Variable value not moved

Question

Given the code below:

let x = 5;
let y = x;
println!("{}", x);

As far as I have been reading, I learned that the above code would end up in error as the value of x has been moved to y. But it doesn't work that way. I have tried the above code with integers and strings, it just works.

type that implement copy are not moved but copied. play.rust-lang.org/… <= "I have tried the above code with integers and strings" press X to doubt — Stargateur
– Stargateur, Commented Nov 27, 2019 at 0:07
Does this answer your question? How does Rust provide move semantics? — Stargateur
– Stargateur, Commented Nov 27, 2019 at 0:08
@Stargateur, thanks for the speedy response, I tried let x = "hello" , the code worked and as you mentioned on your comment when I tried let x = String::new("Hello") it didn't. I guess i am getting whats wrong here. When it is let x = "hello", it is a str which will be in allocated memory and it has copy trait implemented, is that right? — Sumchans
– Sumchans, Commented Nov 27, 2019 at 0:55
"hello" is a &'static str it not allocated in the "heap" but directly "somewhere" depend on your OS etc. Anyway, reference implement copy so yes this work with reference. &str != String == View != Object doc.rust-lang.org/book/ch08-02-strings.html#what-is-a-string — Stargateur
– Stargateur, Commented Nov 27, 2019 at 1:35

apatniv · Accepted Answer · 2019-11-27 01:21:20Z

2

Primitives types by default implement Copy trait. So, in this case, value of x is copied into y. Try doing the same thing with anything that doesn't implement copy trait like String, you will encounter a compile time error. It is inefficient to create a copy every time you assign a variable to another variable. However, certain things can be trivially copied.

answered Nov 27, 2019 at 1:21

apatniv

1,87613 silver badges15 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Sumchans Over a year ago

Okay thanks, Where to find the documentation for that, like I want to know what traits are included with what types?

apatniv Over a year ago

See look at this documentation. This may be meaty but take some time to go through the documentation. It will clarify some of the stuff doc.rust-lang.org/std/marker/trait.Copy.html

Sumchans Over a year ago

have been looking into it. Just got confused with a few stuff. I guess I am getting it. Thanks again.

Collectives™ on Stack Overflow

Variable value not moved

1 Answer 1

3 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Linked

Related