Expanding on Alex's idea, this would be the way to un-interleave,

(defn distribute
  [n coll]
  (apply map vector (partition n coll)))

(distribute 3 [1 2 3 4 5 6 7 8 9]) ; => ([1 4 7] [2 5 8] [3 6 9])

Distribute is a great name. Also now I think about it, "deal", like dealing cards

Yes, it is exactly like dealing cards, 🙂. You have given a nice little mental exercise. With the apply map trick, I am killing the lazyness. Now I am wondering what would be the way to distribute while preserving the potential lazyness of the incoming collection. EDIT: Andy's solution with map and take-nth is lazy. Perhaps there is a solution with partition as well.

I strugle to create a class with gen-class and i have problem to override the toString method

(ns example
 (:gen-class
   :name         test.override
   :methods      [ ^{Override {}} [toString [] String]]
   :state        state
   :init         init
   :constructors {[String] []}))
(defn -init
  [name_]
  [[] (atom name_)])
(defn -toString [this]
  (deref (.state this)))

gives

Caused by: java.lang.ClassFormatError: Duplicate method name "toString" with signature "()Ljava.lang.String;" in class file test/override

any incites why this happens ?

https://github.com/clojure/clojure/blob/8af7e9a92570eb28c58b15481ae9c271d891c028/test/clojure/test_clojure/genclass/examples.clj#L34 suggests you have ^{Override {}} in the wrong place.

:methods [[ ^{Override {}} toString [] String ]]

@seancorfield indeed, but this was after experimentation

i moved it to

:methods      [[^{Override {}}  toString [] String]]   

and the problem  persists

I don't write java but it seems that it should have worked even without the annotation. Could it be a bug ?

When someone gets a chance, I was wondering if I did this correctly:

(def input
  [{:name :isaac :value ["pencil", "pen"]}
   {:name :brian :value ["eraser", "cat"]}])

(reduce
  #(assoc %1 (:name %2) (:value %2)) {} input)

; Output
; {:isaac ["pencil" "pen"], :brian ["eraser" "cat"]}

@isaacballone Clojure's data structures are designed for that usage and are very efficient.

That transform looks like a very reasonable way to get from your input to your output.

Just bear in mind that if you have two hash maps in your input that have the same :name then the later one will overwrite the earlier one(s).

Okay. I originally used let to make a variable and had a for loop doing assoc on it, but I was probably doomed from the start from that approach, right? Since it's immutable anyway, it's not a reference I can write to, and it returns a new one with assoc

The vectors for the :value keys will be shared between the input and the output.

Here's an alternative for you to ponder: (into {} (map (juxt :name :value) input))

Oh okay, that makes sense too. I hadn't thought about that

Oh boy slapping some black magic at me. I'll have to read the docs on those functions lol

Thanks for your help! I really appreciate it

Hi guys, it is not possible to do with-redef inside a test on something from Java, is it?

In one of my tests I’m testing erroneous environment variables for the configuration of the application

So inside the test I’m trying to do: with-redefs [System/getenv something-else] …

However, I always get Unable to resolve var: System/getenv in this context

Does leiningen manage its own JDK?

Is there a way to define the existence of a function in a namespace? e.g. I have a defn that refers a 2nd defn, but the 2nd defn hasn't been defined yet.

declare is what I'm looking for, nevermind