exact (M.cl_exchange (X := ∅) ⟨hef, (nonloop_iff_not_mem_cl_empty he.mem_ground).1 he⟩).1
α : Type u_1
β : Type u_2
M N : Matroid α
e f : α
B L L' I X Y Z F C K : Set α
he : M.Nonloop e
hef : e ∈ M.cl (insert f ∅)
⊢ f ∈ M.cl (insert e ∅)
no goals