Rust

4.6    Mutable and Immutable Binding of References

The references we’ve created so far have been immutable. For instance, consider the code shown in Listing 4.29.

fn main() {    let mut vec_1 = vec![1, 2, 3];    let mut vec_2 = vec![4, 5, 6];    let reference = &vec_1;    reference = &vec_2; // Error}  

Listing 4.29     Immutable Binding of a Reference

In this case, the variable reference itself is immutable, and we cannot update it to point to some other vector. Updating the reference to point to vec_2, therefore, throws an error. This error arises because we have an immutable binding of an immutable reference. To enable mutation of a reference itself, you can make the reference mutable, as shown in Listing 4.30.

fn main() {    let mut vec_1 = vec![1, 2,