Rust provides strict control over mutable and immutable references to data. Rust's approach to mutability and immutability helps to prevent many common programming errors, such as null pointer references, race conditions, and other types of undefined behavior.
In Rust, a variable's mutability is determined by whether or not it was declared with the mut keyword. If a variable is declared with mut, it is mutable, meaning it can be changed. If it is not declared with mut, it is immutable, meaning it cannot be changed.
Here is an example of a mutable variable in Rust:
let mut x = 5;
x = 6; // This is allowed because x is mutable.And here is an example of an immutable variable in Rust:
let x = 5;
x = 6; // This is not allowed because x is immutable.Immutable variables are useful for ensuring that data remains constant and unchanging. They can help to prevent accidental modification of data and make programs easier to reason about. On the other hand, mutable variables can be useful for cases where data needs to be updated or changed.
In Rust, mutability is also closely tied to references to data. Rust uses a concept called borrowing to ensure that mutable and immutable references to data do not overlap in ways that could cause undefined behavior.
When a variable is borrowed as mutable, the borrowing function gains exclusive access to the data, meaning that no other function can access it until the mutable reference goes out of scope. Conversely, when a variable is borrowed as immutable, multiple functions can access the data at the same time, as long as they are not trying to modify it.