Clojurians Log v2

Cool

Add a memoize and you're golden

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

See the Fibonacci example

(Although I don't think its entirely applicable to this, as you'd have to re-write it in a recursive manner)

Why does -> expand to this particular result in this example?:

user => (macroexpand '(-> [1 2 3 4] (reverse) (drop 2)))
(drop (reverse [1 2 3 4]) 2)

the first form as the
second item in second form

(drop 2 (reverse [1 2 3 4]))

(drop 2 (reverse [1 2 3 4])) this is the form of three forms: drop , 2, (reverse [1 2 3 4])

->

(-> [1 2 3 4]     ;; call this o
    (reverse)     ;; this line becomes (reverse o), o is in te second location in this form. This is evaluated and lets still  
                  ;; call the result o
    (drop 2))     ;; this line becomes (drop o 2)

You could use thread last in your example

(->> [1 2 3 4]
     (reverse)
     (drop 2))
=> (2 1)

If I'm correct, Leiningen doesn't have any "watch" support by default? If I would like to automatically rerun tests when files change for example

You can achieve this via lein-auto https://github.com/weavejester/lein-auto

usually this is responsibility of a test runner. For example https://github.com/lambdaisland/kaocha can “watch” for changed files and run subset of your tests affected but the change

thank you both

I love this video. Are there any other good example videos of people debugging and troubleshooting? One of the hardest parts about learning Clojure so far is that the error messages are basically written in Java and I don't know Java, so seeing more examples of troubleshooting would be great. Right now i feel like my only response to troubleshooting in a lot of cases is to ask someone for help. https://youtu.be/lPczdxHt43g

There’s a lein-auto-test plugin I believe

Or lein-test-auto might be the name

i’ve had success with https://github.com/jakemcc/lein-test-refresh too

Thanks. I went with Kaocha, it was easy to set up and use

Thank you @qmstuart. That’s what I thought, but the docs wording is confusing. Doesn’t saying

feeds it into the first argument position in the following form.

inserts the first form as the
second item in second form

Consider the form a list, in the case of (drop 2 o), o is the third item in the list. In the case of (drop o 2),o is the second item.

I agree docs are confusing tho, i hardly ever go to docstring to understand a function

ohhhh that makes much more sense (considering it a list) now this doc line makes sense

making a list of it if it is not a
list already

I'm trying to require closh.zero.macros inside a babashka script, (require '[closh.zero.macros :as closh]) When I run, in the shell, bb ./file.clj I get:

----- Error --------------------------------------------------------------------Type:     java.lang.Exception
Message:  Could not find namespace: closh.zero.macros.
Location: 3:1

closh isn't the same as babashka

Could I interop them? I have a bunch of custom-written functions, and I'm struggling calling them. Basically, I have to eval one by one, right now. That's the underline thing I want to solve

If I can load the closh's macros inside babashka, that would be great

Is there any way to refer to clojure.lang.Keyword in a shorter form? I'm practicing multimethods for the first time and would like to dispatch on a class of keyword or number. Using Number works as expected, but Keyword doesn't seem to exist without the full name of clojure.lang.Keyword.

You could import the class via (import 'clojure.lang.Keyword)

Cool, that seems to do the trick. I tried using a [clojure.lang :refer [Keyword] , but that didn't work 😀

Feel free to join #babashka to discuss

It looks like you are trying to required the class via the ns form. If so, try (ns my-ns (:import [clojure.lang Keyword])) instead.

I am trying to make an SPA based off of leiningen’s reagent template. They have the server set up so that all pages are handled by an index handler that mounts a loading page.

(defn loading-page []
  (html5
   (head)
   [:body {:class "body-container"}
    mount-target
    (include-js "/js/app.js")
    [:script "spotify_client.core.init_BANG_()"]]))

(defn index-handler
  [_request]
  {:status 200
   :headers {"Content-Type" "text/html"}
   :body (loading-page)})

Why isn’t this working? Anybody who knows Specter that could help me out here?

