Induction rule case names (Isabelle)

Question

Some induction rules have case names: the default one has case 0 and case (Suc n) for example. Given a rule, eg int_induct , how do I find out its case names (if, indeed, it has these) without looking in the theory containing this lemma?

Answer 1

I'm not aware of any high-level way to do this. The case names are stored in the tags of a theorem that can be obtained with ML:

ML‹Thm.get_tags @{thm nat.induct}›

This prints:

val it = [("name", "Nat.nat.induct"), ("kind", "theorem"), ("case_names", "zero;Suc")]: Properties.T

As you can see, the case names are available under the key case_names .