如果positions是一个Vec或类似的东西，那么就有slice::chunks和slice::chunks_exact，尽管它们会产生切片，所以需要将它们try_into到固定大小的数组中：

v.chunks(3).map(|c| <[_;3]>::try_from(c).unwrap()).collect::<Vec<_>>()

如果你能改变它，itertools有更好的Itertools::tuples，它可以将元素收集到你想要的大小的元组中，你只需要将它们移到一个数组中，而不会看到任何恐慌：

v.into_iter().tuples().map(|(a, b, c)| [a, b, c]).collect::<Vec<_>>()

如果要转换的矢量很大，并且必须避免复制数据，则可以通过转换矢量来实现：

use std::mem::ManuallyDrop;
pub fn to_arrays<const N: usize, T>(mut v: Vec<T>) -> Vec<[T; N]> {
    assert_eq!(v.len() % N, 0, "length not divisible by {N}");
    if v.capacity() % N != 0 {
        v.shrink_to_fit();
        assert_eq!(v.capacity() % N, 0, "capacity not divisible by {N} and we could not shrink to make it so");
    }
    let mut v = ManuallyDrop::new(v);
    let (ptr, len, cap) = (v.as_mut_ptr(), v.len(), v.capacity());
    // SAFETY:
    // * Global allocator is given `Vec<T> == Vec<T, Global>`
    // * an array has the same alingment as it's items
    // * len / N arrays of [T; N] have been initialized because len items have been initialized before
    // * capacity is divisible by N so the allocation is the same sisze
    unsafe { Vec::from_raw_parts(ptr.cast(), len / N, cap / N) }
}