A D vs. Rust example

[victoroak]

On Thursday, 20 October 2022 at 13:37:07 UTC, Don Allen wrote:
>
> ````
> fn main() {
>     let mut foo = 5;
>     let mut bar = || {
>         foo = 17;
>     };
>     let mut baz = || {
>         foo = 42;
>     };
>     bar();
>     println!("{}", &mut foo);
>     baz();
>     println!("{}", &mut foo);
>
> }
> ````
>

I think the way it would be advised to write it in Rust would be 
something like this instead of using RefCell:
```
fn main() {
     struct State {
         foo: i32
     }

     impl State {
         fn bar(&mut self) {
             self.foo = 17;
         }

         fn baz(&mut self) {
             self.foo = 42;
         }
     }

     let mut state = State {
         foo: 0
     };

     state.bar();
     println!("{}", state.foo);
     state.baz();
     println!("{}", state.foo);
}
```
The problem is that both closures have a mutable reference to the 
same value and this is not allowed in Rust, you could solve this 
making the functions get a mutable reference to the variable but 
using a struct in this case is better IMO.