Clojurians Log v2

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.

yeah same code but in clojure?

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.

no I tried that

(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

(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

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

here’s a full example

(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

kinda bizarre

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

Huh, alright, never even heard about those.

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.

yeah that kinda ruins the whole point

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

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

Yep, I understand

you may be interested in #C02EEAUHSJJ.