For this specific case, saturating_sub would work fine. The checked_sub way would need an additional `.unwrap_or(-1)` Though of course you wouldn't need to do

For this specific case, saturating_sub would work fine. The checked_sub way would need an additional `.unwrap_or(-1)` Though of course you wouldn't need to do either because the usual way to write a Rust API that takes comparators is for that comparator to return std::cmp::Ordering, not a signed integer. And if you do make a PartialOrd / Ord impl that isn't transitive, it is guaranteed by the sorting fns in libstd that sorting may be incorrect, but it won't be undefined behavior.