I do have to say... the people helping out in here for us Clojure newbs are refreshing. Not a judgmental comment anywhere that I've seen, and everyone has been so patient and willing to walk beginners through questions. It is a stark contrast from what I've been used to where asking a question could get your head ripped off... (for example.. the Arch community is notorious for this... at least from what I've seen..).... anyway... kudos to the more experienced Clojure devs in here!! 🙂

I got banned from arch irc channel before even saying anything :rolling_on_the_floor_laughing:

haha.. doesn't surprise me. I've been running arch for about 4 years now... and have never even tried to interact with their community. Great distro (imo)... but yeah... not even worth trying to be a part of the community.

@ryan.russell011 The Clojure community has always had the guidance to be polite, respectful, and welcoming — that comes down from Rich Hickey himself, as well as reinforced by all the Cognitect (formerly Relevance) and Clojure/core folks. The conferences have had a Code of Conduct for several years — and this Slack also has a Code of Conduct — so there’s a culture of treating people decently. And we also deliberately set up a separate #beginners channel here for folks new to Clojure and those folks who opt-in to help them (it’s why there’s nearly 13K people in #clojure and only 4.5K here). There’s also a #programming-beginners channel for folks who are new to programming as a whole.

that is super amazing! Well done!

Besides, how can we take over the world if we don’t encourage more people to use Clojure? 🗺️

How many of you started with Clojure (or other functional-first lang) after feeling burnt-out on imperative? :thinking_face:

Question: how do you require relative namespaces? “Programming Clojure” goes through first imports and mentions > If you see the first 10 Fibonacci numbers as listed here, you have successfully installed the book samples. But doesn’t mention anything about how to install them..

"install" is a weird term for namespaces - clojure looks up code that's required via the classpath

either it's in a jar which is on CP, or there's a directory on the CP with your code in a nested folder relative to the namespace definition

And what is classpath, please?

it's the places a jvm looks for things, a start-time parameter

if you use leiningen, it's leiningen's job to set classpath for you

How do I even retrieve the current classpath?

I found java -cp ... sets it, but that doesn’t help

in the repl, (System/getProperty "java.class.path")

(System/getenv "CLASSPATH") I guess

it can be set from command line and not just env though, use getProperty

but if you are using a tool, it manages that for you

its config decides where source files should be

Aah, I see now

to get more specific I need to know more about your toolchain - leiningen project, boot? raw command line calling java?

Lein

OK, the default with lein is for source to be under a src directory

foo.bar ns would be in src/foo/bar.clj

But does that apply to REPL as well?

if lein starts clojure, that's where it wants your source

Aah, I see now

regardless of repl, run, or build

but there's a config in project.clj that can be modified

Okay, okay, now I get it

Hi guys, As you can imagine, I am a beginner. I am trying to take up Clojure. Managed to convince my boss to let me work on a web service + frontend in Clj/Cljs (Compojure, re-frame). It is a small project and I haven't messed up much so far. I am not a hugely talented programmer like many people here so some of the stuff I mess up because I don't have good understanding. I am just an average programmer (So, you will never find me at Google or Facebook.) I would like to get engaged with any open source project that can use some man hours. Testing, documenting, it doesn't matter. Can you suggest a project been done by decent human beings (Not 200 IQ assholes) which can use some help from a beginner like me? I can probably put in five or six hours a week, and I would like to contribute in any way I can. I think I would learn better and faster that way too.

I am used to relative imports from JS, but this is based on (CLASS)PATH

Okay, thanks a lot! I’ve been literally playing with cding for 30 minutes trying to figure out how to import those files 😂

@kyselyradek yes, it works just like a path in your shell - it controls which places you get code from

Yup, thanks, really! 😄 This channel is a blessing 🙏

one advantage to that method of doing things is it means you can use code that is inside a zip file (a jar is a zip with a special set of contents), or even directly from a URL

and it won't want to load things just because they are in the current directory (which I guess is a kind of security feature)

Actually, weird thing, it works on clj repl but not using lein repl

quick question... is the caret before Currency doing actual type checking? or is just metadata to describe what currency should be (without actually type checking)?

(defrecord Currency [divisor sym desc])
(defrecord Money [amount ^Currency currency]

type hints are not type checks

they are an assistance to the compiler

with records they are not needed

this example is from Clojure Applied

OK

so the book is wrong?

or there might be another reason?

