':use' is kind of old fashioned, ':require' is what is pretty much always used these days, and it has a super set of use's functionality

Also there's no :use in clojurescript

@madstap Sadly, there is :use in ClojureScript, but it must be combined with :only

In terms of ns forms, this is a good pattern to "just follow", IMHO: https://stuartsierra.com/2016/clojure-how-to-ns.html

Oh hey @mfikes thanks! That's actually a very nice breakdown. Haha, I adore the line "Summary: make it look like this." that's exactly what I was hounding for.

👋

Guys, how do i use a native function from ReactNative with Reagent? like fetch() for example

@sujofoceb You can just use js interop syntax. Here’s an example: https://github.com/JulianBirch/cljs-ajax/issues/155#issuecomment-237257235

Can someone point me to the docs on calling clojure from java? I’m assuming the two steps are: 1. add a gen class function that describes the functions you want to generate a class for… though im not sure of the specifics 2. Use the clojure.java.api.Clojure to call these java classes.

Does anybody ever had a problem when dealing with curly brackets in clojure regex? I'm trying to extract a word inside a curly bracket:

(re-matches #"\{\w+\}" "/user/{type}:{id}")

Your string doesn't match

https://clojuredocs.org/clojure.core/re-matches

re-matches only matches if the entire string given matches, and your regex fails to match the /user/ or the :{id}

re-find will get the first match, so return {type}

Is there a quick-start template based on tools.deps that includes nRepl support (so it can be used with CIDER?)

re-seq would return a list of {type} and {id}

Your escaping is correct though

Ah you're right @carr0t, should've read it in clojuredocs:

;; The distinction is that re-find tries to find _any part_ of the string
;; that matches the pattern, but re-matches only matches if the _entire_
;; string matches the pattern.

Thank you very much for pointing it out

I want to model some tree-like data with internal links using basic map/vector/set structures. For example, I might have articles and users and each article could have an author link back to the users vector, in such a way that there is no duplication of the user data. (This is just a modelling experiment, not something that will live in production). I guess the various “mutable” stuff like vars and atoms help here but I wonder if there is a proven way of doing this kind of in-memory modelling?

I’ve expanded my thoughts here: https://clojureverse.org/t/data-modelling-approaches/2118 — any feedback appreciated!

java interop question.. how can i reference / get a handle on the http constant in this class? https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/cloudfront/util/SignerUtils.Protocol.html#http

(say, pass it as an argument to another constructor)

you should be able to use (:import [com.amazonaws.services.cloudfront.util.SignerUtils Protocol]) and then use Protocol$http

so that's what i thought, but then...

(:import [com.amazonaws.services.cloudfront.util.SignerUtils Protocol])
CompilerException java.lang.RuntimeException: Unable to resolve symbol: Protocol in this context, compiling:(/private/var/folders/tx/nvfg34312m31g7gsbkjyxxqh0000gn/T/form-init7297532591394822523.clj:1:1)

and i've confirmed i'm on the latest version. hmmm.

ahh, try (:import [com.amazonaws.services.cloudfront.util SignerUtils SignerUtils$Protocol]) and then SignerUtils$Protocol/http

there is always a bit of guesswork involved to make stuff like this work (at least for me), it’s easier if you can use auto-complete in the REPL 😛

🙃

(:import [com.amazonaws.services.cloudfront.util SignerUtils SignerUtils$Protocol])
CompilerException java.lang.ClassNotFoundException: com.amazonaws.services.cloudfront.util, compiling:(/private/var/folders/tx/nvfg34312m31g7gsbkjyxxqh0000gn/T/form-init7297532591394822523.clj:1:1) 

autocomplete never gets farther than SignerUtils

user=> (import [com.amazonaws.services.cloudfront.util SignerUtils SignerUtils$Protocol])
com.amazonaws.services.cloudfront.util.SignerUtils$Protocol
user=> SignerUtils$Protocol/http
#object[com.amazonaws.services.cloudfront.util.SignerUtils$Protocol 0x238d27ef "http"]

ahh, I think the : at the beginning threw you for a loop

that is for the ns declaration, not the REPL 🙂

whoops, yeah - copied an example from the ns and not the repl

but yes, that one did the trick! thanks a lot.

out of curiosity, what stops me from importing all the way down to the Protocol class?

Protocol is an inner class of SignerUtils, but inner classes don’t exist at the class file level, they just get renamed to OuterClass$InnerClass and then there are a bunch of hacks in the Java compiler to make private variable access and stuff like that work

since Clojure operates on class files it must import it with actual name in the class file, which is SignerUtils$Protocol

incidentally, the inner class hacks will not be required once the concept of “nestmates” are introduced: http://openjdk.java.net/jeps/181

thanks for the excellent explanation

I can never remember the order of arguments to the f in reduce

https://clojuredocs.org/clojure.core/reduce

is val the first argument or the 2nd?

-2nd, the first is always the accumulator-

Ah, just saw the handy source link on the docs entry.

oh, sorry I’m mixing terms - here val is the initial accumulator, so 1st :)

I always begin a reduce with (reduce (fn [acc itm]

"the first is always the accumulator" <---- gotta remember that

I often use fn over #() for reducing functions too - I think it helps to name those

I rather like to have to function for reduce separately defined above. Sometimes taking an extra argument, using partial. Is that an anti-pattern?

