What could go wrong trying to solve AoC in Rust? : programmer

[–] m_f@midwest.social 46 points 2 years ago* (last edited 2 years ago) (2 children)

The collect's in the middle aren't necessary, neither is splitting by ": ". Here's a simpler version

fn main() {
    let text = "seeds: 79 14 55 13\nwhatever";
    let seeds: Vec&lt;_> = text
        .lines()
        .next()
        .unwrap()
        .split_whitespace()
        .skip(1)
        .map(|x| x.parse::().unwrap())
        .collect();
    println!("seeds: {:?}", seeds);
}

It is simpler to bang out a [int(num) for num in text.splitlines()[0].split(' ')[1:]] in Python, but that just shows the happy path with no error handling, and does a bunch of allocations that the Rust version doesn't. You can also get slightly fancier in the Rust version by collecting into a Result for more succinct error handling if you'd like.

EDIT: Here's also a version using anyhow for error handling, and the aforementioned Result collecting:

use anyhow::{anyhow, Result};

fn main() -> Result&lt;()> {
    let text = "seeds: 79 14 55 13\nwhatever";
    let seeds: Vec = text
        .lines()
        .next()
        .ok_or(anyhow!("No first line!"))?
        .split_whitespace()
        .skip(1)
        .map(str::parse)
        .collect::>()?;
    println!("seeds: {:?}", seeds);
    Ok(())
}

[–] MaliciousKebab@sh.itjust.works 6 points 2 years ago

Yeah I was trying to do something like reading the first line by getting an iterator and just looping through the other lines normally, since first line was kind of a special case but it got messy quick. I realized halfway that my collects were redundant but couldn't really simplify it. Thanks

[–] sukhmel@programming.dev 2 points 2 years ago* (last edited 2 years ago)

Also, anyhow::Context provides a convenient way to turn Option<T> and Result<T, Into<anyhow::Error>> into anyhow::Result<T>

Like this:

use anyhow::Context;

// to my understanding it's better to 
// specify the types when their names 
// are the same as in prelude to improve
// readability and reduce name clashing
fn main() -> anyhow::Result<()> {
    let text = "seeds: 79 14 55 13\nwhatever";
    let seeds: Vec<u32> = text
        .lines()
        .next()
        .context("No first line!")?     // This line has changed
        .split_whitespace()
        .skip(1)
        .map(str::parse)
        .collect::<Result<_, _>>()?;
    println!("seeds: {:?}", seeds);
    Ok(())
}

Edit: line breaks

[–] Schmeckinger@lemmy.world 18 points 2 years ago (1 children)

You can't really blame that on rust.

[–] MaliciousKebab@sh.itjust.works 0 points 2 years ago (1 children)

Yeah ngl it's very ugly. But hey as long as it works it's not stupid amirite?

[–] xlash123@sh.itjust.works 6 points 2 years ago

Rust borrows a lot of it's design from functional programming languages like Haskell, which has its good and bad. You could also choose to implement this behavior iteratively like typical C programs, but that tends to be ugly in other ways.

Personally, I've grown fond of the functional style. You see it in other places too, like the higher order functions in JavaScript. What's good about them in Rust is you still get amazing performance due to zero-cost abstraction. Trying to implement it yourself would likely be slower, so use them any chance you get.

[–] GeniusIsme@lemmy.world 2 points 2 years ago (1 children)

Show the alternative, I'll have a good laugh.

[–] janAkali@lemmy.one 2 points 2 years ago* (last edited 2 years ago) (1 children)

It's Nim, but I have no idea why you can't do this in Rust:

var seeds = lines[0].split(": ")[1].splitWhitespace().mapIt(it.parseInt)

Full solution: https://codeberg.org/Archargelod/aoc23-nim/src/branch/master/day_05/solution.nim

[–] GeniusIsme@lemmy.world 1 points 2 years ago

Ahh, it is the same thing. Rust example surely has some cruft, but mostly for the better. I'm sure not all of it is needed.

[+] chinstrap@lemmy.ml -8 points 2 years ago (1 children)

Java 2. World is full of wonders

[–] crispy_kilt@feddit.de 4 points 2 years ago (1 children)

Java 2 didn't have streams nor iterator combinatorics, not sure what you mean?

[–] chinstrap@lemmy.ml 4 points 2 years ago (1 children)

i didn't mean as a version. I meant as overuse of streams

[–] crispy_kilt@feddit.de 3 points 2 years ago (1 children)

How would you have preferred to solve it? Using for loops?

[–] AVincentInSpace@pawb.social 1 points 2 years ago* (last edited 2 years ago) (1 children)

Python style iterator comprehension

(wonder if someone has made that into a macro. if no one has I will)

[–] crispy_kilt@feddit.de 1 points 2 years ago (1 children)

I don't think it would be readable. Too much going on. You'd need an outer iter over lines, an inner over words, a check for number and a conversion. And there would be zero error handling.

[–] AVincentInSpace@pawb.social 2 points 2 years ago (1 children)

No less readable than half the Python comprehensions I've written.

zero error handling.

Not necessarily. The macro could look for a ? at the end of the final expression (the bit that comes first in a comprehension) and return a Result.

[–] crispy_kilt@feddit.de 2 points 2 years ago

Right, of course, I meant no error handling in the Python impl

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