might because it’s Monday 😁

and solution: https://github.com/lambdaisland/aoc_2020/blob/main/src/lambdaisland/aoc_2020/puzzle07.clj I also talk a bit more about yesterday's puzzle, and answer some questions people asked in the comments.

maybe I missed it, have you mentioned that using io/reader without with-open macro is not a good practice?

Oh that's a good point, I'll mention it tomorrow

curious to what’s wrong? :_

have to stay tuned I guess

find out tomorrow in a new episode

I think its because if you call io/reader without with-open (or explicitly try / catch yourself), then you can be left with an open reader in the case of an exception? But I'm guessing here. If thereis an exception I think with-open calls close on its binding

https://github.com/tschady/advent-of-code/blob/master/src/aoc/2020/d07.clj

and viz for fun:

you have a recursive call inside a recur form, that’s atypical

i don’t think he does.. he shadowed bag children in the loop binding

oops, missed. I guess that’s a reason to avoid that.

(defn bag-children [color bags] (let [bags-lookup (into {} (map #(vector (:color %) %) bags))] (loop [colors-to-walk [color] bag-children []] (if (seq colors-to-walk) (let [contained-bags (mapcat contained-bag-colors-as-seq (:contain (bags-lookup (first colors-to-walk))))] (recur (into (subvec colors-to-walk 1) contained-bags) (into bag-children contained-bags))) bag-children))))

yikes formatting

Nope

I edited his gist since I can’t format in slack apparently

it’s concat

cool, thanks for link

Thanks for taking a look!

I had no idea about concat… I had just assumed it was lazy

or that even if it was eager, it would just utilize too much memory vs a stack overflow

it is lazy, which is why you're getting the stack overflow. consider this

(def x (reduce concat (map #(list %) (range 100000))))

(first x)

I'll talk about this on the stream today, it's one of those surprising clojure gotchas.