+(define-record-type <wrapped-exception>
+ (make-wrapped-exception key args stacks)
+ wrapped-exception?
+ (key wrapped-exception-key)
+ (args wrapped-exception-args)
+ (stacks wrapped-exception-stacks))
+
+(define-syntax-rule (propagate-%async-exceptions body)
+ (let ((body-result body))
+ (if (wrapped-exception? body-result)
+ (throw '8sync-caught-error
+ (wrapped-exception-key body-result)
+ (wrapped-exception-args body-result)
+ (wrapped-exception-stacks body-result))
+ body-result)))
+
+(define-syntax 8sync
+ (syntax-rules ()
+ "Run BODY asynchronously (8synchronously?) at a prompt, then return.
+
+Possibly specify WHEN as the second argument."
+ ((8sync body)
+ (8sync-run body))
+ ((8sync body when)
+ (8sync-run-at body when))))
+
+(define-syntax-rule (8sync-run body ...)
+ (8sync-run-at body ... #f))
+
+(define-syntax-rule (8sync-run-at body ... when)
+ (propagate-%async-exceptions
+ (8sync-abort-to-prompt
+ ;; Send an asynchronous request to apply a continuation to the
+ ;; following function, then handle that as a request to the agenda
+ (make-async-request
+ (lambda (kont)
+ ;; We're making a run request
+ (make-run-request
+ ;; Wrapping the following execution to run...
+ (wrap
+ ;; Once we get the result from the inner part, we'll resume
+ ;; this continuation, but first
+ ;; @@: Is this running immediately, or queueing the result
+ ;; after evaluation for the next agenda tick? It looks
+ ;; like evaluating immediately. Is that what we want?
+ (kont
+ ;; Any unhandled errors are caught
+ (let ((exception-stack #f))
+ (catch #t
+ ;; Run the actual code the user requested
+ (lambda ()
+ body ...)
+ ;; If something bad happened and we didn't catch it,
+ ;; we'll wrap it up in such a way that the continuation
+ ;; can address it
+ (lambda (key . args)
+ (cond
+ ((eq? key '8sync-caught-error)
+ (match args
+ ((orig-key orig-args orig-stacks)
+ (make-wrapped-exception
+ orig-key orig-args
+ (cons exception-stack orig-stacks)))))
+ (else
+ (make-wrapped-exception key args
+ (list exception-stack)))))
+ (lambda _
+ (set! exception-stack (make-stack #t 1 0)))))))
+ when))))))
+
+(define-syntax-rule (8sync-run-delay body ... delay-time)
+ (8sync-run-at body ... (tdelta delay-time)))
+
+(define-syntax-rule (8sync-delay args ...)
+ (8sync-run-delay args ...))
+
+(define-syntax-rule (8sync-port port port-request-args ...)
+ (8sync-abort-to-prompt
+ (make-async-request
+ (lambda (kont)
+ (list (make-port-request port port-request-args ...)
+ (make-run-request
+ ;; What's with returning #f to kont?
+ ;; Otherwise we sometimes get errors like
+ ;; "Zero values returned to single-valued continuation""
+ (wrap (kont #f)) #f))))))
+
+(define-syntax-rule (8sync-port-remove port)
+ (8sync-abort-to-prompt
+ (make-async-request
+ (lambda (kont)
+ (list (make-port-remove-request port)
+ (make-run-request
+ ;; See comment in 8sync-port
+ (wrap (kont #f)) #f))))))
+
+
+;; TODO: Write (%run-immediately)
+
+(define-syntax-rule (8sync-immediate body)
+ "Run body asynchronously but ignore its result...
+forge ahead in our current function!"
+ (8sync-abort-to-prompt
+ (make-async-request
+ (lambda (kont)
+ (list (make-run-request
+ ;; See comment in 8sync-port
+ (wrap (kont #f)) #f)
+ (make-run-request body #f))))))
+
+(define-syntax-rule (catch-8sync exp (handler-key handler) ...)
+ (catch '8sync-caught-error
+ (lambda ()
+ exp)
+ (lambda (_ orig-key orig-args orig-stacks)
+ (cond
+ ((or (eq? handler-key #t)
+ (eq? orig-key handler-key))
+ (apply handler orig-stacks orig-args)) ...
+ (else (raise '8sync-caught-error
+ orig-key orig-args orig-stacks))))))