Implement Iterator trait to Counter

counter.rs

/* Counter example can be seen at https://doc.rust-lang.org/std/iter/index.html#implementing-iterator
   I just wanna try out implementing Iterator trait on tuple like struct.
   Due to the IntoIterator blanket implementation in standard library - "impl<I: Iterator> IntoIterator for I" , 
   all Iterator can be treated like IntoIterator. That's why we can call c.into_iter() in the code.
*/
use std::iter::*;

fn main() {
    let mut z = 0u32;
    let ref mut c = Counter(&mut z);

    let iter = c.into_iter();
    while let Some(v) = iter.next() {
        if v > 100 {
            break;
        }
        println!("{}", v);
    }
    println!("{:?}", c);

    c.reset();
    println!("{:?}", c);
}

#[derive(Debug)]
struct Counter<'a>(&'a mut u32);

impl<'a> Counter<'a> {
    fn reset(&mut self) {
        *self.0 = 0
    }
}

impl<'a> Iterator for Counter<'a> {
    type Item = u32;
    fn next(&mut self) -> Option<Self::Item> {
        *self.0 = *self.0 + 1;
        Some(*self.0)
    }
}