Function incomplete_addition

fn incomplete_addition(
    left: Option<Point>,
    right: Option<Point>,
) -> Option<Point>

Incomplete addition on the Pallas curve.

P ∪ {⊥} × P ∪ {⊥} → P ∪ {⊥}

https://zips.z.cash/protocol/protocol.pdf#concretesinsemillahash