Clojurians Log v2

Hi all, I'm reading about the FFI and Java, and I wondering what the JEP 393 [1] will mean in the world of native integration regarding Clojure. Seems that the public state of the art is condensed in this article [2] from @chris441, but I'd like to know what you all think about it. [1]: https://openjdk.java.net/jeps/393 [2]: https://techascent.com/blog/next-gen-native.html

Let's discuss on this thread 😄

I've recently been trying dtype-next and it's pretty great.

I've used ffi to access a few c libraries from clojure and it's been interesting to see that the c apis are often more clojure-friendly then many of the java APIs. Corollary: using ffi to directly talk to a native library is almost always better than trying to use a Java library that wraps a native library.

There are a couple libraries I have my eye on: • libclang: I want to parse c headers and have it produce the c<->clojure api for other libraries • graphviz: shelling out to dot is ok, but directly talking to the c api could be better. • ffmpeg: there's already avclj, but more of ffmpeg's capabilities can still be wrapped more idiomatically.

Does anyone use datadog's javaagent in their clojure app? I gave it at try, but saw that the app took 5x time to start up.

We use it and have not experienced that. If it matters, we AOT compile prod artifacts.

what are the cases when Throwable->map would return multiple maps under the :via key?

i have only noticed a very slow start when instrumentation debugging is on

chained exceptions? if an exception has a cause set using initCause

that's all i can see from the source code of that function

yes, chained exceptions

also, initCause isn't the only way to chain them. Throwable constructor accepts the cause as well

Can I use the fancy new protocol :extend-via-metadata true functionality with Java interfaces somehow? Here’s a contrived example that doesn’t work. What’s the quickest way to make this work?

(def thing
  (with-meta {}
    {'clojure.lang.IDeref/deref
     (fn [this]
       "some value")}))

(deref thing)

@stephenmhopper No, only protocols. You probably want to look at reify for interfaces.

example

(let [x (reify clojure.lang.IDeref
          (deref [_] :foo))]
  @x)
:foo

Quick question about print-dup, is it intended to preserve metadata?

I'd imagine not

Although it looks like it does based on the implementation for persistent map

can you explain your question a bit more?

it is, but print-dup is super rarely used

print-dup is a multimethod for basic serialization, most of the time it constructs read-time evaluation forms. I'm just curious if it's in general intended to produce readable metadata forms as well as the actual data structure itself.

That's fair.

to some degree the use of print -dup is an anti-pattern because it is too specific

That's fair, but I'm not really one to judge what the usage of the library would be. I'm just writing a general ropes library since the existing one only works on byte arrays.

And since the core data structures support print-dup, so will I

user=> (doc *print-dup*)
-------------------------
clojure.core/*print-dup*
  When set to logical true, objects will be printed in a way that preserves
  their type when read in later.

  Defaults to false.
nil
user=> (alter-var-root #'*print-dup* (constantly true))
true
"user=> "{}
#=(clojure.lang.PersistentArrayMap/create {})
"user=> "

Yeah, it's intended mostly to be used with prn or pr-str to my understanding

in the compiler print-dup gets used for serializing arbitrary objects into byte code

so for example if a macro expansion contained one of your rope data structures (not the code to create one)

Ah, makes sense.