# Variables.

# Definition.

## Immutable.

Use the `let` keyword to start declaration. Types are specified after the variable name.

```rust
let x: i32 = 10;
```

Type definition is optional, so you can drop it. I suggest specifying the type for global/class/etc variables, but dropping it in local scope like functions.

```rust
let x = "This is &str"; // Type is detected automatically: &str.
```

## Mutable.

Add `mut` keyword after `let`.

```rust
let mut x: i32 = 10;
x = 12;
```

## Constants.

To declare constant, use the `const` keyword instead of `let`. Constant values always require type definition.

```rust
const NUMBER: i32 = 10;
```

# Shadowing.

You can redefine a variable with the same name but with a different type. This is useful if you cast something, but want to keep the same variable name. To do this, just declare the variable again.

```rust
let x: &str = "&str"; // &str.
let x: i32  = 10;     // i32.
```