Clojurians Log v2

which is surprising to me, given that it was originally written in 2006 (https://github.com/clojure/clojure/commit/1a399df8f3f3bcb9d3a92a584fa9714832ab550f) and fleshed out well before first class sets were added

Alex Miller is typing, gotta hurry to post something stupid. I'd say it is probably because you rarely need pure algorithmic queues. Most time you reach for queues you need them for synchronization, and PersistentQueue doesn't offer that.

the queue stuff is really most useful in single-threaded contexts and those just don't come up that frequently. if you're using them statefully they need to be wrapped into an atom or whatever and at that point you're probably better off just using one of the jdk concurrent queues

that said, I do have on my list of things that I think it would be useful to add queue constructor (so you don't have to reach into PQ) and queue? predicate

Damn, feeling like a boss. @puredanger sniping - success.

the one time I usually use it is in doing like a walk over a tree and maintaining loop state (children etc)

(`queue` and queue? ask: https://ask.clojure.org/index.php/3821/add-queue-and-queue-to-clojure-core)

I've created a PQ memory leak ticket in the past, so I must have used it for something. https://clojure.atlassian.net/browse/CLJ-2397

I do not think #queue is worth doing

Because of a general distaste for data readers?

it's just not common enough to be worth doing imo

should you even be edn serializing a queue?

🤷

data readers are great, I just think they should be used sparingly :)

(def queue PersistentQueue/EMPTY) should probably be enough, but it would squat a tasty name.

reader literal and print support for queues Ask: https://ask.clojure.org/index.php/3365/implement-reader-literal-support-persistentqueue-structure

i think there was another queue related jira that i'm forgetting now... something about how the code path for printing queues never reaches its #= print-method because it implements persistent list or something

lol :)

ah here we go, paula's find: https://ask.clojure.org/index.php/10575/why-does-evaluating-a-queue-not-return-itself

my feeling is that queues would be used more if they were better supported by clojure core, with or without a data reader

before clojure, i almost never used sets because why bother? now i can't imagine life without 'em lol

yeah that seems like a bug that should be fixed

I use Java's queues more than Clojure's

even tho they're not persistent? interesting

usually you are using a queue to communicate across threads and then you need concurrency and Java has lots of great options

Transducing contexts are pretty amenable to mutability that doesn’t escape a small visible area

When you need "Clojure queues", you usually pick core.async channels

yeah, or those, depends on context

why doesn't PQ offer synchronization?

it's immutable ?

oh duh lol

gotta actually remember what words mean before asking questions

if you put it in an atom then you're often both peeking it and conj or popping it, it's just not great for this. with Java's concurrent queues you have all the options - block, try, etc

the deques let you do it either end

Doug Lea probably spent a year optimizing it :)

that's interesting, thanks

single threaded queues are good for tracking arbitrary depth stuff in tree-like form in an algorithm. mostly we deal with regular collections of known-shaped things not arbitrary things to deal with generically, so walking trees of code (but we usually take a local view ala walk or zip), or trees of data (quickly you want a graph api like Loom or a datalog database).

the one prominent place I can remember using a PQ is in the tools.deps dep expansion loop which has a queue of nodes to visit, doing a breadth-first walk

we use it in one spot identifying the shortest join between two tables: (loop [paths (conj clojure.lang.PersistentQueue/EMPTY [start])

It seems like it's used in a number of different libraries, https://cloogle.phronemophobic.com/name-search.html?q=clojure.lang.PersistentQueue&tables=java-class-usages.

I’ve used it for breadth first walking algos before. It’s the canonical data structure for it!

(woah, cloogle is cool!)

grep.app reports 187 https://grep.app/search?f.lang=Clojure&q=PersistentQueue%2FEMPTY of PQ/EMPTY across github, which is pretty small

github itself has 2.6k of persistentqueue itself: https://github.com/search?q=PersistentQueue+language%3Aclojure&type=code

tbh, I trust http://grep.app more than GH's search :)

oh, I searched for EMPTY above so yours is wider, seems to catch some partial class names etc

yeah, we searched different stuff

I count 648 class usages of clojure.lang.PersistentQueue in dewey across 257 repos.

i wonder how many folks have defined #queue lol

or queue? that checks (instance? ...)

At work, in ~150k lines of Clojure, we have two PQ/EMPTY (in atoms!) in src and one PQ/EMPTY in a test.

Oh, one of those src uses is in debug-only code. So, one real usage 🙂

I believe cljs has #queue right?

yes

seems like most uses are people doing #queue [] , would much rather have (queue) for that

what they want is #[] 😈

well I definitely don't think queue is important enough to have syntax like that :)

hah yeah, that won't ever happen

does cljs have the queue fish stuff?

something used to print queues as <-(1 2 3)-< have no idea how to search for that

yes: https://github.com/clojure/clojurescript/blob/9b4225ecaa7b6ceecd025ea3519eeb7884e81cfa/src/main/cljs/cljs/pprint.cljs#L2891

wacky

❯ clj
Clojure 1.12.0
user=> (into clojure.lang.PersistentQueue/EMPTY [1 2 3])
#object[clojure.lang.PersistentQueue 0x5e840abf "clojure.lang.PersistentQueue@7861"]
user=> (pp)
<-(1 2 3)-<
nil

maybe I'm the only one that calls that a queue fish :)

oh, it's in Joy of Clojure whew

rust has turbofish right? i think fish is common enough suffix?

> The ::<Vec<i32>> part is the turbofish and means

LLM pretty decisively disagrees with me that it’s a common enough suffix haha.

it instantly made sense to me

it's a fun way to print it if there's no tag for it

same here. which is why i assumed it was part of a bigger tradition since i knew of the rust turbofish

I blame chouser and fogus :)