doc-src/TutorialI/Misc/arith1.thy

intro_classes by default;

(*<*)
theory arith1 = Main:;
(*>*)
lemma "\<lbrakk> \<not> m < n; m < n+1 \<rbrakk> \<Longrightarrow> m = n";
(**)(*<*)
by(auto);
end
(*>*)