afford more parallelism for sessions (instead of theories in 5eac4b13d1f1): depend on disjoint data areas (notably base.session_theories in 2ad892ac749a);
(*<*)
theory fakenat imports Main begin
(*>*)
text\<open>\noindent
The type \tydx{nat} of natural
numbers is predefined to have the constructors \cdx{0} and~\cdx{Suc}.
It behaves approximately as if it were declared like this:
\<close>
datatype nat = zero ("0") | Suc nat
(*<*)
end
(*>*)