Vec index operator documentation


It seems I don’t know how to read Rust’s documentation. I tried to write code like this:

let v = vec![String::from("one"), String::from("two")];
let first = v[0];

This doesn’t compile because let first = v[0] tries to move the String out of v. So I was looking at the Vec documentation but all I can find is a mention of the Index trait, which has this method:

fn index(&self, index: Idx) -> &Self::Output

So it returns a reference. But what is it that’s being referenced here and how can this possibly result in an attempt move anything?

I know that I can access the Vec element as &v[0] to avoid a move. But why do I have to do that given what the documentation says?


&v[0] is syntax sugar for v.index(0) and v[0] is syntax sugar for *v.index(0).

It’s just how it’s defined, there isn’t much more to it.


Ah I see, so this is a language thing and that’s why it’s not in the library docs. It makes sense because if it was actually a reference it would be inconsistent with how array indexing works.

Thanks for that!


The reason they did it like this is because every other language does the same, for example in C, writing arr[i] on an int array returns an int, not a pointer to an int.

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