@gklijs not at all!

Infact I often consider complex reduce bodies to be a anti-pattern,

(reduce group-by-products {} coll)

i’ve often wondered why clojure and other languages like javascript put the function first. if it were last, it would be easier to deal with complex function bodies because there wouldn’t be so much code before the initial value & collection

Btw, this is why arguments in clojure functions are ordered by "most likely to be partially applied"

oh well maybe that’s why 🙂

For example, in Datomic: (map (partial d/entity db) list-of-ids)

Hi, while doing some scouting around I found that Leiningen is top consensus choice to get a Clojure + Clojurescript learning environment going, is that still the case?

yeah, even if you eventually use boot it's easier to learn leiningen first

Is there a go-to guide that still reflects how the community feels is best to get "up and going"?

(setup-wise)

this is an open discussion still, but most would agree that you should use your favorite editor (whether it integrates with clojure or not, but it probably does if it's any good) and leiningen

I'm sure people will contradict me if I'm off base on that

I see, thanks!

depending what you want, the clj tool may be sufficient - see https://clojure.org/guides/getting_started

and https://clojure.org/guides/deps_and_cli

How foolish is it to explore Clojure without first familiarizing with Java and JVM?

totally fine

Clojure doesn’t hide its host so you will be starting the jvm and may see jvm stack traces, but otherwise, you can largely ignore it at the beginning. over time there are some parts of the JDK that are useful to know about and interop for leveraging Java libs, but you can push that off quite a while

I see, thanks!

there are some “jvm for clojurists” type posts out there too

I'm trying to transition from a Lisp onto Clojure

or actual courses like https://purelyfunctional.tv/courses/jvm-clojure/

I'd first want to do Clojure as long as possible before I have to deal with underlying Java

https://www.braveclojure.com/java/

I was just curious as to how much one could ignore Java (for awhile)

^^ that page is probably sufficient

probably more than sufficient actually

i’m finding it’s impossible to ignore java

there are kind of three parts to java 1. the jvm 2. the libraries that are part of the jre 3. popular 3rd party java libraries

and that is also the order of usefulness of the knowledge about those things

are there alternatives to using nrepl? i got it to work with my editor-setup, but it breaks on the newest version (using the nrepl-middleware)

yeah i haven’t gotten up to java interop yet, just dealing with interpreting stack traces and the current bane of my existence which is the NullPointerException

are you using CIDER by any chance?

i only mention that since it has some good ways to filter stacktraces and nav to code

no just atom and nrepl

i haven’t explored many tools yet, still coming to grips with the language

i managed to implement a* with little difficulty so i’m very excited about learning more!

don't change anything right now. just if you happened to be using it

Hi! Is there a better way to do this kind of destructuring?

(let [new-shape-size (:new-shape-size state)
        current-shape (:current-shape state)
        shape-angle (:shape-angle state)

(let [new-shape-size from state]

(let [{:keys [new-shape-size current-shape shape-angle]} state] ... )

How do people typically install and manage Java?

asdf?

it's normally part of the OS install

On macOS, I've been doing brew cask install java as of late

mmm I must've removed it some time ago -_-a

depends on what you mean though. In production I've never had to manage it, the server VMs came with it

ditto for OSX it comes with a recent enough version

I’ve been using jenv on osx to great effect lately

I mean manage like what nvm does for the Node / JS world

I was also looking into asdf, which apparently some people use to manage Java versions

osx comes with that

but very rarely do you need mroe than one jvm on a single box

I use Java 8 for work, Java 10 + Graal for personal project so I switch around a lot

ah, I'm on Ubuntu, and I must've somehow deleted my installation

apt is what you want then

and the Oracle website comes with an archive format that confuses me 😄

There is a ppa for Ubuntu.

Or you can just apt-get install default-jdk

Isn't asdf the common lisp package system?

is there a nice chart cheatsheet out there of map vs mapv vs run vs doseq, in particular the lazy vs nonlazy versions? i have some kind of mental block about remembering what’s lazy and what to do when i need a nonlazy version

it's` run!` btw, "do", "!" in the name, and returning a vector all mean "not lazy" if that helps

and the difference between run! and doall is whether the sequence i returned? anything else?

you are thinking dorun

i feel like i’ve read you give the same advice a million times and i feel bad for not absorbing it

the difference between dorun and doall is that doall returns the sequence

now that run! exists I rarely find a use for dorun, fwiw - maybe others have coding styles where it still comes up though

i see so when i moved from mapv to map-indexed this is why i got screwed up because vectors are nonlazy (?)

for your actual question, there's no cheatsheet that I know of, but if I made one it would have dorun, doall, doseq, dotimes, run! on one side, and for / map / mapcat on the other

right, vectors are never lazy

maybe i’ll make my own gist and solicit input from you 🙂

in fact we can fudge the specifics and say "only lazy seqs are lazy" (strictly speaking there's a few lazy types but they all act like lazy seqs, that is, linked lists, in being unindexed and having a first and rest)