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1 point by bogomipz 3159 days ago | link | parent

Just a couple of comments on the watch function:

1. Shouldn't the last line be (watch file-name delegate) so that it continues to watch after the first update? Or should that be optional?

2. It might be a good idea to pass file-name to the delegate. Not strictly necessary, and doesn't give any benefit in this example, but it could mean that you sometimes don't need to use a fn as the delegate. If you didn't want to pr "reloaded" for instance, you could just do (watch file-name load).

3. Is the hash table really necessary? Here is a version without it:

  (def watch (file-name delegate)
       (let ts mtime.file-name
         (while (is ts mtime.file-name)
                (sleep 2))
         (delegate)))


1 point by hasenj 3159 days ago | link

I put the call to watch as the last line inside the file itself.

And the hash table is there because I initially wanted to watch multiple files at the same time. But I suppose if the main file in the web app loads the other files, then it's not needed at all.

The other thing I did is running the (asv) thread only once by checking for an unbound symbol, so that when the file is reloaded it doesn't run the server again.

  (def srvr ()
    (if (no (bound 't*))
      (= t* (thread (asv)))))

  (srvr)

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1 point by bogomipz 3157 days ago | link

Ah, so loading the file makes it watch itself. You need to do the load in a thread then?

I still fail to see how the hash table helps since my version above should do exactly the same as yours. I would see the point if you made a thread check all files in the table, and made the first call to watch launch the thread, while subsequent calls just add entries to the table.

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3 points by hasenj 3157 days ago | link

Well actually, I'm putting the (asv) call in a thread and making it so that reloading the file doesn't restart the server:

  (mac set-once (s v)
       `(if (no:bound ',s)
          (= ,s ,v)))

  (set-once t* (thread:asv))
Watching for changes is not running in a thread, it's just the last line in my "web.arc"

And you're right, the hash-table is not needed at all. That was a premature design.

I actually re-wrote it a bit:

  ; watch the result of (func) for change
  ; and run 'on-change' when value changes
  (def watch-fn (func on-change)
       (let init (func)
           (while (is init (func))
              (sleep 2))
       (on-change)))
  
  ; watch the value-exp expression for changes
  ; and run on-change-exp when it changes
  (mac watch (value-exp on-change-exp)
       `(watch-fn (fn() ,value-exp) (fn() ,on-change-exp)))
  
  (def watch-file (file-name deleg)
       (watch (mtime file-name) (deleg file-name)))
  
  (def auto-reload (file-name)
       (prn "w/auto-reloading " file-name)
       (watch-file file-name load))
  
  (auto-reload "web.arc")

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