exact ih
Node : Type
inst✝ : DecidableEq Node
g : Graph Node
visited : List Node
x : Node
stack : List Node
c1 : x ∉ visited
ih :
  ↑(dft_aux g (direct_succ_list g x ++ stack) (x :: visited)).toFinset ⊆
    reachable_from_list g (direct_succ_list g x) ∪ reachable_from_list g stack ∪ ↑(x :: visited).toFinset
⊢ ↑(dft_aux g (direct_succ_list g x ++ stack) (x :: visited)).toFinset ⊆
    reachable_from_list g (direct_succ_list g x) ∪ reachable_from_list g stack ∪ ↑(x :: visited).toFinset
no goals