Stupid code snippet to tell the diff between `map` and `and_then`

map-vs-and_then.rs

fn map_using_if<T, U, F>(s: Option<T>, f: F) -> Option<U>
where
    F: FnOnce(T) -> U,
{
    if let Some(item) = s {
        Some(f(item))
    } else {
        None
    }
}

fn and_then_using_if<T, U, F>(s: Option<T>, f: F) -> Option<U>
where
    F: FnOnce(T) -> Option<U>,
{
    if let Some(item) = s {
        let res_of_f = f(item);
        if let Some(val) = res_of_f {
            Some(val)
        } else {
            None
        }
    } else {
        None
    }
}