proof (rule disjE) for nested disjunction
问题 In Isar-style Isabelle proofs, this works nicely: from `a ∨ b` have foo proof assume a show foo sorry next assume b show foo sorry qed The implicit rule called by proof here is rule conjE . But what should I put there to make it work for more than just one disjunction: from `a ∨ b ∨ c` have foo proof(?) assume a show foo sorry next assume b show foo sorry next assume c show foo sorry qed 回答1: While writing the question, I had an idea, and it turns out to be what I want: from `a ∨ b ∨ c` have