@divyaranjan1905 also suggested to add a set of exercises about closures in #2096. Capturing is one part of closures. So you are welcome to join forces and create a PR :D

I won't include async in these exercises since Rustlings doesn't teach async yet. I am waiting for the new async chapter to be included in the official Rust book to create a set of async exercises then. See #2040

Keep in mind that I won't merge the PR until I want to publish version 7. So I can review it now and automatically merge it later before the next major release.

I think there’s an open PR that adds a bit of closures to the functions lesson.

I feel like that is a good idea to get the student at least a little bit used to closures before going into more depth.

I think closures should be explained after traits and tests. This is in line with the Rust book as well.

I think closures should be explained after traits and tests. This is in line with the Rust book as well.

Indeed, as I proposed in the issue, it would replace the currently 18th set (iterators), so would be after traits and tests.

You are right, I forgot about this PR: #1748

I agree @junderw, that PR only shows the basics. After talking about traits, I would like to have 3 additional exercises where you need to write your own functions that take a closure, one with Fn, one with FnMut and one with FnOnce. What do you think?

After talking about traits, I would like to have 3 additional exercises where you need to write your own functions that take a closure, one with Fn, one with FnMut and one with FnOnce. What do you think?

Yep, @mo8it I think that'll be in line with the chapter from The Book. I'm considering to keep the number of exercises to 4, or at most 5.

I was actually thinking of going a bit more in-depth with closures.

Not too deep, but deep enough to give people a good overview of capturing, the Fn traits and how they're implemented automatically, and other things.

Since Closures are a pretty important part of many aspects of Rust, I think it warrants its own folder.

I have created a sample exercise to get started.

If you have a timeline for v7 I can try to find some time before then.

Thanks.

Actually @divyaranjan1905, @junderw , when I wrote that couple of exercises last year (#1748), I considered them a gentle introduction to closures.

I still think it's a good idea to have a taste of closures early in those chapters (functions and move_semantics), and definitely a very good thing to add a dedicated chapter later to build a deeper understanding (probably between traits and iterators).

@mo8it, I updated the PR #1748 to compile to the new rustlings standard, if you think it's valuable to merge.

I rebased and added a closures2.rs to the PR in #2099