Request: Use pest instead of nom in one of your videos

[egeland]

Hi,

First, thanks for doing the video series, I'm learning a lot!

When I started doing it (before I found your series), I knew I needed a parser, so did some Googling, and it seems that nom and pest are two of the more popular crates.

You have been doing a lot of nom, so I was wondering if you'd be willing to have a go with pest?

Cheers!

[ChristopherBiscardi]

could do that. Might be better to pick a day with some interesting parsing and put a few different crates on display in a separate video. winnow, chumsky, combine, etc all come to mind too.

[egeland]

Thanks for your reply! 😁
winnow looks like a nice successor to nom. I'm still very much a rust n00b, and am struggling with pest - the .pest files are easy, nice and clear, and there's a cool playground to get them correct in, but I don't really understand how to bring the parsed result into the program.. 🤔
I found from-pest, which (in theory) should make it easier to do so, but the example I found doesn't work for me... 😞

Do you know of any parsers with the PEG syntax in a separate file, like pest, but clearer how to use the results..? Or if you can show how to do some AoC parsing in pest, that would really help..
I've basically been spinning my wheels, reading pest stuff and getting more confused.. maybe winnow or nom would be better for me...

[ChristopherBiscardi]

I haven't made the video yet, but I've been working on building up parsing examples in the day-02-parsing crate: https://github.com/ChristopherBiscardi/advent-of-code/tree/2d5c19735e147c2df1ce1efc62d8f74147fba268/2023/rust/day-02-parsing

I did write a Pest example (and I have more to do in the crate). The playground was awesome but as you discovered, bringing it into a program to use feels like its a rough experience.

from-pest doesn't seem to be "ready" yet and the code I had to write to convert between pest Pairs and my own Rust structs was not fun to write for a variety of reasons. I think Pest is probably better used without converting from tokens to an AST but the behavior of needing to check every vec of Pair s for any possible Rule means that a lot of type safety that I enjoy is out the window. I'll cover it more when I get to the video, but in general Pest is not a style of approach I enjoyed writing.

I definitely prefer nom still after the current iteration (I don't enjoy the mutability approach in winnow 0.5 either) but there's still more to do!