A D vs. Rust example

[Stefan Hertenberger]

On Thursday, 20 October 2022 at 22:41:34 UTC, rassoc wrote:
> On 20/10/2022 15:37, Don Allen via Digitalmars-d wrote:
>> Rust has closures. Great. So here's an example of an attempt 
>> to do something along the lines described above with a single 
>> mutable variable:
>> 
>> ````
>> fn main() {
>>      let mut foo = 5;
>>      let mut bar = || {
>>          foo = 17;
>>      };
>>      let mut baz = || {
>>          foo = 42;
>>      };
>>      bar();
>>      println!("{}", &mut foo);
>>      baz();
>>      println!("{}", &mut foo);
>> 
>> }
>> ````
>
> To be honest, these kind of access patterns are smelly and 
> there almost always exists a more elegant alternative.
>
> Regarding that example code above, the burrow checker will be 
> happy if you reorder it slightly:
>
> ```rust
> fn main() {
>     let mut foo = 5;
>     let mut bar = || {
>         foo = 17;
>     };
>     bar();
>     println!("{}", &mut foo);
>         // just moved this down here
>     let mut baz = || {
>         foo = 42;
>     };
>     baz();
>     println!("{}", &mut foo);
> }
> ```

You don't need to reorder, just use references

```rust
fn main() {
     let mut foo = 5;
     let bar = |val: &mut i32| {
         *val = 17;
     };
     let baz = |val: &mut i32| {
         *val = 42;
     };
     bar(&mut foo);
     println!("{}", &mut foo);
     baz(&mut foo);
     println!("{}", &mut foo);

}
```