Trait ArrayLength 

pub unsafe trait ArrayLength: Unsigned + 'static {
    type ArrayType<T>: Sealed;
}

ArrayLength is a type-level Unsigned integer used to define the number of elements in a GenericArray.

Consider N: ArrayLength to be equivalent to const N: usize

fn foo<N: ArrayLength>(arr: GenericArray<i32, N>) -> i32 {
    arr.iter().sum()
}

is equivalent to:

fn foo<const N: usize>(arr: [i32; N]) -> i32 {
    arr.iter().sum()
}

Safety

This trait is effectively sealed due to only being allowed on Unsigned types, and therefore cannot be implemented in user code.

Furthermore, this is limited to lengths less than or equal to usize::MAX.

type Empty = core::convert::Infallible; // Uninhabited ZST, size_of::<Empty>() == 0

// 2^64, greater than usize::MAX on 64-bit systems
type TooBig = typenum::operator_aliases::Shleft<typenum::U1, typenum::U64>;

// Compile Error due to ArrayLength not implemented for TooBig
let _ = GenericArray::<Empty, TooBig>::from_slice(&[]);

Required Associated Types

type ArrayType<T>: Sealed

Associated type representing the underlying contiguous memory that constitutes an array with the given number of elements.

This is an implementation detail, but is required to be public in cases where certain attributes of the inner type of GenericArray cannot be proven, such as Copy bounds.

Copy example:

struct MyType<N: ArrayLength> {
    data: GenericArray<f32, N>,
}

impl<N: ArrayLength> Clone for MyType<N> where N::ArrayType<f32>: Copy {
    fn clone(&self) -> Self { MyType { ..*self } }
}

impl<N: ArrayLength> Copy for MyType<N> where N::ArrayType<f32>: Copy {}

Alternatively, using the entire GenericArray<f32, N> type as the bounds works:

where GenericArray<f32, N>: Copy

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl ArrayLength for UTerm

impl<N: ArrayLength> ArrayLength for UInt<N, B0>

where Self: IsWithinUsizeBound,

impl<N: ArrayLength> ArrayLength for UInt<N, B1>

where Self: IsWithinUsizeBound,

Implementors