removed norm_typ; improved output; refer to Pretty.pp;
(*<*)theory fakenat = Main:;(*>*)text{*\noindentThe type \tydx{nat} of naturalnumbers is predefined to have the constructors \cdx{0} and~\cdx{Suc}. It behaves as if it were declared like this:*}datatype nat = 0 | Suc nat(*<*)end(*>*)