For lisps I've started Land Of Lisp, which is a fun intro, also I've been doing a lot of elisp with emacs so that I find is a great value add, despite the difference in data structures.

If I have a reducible thing and a transducer, what’s the best way to use some with it?

I have (iterate/tree-seq) which returns an IReduceInit impl which iterates over the tree. I’d then like to filter and map the elements, and stop when I meet one matching some criteria.

Something like (some whitespace? (comp (filter string?) (map something)) (iterate/tree-seq element))

Perhaps (some whitespace? (eduction (comp (filter string?) (map something)) (iterate/tree-seq element)))?

The best option I’ve been able to come up with is:

(transduce (filter psi/whitespace?)
           (completing (fn [ret item] (if (psi/whitespace? item) (reduced true) ret)))
           false
           (iterate/tree element))

@cfleming perhaps halt-when?

Or just using reduce directly, but still not easy to understand:

(let [f ((filter psi/whitespace?) (fn [ret item] (if (psi/whitespace? item) (reduced true) ret)))]
  (reduce f false (iterate/tree element)))

@sundarj Thanks! But sadly I’m not on 1.9

To try it out, I copied halt-when into my project.

(transduce (comp (filter psi/whitespace?) (halt-when psi/whitespace?))
           identity
           false
           (iterate/tree element))

It still feels odd. I think the direct reduce version makes the most sense, except for creating the reducing function by invoking the transducer.

I think part of my confusion is that reducing is inherently tied to having an accumulated value, which I never use in this case.

maybe make a true in-order (or whatever traversal) of the tree? and then just do a some first?

Yeah, I actually have a tree-seq which returns a seq over the tree, but I was trying to do it imperatively rather than use the lazy seq.

But in this case I think it makes more sense.

Well, reducively rather than imperatively, eagerly I guess.

Hi, sorry for beginners question. What is the use case for dynamic functions? (defn ^:dynamic …

@fixxer The var is the thing thats dynamic, and this allows you to "rebind" certain vars on a "per thread" basis. Example- lets say that you have somebody else's function that uses println all the time, and you want only the console output from one thread (like, inside a long-running go block) to go to a separate log file. Println uses a dynamic var for its console printing, so if you rebind that then suddenly all those println calls go where you want them.

If go blocks work how I think they do, that is

@fixxer There are no beginner questions. Just go ahead and ask what you want to know, to live means to learn 🙂 Also there is a #beginners channel if you feel more comfortable there.

Yeah, nobody is born knowing Clojure

it would be weird if they were

I'm looking for an efficient way to transform a nested map:

{:n0 {:k1 "key 0 - 1"
      :k2 "key 0 - 2"
 :n1 {:n1.1 {:k1 "key 1.1 - 1"
             :k2 "key 1.1 - 2"}
     :n1.2 {:k1 "key 1.2 - 1"
             :k2 "key 1.2 - 2"}}
 :n2 {:n2.1 {:k1 "key 2.1 - 1"
             :k2 "key 2.1 -2"}}}

{:k1 {:n0 "key 0 - 1"
      :n1 {:n1.1 "key 1.1 -1"
           :n1.2 "key 1.2 - 1"
      :n2 {:n2.1 "key2.1 -1"
 :k2 {:n0 ...}}

not sure how to 'inverse' the nesting (keys of leaf nodes become the root nodes - there are only a limited number of leaf keys)

@kurt-o-sys have you tried looking at a lens library ?

i like https://github.com/ctford/traversy myself

I'll look at it... experimenting with specter now, I'm pretty close. I'll give a look at traversy.

if you're using specter you're already going the right direction 🙂

🙂 got it working...

@dnaeon Maybe not the most elegant but you can write it using trampoline

though for what its worth im not getting any stack overflows running your code

oh right lazy sequence

okay now im getting it

https://gist.github.com/samedhi/1405ff302ef9819f8f4f9d43099d3d38 <= Having some trouble figuring out why I can’t reify this java Interface, any help is appreciated.

Ah, it is this EventListener http://googlecloudplatform.github.io/google-cloud-java/0.37.0/apidocs/com/google/cloud/firestore/EventListener.html

Fudgsicles, forgot to include the this in the implementing method again. I do this like once a week!

hello everyone, any suggestions where to find (libs maybe?) specs for strings contaning datetime in the ISO 8601 format?

answered in #clojure-spec