English
(s.fin n).map Fin.valEmbedding = s.filter (\\% < n)
Русский
(s.fin n).map Fin.valEmbedding = s.filter (только меньше n)
LaTeX
$$(s.fin n).map Fin.valEmbedding = s.filter (fun x => x < n)$$
Lean4
@[simp, deprecated map_valEmbedding_attachFin (since := "2025-04-08")]
theorem fin_map {s : Finset ℕ} : (s.fin n).map Fin.valEmbedding = s.filter (· < n) := by
simp [Finset.fin, Finset.map_map]