Stream: roctoberfest

Topic: Questions

jan kili (Sep 30 2022 at 11:58):

Welcome!

What are you personally curious about in Roctoberfest? Do you expect to make time for multiple/regular sessions? Did you already do Advent of Code 2021?

What questions do you have for the Roc veterans here?

Georges Boris (Sep 30 2022 at 13:33):

Hello!

First time doing advent of code :sweat_smile: and I'd love to maybe stream some sessions trying to tackle it using Roc.

Anton (Sep 30 2022 at 13:41):

I could see streaming definitely being valuable, particularly to help us find all friction points.

Brendan Hansknecht (Sep 30 2022 at 14:16):

I did a few of them in BQN....but i think the solutions will be different enough that it is no big deal. Will be interesting to try this in Roc.

Brendan Hansknecht (Sep 30 2022 at 14:20):

One question: is the plan to collect feedback via threads in this topic?

Shritesh Bhattarai (Oct 02 2022 at 22:48):

I had to ln -s c++/* . inside /opt/homebrew/opt/llvm@13/lib to make it work

Sebastian Porto (Oct 02 2022 at 22:48):

Hi, tried to install roc
I'm on MacOS 11, Intel
Getting

Referenced from: /Users/Sebastian/Downloads/roc_nightly-macos_x86_64-2022-10-01-2b91154/./roc (which was built for Mac OS X 12.0)
Expected in: /usr/lib/libc++.1.dylib
I can't upgrade to 12, because my laptop is too old
So it seems a build for MacOS 11 would be great to have

Richard Feldman (Oct 02 2022 at 22:52):

ah, I was gonna say I could make you an 11 build, but my macOS Intel laptop is on 12 already :confounded:

Sebastian Porto (Oct 02 2022 at 22:54):

maybe there could be one of these for macos 11 https://github.com/roc-lang/roc/blob/main/.github/workflows/nightly_macos_x86_64.yml?

Sebastian Porto (Oct 02 2022 at 22:55):

I suspect this will be a common issue - people stuck in Macos 11

Richard Feldman (Oct 02 2022 at 22:56):

:thinking: if we did it for macOS 11 only, would that binary Just Work on 12?

Richard Feldman (Oct 02 2022 at 22:56):

or would two different binaries be necessary

Gabriel Pickl (Oct 02 2022 at 23:12):

because I just ran into this: how would I combine Effects which might fail with pure functions which return Result?
Specifically, I'm reading a line and want to convert the line to a Nat, which might fail. Is there a nicer way than matching the result and returning Task.succeed and Task.fail?
Also, is there a way to detect when Stdin.line is done with the input? I would try and check for EOF, but since I'm "stuck" on the first question and already here I though I might ask this as well.
The question are specific to the cli-plaform i guess?

Brendan Hansknecht (Oct 02 2022 at 23:24):

Is there a nicer way than matching the result and returning Task.succeed and Task.fail?

I think some variant of the task module had Task.fromResult, but I don't think it is in the cli platform variant. Should be easy enough to write the function once and use it multiple times.

Brendan Hansknecht (Oct 02 2022 at 23:28):

Should be doable with a when clause. Something like:

line <- Stdin.line |> Task.await
when Str.toI64 line is
    Ok num -> Task.succeed num
    Err _ -> Task.fail SomeErr

Brendan Hansknecht (Oct 02 2022 at 23:30):

is there a way to detect when Stdin.line is done with the input?

Looks like the platform isn't setup for this yet. I am pretty sure it will panic if Stdin runs out of data. That is probably something we need to fix. Make it return a Result Str of some sort. That is probably a good advent of code related issue to fix.

Gabriel Pickl (Oct 02 2022 at 23:33):

that's basically what i did. i might extract my own fromResult i guess.
I think I found a... bug in the roc typechecker?
I'm basically doing a recursive task function (simplified):

myTask : Task Nat <the error type> <the effects type>
myTask =
    nextValue <- await readNat
    if <some condition> then
        myTask
    else
        Task.succeed <return value>

Running roc check on this file hangs. maybe indefinitely, maybe for a long time.
I know there's Task.loop which does exactly this looping, and that might work, but it seems that this should not be unresolvable

Brendan Hansknecht (Oct 02 2022 at 23:37):

Can you post an issue to github with your roc code? Would be good for a repro.

Brendan Hansknecht (Oct 02 2022 at 23:38):

Maybe we have a issue with using a task in a recursive way....not sure.

Gabriel Pickl (Oct 02 2022 at 23:44):

hmm... I created a minimal example to post to github, and now I'm getting a compiler panic saying that something's not implemented for InvalidCycle, which seems more intentional. Now I'm wondering if that's a different problem than the hang...

Gabriel Pickl (Oct 02 2022 at 23:48):

nevermind, it just doesn't always hang O.o

Gabriel Pickl (Oct 02 2022 at 23:52):

issue

jan kili (Oct 03 2022 at 05:04):

What am I doing wrong? I solved day 1 but got stuck in refactoring it for tidiness. I've removed all of my parsing and calculating and it's still angry:

app "1a"
    packages { pf: "../roc/examples/interactive/cli-platform/main.roc" }
    imports [
        pf.File,
        pf.Path,
        pf.Program.{ Program },
        pf.Stdout,
        pf.Task,
    ]
    provides [main] to pf

main =
    Task.attempt solve exit
    |> Program.noArgs

solve =
    read =
        "1a_input.txt"
        |> Path.fromStr
        |> File.readUtf8
    input <- Task.await read
    input
    |> Stdout.line

exit = \result ->
    code = when result is
        Ok _ -> 0
        Err _ -> 1
    Task.succeed {}
    |> Program.exit code

[jan@framey roctoberfest]$ export RUST_BACKTRACE=1 && roc dev 1a.roc
roc: /lib64/libtinfo.so.6: no version information available (required by roc)
🔨 Rebuilding platform...
thread 'main' panicked at 'not yet implemented: Report a file open error', src/lib.rs:247:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
fatal runtime error: failed to initiate panic, error 5
Aborted (core dumped)
[jan@framey roctoberfest]$

Ghislain (Oct 03 2022 at 08:42):

Are you sure to have a file named 1a_input.txt?

Anton (Oct 03 2022 at 10:06):

I'll try out making macos 11(x86_64) nightlies.

Anton (Oct 03 2022 at 10:08):

We should probably make a separate topic for every question, zulip works best that way :)

jan kili (Oct 03 2022 at 12:56):

@Ghislain ! I forgot to change my file name from _data... :face_palm:

Brian Carroll (Oct 03 2022 at 20:24):

We should have better behaviour than this for a missing file though!

Johannes (Oct 05 2022 at 09:31):

Sorry for being dumb/blind, where do I find the tasks of each day? :grinning_face_with_smiling_eyes:

Anton (Oct 05 2022 at 09:37):

There are no dumb questions here :) It was easy to miss, here you go: https://adventofcode.com/2021

Johannes (Oct 05 2022 at 09:38):

@Anton thanks, mate! :big_smile:

Last updated: Jul 26 2025 at 12:14 UTC