is :once documented anywhere for fn*?

@dpsutton It's documented somewhere because I was just reading about it the other day. I just can't remember where.

Hmm, it's documented in Clojure, The Essential Reference and the section about fn* was contributed by @bronsa so maybe he knows where it officially documented?

It has a footnote linking to https://groups.google.com/g/clojure/c/FLrtjyYJdRU?pli=1 and says Rich discusses the locals clearing aspect of fn* there.

(I don't see fn* mentioned there, only the general concept of locals clearing)

there's a comment talking about issue 232 and that's the commit where it shows up but i can't follow the logic of the commit. https://clojure.atlassian.net/browse/CLJ-232

A blast from the past, that ticket is littered with former co-workers. The issue there is delays used to try and run again if derefed again and the first time threw an exception

And you would get npes because the once fn would clear any locals so they would be nil the second time the fn was run

Hmm, or not and I am misremembering

Because delay wraps the ^:once fn* thing...

(defmacro delay
...
  {:added "1.0"}
  [& body]
    (list 'new 'clojure.lang.Delay (list* `^{:once true} fn* [] body)))

Interesting bit of history in that ticket.

Testing against 1.10, it seems it all got fixed even tho' there's no indication of what the resolution was in that ticket?

I didn't realize delay used the :once fn* thing until just now.

Yeah, the patch looks like it does what it says on the commit message https://github.com/clojure/clojure/commit/93fecbd825c26e2570f8449cd64d0df0cc520c1d it disables the code that would cleared closed over locals at the end of a function of possible, and adds that functionality to the system for clearing regular locals, which already correctly handled try/finally which was the source of the bug

Ah, I missed that link (I'm not signed into JIRA on this machine).

Oh, that's what Rich links in the first comment?

I dunno, I searched GitHub for 232

(which I guess was the last comment before the importer messed up the timeline?)

Looks like it

thanks both of you 🙂

How do I re-throw an exception preserving the stacktrace while adding an informative message to the top?

(try (read-raw fname)
     (catch Exception e
       (throw (ex-info
                (str "error parsing file: \n  "
                  fname "\n  " (ex-message e))
                (into  {} (ex-data e))))))

you can use .getStackTrace` and .setStackTrace

@dpsutton @seancorfield @hiredman afaik, there is no official doc about ^:once (possibly intentionally to not encourage its use outside of core). generally most things should build upon the core stuff like lazy-seq instead

What’s an easy way to split a byte array in two with a given delimiter (ala (clojure.string/split s re 2))?

Simply take with n (your delimeter), and drop with n again.

(juxt (partial take n) (partial drop n))

Well, I’d need to find the delimiter first. Also, the byte array is huge and I need this to be performant.

That goes way past the initial requirement of it being easy. :)

What kind of performance do you need ?

I don’t want to make any unnecessary copies and I don’t want to iterate over the entire array

also, I want two byte arrays at the end

You should need to work on Clojure Data Types and why they are simply amazing for Functional Programming.

There is no unnecessary copy or something fool-ish.

The information, shared with absolute control between derived datas…

Don’t worry about that; I’m perfectly familiar with Clojure’s data types 🙂

Sometimes you still need to drop down to raw byte arrays

I think, if your requirements are beyond the performance Clojure gave, you should think about technologies like C++ or D or V.

Or just find a Java solution and use it as is or translate it to Clojure, either directly with interop or by using Clojure alternatives to what Java uses.

Yeah I’m gonna go with that. I was just hoping there’d be a more straightforward solution :)

I copied a project from one machine to another, and I'm having this weird problem fetching javase when using leinengen. Deleting ~/.m2 didn't fix it and I'm a bit stumped after googling for a solution. Any clues? Using Java 11 and clojure 1.10.1 for now.

Could not find artifact com.github.kenglxn.qrgen:javase:jar:2.6.0 in central ()
Could not find artifact com.github.kenglxn.qrgen:javase:jar:2.6.0 in clojars ()
Could not find artifact com.github.kenglxn.qrgen:javase:jar:2.6.0 in sonatype-oss-public ()
Could not transfer artifact com.github.kenglxn.qrgen:javase:jar:2.6.0 from/to jitpack (): NullPointerException
Could not find artifact com.github.kenglxn.qrgen:javase:jar:2.6.0 in sonatype ()
Could not find artifact com.github.kenglxn.qrgen:javase:jar:2.6.0 in sonatype-snapshots ()
Failed to read artifact descriptor for com.github.kenglxn.qrgen:javase:jar:2.6.0
This could be due to a typo in :dependencies, file system permissions, or network issues.
If you are behind a proxy, try setting the 'http_proxy' environment variable.

A lein repl in a non-project directory works fine.

Debian Clojure Packaging Bof is happening right now https://debconf20.debconf.org/schedule/venue/1/ https://pad.online.debconf.org/p/33-clojure-packaging-team-bof

one of the big issues related to packaging is that clojure is not reproducible https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/clojure.html Some context: https://reproducible-builds.org/

I remember a talk about debugging by defing vars inline and iterating at the REPL, but I can't find it by Googling. There may have been a library and/or editor integration to assist in creating the vars. Anyone recall the name?

@robert.mather.rmm ScopeCapture I think? I just have a hotkey bound to eval (def <selection>) so that I can highlight a binding in a let and turn it into a global for debugging.

https://github.com/vvvvalvalval/scope-capture

@seancorfield That's the one, thanks!

I prefer not to need to add any code while I'm working, and I use REBL, so I can create a def from any value sent to the REBL and between that and my hotkey to turn let bindings into def that's pretty much all I ever need.

Cool. I haven't played with REBL yet, I mostly just abuse the EOF comment block

Heh, my Rich Comment Forms are all over my code! Since I work with Atom/Chlorine, the REPL panel there is readonly so you're never tempted to type into it -- so you use RCFs instead.

I've written a test.check test, but I don't want to use it with clojure.test, but instead separately with it's own params. Is there a pre-written script or main I can use?

(I want to avoid clojure.test, because I don't want to run it with the tests all the time, as it may fail unreliably)

I thought clojure itself had a script for this, but I cannot find it.

Ah, clojure.test.generative.runner :) It would seem that test.generative is not the same as test.check. But this must be the split itself in clj.

I am using Datomic Cloud and am trying to compile my code before deployment -- to catch any errors without incurring AWS costs. I am using @seancorfield’s excellent depstar but I don't have a -main since I am deploying Ions. Can anyone advise me how to do the compilation? thanks!

I think the way to do that is to still use clojure.test, but have a separate test suite, in another source directory

@hiredman With a -main?

@hiredman Yes, that works! Thanks!

I was talking to @dominicm, but cool

@hiredman that's what I initially reached for, but wanting to run the generative tests by themselves when otherwise running all the tests (e.g. Cider-run-tests) brings it back to a problem.

does it? surely you have someway to take two commands and turn them in to one command?

like run-test.sh && run-generative-tests.sh

@dominicm What about test selectors?

Both lein test and Cognitect's test-runner have ways to select tests based on metadata...

I talk about that for the clojure.test-compatible version of Expectations: https://cljdoc.org/d/expectations/clojure-test/1.2.1/doc/fixtures-focused-execution#focused-test-execution

(it's about the core clojure.test / test runner approach, nothing specific to Expectations)