2025-12-10 beginners | Clojure Slack Archive

beginners 2025-12-10

2025-12-10T07:14:30.024169Z

Hey, how do I run a code with Clojure AOT? I'm trying to run the following code on http://atcoder.jp but get an error (see at the bottom):

(ns foo
  (:gen-class))

(import java.util.Scanner)

(defn -main [& args]
  (let [s (Scanner. System/in)
      n (.nextLong s)] ; 4
  (loop [a (.nextLong s) ;; 4
         res 1] ;; 2
    (if (<= res n) ;; true
      (if (= a 1) ; false
        (println res)
        (let [cnt (dec a)] ; 3
          (if (>= (+ res cnt) n)
            (println n)
            (do
              (dotimes [_ (dec cnt)] (.next s)) ; 1
              (recur (.nextLong s) ; 4
                     (+ res cnt)))))) ; 2
      (println res)))))

Here is the error:

; Could not locate foo__init.class, foo.clj or foo.cljc on classpath.
; Execution error (FileNotFoundException) at user/eval153$fn (form-init15451739026821950811.clj:1).
; Could not locate foo__init.class, foo.clj or foo.cljc on classpath.

Without ns I get another error:

Error: The Main-Class specified does not exist within the jar. It may not be executable as expected. A gen-class directive may be missing in the namespace which contains the main method, or the namespace has not been AOT-compiled.

2025-12-10T13:39:18.818979Z

Hi! So for the very basics of AOT you can use clojure https://clojuredocs.org/clojure.core/compile function. You can create a dir like this :

.
├── classes
└── src
    └── foo.clj

with your foo file, with a ns like :

(ns foo
  (:import [java.util Scanner])
  (:gen-class))

The start a repl and compile the file :

$ clj
Clojure 1.12.3
(compile 'foo)
foo

You will get your files there :

$ ls classes         
 clojure  'foo$fn__128.class'  'foo$loading__6814__auto____126.class'  'foo$_main.class'   foo.class   foo__init.class

Now to run your foo.class you need the clojure and spec jars, so you can run them like :

$ java -cp /home/USER/.m2/repository/org/clojure/clojure/1.12.3/clojure-1.12.3.jar:/home/USER/.m2/repository/org/clojure/spec.alpha/0.5.238/spec.alpha-0.5.238.jar:. foo

2025-12-10T13:40:15.132409Z

But that is not what people normally do, we build an uberjar (with AOT if needed), and then run with java -jar your-uber-jar.jar

2025-12-10T13:40:38.996379Z

Here is one way to do it using tools build https://clojure.org/guides/tools_build#_compiled_uberjar_application_build

2025-12-10T13:45:09.198969Z

The problem is that I’m trying to run the code on a competitive programming site http://AtCoder.jp that doesn’t allow to create any directories

2025-12-10T13:48:30.894919Z

Then the easiest if you have leiningen installed, just run lein new my-app for it to create a full structure or create a project.clj on your directory (where you have "src/foo.clj", with something like :

(defproject app "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url ""
  :license {:name "EPL-2.0 OR GPL-2.0-or-later WITH Classpath-exception-2.0"
            :url ""}
  :dependencies [[org.clojure/clojure "1.11.1"]]
  :main foo
  :repl-options {:init-ns foo})

Then run lein uberjar. That should create a *-standalone.jar file that you can submit and run with java -jar your-standalone.jar

2025-12-10T13:49:07.806869Z

that will AOT compile by default, which you probably don't need

2025-12-10T13:50:09.772299Z

With that you just submit one file and a command on how to run that file. Whatever they recommend for Java if they don't have Clojure instructions

2025-12-10T13:54:27.724489Z

To summarize one way: • Run lein new my-app • Modify the created "src/my_app/core.clj" with your code • add a :main my-app.core to your project.clj • run lein uberjar • run the jar with java -jar my-app-0.1.0-SNAPSHOT-standalone.jar

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beginners 2025-12-10