match (get-wait-time)
655 (select (hash-keys (agenda-read-port-map agenda))
656 (hash-keys (agenda-write-port-map agenda))
657 (hash-keys (agenda-except-port-map agenda))
659 (lambda (key . rest-args)
663 (_ (error "Unhandled error in select!" key rest-args))))))))
664 (define (get-procs-to-run)
665 (define (ports->procs ports port-map)
666 (lambda (initial-procs)
670 ((hash-ref port-map port) port))
675 ((read-ports write-ports except-ports)
676 ;; @@: Come on, we can do better than append ;P
677 ((compose (ports->procs
679 (agenda-read-port-map agenda))
682 (agenda-write-port-map agenda))
685 (agenda-except-port-map agenda)))
687 (define (update-agenda)
688 (let ((procs-to-run (get-procs-to-run))
689 (q (agenda-queue agenda)))
695 (define (ports-to-select?)
696 (define (has-items? selector)
698 ;; ... we could use hash-for-each and a continuation to jump
699 ;; out with a #t at first indication of an item
700 (not (= (hash-count (const #t)
703 (or (has-items? agenda-read-port-map)
704 (has-items? agenda-write-port-map)
705 (has-items? agenda-except-port-map)))
707 (if (or (ports-to-select?)
708 ;; select doubles as sleep...
709 (not (schedule-empty? (agenda-schedule agenda))))
713 (define (agenda-handle-port-request! agenda port-request)
714 "Update an agenda for a port-request"
715 (define (handle-selector request-selector port-map-selector)
716 (if (request-selector port-request)
717 ;; @@: Should we remove if #f?
718 (hash-set! (port-map-selector agenda)
719 (port-request-port port-request)
720 (request-selector port-request))))
721 (handle-selector port-request-read agenda-read-port-map)
722 (handle-selector port-request-write agenda-write-port-map)
723 (handle-selector port-request-except agenda-except-port-map))
726 (define (agenda-handle-port-remove-request! agenda port-remove-request)
727 "Update an agenda for a port-remove-request"
728 (let ((port (port-remove-request-port port-remove-request)))
729 (hash-remove! (agenda-read-port-map agenda) port)
730 (hash-remove! (agenda-write-port-map agenda) port)
731 (hash-remove! (agenda-except-port-map agenda) port)))
734 (define (stop-on-nothing-to-do agenda)
735 (and (q-empty? (agenda-queue agenda))
736 (schedule-empty? (agenda-schedule agenda))
737 (= 0 (hash-count (const #t) (agenda-read-port-map agenda)))
738 (= 0 (hash-count (const #t) (agenda-write-port-map agenda)))
739 (= 0 (hash-count (const #t) (agenda-except-port-map agenda)))))
742 (define* (start-agenda agenda
744 ;; @@: Should we make stop-on-nothing-to-do
745 ;; the default stop-condition?
746 (stop-condition stop-on-nothing-to-do)
747 (get-time gettimeofday)
748 (handle-ports update-agenda-from-select!))
749 ;; TODO: Document fields
750 "Start up the AGENDA"
751 (let loop ((agenda agenda))
753 ;; @@: Hm, maybe here would be a great place to handle
754 ;; select'ing on ports.
755 ;; We could compose over agenda-run-once and agenda-read-ports
756 (agenda-run-once agenda)))
757 (if (and stop-condition (stop-condition agenda))
760 ;; We have to update the time after ports handled, too
761 ;; because it may have changed after a select
764 ;; Adjust the agenda's time just in time
765 ;; We do this here rather than in agenda-run-once to make
766 ;; agenda-run-once's behavior fairly predictable
767 (set-field agenda (agenda-time) (get-time)))
768 (agenda-time) (get-time))))
769 ;; Update the agenda's current queue based on
770 ;; currently applicable time segments
771 (add-segments-contents-to-queue!
772 (schedule-extract-until! (agenda-schedule agenda) (agenda-time agenda))
773 (agenda-queue agenda))
777 (define (print-error-and-continue key . args)
778 "Frequently used as pre-unwind-handler for agenda"
780 ((eq? key '8sync-caught-error)
782 ((orig-key orig-args stacks)
783 (display "\n*** Caught async exception. ***\n")
784 (format (current-error-port)
785 "* Original key '~s and arguments: ~s *\n"
787 (display "* Caught stacks below (ending with original) *\n\n")
790 (display-backtrace s (current-error-port))
791 (newline (current-error-port)))
794 (format (current-error-port)
795 "\n*** Caught exception with key '~s and arguments: ~s ***\n"
797 (display-backtrace (make-stack #t 1 0)
798 (current-error-port))
799 (newline (current-error-port)))))
801 (define-syntax-rule (maybe-catch-all (catch-handler pre-unwind-handler)
803 (if (or catch-handler pre-unwind-handler)
808 (or catch-handler (lambda _ #f))
809 (or pre-unwind-handler (lambda _ #f)))
812 (define (agenda-run-once agenda)
813 "Run once through the agenda, and produce a new agenda
814 based on the results"
815 (define (call-proc proc)
817 (agenda-prompt-tag agenda)
819 (parameterize ((%current-agenda agenda))
821 ((agenda-catch-handler agenda)
822 (agenda-pre-unwind-handler agenda))
824 (lambda (kont async-request)
825 (setup-async-request kont async-request))))
827 (let ((queue (agenda-queue agenda))
828 (next-queue (make-q)))
829 (while (not (q-empty? queue))
830 (let* ((proc (q-pop! queue))
831 (proc-result (call-proc proc))
833 (lambda (run-request)
834 (define (schedule-at! time proc)
835 (schedule-add! (agenda-schedule agenda) time proc))
836 (let ((request-time (run-request-when run-request)))
838 ((? time-delta? time-delta)
839 (let ((time (time-delta+ (agenda-time agenda)
841 (schedule-at! time (run-request-proc run-request))))
843 (let ((time (cons sec 0)))
844 (schedule-at! time (run-request-proc run-request))))
845 (((? integer? sec) . (? integer? usec))
846 (schedule-at! request-time (run-request-proc run-request)))
848 (enq! next-queue (run-request-proc run-request))))))))
849 (define (handle-individual result)
850 ;; @@: Could maybe optimize by switching to an explicit cond...
852 ((? run-request? new-proc)
854 ((? port-request? port-request)
855 (agenda-handle-port-request! agenda port-request))
856 ((? port-remove-request? port-remove-request)
857 (agenda-handle-port-remove-request! agenda port-remove-request))
860 ;; @@: We might support delay-wrapped procedures here
863 (for-each handle-individual results))
864 (one-result (handle-individual one-result)))))
865 ;; TODO: Alternately, we could return the next-queue
866 ;; along with changes to be added to the schedule here?
867 ;; Return new agenda, with next queue set
868 (set-field agenda (agenda-queue) next-queue)))