Some lemmas about lists involving sets #
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Split out from data.list.basic
to reduce its dependencies.
theorem
list.inj_on_insert_nth_index_of_not_mem
{α : Type u_1}
(l : list α)
(x : α)
(hx : x ∉ l) :
set.inj_on (λ (k : ℕ), list.insert_nth k x l) {n : ℕ | n ≤ l.length}