Stream: advent of code

Topic: Day 3

Luke Boswell (Dec 03 2022 at 06:36):

My day 3 solution. :big_smile:

Notification Bot (Dec 03 2022 at 06:42):

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Notification Bot (Dec 03 2022 at 06:43):

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Shritesh Bhattarai (Dec 03 2022 at 07:09):

Here's my Day 3 . I'm happy with the solution but I found myself wishing Roc had these 3 2 things:

• List.chunks to chunk a list into sub lists of a specified length
• List.reduce that uses the first element of the list as the initial state
• Some way of doing "char to int" Looking at @Luke Boswell 's solution, turns out "scalar arithmetic" works as expected. updated my solution

Andy Kluger (Dec 03 2022 at 07:34):

Another Day 3 solution. I know there's a way to do some nifty destructuring on the way from lists to function parameters...

JesterXL (Dec 03 2022 at 14:54):

Dude, I am learning waayyyyy more than I ever thought possible about basic adding/subtraction against various number types. I thought I was all ballin' when I understood the difference between / and // in Elm, but this U8 vs. U32 insanity is breaking my brain. I didn't realize math with these various number types was so dangerous.

JesterXL (Dec 03 2022 at 15:01):

Case in point "List.sum blows up" because U8 maxes at 256... like... man am I spoiled rotten in other languages.

Tommy Graves (Dec 03 2022 at 15:39):

Here's my day 3. I didn't know anything about scalar arithmetic so I went with a much dumber approach :rolling_on_the_floor_laughing:.

I was really surprised that Str.split "abc" "" returns ["abc"] and not ["a", "b", "c"]. I understand the reasoning, but I wish the compiler could blow up if you do Str.split with an empty separator. I'm not familiar with other languages that have the same behavior as Roc, but plenty (JS, Ruby, Rust) split the string into individual characters.

Brendan Hansknecht (Dec 03 2022 at 16:39):

That's an interesting note on Str.split. i guess we just have a few other methods that theoretically are for that. Like Str.toUtf8 or one of the methods that walks the code points/graphemes, but yeah...less clear

Ghislain (Dec 03 2022 at 17:26):

My solution

Srinivas Rao-Mouw (Dec 03 2022 at 17:54):

My solution!

Srinivas Rao-Mouw (Dec 03 2022 at 17:58):

ooh I love your recursive grouping strategy @Luke Boswell

Ayaz Hafiz (Dec 03 2022 at 18:16):

my day 3 - definitely looking forward to hash-based set/dict :nerd:

Luke Boswell (Dec 03 2022 at 18:58):

@Ayaz Hafiz the way you formatted that ifwas neat. I wonder if we could support that without braces for smaller use cases like this?

(if item >= 'a'
then item - 'a' + 1
else item - 'A' + 27)
|> Num.toU64

Richard Feldman (Dec 03 2022 at 19:01):

I actually want to support Num.toU64 if item >= 'a' then ... like CoffeeScript does!

Ayaz Hafiz (Dec 03 2022 at 19:04):

it might work without braces or richards way, i just didn’t try it

Sebastian Porto (Dec 03 2022 at 22:24):

Oh, I can do 'E' - 'A', that is pretty cool

JesterXL (Dec 03 2022 at 22:25):

My Day 3 (shrink took wayyy too long)

JesterXL (Dec 03 2022 at 22:25):

BTW, I left in all the compiler bugs in separate files in case you're interested in duplication compiler issues.

Last updated: Jul 26 2025 at 12:14 UTC