firefox/third_party/rust/generic-array

generic-array

This crate implements generic array types for Rust.

Requires minumum Rust version of 1.36.0, or 1.41.0 for From<[T; N]> implementations

Documentation

Usage

The Rust arrays [T; N] are problematic in that they can't be used generically with respect to N, so for example this won't work:

struct Foo<N> {
	data: [i32; N]
}

generic-array defines a new trait ArrayLength<T> and a struct GenericArray<T, N: ArrayLength<T>>, which let the above be implemented as:

struct Foo<N: ArrayLength<i32>> {
	data: GenericArray<i32, N>
}

The ArrayLength<T> trait is implemented by default for unsigned integer types from typenum crate:

use generic_array::typenum::U5;

struct Foo<N: ArrayLength<i32>> {
    data: GenericArray<i32, N>
}

fn main() {
    let foo = Foo::<U5>{data: GenericArray::default()};
}

For example, GenericArray<T, U5> would work almost like [T; 5]:

use generic_array::typenum::U5;

struct Foo<T, N: ArrayLength<T>> {
    data: GenericArray<T, N>
}

fn main() {
    let foo = Foo::<i32, U5>{data: GenericArray::default()};
}

In version 0.1.1 an arr! macro was introduced, allowing for creation of arrays as shown below:

let array = arr![u32; 1, 2, 3];
assert_eq!(array[2], 3);