updating_variables.md

Updating Variables

By default, variables cannot change their values. For example:

let n = 1;
n = 2;

We will get a compiler error when we run cargo build with the code.

error[E0384]: cannot assign twice to immutable variable `n`
 --> src/main.rs:3:5
  |
2 |     let n = 1;
  |         -
  |         |
  |         first assignment to `n`
  |         help: consider making this binding mutable: `mut n`
3 |     n = 2;
  |     ^^^^^ cannot assign twice to immutable variable

To overwrite the value of a variable, we can use mut in the following way.

let mut n = 1;
println!("{}", n);
n = 2;
println!("{}", n);

mut allows a variable to update its value. We can see from the output that the value of n changes.

Output:

1
2

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