Add logging functions for debugging

[nbeloglazov]

Debugging Quil sketches is quite hard. Often you need to see state of the sketch but adding println to sketch causes never ending stream of text in console. Quil should provide some functionally to aid debugging. For example we could add print-first-n function that when called prints provided arg only the first n iterations. Similarly we could add print-every-n-sec to see samples during sketch run.

[anthonygalea]

Is this what you have in mind?

(def p (volatile! nil))

(defn print-first-n
  [n & more]
  (locking p
    (when (nil? @p)
      (vreset! p n))
    (when (pos? @p)
      (vswap! p dec)
      (apply print more))))

You can see it in use in this sketch: http://quil.info/sketches/show/7f7cc14db3a5ba44cb528cb7f3fd69763cabf8e53183f13bb8ba9e5a8ac35469

[nbeloglazov]

Yes, something like that. Though we can use frame-count instead of mutable object to keep things simpler. Otherwise you'd need to store the p on sketch itself as it can't be global?

[anthonygalea]

Ah yes, using frame-count is a lot better:

(defn print-first-n
  [n & more]
  (when (<= (q/frame-count) n)
    (apply print more)))

Regarding printing every n seconds, do you see an alternative to the following approach which requires storing the last-time?

(def last-time (atom 0))

(defn print-every-n-millisec
  [n & more]
  (let [elapsed (q/millis)]
    (when (< n (- elapsed last-time))
      (reset! last-time elapsed)
      (apply print more))))

[nbeloglazov]

Trying to think if we can avoid atom, but can't think of any approach. So probably yeah - that would be the way to do it. The only thing I mentioned before, it would be good if last-time is tied to sketch instead of being global variable shared between all sketches.

[nbeloglazov]

We have internal-state function for similar purposes (though doc string lies, this state should not be visible to users).