AoC standard library · beginners

I'm interested to know what utility functions people commonly use when writing advent of code solutions (or anything else). I'm thinking along the lines of simple things which are somewhat general-purpose rather than very specific to the kind of puzzles you get. Mine are:

List sumBy

three = [[1, 2], [3]] |> sumBy List.len

This one feels quite intuitive to use. On the other hand, it's not much more concise than map + sum. I learnt FSharp for a while before Roc, so I became use to these 'map+' functions (see also sortBy). As I understand it the performance reasons for wanting this kind of function may be negated by future language features like iterators?

Dict upsert

upsert dict key 1 (\value -> value + 1)

The alternative seems quite verbose:

Dict.update dict key \current ->
    when current is
        Ok value -> Ok (value + 1)
        Err Missing -> Ok 1

String bisect

string = "Button A: X+94, Y+34"
(_, xyStr) = try bisect string ": "
(xStr, yStr) = try bisect xyStr ", "

This seems quite powerful for writing an off-the-cuff parser without nested pattern matching, in combination with Str.dropPrefix and other things.

Brendan Hansknecht (Dec 13 2024 at 18:21):

bisect is just a single split?

Brendan Hansknecht (Dec 13 2024 at 18:21):

Also, upsert sounds like something we should add...I wonder if there is a better name.

Alex Nuttall (Dec 13 2024 at 18:27):

Brendan Hansknecht said:

bisect is just a single split?

Yes, I originally called it splitTwo:

splitTwo : Str, Str -> Result (Str, Str) [CouldNotSpli]
splitTwo = \str, on ->
    when Str.splitOn str on is
        [a, b] -> Ok (a, b)
        _ -> Err CouldNotSplit