English
For a measurable cylinder membership ht, the corresponding base set can be extracted as a set-valued function over ht.
Русский
Для принадлежности ht измеримому цилиндру соответствующее основание может быть извлечено как множество-функция над ht.
LaTeX
$$$ \\mathrm{set}(ht) : \\{ \\text{functions on } (\\text{domain of ht}) \\} \\text{ with base } S $$$
Lean4
/-- A set `S` such that `t = cylinder s S`. `s` is given by `measurableCylinders.finset`. -/
def set (ht : t ∈ measurableCylinders α) : Set (∀ i : measurableCylinders.finset ht, α i) :=
((mem_measurableCylinders t).mp ht).choose_spec.choose