Lean4
/-- The image of a binary function `f : α → β → γ` as a function
`WithOne α → WithOne β → WithOne γ`.
Mathematically this should be thought of as the image of the corresponding function `α × β → γ`. -/
@[to_additive /-- The image of a binary function `f : α → β → γ` as a function
`WithZero α → WithZero β → WithZero γ`.
Mathematically this should be thought of as the image of the corresponding function `α × β → γ`. -/
]
def map₂ : (α → β → γ) → WithOne α → WithOne β → WithOne γ :=
Option.map₂