Re: make-thread with lambda form instead of function symbol

[Noam Postavsky <npostavs@users.sourceforge.net>]

On Sun, Apr 16, 2017 at 12:05 PM, Eric Abrahamsen
<eric@ericabrahamsen.net> wrote:
> I'm trying to do something that seems like it would be a normal use
> case: spawn a series of threads which call the same function using
> different external processes. Practically what this means is that I want
> to pass a function-plus-argument form to make-thread, not a function
> symbol. Something like:
>
> (let* ((results)
>        (sources '(source1 source2))
>        (threads
>         (mapcar
>          (lambda (s)
>            (make-thread
>             (funcall
>              (lambda ()
>                (push (get-stuff-from-source s) results)))))
>          sources)))
>   (mapc #'thread-join threads)
>   results)
>
> The (funcall (lambda () thing was the only way I could get anything but
> nil out of the thread functions. I think I'm fooling myself, though: so
> far as I can tell, `get-stuff-from-source' is fully evaluated before the
> thread is made, and nothing at all happens during the #'thread-join
> loop.

Just drop the funcall: (make-thread (lambda () ...)) should do what
you want, assuming you have lexical-binding set (if not, you can
construct a lambda-list with backquote or similar).