Trait generic_array::ArrayLength

source ·

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

Expand description

Trait used to define the number of elements in a GenericArray.

ArrayLength is a superset of typenum::Unsigned.

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.

Required Associated Types§

source

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 {}