Hacker News Reader

There is also &mut str. The nice thing about Rust is that the same memory area can be used as a "StringBuilder" with &mut str, and then as a "String" with &str. Once you have a &str reference, Rust statically guarantees that no one else cam mutate it.

View on HN

You can't really do anything useful with a `&mut str`. For example, you can't change the length of the string or any characters in the string (without unsafe code). The latter is perhaps surprising, but it's because strings in Rust are always UTF-8, so changing a logical character could imply changing the length of the string, and changing a byte could result in invalid UTF-8.

You're right, but just to add a bit more to this, you can call make_ascii_lowercase and make_ascii_uppercase on &mut str, which can sometimes be useful.

Yeah the type is really just str but I didn’t want to get into it. &mut str is kinda weird.

Reply on news.ycombinator.com