Clojurians Log v2

@sova if you have the data ready in a vector, and it’s a lot of data, subvec might be worth it since will be constant time (i.e. faster than take/drop, etc)

But for most UI cases, and if you have a few hunded items, etc; linear will most likely be good enough

@sova highly dependent on context, but you could also partition the sequence into indexable blocks of fifty each and keep that in memory

What's the general go-to approach of handling errors? I have recently been writing a lot of go so my head is stuck in the return value, error way of doing things. The two things I can think of are: • just return nil (loses error context) • throw exception (loses nice control flow, easy ability to aggregate errors before reporting them, etc)

Also a pattern used is [error-code-or-true/false related-value] exceptions are not very common

Not sure how idiomatic: You can return a map of (possibly) result, and (possibly) list-of-errors

(What gon says, but then a map instead of a tuple ^^)

I'm happy to hear exceptions aren't that common

I don't mind returning a vec of errcode/value, I just don't want to transplant my recent go experience onto Clojure if there's a more idiomatic way

@anders152 As a data point, aws-api is often cited as a great lib. Here’s how it handles errors:

Barring client side exceptions, every operation on every service will return a map. If the operation is successful, the map will be in the shape described by (-> client aws/ops op :response). If AWS indicates failure with an HTTP status code >= 400, the map will include a :cognitect.anomalies/category key, so you can check for the absence/presence of that key to determine success/failure.

AFAIK both exceptions and values representing errors are idiomatic, depends on context when to use one or the other

What would you guys recommend as a good Clojure backend framework that also has support for websockets?

I’ve found Immutant and Pedestal to work perfectly well for me. Different approaches, but both have served me well. http://immutant.org/documentation/2.1.9/apidoc/guide-web.html#h3380 & https://github.com/pedestal/pedestal/tree/master/samples/jetty-web-sockets

There’s also a slightly outdated blog post that might be helpful at https://heykieran.github.io/post/using-sse-and-websockets/

I have used Pedestal but it required quite a bit of setup. Ring with the Jetty9 adapter is far simpler for hobby projects. https://github.com/sunng87/ring-jetty9-adapter#websocket

Check this guide for more options: https://purelyfunctional.tv/mini-guide/clojure-web-servers/

Thanks for these suggestions. I had seen Luminus after a simple Google search. Is it a suitable alternative?

I have not used Luminus myself. But everyone suggests that as a good beginner framework. Definitely worth trying.

Beginner friendly would be exactly what I need 😅

Yup, Luminus is a good option; it uses immutant as the web server, so you’ll be fine. Good luck.

I'm trying to make a turn based game server in Clojure so there's certainly going to be a lot of "fun" problems to solve

Hello !

I'm a hobbyist , learning clojure ..

Clojure is my first functional programming language ..I know a bit of python

Welcome! If you like map and filter and reduce of Python’s stdlib, or the entirety of functools or itertools you will feel right at home here ;)!

and if you like python's list comprehensions, you are going to love clojure's for /`doseq` macros

(let [foo {:people [{:name "Bob" :id 1} {:name "Alice" :id 0} {:name "Eve" :id 2}]}
      current-name "Bob2"
      selected-id 1]
          
  
  )

i.e. like this

(let [db {:people [{:name "Bob" :id 1} {:name "Alice" :id 0} {:name "Eve" :id 2}]
          :current-name "Bob2"
          :selected-id 1}]
  (let [new-item (-> (filter #(= (:id %) (db :selected-id)) (:people db))
                      (first)
                      (assoc :name (db :current-name)))
        updated-people (-> (remove #(= (:id %) (db :selected-id)) (:people db))
                           (conj new-item))]
    (assoc db :people updated-people)
    ))

(let [foo {:people [{:name "Bob" :id 1} {:name "Alice" :id 0} {:name "Eve" :id 2}]}
      current-name "Bob2"
      selected-id 1]
  (->> (:people foo)
       (map (fn [m]
              (if (= (:id m) selected-id)
                (assoc m :name current-name)
                m)))
       (assoc foo :people)))

there are a lot of ways... how about this with specter:

(let [db {:people [{:name "Bob" :id 1} {:name "Alice" :id 0} {:name "Eve" :id 2}]
          :current-name "Bob2"
          :selected-id 1}]
  (setval [:people ALL #(= (:id %) (:selected-id db)) :name] (:current-name db) db))

oh nice! I've never used Spectre before. I'll look into it! That seems pretty slick

powerful, maybe a rather steep learning curve

but it's not too hard to get started with things like this

(let [update-if (fn [pred f] (fn [x] (if (pred x) (f x) x)))]
  (let [foo {:people [{:name "Bob" :id 1} {:name "Alice" :id 0} {:name "Eve" :id 2}]}
        current-name "Bob2"
        selected-id 1
        maybe-correct (update-if (comp #{selected-id} :id) #(assoc % :name current-name))]
    (update foo :people #(mapv maybe-correct %))))
{:people [{:name "Bob2", :id 1} {:name "Alice", :id 0} {:name "Eve", :id 2}]}

with a bit more tasteful naming it could be quite nice. maybe-correct named apply-edit might make it a bit more clear. update-if could use a better name but i put it in a separate let as it feels very library-ish

Thanks! Yeah that's nicer than what I had.

I would do something like this

Yeah, i should definitely learn specter

For updating deeply nested immutable data, Specter does it in a very concise and quite performant way

One important note though: I always try to de-nest my data as much as possible; more often than not, you can use more shallow data structures which makes your life way easier;

Specter can be super useful if you’re dealing with incoming data that you don’t have initial control over.

Say, you have some value, 10 levels deep in some JSON, and you need to just (inc some-value), while preserving the whole shape.

Specter is the best for that.