more robust range on preceding comment-line;
no range for blank lines;
avoid recursive output_text/mark_range;
clarified Latex.output_token (no range) vs. Thy_Output.present_token (with range);
(*<*)
theory Plus imports Main begin
(*>*)
text{*\noindent Define the following addition function *}
primrec add :: "nat \<Rightarrow> nat \<Rightarrow> nat" where
"add m 0 = m" |
"add m (Suc n) = add (Suc m) n"
text{*\noindent and prove*}
(*<*)
lemma [simp]: "!m. add m n = m+n"
apply(induct_tac n)
by(auto)
(*>*)
lemma "add m n = m+n"
(*<*)
by(simp)
end
(*>*)