I like how Rust does it with the `Ordering` type and associated combinators: https://doc.rust-lang.org/stable/std/cmp/enum.Ordering.html

For two values `x` and `y` of the same type with fields `a` and `b`, this lets you compare on `a` first and then on `b` by writing

``` x.a.cmp(&y.a).then(x.b.cmp(&y.b)) ```