Clojurians Log v2

👋

Maidin mhaith

I see that freenode is imploding. It had been a while since I was in #clojure on there (it was pretty quiet when I was last in). But looks like at least some people have moved over to libera now.

(Annoying that Slack won't let you type #foo without it linking to #foo, if that exists as a channel)

a netsplit

The downside to text-based communication - I can't tell if you're aware of what's going on, and that's a joke, or if you're unaware and are referring to a literal netsplit

morning

freenode imploding? to me it seemed like a successful hostile takeover

Sure, followed by lots of staff and at least some users leaving.

It seemed like a lot of staff. No idea how many staff freenode has altogether these days.

I see what you mean

morning

Good Morning™

Morn'

morning

Hey, are there any tutorials or anything that really walk someone through core.async or promises in clojurescript? I'm really trying to understand what's going on here and it just ends up being a confusing mess. It's really quite frustrating because I can write async code in python et al really easily, but doing so in clojurescript just doesn't seem to click at all. I invariably get a channel or a promise and I can't get the value out of it... Actually is there some way to drive it in the REPL better? Part of my frustration is that it's very hard to tell if things are working at the REPL. I just get back a ManyToManyChannel, so I feel like I have very little visibility into how it's working.

what constructs would you use in python @folcon? not promises ?

primarily multiprocessing

if i need to inspect something in the cljs repl i do something like (defn pval [p] (let [a (atom ::undefined)] (p/then p #(reset! a %)) a))

I think my primary issue is not being clear what I'm working against and the different constructs that I've seen give me inconsistent results. For example, Using promises, I'm currently reading in a zip file and walking through the entries. I console.log the entry name and contents and they don't match. The entry name changes, but the contents seem to be permanently pointing to the first entry. Not really sure what's going on there. I'd prefer to use core.async, but I'm not sure how to work with it in a repl in clojurescript. As I mentioned previously I constantly get ManyToManyChannel being the evaluation result, so how do you evaluate functions and get the output to test your assumptions?

(since there's no deref available for js promises)

Hmm

Then bind a to some def and poke it?

yep... same idea works for core.async too

although unless you are talking promise-chans then chans are going to behave differently

if you are wanting to test the async outputs in unit-tests then async is your friend - https://clojurescript.org/tools/testing#async-testing

I've not even gotten that far yet 😃

what sort of async ops are you doing ?

broadly this: https://github.com/transcend-io/conflux/issues/63

Got a bunch of xml files inside a zip I'm trying to read

so you are having to convert from a js promises/streams API into something cljs ?

Getting lost trying to work with this and then mixing in streams and file api's stuff not working and having to convert to blobs etc...

well that would be the ideal outcome

I'm trying to read the file in chunks if at all possible

I've gotten it working in the past where I get a massive string for the file contents, but that's really unhelpful when someone loads a giant file

it sounds entirely doable, but the mix of promises and streams in the js api probably presents some challenges mapping it over to cljs

we do loads of stuff like that on the backend, where we use manifold for both promises+streams, but i don't think we do anything like it in js

I'm pretty sure it's doable, just currently not clear how to attack it 😃...

my default line of attack would be to use promesa for promises, write something to convert between js streams and core.async chans, and write something which reduces a core.async chan to a promise - that would give you something which looks roughly like the manifold api

Not use the new <p!? https://github.com/clojure/core.async/blob/master/src/main/clojure/cljs/core/async/interop.clj

Thanks for the tip though 😃... I'll try it out!

oh, i hadn't seen <p! , that looks ok too

Are there any good resources around working with streams in clojurescript?

I'm writing a lot of ad-hoc code and it feels very inelegant 😃...

don't know - I've never worked with js streams directly... but if you convert pipe then to/from core.async chans then you can just work with the chans

Thanks anyway 😃

Finally figured it out, you're supposed to request a promise nested within the entry promise >_<...