Re: [QUESTION] How to use :filter in `make-process'?

[stardiviner <numbchild@gmail.com>]

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Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> (let ((op-fn (lambda () (message "call the fn"))))
>>   (make-process
>>    :name "sleep command test"
>>    :command (list "sleep" "3")
>>    :filter `(lambda (proc event)
>>               (message "event catched!")
>                                 ^^^^^^^
>                                 caught ;-)
>>               (funcall ,op-fn))
>>    :buffer "*sleep test*"))
>
> More importantly, the ,op-fn is incorrect, it should be ',op-fn
> otherwise the value contained in op-fn will be re-interpreted as an
> expression (which will sometimes be harmless but sometimes not,
> depending on how the function value ends up represented).
>
> Of course, the better solution is to use `lexical-binding` so you can
> just write:
>
>     (let ((op-fn (lambda () (message "call the fn"))))
>       (make-process
>        :name "sleep command test"
>        :command (list "sleep" "3")
>        :filter (lambda (proc event)
>                  (message "event catched!")
>                  (funcall op-fn))
>        :buffer "*sleep test*"))
>
Use lexical-binding in your example, it does not work. report error:

: error in process sentinel: Symbol’s value as variable is void: op-fn [2 times]

>
> -- Stefan


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