doc-src/TutorialI/Misc/document/fakenat.tex

added state: 'a * 'b -> 'a * ('a * 'b);

\begin{isabelle}%
%
\begin{isamarkuptext}%
\noindent
The type \isaindexbold{nat} of natural numbers is predefined and
behaves like%
\end{isamarkuptext}%
\isacommand{datatype}~nat~=~{"}0{"}~|~Suc~nat\end{isabelle}%