Clojurians Log v2

are there any good guides on starting a simple clojurescript project that doesn’t need the browser (eg a library of functions). i know i can use node. but i cant seem figure out what my deps.edn should look like, what the command line is to open a repl and play with my code, and what the command line is to run my tests.

clj -M --main cljs.main --compile foo.core --repl works fine to open a repl connected to a browser and im able to run my code but when i try `clj -M --main cljs.main --repl-env node --compile foo.core --repl` the repl loads (without the browser) but i can’t run my code. `Execution error (ReferenceError) at (<cljs repl>:1). foo is not defined`

Hello, beginner question: how do I import SQLite from 'sqlite-react-native-storage' in cljs? I tried (require '[sqlite-react-native-storage :refer [SQLite]]) but it fails with TypeError: undefined is not an object (evaluating 'dondai.core.node$module$react_native_sqlite_storage.SQLite')

I see a space in “: refer”. There should be no space.

sorry. just a typo here on slack. The es5 way to require the library would be just require('react-native-sqlite-storage'), but for some reason doing that returns nil on my repl.

I mean, doing it the cljs way - I tried both (require '[react-native-sqlite-storage :as foo]) and (js/require "react-native-sqlite-storage"). I checked the library is working correctly by requiring it from krell_repl.js from the build output directory (`target/`)

in react-native things cannot be required dynamically as metro needs to fill them in

so you can only use it if one of your source file requires it already and you reload that app

Hi folks! Any good React intro for a would-be Reframe/Fulceo/etc. user, one that explains all the important things without wasting too much time on things irrelevant for us? The best I found after hours of digging is https://dzone.com/articles/fun-with-react-a-quick-overview and a few pages from React's own tutorial (linked to from https://fulcro-community.github.io/guides/tutorial-minimalist-fulcro/index.html#_prerequisites) 🙏

I see! that did the trick, thanks ^^

I initially tried requiring from a source file but failed - but after cleaning the target directory up and restarting it worked

does anyone happen to have a figwheel-main example app using the bundle target and react from npm? would love a simple hello world, or perhaps the flappy bird repo updated for bundle

There must be something about clojure reader conditionals that I’m not understanding, maybe regarding their use in macros. I have the following code in a macro; the java part of it, java.lang.Exception, is getting into my .js (compiled through shadow-cljs): (try ~@body #?(:clj (catch Exception e# {:error (.getMessage e#) :pstate ~pstate}) :cljs (catch js/Error e# {:error (str e#) :pstate ~pstate}))))

@peterd reader conditionals are resolved at read-time, you cannot use them to emit conditional code in macros. the typical check is (if (:ns &env) :cljs :clj)

Oh, I see. Thanks!

Or, maybe I don’t see. Where do I put this ‘if’ ?

(try ~@body
     ~(if (:ns &env)
        `(catch js/Error e# {:error (str e#) :pstate ~pstate})
        `(catch Exception e# {:error (.getMessage e#) :pstate ~pstate})
        ))

something like that

Thank you!

There is a library for helping with that, can't remember the name. Maybe @adam678 know?

That would be good to see.

macrovich

What reason might a file of macros not find something like printf? I get Use of undeclared Var cljs.core/printf

Ah, I see. And it uses a namespace “being.john” 😄

Understand reader conditionals is a bit tricky in that regard. Using them in a macro is only useful when you use self hosted CLJS. What Thomas suggests is using a little trick, knowing that when a macro expands code for CLJS, its &env value contains :ns.

Agreed. Tricky.

cljs doesn't have a printf

So yeah, Macrovitch is a lib that leverage that, and this one as well but a bit differently : https://github.com/helins/medium.cljc (it tries to distinguish even between CLJS for dev and CLJS for release)

the key shift in thinking is that macros are about WRITING code so you need conditional write, not conditional read

My mistake. Googling I found it defined in the clojure/clojurescript repository. But didn’t notice that I was looking at a view from 2013!

Yes, and the &env trick is about the time of the evaluation of the conditional to perform the write, I suppose.

@adam678 your library gets right to the point. Thanks!

What should I be looking at for space-efficient Clojurescript serialisation? I’m currently using edn, but it’s creating files which are rather too big for comfort. I’m aware of Transit, but the documentation suggests that it’s not ideal for data which needs to be stored durably (which I do need). Nippy doesn’t support Clojurescript. Is there anything else that I should be looking at?

What size are you talking about? And can you use a database?

The data is of the order of 10s to 100s of megabytes when serialised (much less when in RAM).

I could use a database, but right now the data is just files on an S3 bucket and I would rather keep it that way unless there’s a strong reason to introduce a database.

i'd say at the tune of 100s of megabytes you are firmly in database territory

at that point you really need random access to the data, or perhaps if you can partition it into multiple files and basically index it yourself

It should be fine to use transit as long as you use the very same library version and the same settings to both read and write the same file. As soon as the version changes or some config changes, all bets are off.

I see why you are thinking database, but these are "all or nothing" files (they're data logs from racecar telemetry, as it happens). The Clojurescript is mainly just passing them along to Vega for visualisation.

Thanks @p-himik. It's the "all bets are off" bit that's worrying me.

another option is to just use edn and use something like gzip on the result

@smith.adriane: that's where I suspect I may be headed. But I thought I'd check to see if there was a better option first 👍