✔ advent of code sample · beginners

Stream: beginners

Topic: ✔ advent of code sample

drew (Oct 19 2024 at 18:34):

Hey folks, I put together a quick skeleton for advent of code here https://github.com/drewolson/aoc-roc, a few questions

drew (Oct 19 2024 at 18:35):

i didn't expect to need this line https://github.com/drewolson/aoc-roc/blob/635f62f26928ea4b2c1c32f83bb633ef030e032a/main.roc#L72. my understanding is that i should be able to handle my custom errors and let everything else flow to the top of the program

drew (Oct 19 2024 at 18:36):

when i open https://github.com/drewolson/aoc-roc/blob/main/Aoc/Year2023/Day09.roc in my editor (nvim), the LSP crashes with the following error:

[ERROR][2024-10-19 13:35:51] .../lean/stderr.lua:74 "rpc" "/Users/drew/.local/bin/roc_language_server" "stderr" "An internal compiler expectation was broken.\nThis is definitely a compiler bug.\nPlease file an issue here: < https://github.com/roc-lang/roc/issues/new/choose>\nOutstanding references to the derived module\nLocation: crates/compiler/load_internal/src/file.rs:3299:29\n"

drew (Oct 19 2024 at 18:36):

let me know if i should actually file a bug for this

drew (Oct 19 2024 at 18:38):

i get the same error when i open https://github.com/drewolson/aoc-roc/blob/main/Aoc/Args.roc, which just consists of type synonyms

drew (Oct 19 2024 at 18:38):

and final question 3. is there a library for arbitrary sized ints in roc?

drew (Oct 19 2024 at 18:40):

One more observation -- i find it interesting that record builders are basically syntax sugar for applicatives using <-, but that roc plans to deprecate backpassing, which is sugar for monads (among other things) using <-

drew (Oct 19 2024 at 18:40):

this is the farthest i've gotten in writing a reasonably sized skeleton for aoc without hitting major compiler bugs, so that's awesome!

Brendan Hansknecht (Oct 19 2024 at 19:13):

For 1

On line 65, you call Stdout.line! e. That puts StdoutErr as one of the possible error outputs. When mapping the errors, you have to map all possible errors. That includes the error produced there.

drew (Oct 19 2024 at 20:55):

Weirdly, though, a catch all doesn't work

drew (Oct 19 2024 at 20:55):

meaning if i instead have e -> e i get a compiler error

drew (Oct 19 2024 at 20:56):

actually, i guess i get a compiler bug :smile:

drew (Oct 19 2024 at 20:56):

$ roc run
thread 'main' panicked at crates/compiler/mono/src/borrow.rs:396:34:
internal error: entered unreachable code:
        No borrow signature for LambdaName { name: `16.IdentId(42)`, niche: Niche(Captures([InLayout(25), InLayout(44)])) } layout.

        Tip 1: This can happen when you call a function with less arguments than it expects.
        Like `Arg.list!` instead of `Arg.list! {}`.
        Tip 2: `roc check yourfile.roc` can sometimes give you a helpful error.

note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

drew (Oct 19 2024 at 20:58):

roc check main.roc seems to think that i'm not narrowing the type at all https://gist.github.com/drewolson/c126c3a1981bcb15318dce6f95060d57

drew (Oct 19 2024 at 20:59):

with the e -> e arm rather than StdoutErr e -> StdoutErr e

drew (Oct 19 2024 at 21:00):

oh, and i reproduced the LSP error like this

drew (Oct 19 2024 at 21:01):

$ roc check Aoc/Args.roc
An internal compiler expectation was broken.
This is definitely a compiler bug.
Please file an issue here: <https://github.com/roc-lang/roc/issues/new/choose>
Outstanding references to the derived module
Location: crates/compiler/load_internal/src/file.rs:3299:29

Brendan Hansknecht (Oct 19 2024 at 21:25):

Yeah, e -> e does not narrow the type in roc.

Brendan Hansknecht (Oct 19 2024 at 21:25):

That would be a form of gradual typing, which roc does not have

Brendan Hansknecht (Oct 19 2024 at 21:30):

when err is
    BadDayPart day part -> Exit 1 "Invalid day and part: $(Inspect.toStr day), $(Inspect.toStr part)"
    BadInput path -> Exit 1 "Invalid input file: $(path)"
    BadYear year -> Exit 1 "Invalid year: $(Inspect.toStr year)"
    e -> e

Type of err is [BadDayPart U8 U8, BadInput Str, BadYear U16, StdoutErr [...]]*

Type of the first three branches is [Exit U8 Str]*
Type of the final brach is the type of e. The type of e is the type of err. So the type of the final branch is [BadDayPart U8 U8, BadInput Str, BadYear U16, StdoutErr [...]]*

unifying the branches, we get:
[BadDayPart U8 U8, BadInput Str, BadYear U16, Exit U8 Str, StdoutErr [...]]*

Anton (Oct 21 2024 at 07:58):

let me know if i should actually file a bug for this

Yes please for 2.

Anton (Oct 21 2024 at 08:00):

is there a library for arbitrary sized ints in roc?

Not that I'm aware of, does I128 not fit your needs?

drew (Oct 21 2024 at 11:50):

Anton said:

is there a library for arbitrary sized ints in roc?

Not that I'm aware of, does I128 not fit your needs?

I128 may work, i’m just anticipating problems in advent of code designed to push towards very large ints

drew (Oct 21 2024 at 15:19):

Anton said:

let me know if i should actually file a bug for this

Yes please for 2.

For posterity, this is done https://github.com/roc-lang/roc/issues/7175. I see you've already labeled it :smile:

Notification Bot (Oct 21 2024 at 18:58):

drew has marked this topic as resolved.

Last updated: Jul 26 2025 at 12:14 UTC