Wraps an arbitrary value into a synchronizable event. The
synchronization result of the event is the original value, with two
exceptions: procedures sync to their return value and lists sync
recursively. Both of these values can be disabled via keywords.
The package server is telling me that it needs documentation. That
confuses me since it has a .scrbl file and the .html was already
present in the repository. ISTR that the docs are only built once
every 24 hours, so presumably they will pop up at some point?
Examples:
; value-evts are both evt? and value-evt?. They sync to their argument
> (define e (value-evt 9))
> e
#<value-evt>
> (evt? e)
#t
> (value-evt? e)
#t
> (sync e)
9
;
; By default, syncing on a procedure syncs to the return value
> (define proc (lambda () (+ 2 2)))
> (sync (value-evt proc))
4
;
; You can instead get the procedure itself back
> (sync (value-evt proc #:eval-proc? #f))
#<procedure:proc>
;
; It's not a problem to specify #:eval-proc? on something that isn't a procedure
> (sync (value-evt "eval-proc? keyword is ignored for non-proc" #:eval-proc?
> #f))
"eval-proc? keyword is ignored for non-proc"
;
; eventify always returns an evt
; Things that are evts are unchanged
> (define ch (make-channel))
> (evt? ch)
#t
> (eq? ch (eventify ch))
#t
;
; Things that are not evts become value-evts
> (evt? 'bob)
#f
> (evt? (eventify 'bob))
#t
;
; by default, value-evts containing a list sync recursively
> (let ([result-ch (make-channel)]
[arg-ch1 (make-channel)]
[arg-ch2 (make-channel)])
(void (thread (λ () (channel-put result-ch (sync (value-evt (list
arg-ch1 arg-ch2)))))))
(channel-put arg-ch1 'arg1-ch-ok)
(channel-put arg-ch2 'arg2-ch-ok)
(sync result-ch))
'(arg1-ch-ok arg2-ch-ok)
;
; You can ask for it to return the original list
> (let ([arg-ch1 (make-channel)]
[arg-ch2 (make-channel)])
(sync (value-evt (list arg-ch1 arg-ch2) #:recurse-lists? #f)))
'(#<channel> #<channel>)
;
; all-evt is the same as value-evt but takes a rest argument
; so you don't have to supply your own list
> (let ([result-ch (make-channel)]
[arg-ch1 (make-channel)]
[arg-ch2 (make-channel)])
(define e (all-evt arg-ch1 arg-ch2))
(printf "all-evt returns: ~v" e)
(void (thread (λ () (channel-put result-ch (sync e)))))
(channel-put arg-ch1 'arg1-ch-ok)
(channel-put arg-ch2 'arg2-ch-ok)
(sync result-ch))
all-evt returns: #<value-evt>
'(arg1-ch-ok arg2-ch-ok)
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