Can you create a function that takes another function and a parameter and returns a lazy stream of nested function calls?

Question

In Clojure, I use a function called iterate that:

Returns a lazy sequence of x, (f x), (f (f x)) etc. f must be free of side-effects

Answer 1

As of Rust 1.34, you can use iter::successors:

fn coltz(n: u64) -> Option {
    match n % 2 {
        0 => Some(n / 2),
        _ => Some(3 * n + 1),
    }
}

use std::iter;

fn main() {
    let sequence = iter::successors(Some(10), |&v| coltz(v)).take_while(|&v| v != 1);
    for v in sequence {
        println!("{}", v);
    }
}

12
6
3
10
5
16
8
4
2