Stream: roctoberfest

Topic: 2023 day 3

Fabian Schmalzried (Oct 03 2023 at 17:25):

It definetly needs more cleanup: https://gist.github.com/FabHof/d65eab72dceca521642e90f8e5dd5ad7
But I did find a bug with dbg: https://github.com/roc-lang/roc/issues/5883

Elias Mulhall (Oct 03 2023 at 18:39):

https://github.com/mulias/roctoberfest/blob/main/advent_2022/day_03/main.roc

• I think List.partition : List a, Nat -> List (List a) would be a reasonable addition to the builtins, it's something that comes up frequently, at least in AoC, and I couldn't find it.
• List.sum tripped me up, I waned to sum up a list of U8s into an U64 but got a type error. I ended up doing priorities |> List.map Num.intCast |> List.sum.
• Used the official release of roc-parser, works like :butter:

Isaac Van Doren (Oct 04 2023 at 01:28):

Yes, partition would be great

Brendan Hansknecht (Oct 04 2023 at 01:59):

What is partition in this case? Like what does the function do?

Isaac Van Doren (Oct 04 2023 at 02:01):

What I would expect is that it would break the input list into chunks of size n. With the last chunk potentially containing less than n elements.

Elias Mulhall (Oct 04 2023 at 02:03):

Here's what I did

partition : List a, Nat -> List (List a)
partition = \lst, idx ->
    { before, others } = List.split lst idx
    if List.isEmpty others then
        [before]
    else
        List.prepend (partition others idx) before

expect partition [1, 2, 3, 4, 5, 6, 7, 8] 3 == [[1, 2, 3], [4, 5, 6], [7, 8]]

Brendan Hansknecht (Oct 04 2023 at 02:03):

Ah, that form of partition.

Brendan Hansknecht (Oct 04 2023 at 02:04):

I wonder if there is a better name for it.

Elias Mulhall (Oct 04 2023 at 02:04):

Yes, not sorting partition. Uhhhh, chunk?

Isaac Van Doren (Oct 04 2023 at 02:05):

Or possibly chunksOf

Isaac Van Doren (Oct 04 2023 at 02:06):

Personally partition is what I would think of first if I was searching for it

Elias Mulhall (Oct 04 2023 at 02:08):

I think Brendan is right that partition is overloaded, since partitioning in half/around a pivot point is a common operation in sorting.

Anton (Oct 04 2023 at 09:39):

In the haskell split package this is called chunksOf, that seems like a great name.

Anton (Oct 04 2023 at 09:45):

List.sum tripped me up, I waned to sum up a list of U8s into an U64 but got a type error.

I think making that work could be very complicated

Elias Mulhall (Oct 04 2023 at 16:04):

Anton said:

I think making that work could be very complicated

sure sure. It wasn't a particularly constructive comment, mostly that I'm not used to a functional language caring so much about number encodings.

Brendan Hansknecht (Oct 04 2023 at 23:37):

I think we should look at adding automatic upcasting. If integer and the same sign with more bits, just automatically convert. This could be done automatically during the underlying list walk that sum should be calling. That will also be more performance than making the entire list first

Anton (Oct 06 2023 at 08:59):

Interesting!

Last updated: Jul 26 2025 at 12:14 UTC