Exercise: Generic min

In this short exercise, you will implement a generic min function that determines the minimum of two values, using a LessThan trait.

trait LessThan {
    /// Return true if self is less than other.
    fn less_than(&self, other: &Self) -> bool;
}

#[derive(Debug, PartialEq, Eq, Clone, Copy)]
struct Citation {
    author: &'static str,
    year: u32,
}

impl LessThan for Citation {
    fn less_than(&self, other: &Self) -> bool {
        if self.author < other.author {
            true
        } else if self.author > other.author {
            false
        } else {
            self.year < other.year
        }
    }
}

// TODO: implement the `min` function used in `main`.

fn main() {
    let cit1 = Citation {
        author: "Shapiro",
        year: 2011,
    };
    let cit2 = Citation {
        author: "Baumann",
        year: 2010,
    };
    let cit3 = Citation {
        author: "Baumann",
        year: 2019,
    };
    debug_assert_eq!(min(cit1, cit2), cit2);
    debug_assert_eq!(min(cit2, cit3), cit2);
    debug_assert_eq!(min(cit1, cit3), cit3);
}