Will do! Thanks for the invite

all the :case1 entries are numbers, and MAP-VALS expects maps

That's even better, thanks a lot!

Awesome, this worked:

(s/select [:employees ALL :case2] employees)

Is there some way to exclude stuff? I was looking for it in the documentation and struggling. See the bottom bit of code, which doesn’t work

I thought any function would work as a filter predicate

#(not= % :name)

Hmm that still doesn’t filter out the names

So you want to select a set of keys that doesn't include name?

I want the output here to exclude :name 1, :name 2, etc. but keep all of the cases and their values. Desired output below.

[{:case1 600, :case2 800, :case3 1000}
 {:case1 1000, :case2 900, :case3 800}
 {:case1 800, :case2 700, :case3 700}
 {:case1 800, :case2 1000, :case3 1000}]

(s/select [:employees ALL (s/view #(dissoc % :name))] employees)

Awesome. So if I understand this correctly, :employees ALL will take me to a map of all of the employee data, and then view allows me to apply the dissoc function to the resulting list?

Yeah, basically. I'd make a key distinction that it doesn't take you to a map, but navigates you to every map. Specter is kinda weird in that it has ways to deal with "collections" but individually by way of navigation.

Is there some way to get better error messages? I'm editing a babashka script, running some things in my repl. I often get messages like: > clojure.lang.ExceptionInfo: No implementation of method: :as-file of protocol: #'http://clojure.java.io/Coercions found for class: clojure.lang.Keyword Is there some way to get line numbers or something in the error message?

@randumbo what is "my repl", is that JVM Clojure or babashka?

babashka should give you line numbers about this, or a nice stacktrace

it also has a REPL

@borkdude Babashka. Started it using :IcedInstantConnect babashka with it set to nrepl.

That's from vim-iced: https://liquidz.github.io/vim-iced/#_connecting_socket_repl

ah right, yeah in nREPL you don't get the errors you get when running it on the command line

Hmm, so I'd be better off using socket repl? I thought nrepl would be the preferred option as it returns data.

No, nREPL is fine, it just needs to do better on the error handling there I think. To explain the error though: When you call <http://clojure.java.io/file|clojure.java.io/file> on a something, it tries to convert that something to a file. This conversion is implemented using a protocol called Coercions. But there is no implementation of that protocol for the Keyword type.

Long story short: <http://clojure.java.io/file|clojure.java.io/file> does not accept keyword.

Yeah, I understand the error and can debug it, but without line numbers it's quite a hunt sometimes. Do you have some suggestions for getting better debugging hints when I run into situations like this?

@randumbo I think this is a specific issue with how nREPL is implemented in babashka: https://github.com/babashka/babashka.nrepl/issues/40 You should get better errors when you execute the script from the command line, so that might be the best debugging for now

@borkdude fair enough, thanks very much.

Unrelated to my previous question.. I understand that doseq is basically for when I need to loop over something and produce side effects in the body. Is it weird that I often have nested doseqs when I need to iterate over an inner list?

@randumbo doseq already supports multiple nestings

I’d like to add an item to a collection within a map and return the map with the new collection. If I use conj it’ll return just the collection. Is there an idiomatic way to update a collection w/i a map whilst returning the map? Thank you

Oh I didn’t know doseq allowed for nested bindings. Neat

you can arbitrarily mix & match further nesting, :when or :while clauses, and :let clauses

How do the nested doseq bindings work?

same as for basically

This website has some nice examples: https://clojuredocs.org/clojure.core/doseq

lol yes I've been staring at this page

@randumbo supposing you have a list of lists of numbers

(doseq [l z :when (> (count l) 3)
        n l :while (< n 5)]
  (println n))

z is the list of lists

that will iterate through the elements of z filtering out any that are shorter than 4

for each of those it will iterate through the numbers in that list and print them until it encounters one >= 5

same as what you're doing with nesting doseqs

Got it. I think I understand. Gonna refactor what I have to test myself. Thanks 🙂

@titanroark (update the-map :coll conj new-item)

🙌 thank you

Yes this is unusual