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Carsten Behring10:02:59

I just started to use Clerk, even without thinking a lot about the "output" in the browser. It is very useful to just press "Ctrl-c c" (clerk/show! ) after any code change anywhere in my clojure file, and just knowing that clerk will do the right thing and evaluate exactly what needs to be evaluated. (and do it immediately, because all is cached in-memory) I do not need to think myself "which forms" to evaluate after a code change. I would even call this a new paradigm to work with Clojure apart from "repl first" and "clj-file first" 🙂

Carsten Behring10:02:28

This is super useful in any situation where evaluation of forms takes more then a second, so a blind "eval buffer" would be too slow. With Clerk we get a kind of "eval buffer", but it will only eval what is strictly needed , so what has changed and the dependencies of the changed forms. It avoids the need to actively decide which forms to evaluate after a change.

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Carsten Behring11:02:38

As forms in Clerk notebooks can be out of order, this can result in "notebooks" which are not "valid" clojure files, "valid" in the sense of failing to be running via

clj notebook.clj

Carsten Behring11:02:07

I would not call this being an "issue", but just a consequence of the way Clerk works.

Daniel Slutsky11:02:30

Could you give an example?

Carsten Behring11:02:49

I can have a valid notebook, where defs are out of order:

(def a (+ b 1)
(def b 2)

Carsten Behring11:02:40

Clerk evaluates and renders it, as it detect the order of dependencies. Running the same as clj xx.clj will fail.

Carsten Behring11:02:14

That's why clerk does not support redefining of defs... But we can detect this and fail on it.

Carsten Behring11:02:14

So that why Clerk is really a "different way" to render a "file full of Clojure forms"

Carsten Behring11:02:40

But ok, the forms above you can as well render in Cider doing the correct order by hand. So Clerk just automates this....

Carsten Behring11:02:26

Otherwise said: "valid" Clerk notebooks are not guaranteed to work via (require ...) So they are not guaranteed to be valid namespace definitions. Which is perfectly fine for "top level" files which are never required.

Carsten Behring11:02:54

(this is different in notespace). An notespace file is always a valid namespace


actually, clerk won’t eval this either:

(ns fw)
(def a (+ b 1))
(def b 2)
giving you
validate.clj:   28
      229  clojure.lang.MultiFn/invoke
              validate.clj:  265
              validate.clj:  240
          384  clojure.lang.Var/invoke
                passes.clj:  166
                passes.clj:  168
                passes.clj:  168
                passes.clj:  168
                  core.clj: 2635  clojure.core/partial/fn


it will work once you’ve evaluated the (def b 2)


this should be true for Clerk and regular Clojure

Carsten Behring20:03:23

But it would work after JVM restart, which in normal Clojure does not. (via clj file.clj) But I agree that a 2 times (`cider-eval-buffer`) can make it work as well. So not a big deal. But I would somehow like to be sure that my Clerk notebooks can be run via clj from the command line.


@carsten.behring that still requires Clerk to be on the Java classpath, right? Otherwise no extra setup?


I've used an alias to add clerk as an optional dependency and then I launch my REPL using that alias for when I want to have clerk available at dev time without introducing a strict dependency on it.

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Carsten Behring11:02:05

Yes, but no extra setup needed. The clerk/show! does both, evaluates the needed forms and send updates to browser. Having it bound to a key is help full, if not the "files watcher" works as well (= evaluation on save)

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