Am I missing something or is apply really this slow? What would be an efficient way to get the minimum from a collection?

(time
 (dotimes [_ 1000000]
   (apply max '(1 3 5 7 9 2 4 6 8))))

;; => "Elapsed time: 429.3991 msecs"

(time
 (dotimes [_ 1000000]
   (apply max [1 3 5 7 9 2 4 6 8])))

;; => "Elapsed time: 274.5674 msecs"

(time
 (dotimes [_ 1000000]
   (max 1 3 5 7 9 2 4 6 8)))

;; => "Elapsed time: 9.2664 msecs"

Thanks for all the help on my question to serialise stuff! I'll have a look at transit and nippy. Are there any preferences when the main criteria is easiness to extend to non-standard datatypes?

Hi! Following a tutorial, there’s this piece of code that should get me clojure.set as set in scope, but when I try to compile, I get an error.

(ns pegthing.core
  (require [clojure.set :as set])
  (:gen-class))

2. Unhandled clojure.lang.Compiler$CompilerException
   Error compiling src/pegthing/core.clj at (1:1)
   #:clojure.error{:phase :macro-syntax-check,....

1. Caused by clojure.lang.ExceptionInfo
   Call to clojure.core/ns did not conform to spec

Is there a way to modify the reader so that all literal maps are read as array-maps?

Also more of a meta question when should one ask here and when is it ok to ask #clojure ?

Is (load filename) the correct way to pull in other files with their own namespace? If so, is there some kind of init function that needs to be present? I tried swapping load-files out for loads while breaking a project into namespaces and it told me I'm missing a init class.

usually, you should use require to initiate loading

and not use load or load-file directly

Ah, cool. I didn't realize that would work for files that were hanging out in my project instead of being defined in the project.clj

well, you haven't shared enough other info to determine whether you are in or out of "usually" here

require will use the classpath to find the namespaces, so it depends on having your source files in the classpath, in a directory corresponding to the namespace

if that's not true, load-file is probably most straightforward. load is classpath focused, but has rules about how things are found based on its doc string

so just switching from one to the other probably requires changing the argument path

Ah, ok. The file structure is src/project-name/several-files-each-with-a-name-space so project.core loads and expects to be able to load project.server, for instance. This is just how the project ended up, I can move things to get require to work.

Hey everyone, Sorry to interrupt. I've been struggling with a Clojure deploy error for more than a week. Please take a look at: https://stackoverflow.com/questions/59938002/java-lang-noclassdeffounderror-for-clojure-java-api-clojure I would really appreaciate any advise. I do not know what to do anymore. Tks!

Almost certainly something related to the context classloader. Also, there were some changes in Clojure 1.10.1 vs 1.10.0 to mitigate a Java issue introduced in Java 1.8.0 u201 (give or take, don’t remember precisely). Any Clojure version diff between them?

Good call. I am using Clojure 1.9.0. I will try 1.10.1 instead.

@alexmiller Sorry... Let me correct myself. We've tried 1.10.0 and 1.10.1 already and got the same error. It was the first thing we did. No luck.

ok, good to check on that at least

your stack trace indicated that clojure failed static initialization, not that the class wasn't found

if the class wasn't present, you'd get a ClassNotFoundException

this exception indicates: Caused by: java.lang.NoClassDefFoundError: Could not initialize class clojure.java.api.Clojure

you are missing some trace elements in the output that might be useful

Yep. I've inspected the source code of clojure.java.api.Clojure but did not find anything unusual.

any chance you have a user.clj file somewhere?

on the classpath

I do not. Should I?

no, but that affects early initialization

just checking it wasn't on one but not the other

is ClojureHandler source somewhere?

I've inspected the source code at Github. I am using the official distribution.

can you point to it?

ClojureHandler isn't something in the clojure distribution

com.nitryx.brkmopt.util.ClojureHandler

oh.. sorry. Yes. This is my program.

