English
The size of the deduplicated keys is no greater than the size of the original list; equivalently, the size measure decreases under deduplication.
Русский
Размер dedupKeys не превосходит размера исходного списка.
LaTeX
$$SizeOf.sizeOf (dedupKeys l) ≤ SizeOf.sizeOf l$$
Lean4
theorem sizeOf_dedupKeys [SizeOf (Sigma β)] (xs : List (Sigma β)) : SizeOf.sizeOf (dedupKeys xs) ≤ SizeOf.sizeOf xs :=
by
simp only [SizeOf.sizeOf, _sizeOf_1]
induction xs with
| nil => simp [dedupKeys]
| cons x xs =>
simp only [dedupKeys_cons, kinsert_def, Nat.add_le_add_iff_left, Sigma.eta]
trans
· apply sizeOf_kerase
· assumption