I think he is just saying ordinarily they aren't needed... which doesn't mean you can't have them

Not that there is a "wrong" or "right"

seems noise then?

the compiler doesn't throw errors for nonsense type hints in most cases, and I guess there might be a case where the compiler could make better numeric code if it knows something about what's in Currency...

I found this somewhat helpful: https://kotka.de/blog/2012/06/Did_you_know_IX.html

and this: https://www.quora.com/When-should-I-use-type-hinting-to-make-Clojure-statically-typed (don't let the title mislead you... the first response clarifies a poorly written question here)

so.. here is the whole record from the book

(defrecord Money [amount ^Currency currency]
  java.lang.Comparable
    (compareTo [m1 m2]
      (validate-same-currency m1 m2)
      (compare (:amount m1) (:amount m2))))

@noisesmith but is that type hint telling the compiler what's in Currency?

well that code isn't even using currency so there's not enough there to really say - the definition of Currency is what would tell it what's expected to be in there

he pasted the definition of Currency before

(defrecord Currency [divisor sym desc])

well he posted Money before too and that was empty

so...

ok 😉

I'm assuming clojure applied is building up to something interesting where there's a point to the type hint, I'd have to double check it's been ages and there's parts I only skimmed

lol... to alleviate some of the confusion about my amazing copy/paste skillzzzz

obviously there is more... I was just curious as the the functionality of the ^ lol... the actual code is pg 8 in the Clojure Applied book

@noisesmith so in general you don't need type hints for defrecords because the clojure compiler already knows about its methods?

right, and the way defrecords and protocol methods dispatch it doesn't need the same kind of expensive reflection it needs to use on classes and interface methods from native java

hmm, slack was down for me

Is it necessary to clear ~/.m2/ old (deprecated) dependencies? And How ?

you can safely delete anything in m2 as long as you only install by normal methods

it's a cache, you'll just need to wait for the stuff to download again

if you use mvn or lein etc. to install something local by hand, it will be missing until you do that again, for obvious reasons

Any way to say (require [korma.core :refer :all :except update])?

@noisesmith I see, thanks

I don't know of a way to figure out which versions your projects use or not, but deleting the whole thing is a thing people do

@duminda you can use :rename to give update a name that doesn't clash with clojure

or use a db library that has been updated since the clojure.core/update function came out :P

@noisesmith: "or use a db library that has been updated since the clojure.core/update function came out :P" Any suggestion?

I am learning about providing support for inserting Clojure maps into JSON columns in a postgres db. An article explain that, its as easy as extending a protocol. It provides an example

(extend-protocol jdbc/ISQLValue
    clojure.lang.IPersistentMap
  (sql-value [value]
    (doto (PGobject.)
      (.setType "json")
      (.setValue (json/write-str value)))))

@duminda honeysql and hugsql were both kept up to date last I checked - at least more active than korma

The protocol is implemented by someone and in that example listed, it is being called by the JDBC driver?

clojure.java.JDBC is invoking that protocol method on its argument

by extending that method to map, that tells clojure.java.jdbc what to do when it sees a map

I see thanks

1. Unhandled org.sqlite.SQLiteException
   [SQLITE_ERROR] SQL error or missing database (incomplete input)

Why it report missing database?

incomplete input = SQL error methinks

is there a reason your query vector is 2 strings instead of one?

I think you need to mention a database in the configuration [db] and that database must be already created ... here is sample configuration (def mysql-db {:dbtype "mysql" :dbname "clojure_test" :user "clojure_test" :password "clojure_test"})

maybe (sql/query ["" ""']) is happy with 2 strings or however-many, after i have read the docs it seems like that would work. check out: https://en.wikibooks.org/wiki/Clojure_Programming/Examples/JDBC_Examples

Is there a way to undo evaluation of all the forms in a file? Sort of like un-intern defs and stuff

Without restarting the repl?

@ackerleytng You can do this, maybe this is what you’re looking for? (require :reload '[my.thing :as thing])

It’s not quite what you asked for, and it sometimes leaves things hanging around that you want to get rid of, but it’s useful in a lot of cases.

There’s also https://github.com/clojure/tools.namespace but I haven’t used it personally.

seems like it might have something you could use, though.

Is there a test coverage tool that supports boot? I can only find Cloverage, which apparently only supports lein