# Primitives

Rust provides access to a wide variety of `primitives`. A sample includes:

### Scalar Types

- signed integers: `i8`, `i16`, `i32`, `i64`, `i128` and `isize` (pointer size)
- unsigned integers: `u8`, `u16`, `u32`, `u64`, `u128` and `usize` (pointer size)
- floating point: `f32`, `f64`
- `char` Unicode scalar values like `'a'`, `'α'` and `'∞'` (4 bytes each)
- `bool` either `true` or `false`
- and the unit type `()`, whose only possible value is an empty tuple: `()`

Despite the value of a unit type being a tuple, it is not considered a compound type because it does not contain multiple values.

### Compound Types

- arrays like `[1, 2, 3]`
- tuples like `(1, true)`

Variables can always be type annotated. Numbers may additionally be annotated via a suffix or by default. Integers default to `i32` and floats to `f64`. Note that Rust can also infer types from context.

    fn main() {
        // Variables can be type annotated.
        let logical: bool = true;

        let a_float: f64 = 1.0;  // Regular annotation
        let an_integer   = 5i32; // Suffix annotation

        // Or a default will be used.
        let default_float   = 3.0; // `f64`
        let default_integer = 7;   // `i32`

        // A type can also be inferred from context
        let mut inferred_type = 12; // Type i64 is inferred from another line
        inferred_type = 4294967296i64;

        // A mutable variable's value can be changed.
        let mut mutable = 12; // Mutable `i32`
        mutable = 21;

        // Error! The type of a variable can't be changed.
        mutable = true;

        // Variables can be overwritten with shadowing.
        let mutable = true;
    }

### See also:

the `std` library, `mut`, inference, and shadowing