generalize h : cs ++ [c] = cs' at path
nfa : NFA
i l : ℕ
cs : List Char
c : Char
start : ℕ
path : nfa.pathIn start i l (cs ++ [c])
⊢ ∃ j k, nfa.pathIn start i j cs ∧ k ∈ nfa.charStep j c ∧ l ∈ nfa.εClosure k
nfa : NFA
i l : ℕ
cs : List Char
c : Char
start : ℕ
cs' : List Char
h : cs ++ [c] = cs'
path : nfa.pathIn start i l cs'
⊢ ∃ j k, nfa.pathIn start i j cs ∧ k ∈ nfa.charStep j c ∧ l ∈ nfa.εClosure k