Lean4
/-- Right-biased version of `List.map₂`. `map₂Right f as bs` applies `f` to each
pair `aᵢ ∈ as` and `bᵢ ∈ bs`. If `as` is shorter than `bs`, `f` is applied to
`none` for the remaining `bᵢ`.
```
map₂Right Prod.mk [1, 2] ['a'] = [(some 1, 'a')]
map₂Right Prod.mk [1] ['a', 'b'] = [(some 1, 'a'), (none, 'b')]
map₂Right f as bs = (map₂Right' f as bs).fst
```
-/
def map₂Right (f : Option α → β → γ) (as : List α) (bs : List β) : List γ :=
map₂Left (flip f) bs as