use std::iter::Product;
use std::ops::RangeInclusive;


fn factorial_iterative<T, Out>(m: T, n: T) -> Out
where
    T: Product, RangeInclusive<T>: Iterator<Item = T>,
    Out: Product<T>
{
    let ret = (m..=n).product();
    return ret;
}

fn main()
{
    let x:i32 = factorial_iterative::<i32, _>(1, 5);
    dbg!(x);
}