unsafe fn very_long_unsafe_function(vec: &Vec<usize>) -> &Vec<usize> {
vec
}
fn long_outer_function<'a, F>(index: usize, function: F) -> &'a usize where F: Fn(usize) -> &'a usize {
function(index)
}
fn main() {
let vec = vec![1, 2, 3, 4]
let output:Vec<_> = vec![0, 0, 1, 1, 2, 2].iter().map(|&index| long_outer_function(index, |index| &unsafe  {
very_long_unsafe_function(&vec)
}[index])).collect()
println!("{:?}", output);
}