(* -*- isar -*- Example proof document for Isabelle/Isar Proof General. $Id$ The first line forces Isabelle/Isar Proof General, otherwise you may get the theory mode of ordinary Isabelle Proof General *) theory Example = Main:; theorem and_comms: "A & B --> B & A"; proof; assume "A & B"; thus "B & A"; proof; assume A B; show ?thesis; ..; qed; qed; end;