diff -r 93d5408eb7d9 -r fbd097aec213 doc-src/TutorialI/Misc/document/AdvancedInd.tex --- a/doc-src/TutorialI/Misc/document/AdvancedInd.tex Sun Oct 21 19:48:19 2001 +0200 +++ b/doc-src/TutorialI/Misc/document/AdvancedInd.tex Sun Oct 21 19:49:29 2001 +0200 @@ -1,6 +1,7 @@ % \begin{isabellebody}% \def\isabellecontext{AdvancedInd}% +\isamarkupfalse% % \begin{isamarkuptext}% \noindent @@ -11,9 +12,11 @@ and even derive (\S\ref{sec:derive-ind}) new induction schemas. We conclude with an extended example of induction (\S\ref{sec:CTL-revisited}).% \end{isamarkuptext}% +\isamarkuptrue% % \isamarkupsubsection{Massaging the Proposition% } +\isamarkuptrue% % \begin{isamarkuptext}% \label{sec:ind-var-in-prems} @@ -23,8 +26,11 @@ Since \isa{hd} and \isa{last} return the first and last element of a non-empty list, this lemma looks easy to prove:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{lemma}\ {\isachardoublequote}xs\ {\isasymnoteq}\ {\isacharbrackleft}{\isacharbrackright}\ {\isasymLongrightarrow}\ hd{\isacharparenleft}rev\ xs{\isacharparenright}\ {\isacharequal}\ last\ xs{\isachardoublequote}\isanewline -\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ xs{\isacharparenright}% +\isamarkupfalse% +\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ xs{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptxt}% \noindent But induction produces the warning @@ -56,7 +62,11 @@ \attrdx{rule_format} (\S\ref{sec:forward}) convert the result to the usual \isa{{\isasymLongrightarrow}} form:% \end{isamarkuptxt}% -\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}% +\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}\isamarkupfalse% +\isamarkupfalse% +% \begin{isamarkuptxt}% \noindent This time, induction leaves us with a trivial base case: @@ -73,6 +83,8 @@ can remove any number of occurrences of \isa{{\isasymforall}} and \isa{{\isasymlongrightarrow}}.% \end{isamarkuptxt}% +\isamarkuptrue% +\isamarkupfalse% % \begin{isamarkuptext}% \index{induction!on a term}% @@ -115,9 +127,11 @@ single theorem because it depends on the number of free variables in $t$ --- the notation $\overline{y}$ is merely an informal device.% \end{isamarkuptext}% +\isamarkuptrue% % \isamarkupsubsection{Beyond Structural and Recursion Induction% } +\isamarkuptrue% % \begin{isamarkuptext}% \label{sec:complete-ind} @@ -139,8 +153,11 @@ As an application, we prove a property of the following function:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{consts}\ f\ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}nat\ {\isasymRightarrow}\ nat{\isachardoublequote}\isanewline -\isacommand{axioms}\ f{\isacharunderscore}ax{\isacharcolon}\ {\isachardoublequote}f{\isacharparenleft}f{\isacharparenleft}n{\isacharparenright}{\isacharparenright}\ {\isacharless}\ f{\isacharparenleft}Suc{\isacharparenleft}n{\isacharparenright}{\isacharparenright}{\isachardoublequote}% +\isamarkupfalse% +\isacommand{axioms}\ f{\isacharunderscore}ax{\isacharcolon}\ {\isachardoublequote}f{\isacharparenleft}f{\isacharparenleft}n{\isacharparenright}{\isacharparenright}\ {\isacharless}\ f{\isacharparenleft}Suc{\isacharparenleft}n{\isacharparenright}{\isacharparenright}{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptext}% \begin{warn} We discourage the use of axioms because of the danger of @@ -155,14 +172,18 @@ be proved by induction on \mbox{\isa{f\ n}}. Following the recipe outlined above, we have to phrase the proposition as follows to allow induction:% \end{isamarkuptext}% -\isacommand{lemma}\ f{\isacharunderscore}incr{\isacharunderscore}lem{\isacharcolon}\ {\isachardoublequote}{\isasymforall}i{\isachardot}\ k\ {\isacharequal}\ f\ i\ {\isasymlongrightarrow}\ i\ {\isasymle}\ f\ i{\isachardoublequote}% +\isamarkuptrue% +\isacommand{lemma}\ f{\isacharunderscore}incr{\isacharunderscore}lem{\isacharcolon}\ {\isachardoublequote}{\isasymforall}i{\isachardot}\ k\ {\isacharequal}\ f\ i\ {\isasymlongrightarrow}\ i\ {\isasymle}\ f\ i{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptxt}% \noindent To perform induction on \isa{k} using \isa{nat{\isacharunderscore}less{\isacharunderscore}induct}, we use the same general induction method as for recursion induction (see \S\ref{sec:recdef-induction}):% \end{isamarkuptxt}% -\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ k\ rule{\isacharcolon}\ nat{\isacharunderscore}less{\isacharunderscore}induct{\isacharparenright}% +\isamarkuptrue% +\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ k\ rule{\isacharcolon}\ nat{\isacharunderscore}less{\isacharunderscore}induct{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptxt}% \noindent We get the following proof state: @@ -174,9 +195,13 @@ distinction on \isa{i}. The case \isa{i\ {\isacharequal}\ {\isacharparenleft}{\isadigit{0}}{\isasymColon}{\isacharprime}a{\isacharparenright}} is trivial and we focus on the other case:% \end{isamarkuptxt}% +\isamarkuptrue% \isacommand{apply}{\isacharparenleft}rule\ allI{\isacharparenright}\isanewline +\isamarkupfalse% \isacommand{apply}{\isacharparenleft}case{\isacharunderscore}tac\ i{\isacharparenright}\isanewline -\ \isacommand{apply}{\isacharparenleft}simp{\isacharparenright}% +\ \isamarkupfalse% +\isacommand{apply}{\isacharparenleft}simp{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptxt}% \begin{isabelle}% \ {\isadigit{1}}{\isachardot}\ {\isasymAnd}n\ i\ nat{\isachardot}\isanewline @@ -184,7 +209,9 @@ \isaindent{\ {\isadigit{1}}{\isachardot}\ \ \ \ }{\isasymLongrightarrow}\ n\ {\isacharequal}\ f\ i\ {\isasymlongrightarrow}\ i\ {\isasymle}\ f\ i% \end{isabelle}% \end{isamarkuptxt}% -\isacommand{by}{\isacharparenleft}blast\ intro{\isacharbang}{\isacharcolon}\ f{\isacharunderscore}ax\ Suc{\isacharunderscore}leI\ intro{\isacharcolon}\ le{\isacharunderscore}less{\isacharunderscore}trans{\isacharparenright}% +\isamarkuptrue% +\isacommand{by}{\isacharparenleft}blast\ intro{\isacharbang}{\isacharcolon}\ f{\isacharunderscore}ax\ Suc{\isacharunderscore}leI\ intro{\isacharcolon}\ le{\isacharunderscore}less{\isacharunderscore}trans{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptext}% \noindent If you find the last step puzzling, here are the two lemmas it employs: @@ -214,13 +241,18 @@ The desired result, \isa{i\ {\isasymle}\ f\ i}, follows from \isa{f{\isacharunderscore}incr{\isacharunderscore}lem}:% \end{isamarkuptext}% -\isacommand{lemmas}\ f{\isacharunderscore}incr\ {\isacharequal}\ f{\isacharunderscore}incr{\isacharunderscore}lem{\isacharbrackleft}rule{\isacharunderscore}format{\isacharcomma}\ OF\ refl{\isacharbrackright}% +\isamarkuptrue% +\isacommand{lemmas}\ f{\isacharunderscore}incr\ {\isacharequal}\ f{\isacharunderscore}incr{\isacharunderscore}lem{\isacharbrackleft}rule{\isacharunderscore}format{\isacharcomma}\ OF\ refl{\isacharbrackright}\isamarkupfalse% +% \begin{isamarkuptext}% \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}% -\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}% +\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}\isamarkupfalse% +\isamarkupfalse% +% \begin{isamarkuptext}% \begin{exercise} From the axiom and lemma for \isa{f}, show that \isa{f} is the @@ -251,9 +283,11 @@ \end{isabelle} where \isa{f} may be any function into type \isa{nat}.% \end{isamarkuptext}% +\isamarkuptrue% % \isamarkupsubsection{Derivation of New Induction Schemas% } +\isamarkuptrue% % \begin{isamarkuptext}% \label{sec:derive-ind} @@ -264,16 +298,22 @@ available for \isa{nat} and want to derive complete induction. We must generalize the statement as shown:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{lemma}\ induct{\isacharunderscore}lem{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isasymAnd}n{\isacharcolon}{\isacharcolon}nat{\isachardot}\ {\isasymforall}m{\isacharless}n{\isachardot}\ P\ m\ {\isasymLongrightarrow}\ P\ n{\isacharparenright}\ {\isasymLongrightarrow}\ {\isasymforall}m{\isacharless}n{\isachardot}\ P\ m{\isachardoublequote}\isanewline -\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ n{\isacharparenright}% +\isamarkupfalse% +\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ n{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptxt}% \noindent The base case is vacuously true. For the induction step (\isa{m\ {\isacharless}\ Suc\ n}) we distinguish two cases: case \isa{m\ {\isacharless}\ n} is true by induction hypothesis and case \isa{m\ {\isacharequal}\ n} follows from the assumption, again using the induction hypothesis:% \end{isamarkuptxt}% -\ \isacommand{apply}{\isacharparenleft}blast{\isacharparenright}\isanewline -\isacommand{by}{\isacharparenleft}blast\ elim{\isacharcolon}less{\isacharunderscore}SucE{\isacharparenright}% +\ \isamarkuptrue% +\isacommand{apply}{\isacharparenleft}blast{\isacharparenright}\isanewline +\isamarkupfalse% +\isacommand{by}{\isacharparenleft}blast\ elim{\isacharcolon}less{\isacharunderscore}SucE{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptext}% \noindent The elimination rule \isa{less{\isacharunderscore}SucE} expresses the case distinction: @@ -288,8 +328,11 @@ happens automatically when we add the lemma as a new premise to the desired goal:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{theorem}\ nat{\isacharunderscore}less{\isacharunderscore}induct{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isasymAnd}n{\isacharcolon}{\isacharcolon}nat{\isachardot}\ {\isasymforall}m{\isacharless}n{\isachardot}\ P\ m\ {\isasymLongrightarrow}\ P\ n{\isacharparenright}\ {\isasymLongrightarrow}\ P\ n{\isachardoublequote}\isanewline -\isacommand{by}{\isacharparenleft}insert\ induct{\isacharunderscore}lem{\isacharcomma}\ blast{\isacharparenright}% +\isamarkupfalse% +\isacommand{by}{\isacharparenleft}insert\ induct{\isacharunderscore}lem{\isacharcomma}\ blast{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptext}% HOL already provides the mother of all inductions, well-founded induction (see \S\ref{sec:Well-founded}). For @@ -297,6 +340,8 @@ a special case of \isa{wf{\isacharunderscore}induct} where \isa{r} is \isa{{\isacharless}} on \isa{nat}. The details can be found in theory \isa{Wellfounded_Recursion}.% \end{isamarkuptext}% +\isamarkuptrue% +\isamarkupfalse% \end{isabellebody}% %%% Local Variables: %%% mode: latex