Function init_array::init_boxed_slice

pub fn init_boxed_slice<T, F>(n: usize, f: F) -> Box<[T]> where
    F: FnMut(usize) -> T, 

Initialize a dynamically-sized heap-allocated slice.

This function takes in the length of the returned slice as well as a function, which can use the index in the array to compute the value for the item at that index. The function needs to implement FnMut, which means it can also carry internal mutable state which persists for all items.

Examples

use init_array::init_boxed_slice;
assert_eq!(&*init_boxed_slice(3, |_| 0), &[0; 3]);

assert_eq!(&*init_boxed_slice(5, |i| i + 1), &[1, 2, 3, 4, 5]);

let mut state = 0;

// arr[i] represents the sum of the first `i + 1` natural numbers.
let arr = init_boxed_slice(5, |i| {
    state += i + 1;
    state
});
assert_eq!(&*arr, &[1, 3, 6, 10, 15]);