English
If s is countable with default ∈ s, then range(enumerateCountable h default) = s.
Русский
Если s счётно и default ∈ s, то range(enumerateCountable h default) = s.
LaTeX
$$$\operatorname{range}(\operatorname{enumerateCountable}(h,\text{default})) = s$$$
Lean4
theorem range_enumerateCountable_of_mem {s : Set α} (h : s.Countable) {default : α} (h_mem : default ∈ s) :
range (enumerateCountable h default) = s :=
subset_antisymm ((range_enumerateCountable_subset h _).trans_eq (insert_eq_of_mem h_mem))
(subset_range_enumerate h default)