Using Rust with Ruby, a Deep Dive with Yehuda Katz

If you don't want to invest in a two-hour long video:

TL;DR:

Rails has a library, `ActiveSupport`, which adds methods to Ruby core classes. One of those methods is `String#blank?`, which returns a boolean (sometimes I miss this convention in Rust, the `?`) if the whole string is whitespace or not. It looks like this: https://github.com/rails/rails/blob/b3eac823006eb6a346f88793...

It's pretty slow. So Discourse (which you may know from {users,internals}.rust-lang.org) uses the [`fast_blank`](https://rubygems.org/gems/fast_blank) gem, which provides this method via a C implementation instead. It looks like this: https://github.com/SamSaffron/fast_blank/blob/master/ext/fas...

For fun, Yehuda tried to re-write `fast_blank` in Rust. Which looks like this:

    extern crate libc;
    mod buf; // a small buffer struct + impl, not shown
    use buf::Buf;

    #[no_mangle]
    pub extern "C" fn tr_str_is_blank(b: Buf) -> bool {
        let s = b.as_slice().unwrap();

        s.chars().all(|c| c.is_whitespace())
    }

Turns out, this implementation ends up being faster than that C one, while also being significantly more straightforward. This video is a two-hour dive into why that is.