Theorem: Matroid.Basis'.card (Matroid/Rank.lean)

State before:
α : Type u_1
ι : Type u_2
M N : Matroid α
I B X X' Y Y' Z R : Set α
n : ℕ∞
e f : α
h : M.Basis' I X
⊢ I.ncard = M.r X
Tactic:
rw [ncard_def, h.encard, ← er_toNat_eq_r]
State after:
no goals