Variable mutability

Unlike many other languages, Rust defaults to non-mutability of variables. That means that variable bindings are actually constants if not explicitly defined as mutable. The compiler checks against all variable mutations and refuses to accept mutating non-mutable variable bindings.

Note

If you come from one of the C family of languages, a non-mutable can be considered to be roughly the same as a const type.

Creating a variable

To create a new variable binding in Rust, we use the following form:

let x = 1; 

This means that we create a new variable binding called x whose content will be 1. The default type for numbers depends on the situation a bit, but usually it's a 32-bit signed integer. If we need a variable that can change, we use this form:

let mut x = 1; 

By default, all variables in Rust are non-mutable; therefore, we have to explicitly define a variable as being mutable.

How can we tell the compiler that we want x to be an int?

Rust has a way of informing both the compiler...