use std::ops::Add;
use std::iter::Sum;

#[derive(Debug)]
struct MyInt(i32);

impl Sum<i32> for MyInt {
    fn sum<I>(iter: I) -> Self where I: Iterator<Item=i32> {
        let sum: i32 = iter.sum();
        MyInt(sum)
    }
}

fn main() {
    let v = vec![1,2,3,4,5];
    let sum: MyInt = v.into_iter().sum();
    println!("{:?}", sum);
}