2026-05-29 clojure | Clojure Slack Archive

clojure

roklenarcic 2026-05-29T07:49:59.890169Z

I am trying to do this:

private static final VarHandle BYTE_ARRAY_LONG_VIEW =
    MethodHandles.byteArrayViewVarHandle(long[].class, ByteOrder.BIG_ENDIAN);

static long longFromBytes(byte[] digest, int offset) {
    return (long) BYTE_ARRAY_LONG_VIEW.get(digest, offset);
}

The issue is the polymorphic nature of .get so I am trying to use param tags but it doesn’t seem to work?

p-himik 2026-05-29T08:05:09.582409Z

Could you please be more clear? By "trying to do this", do you mean you're trying to replicate the same code but in Clojure? What's VarHandle - java.lang.invoke.VarHandle or something else? If it is, what do you mean by "polymorphic nature"? There's only one .get method.

roklenarcic 2026-05-29T08:06:19.388999Z

yeah same code but in clojure?

p-himik 2026-05-29T08:06:31.037879Z

Given MethodHandles.byteArrayViewVarHandle, the package is probably java.lang.invoke, right. And I assume you do want to call .get from Clojure. The problem is that .get is a varargs method. You gotta construct an object array.

roklenarcic 2026-05-29T08:06:45.341339Z

no I tried that

roklenarcic 2026-05-29T08:06:53.797859Z

(println (long (^[Object/1] VarHandle/.get vh (object-array [ba (int 0)])))) Execution error (WrongMethodTypeException) at java.lang.invoke.MethodHandle/asTypeUncached (MethodHandle.java:915). cannot convert MethodHandle(VarHandle,byte[],int)long to (VarHandle,Object[])Object

roklenarcic 2026-05-29T08:07:04.480129Z

(println (long (^[Object/1] VarHandle/.get vh (object-array [ba (int 0)]))))
Execution error (WrongMethodTypeException) at java.lang.invoke.MethodHandle/asTypeUncached (MethodHandle.java:915).
cannot convert MethodHandle(VarHandle,byte[],int)long to (VarHandle,Object[])Object

roklenarcic 2026-05-29T08:07:40.961079Z

it’s kinda weird, the get method expects object array, but when you try to use it, it expects something else

roklenarcic 2026-05-29T08:07:58.887279Z

here’s a full example

roklenarcic 2026-05-29T08:08:01.572929Z

(import (java.lang.invoke MethodHandles VarHandle) (java.nio ByteOrder))
=> java.nio.ByteOrder
(def vh (MethodHandles/byteArrayViewVarHandle (class (long-array 0)) ByteOrder/BIG_ENDIAN))

=> #'memento.filecache.bloom/vh
(def ba (byte-array [1 2 3 4 5 6 7 8]))
=> #'memento.filecache.bloom/ba
(println (long (^[byte/1 int] VarHandle/.get vh ba (int 0))))
Syntax error (IllegalArgumentException) compiling VarHandle/.get at (/private/var/folders/fm/5mzhclpd7mj0tzjjq796ftc00000gn/T/form-init3541479456779296948.clj:1:16).
Error - param-tags [byte/1 int] insufficient to resolve method get in class java.lang.invoke.VarHandle
(println (long (^[Object/1] VarHandle/.get vh (object-array [ba (int 0)]))))
Execution error (WrongMethodTypeException) at java.lang.invoke.MethodHandle/asTypeUncached (MethodHandle.java:915).
cannot convert MethodHandle(VarHandle,byte[],int)long to (VarHandle,Object[])Object

roklenarcic 2026-05-29T08:08:49.365759Z

kinda bizarre

leonoel 2026-05-29T08:09:35.885049Z

this method is signature polymorphic, you cannot call that from clojure

p-himik 2026-05-29T08:10:11.751939Z

Huh, alright, never even heard about those.

p-himik 2026-05-29T08:16:33.697219Z

From https://clojure.atlassian.net/browse/CLJ-2921: > A workaround from Clojure is to instead call invokeWithArguments and package the arguments into a list. This call is inexact and probably slower (as it does more work and requires more arg packaging) than invokeExact would be.

roklenarcic 2026-05-29T08:17:05.557939Z

yeah that kinda ruins the whole point

Alex Miller (Clojure team) 2026-05-29T13:20:32.989639Z

Yeah, this is a frustrating gap right now, I have a ticket for this. We should be able to detect these methods and do the right thing in the compiler

roklenarcic 2026-05-29T13:23:26.690749Z

Yeah this also relates to boxing and other topics, a lot of these paths make sense performance wise if you can pass these primitives, as soon as you need to wrap things in object array etc they become inappropriate for hot paths

Alex Miller (Clojure team) 2026-05-29T13:23:58.568179Z

Yep, I understand

phronmophobic 2026-05-29T16:02:53.146409Z

you may be interested in #C02EEAUHSJJ.

Clojurians Log v2

clojure