Exclusive References

Exclusive references, also known as mutable references, allow changing the value they refer to. They have type &mut T.

# // Copyright 2023 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
fn main() {
    let mut point = (1, 2);
    let x_coord = &mut point.0;
    *x_coord = 20;
    println!("point: {point:?}");
}

Key points:

• "Exclusive" means that only this reference can be used to access the value. No other references (shared or exclusive) can exist at the same time, and the referenced value cannot be accessed while the exclusive reference exists. Try making an &point.0 or changing point.0 while x_coord is alive.

• Be sure to note the difference between let mut x_coord: &i32 and let x_coord: &mut i32. The first one is a shared reference that can be bound to different values, while the second is an exclusive reference to a mutable value.