The Box Smart Pointer in Rust

The ultimate Rust lang tutorial. Follow along as we go through the Rust lang book chapter by chapter.

Chapters:
0:00​ Intro
0:29 Pointers, References, and Smart Pointers
2:38 Using a Box to Store Data
4:43 Enabling Recursive Types with Boxes
11:53 Outro

#letsgetrusty​​ #rust​lang​ #tutorial

[long-live-linux]

The following code works:

#[derive(Debug)]
enum List<'a> {
Cons(i32, &'a List<'a>),
Nil,
}

use List::{Cons, Nil};

fn main() {
let list = Cons(1, &Cons(2, &Cons(3, &Nil)));
println!("{:?}", list);
}

$ cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.01s
Running `target/debug/rust-demo`
Cons(1, Cons(2, Cons(3, Nil)))

So I think using cons list as an example is inappropriate to show what Box can do, but regular reference cannot do.

[brianteague]

Congrats! You are half way through the tutorial series! Keep up the momentum!
Thanks for the great videos bogdan!

[thingsiplay]

You do a great job in explaining these things. Thank you for the videos.

[GolangDojo]

Golang beginners - Pointers are so hard to understand
Rusty Bogdan - Regular pointers aren't cool enough

[dazealex]

Didn't even want to learn Rust... But, the presentation and bite sized nature is easily digestable!

[高主任-gj]

A very clear explanation and a good example. Thanks for the video!

[jonxslays]

i have gotten a lot out of your videos thanks dude!!

[babajagaisyou]

I know that you are calling this a "cons list" but this is just an old school linked list. Cons might be from lisp, but linked lists are language agnostic

[EbonySeraphim]

Seems like you could also get away with using Option<List> right? Is Option<T> a smart pointer type as well since it can be None?

EDIT: Nope. Option<T> needs to know the size of T

[sakuranooka]

Why we need the use statement at 6:43? Assuming an enum is like a type, what does it mean "to bring a type into scope", and why isn't it already in scope right after being defined?

[Michael-enub]

Interesting! But now I'm wondering: could a & reference be used instead of Box? What are the upsides to using Box in this example?

[Comdevsunion]

Learning and enjoying your videos 👍 I think none would be the proper syntax here. No nils in Rust

[reinismu]

Awesome! Keep it up! Hope you will soon switch to 2 videos per week :)

[tandex]

more usefull use of Box is using traits, when you just store object as trait

[alagaika]

Doesn't an enum need additional memory to specify which of the variants is actually stored?

[xad]

I really liked your explanations. I just have a question about the recursive list structure. You mentioned at the end of the video that line 9 is not very readable. It got me thinking if there would be any other nicer way of making it more readable but using the same recursive data structure approach. Do you have any idea in mind? keep rolling the videos!! :)

[Nico-rlbo]

7:20 getting flashbacks from functional programming pls put a trigger waring there xd

[redcrafterlppa]

O wow I just realized that a rust enum is basically a union

[DaviAreias]

I found this part of the book confusing :(, in the book it doesn't show that rust knows list is of type List, but in your VScode we can see the type, but it's not clear how it was able to infer the type. Why it doesn't treat list as "Cons" for example?

[XFajk]

Isnt that just a link list and if not what is the difference 🤨