I also wondered this recently 🙂 https://github.com/clojure-goes-fast/clj-java-decompiler answered, e.g. Clojure is smart enough make fns once, in advance, rather than many, on-the-fly

@U45T93RA6 in which case tho, in a loop?

(do (println (fn [x] x)) (println (fn [x] x))) creates two different objects obviously

you must store function instance returned by fn somewhere, be it local binding or Var or even java reference type

here's the decompilation of

(defn sample []
  (do
    (println (fn [x] x))
    (println (fn [x] x))))

@U45T93RA6 how you decompiled sample function, i can't make it work for some reason

i mean how you called clj-java-decompiler exactly

@U45T93RA6 its still created two classes for each function, instantiated and called both of them, no optimization there

public static Object invokeStatic() {
        ((IFn)const__0.getRawRoot()).invoke(new endpoint$sample$fn__528376());
        return ((IFn)const__0.getRawRoot()).invoke(new endpoint$sample$fn__528378());
}

> its still created two classes for each function, yeah, I don't expect Clojure to try comparing different fns searching for equality > instantiated object creation and short-lived GC are extremely cheap AFAICT the classes are created once, statically, that was my point. Perhaps a naive compiler would create the classes in runtime

> i mean how you called clj-java-decompiler exactly plain usage, wrapped in (with-out-str), using 0.2.1

hmm

(defn my-identity [x] x)
=> #'playsync.core/my-identity
(with-out-str (decompile (my-identity 5)))
=>
"
 // Decompiling class: cjd__init
 import clojure.lang.*;
 
 public class cjd__init

it outputs cjd__init class

or

(with-out-str (decompile (fn [] (my-identity 5))))
=>
"
 // Decompiling class: playsync/core$fn__13171
 package playsync;
 
 import clojure.lang.*;
 
 public final class core$fn__13171 extends AFunction

but your version produced endpoint$sample class

where sample is a named function i guess

i'm missing something here

wrap the defn call with decompile

great ty

thanks @U45T93RA6. just saw this thread. that's what i thought!

anonymous functions do not equal true when compared (of course), however they're reused under the hood

@joshkh no, two different(unequal) functions will be used independently

or we don't understand each-other 😃

hmm. i'm trying out clj-java-decompiler but i get the following when i run decompile

Execution error (ClassNotFoundException) at jdk.internal.loader.BuiltinClassLoader/loadClass (BuiltinClassLoader.java:582).
sun.misc.URLClassPath

@joshkh try jdk8

okay i'll get around to installing jdk8 when i have some downtime 🙂 just reread the conversation between you and vemv and i understand now. separate objects but cheaply created and GC'ed? i'm happy to def functions when used often. i was just curious how it all worked underneath.

thanks for explaining

yeah separate classes for each, but one instance per function

(let [fx (fn [x] x)
      fy (fn [y] y)]
             (println (fx 5))
             (println (fx 5))
             (println (fy 10))
             (println (fy 10))
             (while nil
               (println (fy 10)))

public static Object invokeStatic() {
        final Object fx = new core$fn__14873$fx__14874();
        final Object fy = new core$fn__14873$fy__14876();
        ((IFn)const__0.getRawRoot()).invoke(((IFn)fx).invoke(const__1));
        ((IFn)const__0.getRawRoot()).invoke(((IFn)fx).invoke(const__1));
        ((IFn)const__0.getRawRoot()).invoke(((IFn)fy).invoke(const__2));
        ((IFn)const__0.getRawRoot()).invoke(((IFn)fy).invoke(const__2));
        while (true) {
            final Boolean true = Boolean.TRUE;
            if (true == null) {
                break;
            }
            if (true == Boolean.FALSE) {
                break;
            }
            ((IFn)const__0.getRawRoot()).invoke(((IFn)fy).invoke(const__2));
        }
        return null;
    }

as you can see only two objects are created one per function

stop the repl, clean cache dirs, drink a coffee and try again?

Good idea 🙂

Stopping the REPL and cleaning the cache solved the problem. Thanks for the reminder 🙂