https://gist.github.com/didibus/6e5ff960b25fdc1a5f8f97acede614b0

That should answer most of your questions in details. If you want a TL;DR, it's anything that uses Java like desktop apps and back-end servers and services, as well as anything that uses JavaScript, like NodeJS back-end servers, front-ends in browser or on mobile or Electron like desktop apps, various extensions like for VSCode extensions, as well as some odd ones like scripting and AWS lambda or command line applications. You can also use it for machine learning and data-science, and anything that Python is good at, since you can use all Python libs with it as well.

https://youtu.be/XMIKfOmAMjQ

+ flutter apps using #clojuredart

Do you mean something like this?

dev=> (let [x *ns*] (ns foo.bar) (defn quux [x] (println (* x x) "in" *ns*)) (quux 42) (in-ns (symbol (str x))))
1764 in #object[clojure.lang.Namespace 0x3ff8a3ad foo.bar]
#object[clojure.lang.Namespace 0x3c27f72 "dev"]
dev=> 

Something like that, but I'd like to be able to return a value from the let, not use the last form to go back to the previous namespace.

I was hoping there was something like

user=>
(with [*ns* other-ns]
  (fn-in-other-ns 1))
2
user=>

The problem with using a single form like a macro to do this is a single form will be read all at once before any of it is executed, where the value of *ns* can effect how forms are read

So ::foo in your with-ns won't be qualified with the ns from with-ns but the original value of *ns*

Spec 2 (wip) has support for schema and select similar to described in the talk (as an alternative to s/keys)

So the select is the “when” effectively

https://github.com/clojure/spec-alpha2/wiki/Schema-and-select#select Thanks!

Seems like the quux function ended up being defined in the user namespace. Not entirely sure why that is, but I will note that this isn't exactly a surprise. def, defn, in-ns, and similar are not really designed to be used inline like this.

Another example of this came up recently. I think if you think of Clojure as interpreted your expectations make sense. But if you remember the Clojure is compiled the reality makes sense. Think of what it would compile to and then what happens when it runs

immediately after evaluating the definition of c and before calling c, check out what the definition of quux is:

quux
#object[clojure.lang.Var$Unbound
        "0x5f95be9f"
        "Unbound: #'nocommit.qp/quux"]

That it defines an undefined var does make some sense to me. However, that it is defined in user namespace doesn't. If I run a simple (do (ns bar ) (def a 42) (in-ns 'user)), then it does exactly what you would expect.

there's a special case in the compiler for top-level do forms

this might be related

yeah. top level do i think compiles the first case, runs it, and then continues

Interesting. Anyhow as you already said: def probably shouldn't be used inside def. The only useful context I know of is during debugging.

right, but in-ns and ns also fall into the category of "probably shouldn't be used inside a def"

in-ns is mostly a repl utility, and ns is designed for file-header namespace declarations, neither is particularly good to use inside a definition.

Thanks for the explanations 🙂

This works though:

(def ns-def
  '((ns imoen (:require [clojure.string :as str]))
    (defn j [coll] (str/join " " coll))))
(doseq [form ns-def] (eval form))
(in-ns 'user)
(imoen/j ["Hiya," "it's" "me"])

Yeah you've made it an interpreter with eval basically

Which if you haven't seen this before, using eval is almost always a bad idea. There are genuine usecases for it, but they are few and far between. You should consider alternative ways to do this. For example, using clojure.core/intern to create a var in another namespace and assign it a default value.

Although I do question why you need to create a var in another ns in this code.

yeah, let me give you a snippet

ah crud, i was wrong, it only does the map case

(pp/with-pprint-dispatch pp/code-dispatch (pp/pprint {:a 1 :b 2})) => {:a 1, :b 2}

you might check out https://github.com/kkinnear/zprint

Got it. :)

i haven’t verified it’ll print with commas, but as i understand it gives a ton of control over printing, so i’m pretty confident it’ll do the trick

heck, there may be a way to do it with pprint as well, looking now

This 'works' as well. ¯\(ツ)/¯

(require '[clojure.pprint])
(require '[clojure.data.json :as json])

(binding [clojure.pprint/*print-right-margin* 10]
  (json/pprint ["10.195.0.0/16"
                "10.196.0.0/16"
                "10.197.0.0/16"
                "10.198.0.0/16"
                "10.200.0.0/13"]
               :escape-slash false))
;; => nil
;; stdout:
;; ["10.195.0.0/16",
;;  "10.196.0.0/16",
;;  "10.197.0.0/16",
;;  "10.198.0.0/16",
;;  "10.200.0.0/13"]

ah yeah good call. i knew i’d seen these print with newlines on vectors

it looks like if you make whatever you’re printing an array it’ll comma-fy it for you?

(pp/pprint (into-array [1 2 3 4]))
[1, 2, 3, 4]

Ah interesting.

Yeah that's better for this particular case. :D

Also looks like it works on hashmaps at least. :)

(with-out-str (pprint {"a" "b" "c" "d"}))
;; => "{\"a\" \"b\", \"c\" \"d\"}\n"

Neat! I like this better than encoding to cussing json. xD

🙂

Which JDK are you using?

Good question. Just the default. I didn’t know Heroku offered options.

> Heroku currently uses OpenJDK 8 to run your application by default Try switching to 17 or even 18.

Oh wow… ok let me check that out.

or just limit the memory setting if you haven't done so yet

-Xmx1G command line option for 1gig or however much your instance is supposed to have

That's one of the things that'll happen (or supposed to happen) when switching to a JDK > 15, IIRC. Due to an improved containerization support.

still useful to manually tweak

And Heroku by itself already sets that flag as well. But it doesn't always help. E.g. I currently have -Xmx600m. The app can still balloon to 1.3 GB from time to time. Not sure why, haven't really tried delving into it.

But I should add that you're right, setting it manually to a lower value could be useful. It's just that 1G specifically shouldn't make a difference at all.

That setting is for Java heap. The JVM also has off heap memory for other things.

https://github.com/devn/getclojure/blob/main/system.properties is how you specify a version fwiw

add that file and it picks the desired jvm

once upon a time there were a lot of settings for tuning performance for clojure in heroku. one note is that if you're running with lein, make sure to trampoline like lein trampoline run -m foo.bar

Good reminder, I'll do that.

I would say that both https://github.com/hoplon/hoplon and https://reagent-project.github.io/ have a reactive model similar to your description.

I think https://github.com/kennytilton/matrix is also in the same reactive space, but it's much newer and I'm less familiar with it.

and https://github.com/leonoel/missionary too, not sure how to tie it in with a UI though