Theorems · Theorem · combinatorics

Multiset.count_map_eq_count

∀ {α : Type u_1} {β : Type v} [inst : DecidableEq α] [inst_1 : DecidableEq β] (f : α → β) (s : Multiset α),
  Set.InjOn f {x | x ∈ s} → ∀ x ∈ s, Multiset.count (f x) (Multiset.map f s) = Multiset.count x s

Multiset.map f preserves count if f is injective on the set of elements contained in the multiset

Defined in

Mathlib.Data.Multiset.Filter

Cited by

1 results in Mathlib

Foundations

Depth 20 from the axioms · uses propext, Quot.sound

Assumes

DecidableEqDecidableEq