loop.rs

pub fn combine_all_option<T>(xs: &Vec<T>) -> Option<T>
where
    T: Semigroup + Clone,
{
    xs.iter().skip(1).fold(
        xs.first().map(|v| v.clone()),
        |acc, next| acc.map(|v| v.combine(next)),
    )
}

// added a few more tests just because
#[test]
fn test_combine_all_option() {
    let v0 = &Vec::<i32>::new();
    assert_eq!(combine_all_option(v0), None);
    let v1 = &vec![1, 2, 3];
    assert_eq!(combine_all_option(v1), Some(6));
    let v2 = &vec![Some(1), Some(2), Some(3)];
    assert_eq!(combine_all_option(v2), Some(Some(6)));
    let v3 = &vec![1];
    assert_eq!(combine_all_option(v3), Some(1));
}