Am I right that (transduce indentity f xs) is equivalent to (f (reduce f (f) xs)) ?

Working on advent of code, day 23. I created a bunch of input and output channels, so channels is of the shape {addr {:in-chan <channel> :out-chan <channel>}} , and then I have this router block, which i'm running in the repl over cider.

(let [channels (zipmap (range 50)
                         (repeatedly (fn [] {:in-chan (a/chan 10) :out-chan (a/chan 10)})))]
    ;; Boot all computers
    (doseq [[addr {:keys [in-chan out-chan] :as inout}] channels]
      (intcode-computer inout addr))

    ;; Do routing
    (while true
      (let [[msg _] (a/alts!! (map :out-chan (vals channels)))
            [addr x y] msg]
        (println "msg" msg)
        (if (= addr 255)
          (do (close-all channels)
              (println "=================================>>>" y))
          (do
            (println "routed" [x y] "to" addr)
            (a/onto-chan
             (get-in channels [addr :in-chan])
             [x y]
             false))))))

I figured alts!! isn't what i want since i'm not sure what happens to the other messages on the channel when one of them resolves, so i switched the implementation

(let [channels (zipmap (range 50)
                         (repeatedly (fn [] {:in-chan (a/chan 100) :out-chan (a/chan 100)})))]
    ;; Boot all computers
    (doseq [[addr {:keys [in-chan out-chan] :as inout}] channels]
      (intcode-computer inout addr))

    ;; Do routing
    (while true
      (let [[addr x y] (a/<!! (a/merge (mapv :out-chan (vals channels))))]
        (println "msg" [addr x y])
        (if (= addr 255)
          (do (close-all channels)
              (println "=================================>>>" y))
          (do
            (println "routed" [x y] "to" addr)
            (a/onto-chan
             (get-in channels [addr :in-chan])
             [x y]
             false))))))

They were talking about the conj function on #clojure earlier. Can be seen here: https://stackoverflow.com/questions/59463747/how-does-clojure-bind-variable-parameters/59465336#59465336 Why if fn being used in the def's body (seems it can be removed without messing anything up)? Is it because of the :static metadata?

the static metadata does nothing, it's a vestigial thing

(def foo (fn .. is like writing (defn foo ..

conj is defined before defn exists in clojure.core

I just finished watching @ericnormand 's excellent "REPL Driven Development" course in https://purelyfunctional.tv/. I really recommend to purchase that course if you are learning Clojure or you want to learn more productive REPL driven development practices as I did. I'm not a complete newbie in Clojure but I must say that I learned a lot watching a seasoned Clojurian working with the code and REPL and explaining what he was doing and why. That is definitely something you cannot learn just by reading Clojure books.

@bronsa Yeah my bad, I actually read that as 'defn', but it's actually 'def'

How to check if file exists?

(.exists (io/file ...))

Anyone knows a good book or course about topic "Clojure standard library hidden gems"? 🙂

@kari.marttila This perhaps? https://www.manning.com/books/clojure-the-essential-reference

Anyone here subscribe to Manning liveBook?

Yes! Definitely going to buy that Clojure book as well!