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

 \attrdx{rule_format} (\S\ref{sec:forward}) convert the
 result to the usual \isa{{\isasymLongrightarrow}} form:%
 \end{isamarkuptxt}%
 \isamarkuptrue%
 \isamarkupfalse%
-\isacommand{lemma}\ hd{\isacharunderscore}rev\ {\isacharbrackleft}rule{\isacharunderscore}format{\isacharbrackright}{\isacharcolon}\ {\isachardoublequote}xs\ {\isasymnoteq}\ {\isacharbrackleft}{\isacharbrackright}\ {\isasymlongrightarrow}\ hd{\isacharparenleft}rev\ xs{\isacharparenright}\ {\isacharequal}\ last\ xs{\isachardoublequote}\isanewline
-\isamarkupfalse%
+\isacommand{lemma}\ hd{\isacharunderscore}rev\ {\isacharbrackleft}rule{\isacharunderscore}format{\isacharbrackright}{\isacharcolon}\ {\isachardoublequote}xs\ {\isasymnoteq}\ {\isacharbrackleft}{\isacharbrackright}\ {\isasymlongrightarrow}\ hd{\isacharparenleft}rev\ xs{\isacharparenright}\ {\isacharequal}\ last\ xs{\isachardoublequote}\isamarkupfalse%
 \isamarkupfalse%
 %
 \begin{isamarkuptxt}%
 \noindent
 This time, induction leaves us with a trivial base case:

 \noindent
 The final \isa{refl} gets rid of the premise \isa{{\isacharquery}k\ {\isacharequal}\ f\ {\isacharquery}i}. 
 We could have included this derivation in the original statement of the lemma:%
 \end{isamarkuptext}%
 \isamarkuptrue%
-\isacommand{lemma}\ f{\isacharunderscore}incr{\isacharbrackleft}rule{\isacharunderscore}format{\isacharcomma}\ OF\ refl{\isacharbrackright}{\isacharcolon}\ {\isachardoublequote}{\isasymforall}i{\isachardot}\ k\ {\isacharequal}\ f\ i\ {\isasymlongrightarrow}\ i\ {\isasymle}\ f\ i{\isachardoublequote}\isanewline
-\isamarkupfalse%
+\isacommand{lemma}\ f{\isacharunderscore}incr{\isacharbrackleft}rule{\isacharunderscore}format{\isacharcomma}\ OF\ refl{\isacharbrackright}{\isacharcolon}\ {\isachardoublequote}{\isasymforall}i{\isachardot}\ k\ {\isacharequal}\ f\ i\ {\isasymlongrightarrow}\ i\ {\isasymle}\ f\ i{\isachardoublequote}\isamarkupfalse%
 \isamarkupfalse%
 %
 \begin{isamarkuptext}%
 \begin{exercise}
 From the axiom and lemma for \isa{f}, show that \isa{f} is the