English
Mapping with f preserves the Some value: map f (some a) = some (f a).
Русский
Преобразование через f сохраняет значение Some: map f (some a) = some (f a).
LaTeX
$$$ \forall {a} {f}, \mathrm{Part.map} f (\\mathrm{some } a) = \\mathrm{some }(f(a)) $$$
Lean4
@[simp]
theorem map_some (f : α → β) (a : α) : map f (some a) = some (f a) :=
eq_some_iff.2 <| mem_map f <| mem_some _