English
Same as closure_exchange_iff: the exchange condition is equivalent to the stated symmetric form.
Русский
То же самое, что и closure_exchange_iff: условие обмена эквивалентно симметричной форме.
LaTeX
$$$ e \\in M.\\mathrm{closure}(\\mathrm{insert}(f,X)) \\setminus M.\\mathrm{closure}(X) \\leftrightarrow f \\in M.\\mathrm{closure}(\\mathrm{insert}(e,X)) \\setminus M.\\mathrm{closure}(X) $$$
Lean4
theorem closure_exchange_iff : e ∈ M.closure (insert f X) \ M.closure X ↔ f ∈ M.closure (insert e X) \ M.closure X :=
⟨closure_exchange, closure_exchange⟩