Theorems · Theorem · combinatorics

Multiset.count_map

∀ {α : Type u_3} {β : Type u_4} (f : α → β) (s : Multiset α) [inst : DecidableEq β] (b : β),
  Multiset.count b (Multiset.map f s) = (Multiset.filter (fun a => b = f a) s).card

Defined in

Mathlib.Data.Multiset.Filter

Cited by

4 results in Mathlib

Foundations

Depth 19 from the axioms · uses propext, Quot.sound

Assumes

DecidableEq