types

primitives

type	size	description
bool	1 byte	true or false
uint8	1 byte	unsigned 8-bit integer
uint16	2 bytes	unsigned 16-bit integer
uint32	4 bytes	unsigned 32-bit integer
uint64	8 bytes	unsigned 64-bit integer
usize	based on CPU bits	unsigned integer
int8	1 byte	signed 8-bit integer
int16	2 bytes	signed 16-bit integer
int32	4 bytes	signed 32-bit integer
int64	8 bytes	signed 64-bit integer
isize	based on CPU bits	signed integer
float16	2 bytes	16-bit floating point number
float32	4 bytes	32-bit floating point number
float64	8 bytes	64-bit floating point number
str	—	utf-8 string

fixed arrays

fixed-size arrays are stack-allocated. the size must be known at compile time.

let a: [int32; 4] = [1, 2, 3, 4];

if the initializer has fewer elements than the declared size, the remaining elements are zero-initialized — but only if the type implements the Default trait. otherwise it is a compile error.

let a: [int32; 4] = [1]; // a[1], a[2], a[3] == 0
let a: [MyStruct; 4] = [s]; // compile error if MyStruct: !Default

dynamic arrays

dynamic arrays are heap-allocated. see stdlib/array for the full API.

let mut b: Array[int32] = [1, 2, 3];

generics

void uses [] for generic type parameters.

struct Pair[A, B] {
    first: A,
    second: B,
}

let p: Pair[str, int32] = Pair { first: "hello", second: 42 };

option and result

Option[T] = Some(T) | None
Result[T, E] = Ok(T) | Err(E)

see error handling for usage.