Let me copy the line that throws the error for you. Just 1 min...

there is almost certainly an exception thrown during the static initializer of clojure.java.api.Clojure - whatever that is would probably point to the problem. the trick is getting to it.

more than the line would be helpful

presumably the line is loading the Clojure class :)

there it is:

public static Object invoke(String ns, String function, Object... parameters) {
        IFn func = Clojure.var(ns, function);
        Object ret;
        int n = parameters.length;
        switch (n) {
            case 0:
                ret = func.invoke();
                break;
            case 1:
                ret = func.invoke(parameters[0]);
                break;

the line that throws the Exception is:

IFn func = Clojure.var(ns, function);

my guess: you need to require that ns

well, load

(Sorry for the interruption) I have a global state that needs to be modified by multiple threads. More specifically, I have a map that will have a key/val pair added to it some amount of times (always a new key/val pair), but from a separate thread (or threads). What’s the most idiomatic way to implement this in Clojure? Should I be using transients, or some other type of thread-safe protection (e.g. atoms)?

although that does not explain it working on one server and not the other

well, first - what ns / function is it

@bfabry yes... thats the problem. The very same app. Just in case, I will print ns in the log just to be sure if we are not missing something.

This is the same .war. The same build. On different servers.

Different loading order for classes, causing the ns to be required (and loaded) on one server but not the other?

Looking again the code. ns cannot be the problem. It is hardcoded.

you could try loading the Clojure class earlier - maybe in the static initializer of ClojureHandler for example. like

static {
  Class.forName("clojure.java.api.Clojure");
}

@seancorfield ns is "com.nitryx.brkmopt.opt.scenario". I do not see how the order would make difference because it is something I created. But it was a good call.

@alexmiller trying your suggestion right now. I'll get back to you shortly. Thanks very much.

I notice that Tomcat 8.5.50 includes a Catalina that has a big slew of "Correct a regression in the static resource caching changes..."

perhaps Tomcat 8.5.49 is bad - have you tried bumping up? (or going back to 8.5.37)

https://tomcat.apache.org/tomcat-8.5-doc/changelog.html

Ohh... nice! I'll try it too.

@rodrigo759 could you share the whole stacktrace? Isn't there really anything interesting apart from what you shared in https://stackoverflow.com/questions/59938002/java-lang-noclassdeffounderror-for-clojure-java-api-clojure ?

something with resource caching/loading could certainly break Clojure, which loads clj files as resources

I'm putting my money on Tomcat as the likely culprit

@jumar I am editing the stackoverflow post to include the full stacktrace

@alexmiller my team is changing Tomcat as we speak.

I have a reaction gif ready for if a critical detail was being elided from the stacktrace

Full stacktrace is there.

@alexmiller YES! Downgrading Tomcat to 8.5.37 did the trick. Not easy because other apps are running in production using version 8.5.49. I had to convince the customer's IT guys that I need this version. So far, so good. Thank you all very much. @alexmiller, do you have a Stackoverflow account? If you do, you might want to publish the solution. I will accept and upvote it.

added

finally, something to boost my stackoverflow rep

I keep sending my stackoverflow points to my mortgage company but the exchange rate for fake internet points is terrible

I need to block in my main thread until another thread has a value that I need to continue—essentially just blocking until I get a message. How should this be done?

Or is it more likely I’m looking at this problem the wrong way, and there’s a better solution or something like that.

You could use a promise

https://clojuredocs.org/clojure.core/promise

Huh. Was looking through https://clojure.org/reference/…, didn’t think that that wouldn’t include core.async. Thank you.

Yeah, this seems to be what I want. 🙏

Noob question here. How to I get the value passed in because % doesn't seem to work here

(->  (GetResult url)
     (let [body (:body %)] (println body)) )))

% is a special syntax inside #()

just use a let for that:

(let [res (GetResult url)
      body (:body res)]
  (println body))

or (-> url (GetResult) (:body) (println))

okay think I get it now thanks

sometimes people use % with as->

that's true (as-> (GetResult url) % (:body %) (println %))

is (-> url (GetResult) (:body) (println)) the preferred way or (as-> (GetResult url) % (:body %) (println %))

the first one - though you might prefer to move url over into the GetResult call (it expands to the same thing)

most people would actually do (-> (GetResult url) :body println) - same result still

Thanks

Any opinions about http://purelyfunctional.tv? Sorry for posting the link, let me know if I have to remove it. I’m thinking about getting a membership to learn clojure but would like to hear opinion of somebody that’s used it