Crate array_init

The array-init crate allows you to initialize arrays with an initializer closure that will be called once for each element until the array is filled.

This way you do not need to default-fill an array before running initializers. Rust currently only lets you either specify all initializers at once, individually ([a(), b(), c(), ...]), or specify one initializer for a Copy type ([a(); N]), which will be called once with the result copied over.

Care is taken not to leak memory shall the initialization fail.

Examples:

// Initialize an array of length 50 containing
// successive squares

let arr: [u32; 50] = array_init::array_init(|i: usize| (i * i) as u32);

// Initialize an array from an iterator
// producing an array of [1,2,3,4] repeated

let four = [1,2,3,4];
let mut iter = four.iter().copied().cycle();
let arr: [u32; 50] = array_init::from_iter(iter).unwrap();

// Closures can also mutate state. We guarantee that they will be called
// in order from lower to higher indices.

let mut last = 1u64;
let mut secondlast = 0;
let fibonacci: [u64; 50] = array_init::array_init(|_| {
    let this = last + secondlast;
    secondlast = last;
    last = this;
    this
});

Functions

array_init

Initialize an array given an initializer expression.

from_iter

Initialize an array given an iterator

from_iter_reversed

Initialize an array in reverse given an iterator

map_array_init

Initialize an array given a source array and a mapping expression. The size of the source array is the same as the size of the returned array.

try_array_init

Initialize an array given an initializer expression that may fail.