Hi everyone

Since into requires the input channel to be closed before it produces a result, and to-chan does indeed close the channel that it creates, the result is as expected.

(<!! (into [] (to-chan (range 10))))
;; => [0 1 2 3 4 5 6 7 8 9]

(def c (chan))
(onto-chan c (range 10) false)
(close! c)
(<!! (into [] c))
;; => [0]

I guess that to-chan creates a buffer of the length required by the collection, whereas the pending puts onto c are discarded. I would then expect the second variant to produce [].

(chan) acts as a rendezvous point so one adding a value (`0`) onto it parks, then you close it, then you read from it, which picks up the parked 0, and then it's a closed channel.

Thanks Sean.

If you use (chan 1), you actually get two values out of it:

user=> (def c (chan 1))
  #_=> (onto-chan c (range 10) false)
  #_=> (close! c)
  #_=> (<!! (into [] c))
...
[0 1]

(for the same reason)

Got you - subtle stuff!

core.async is tricky.

I'm still a hobbyist and haven't used it in any project yet, but I'm really excited by its potential.

onto-chan pours some values into an existing channel. Your call to onto-chan returns immediately and the pouring happens in the background (subject to the flow of the channel that you're pouring into) the close! call closes the destination channel of that background pouring process.

since you used a rendezvous chan (an unbuffered channel), the pouring process is going to be driven by the takers on the destination channel the 3 calls to 1) launch the background pouring (onto-chan), 2) close the channel, and 3) launch the async/into process - those call proceed rapidly in succession

This question was asked in the wrong channel and removed: > in rich4clojure. I press the atl+enter key and the tests fun return nil. how can i know its pass or fail Reposting it here to be able to provide an answer. 😃 I'm assuming this is a problem when running Rich4Clojure locally (as opposed to the GitPod option). The solution is to first load dev/repl.cljc, to initialize the testing facility. It's mentioned here: https://github.com/PEZ/rich4clojure#on-your-machine

Is there a core fn to change from [{:name "Foo" :value 1}, {:name "Bar" :value 2}] to {"Foo": 1, "Bar": 2}?

Hi fellow Clojurists, I’m struggling to understand how to compose predicates with the every-pred, especially how to explain why an execution error in thrown here:

user=>((every-pred even? integer?) 4.99)
; Execution error (IllegalArgumentException) at ghostly.core/eval7861 (form-init12829955687297635352.clj:100).
; Argument must be an integer: 4.99

you are doing it correctly. even? is just a little picky. (even? 3.45) throws an error that its argument must be an integer

but you’l want to switch the order here

((every-pred integer? even?) 4.99) returns false.

In CojureScript, is it safe to use the namespace clojure.browser.dom or should it be considered as implementation?

https://github.com/clojure/clojurescript/blob/master/src/main/cljs/clojure/browser/dom.cljs

I would like to add a docstring to my multimethod. Are there conventions around this?

A multimethod has a single doc string, you can set with the defmulti that creates the multimethod

There is no place to hang a docstring for individual implementations

thank you, that answers my question

Can specs have a docstring?

No, but it is one of the most-requested features.

ah cool. I will use comments for now 🙂

you can also make your own table of {spec-kw-or-sym -> metadata} and store whatever metadata you want

docstring, related specs, author, hyperlinks

it just won't be directly integrated with clojure.spec's registry

Another core.async misunderstanding! map is core.async/map and the example is a modification of the documentation.

(defn inc-async
  [num]
  (let [ret (promise-chan)]
    (go
      (<! (timeout (rand-int 2000))) ;; Randomly sleep up to 2 seconds
      (put! ret (inc num)))
    ret))

(def a (atom nil))

(go
  (let [v1 (inc-async 1)
        v2 (inc-async 10)
        v3 (inc-async 100)]
    (reset! a (take! (map vector [v1 v2 v3]))))

Why does @a return nil?

Look at the docstring of take!

(I’m not shouting)

🙂

What about using <!?

Yeah that would change the result

put!/take! are asynchronous, intended for integrating with non-chan aware things

<! and friends are sync

Using <! still returns nil

firing up a repl

kk

I'm making slides in revealjs, and I want to do line-by-line animations. What's an idiomatic way to turn this:

[[:h2 "title"] [:p "some info"] [:li "an item"] [:li "another item"]]

[:section
 [:section {:data-auto-animate ""} [:h2 "title"]]
 [:section {:data-auto-animate ""} [:h2 "title"]
  [:p "some info"]]
 [:section {:data-auto-animate ""} [:h2 "title"]
  [:p "some info"]
  [:li "an item"]]
 [:section {:data-auto-animate ""} [:h2 "title"]
  [:p "some info"]
  [:li "an item"]
  [:li "another item"]]]

Curious how Clojure developers deal with lack of types? I am Curious about Clojure and have played with it, but not being able to get type-checking really crippled me Since I was blindly writing code without knowing if it was correct or not until I tried to run it Are there any tools/options for this?