I am doing Advent of Code 2021.

I am also learning Kotlin.

I am also trying to code on Windows with Sublime Text 4 and GitSavvy.

Learnings

• Kotlin is a hell of a lot of fun. The collections API has a lot of method stringing capabilities, so you can do something like this, which will tell you if any of the lowercase values in rp appear more than once:

  val doubled = rp
    .filter{ it == it.lowercase() }
    .map{ s: String -> rp.filter{ it == s }.size }
    .filter{ it > 1 }
    .any()
  

• The null handling is also kind of cool. Definitely like that you can easily distinguish between "nullable variable" and "not nullable variable" with just a ? on the type. (Like std::optional but more concise.)

• The constiness in the language is confusing, though. val and var are too similar, they're hard to distinguish at a glance. And why do I have MutableList and List (unmutable), isn't that what var/val are for?

• Delayed initialization of vals is nice, but I wish it played a little better with loops (is the val initialized after the loop? Kotlin can't predict!)

• fold()/reduce() on collections is fun and powerful

• When I go back to coding Go, I miss two things: if/when as expressions, and the always-on string templates.

• ?.let() is very very cool, but it's also incredible poorly named.

• Every GitSavvy doc assumes you're already good at Git. Here's the workflow for non-Git folks:

  • ctrl-shift-P
  • "git: quick stage"
  • go to each file you want to commit and hit enter
  • after you've selected them all, go to "git: quick commit" and hit enter
  • type in a good commit message
  • ctrl-shift-P and "git: push" to push to Github

• The Advent of Code challenges themselves were great. For the most part I was able to complete each day in an hour or so, with a few exceptions:

  • Day 5: my code for part 2 passed with the example in the question, but not the full input. I rewrote it a couple days later and that worked.
  • Day 20 stumped me for a lonnnnggggg time. Finally I looked at reddit.com/r/adventofcode and I realized that (spoiler alert) my code wasn't taking into account that a value of 0 turned pixels on.
  • Day 24 I couldn't do with code. So I did it with some hard thinking and a spreadsheet