Clojurians Log v2

What is the Clojure equivalent of Python’s Iterable? For example say I wanted to implement “paging” in a REST API client. So that the next result set is loaded once you are at the end of a page?

clojure.core/lazy-seq or clojure.core/iterate are decent options for implementing such a thing. ghadi also wrote a patch to add a function called iteration that might make it into clojure.core some day

https://clojure.atlassian.net/browse/CLJ-2555

Thank you

Lazy seqs are sort of the classic approach people have used for that kind of thing since the initial release of clojure, but lazy seqs have inherent problems managing things like connection state

https://ce2144dc-f7c9-4f54-8fb6-7321a4c318db.s3.amazonaws.com/reducers.html is a at this point dated screed about using reduce based things instead, specifically there reducers, but there are core protocols and interfaces for defining reducible things

https://gist.github.com/hiredman/4d8bf007ba7897f11594 unfold or something like it is what I like for this kind of thing, and it is a similar kind of thing that what those patches might add to core some day

Wait, @hiredman. I didn’t know we were only one degree apart! I worked w/ Joe Gallo at Elastic for a minute.

A lot of the "past and present co-workers" from the time that was written ended up at elastic after sonian

that’s what I hear 🙂

@st3fan java.lang.Iterable and java.lang.Iterator, basically. lazy-seqs and whatnot are a convenient way to implement those interfaces, but have drawbacks around chunking and resources that might end up "closed" when you leave the context the lazy-seq was created in. You can always reify an Iterator directly with whatever internal state you need if those drawbacks apply to you. Something that isn't equivalent, but can accomplish the same goal would be reducible things. Defining and using a reducible would probably lead to more idiomatic code, depending on what you are doing. https://juxt.pro/blog/ontheflycollections-with-reducible

Hi how do we remove table name from jdbc responses? I am using postgres.

accounts/email: "email",
accounts/created_on: "2020-09-20T09:33:23Z",
accounts/last_login: "2020-09-20T09:33:23Z"

email: "email",
created_on: "2020-09-20T09:33:23Z",
last_login: "2020-09-20T09:33:23Z"

what library are you using? next.jdbc?

Hi there !! I have recently written a clojure app using lein + compojure + clj-http and created an uberjar. Now wondering if i can enable the nrepl on the built jar file? Something like - having an api endpoint to start/stop nrepl inside the uberjar. That will help me debug issue in the built jar file when it interacts with test data. P.S.: I am doing this in my UAT environment debugging and Production will be getting rid of this (security concerns).

Yes, by adding code to your app that starts an nrepl server when you hit your api endpoint and then connecting to that nrepl server with your local client. https://nrepl.org/nrepl/usage/server.html#embedding-nrepl

thanks @rutledgepaulv i am trying that only currently.

it is stuck in compiling while running lein uberjar

Is it possible to use something like with-redefs except swapping out entire namespace definitions?

following is how code looks like - one route added to call the start-nrepl method

Hi! Is there something like add-watch on the namespace level, so that I can subscribe to when vars on a namespace are added / changed, etc?

cljsrn seems abandoned

anyone can point me to a more updated resource on making ios apps with clojure?

Follow-up: Can I watch for redefinitions with (def ...)? add-watch seems to pick up only redefinitions with alter-var-root. I assume that's because def creates a new var instead of changing the previous var.

@danieltanfh95 perhaps Krell: https://github.com/vouch-opensource/krell

found the silly mistake in my code (calling (start-server server) and (defonce server) also contained the same command 😞 . Fixed it now and able to do it.

@teodorlu it works! 🎉

spend way too much time finding one that works

thanks!

1. I do lein new test-project, create a file src/user.clj with content

(ns user
  (:require [clojure.java.shell :refer [sh]]))

(sh "ls")

3. If the :init-ns is set to user2 and the file above is changed to be user2 ns, it doesn't hang anymore.

I tried reproducing the hanging behavior following the steps you gave above, but do not get any hanging behavior. Nor does it load that namespace named user, either, when I do lein repl. I am using this version of Leiningen and JDK, in case that might make any difference:

$ lein version
Leiningen 2.9.3 on Java 1.8.0_192 Java HotSpot(TM) 64-Bit Server VM

Actually, I guess it does load that namespace named user, but it is not obvious because (sh "ls") does not print anything. If I change it to (println (sh "ls")), then run lein repl, it does print the return value before starting the REPL.

Updating clojure from 1.10.0 to 1.10.1 fixed this!

Hmm. I was testing with Clojure 1.10.1. There were some changes in Clojure 1.10.1 to fix some bad performance issues with loading user.clj with some JDK versions: https://github.com/clojure/clojure/blob/master/changes.md#11-workaround-java-performance-regression-when-loading-userclj

I am using OpenJDK 14, which is not mentioned there. I also had a problem before with cognitect's aws library where it would hang if loaded from the namespace, but worked ok if loaded from a function after startup, I guess that's the same problem.

Hey folks, is it possible to generatively define functions in a given namespace? For example, I have a function (defn createNode [type props] ...dostuff...) and for a known set of types, I would like to create aliases in my namespace. That is, I might write (createNode "myNode" {:hi "bye"}), but I would like to alias (myproj/myNode {:hi "bye"}) to invoke the previous form. I have a list of these types... "myNode, myOtherNode, coolNode," etc

Sketching out what I'm imagining...

(doseq [i ["myNode" "myOtherNode" "coolNode"]]
  (make-alias i (fn [props] (createNode i props))))

I imagine a macro could do this?

If a change from Clojure 1.10.0 to 1.10.1 makes a difference, and it is is code in a file named user.clj in your classpath, then likely it is the performance issue I linked to. JDK 14 wasn't explicitly mentioned there at the text I linked to, probably because it wasn't released yet at the time the note was written. I would expect that if the issue exists in JDK 11, 12, and 13, it is likely to be common JDK code that interacts poorly with Clojure 1.10.0 that continues on into JDK 14 and probably later versions, too.

Yeah, makes sense.

Thank you!

I think you are looking for intern: https://clojuredocs.org/clojure.core/intern

It should be (intern 'myproj (symbol i) (fn [props] ...)).

Found thanks to hugsql, it generates functions from an sql-like file, and fills a namespace with them. https://github.com/layerware/hugsql/blob/master/hugsql-core/src/hugsql/core.clj#L500

yesss thanks @posobin!

@posobin you should try babashka maybe.

This interop with sh is not my primary goal, one of the libraries I am using was preventing the repl from starting and I tried to find the reason why.

Hello everyone, started learning clojure a few weeks ago, can I pick someone's mind on a project I'm working on?

yup its next.jdbc