src/Doc/Tutorial/Misc/fakenat.thy

standardize mixfix annotations via "isabelle update -a -u mixfix_cartouches" --- to simplify systematic editing;

(*<*)
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 (\<open>0\<close>) | Suc nat
(*<*)
end
(*>*)