diff -r 93d5408eb7d9 -r fbd097aec213 doc-src/TutorialI/Trie/document/Trie.tex --- a/doc-src/TutorialI/Trie/document/Trie.tex Sun Oct 21 19:48:19 2001 +0200 +++ b/doc-src/TutorialI/Trie/document/Trie.tex Sun Oct 21 19:49:29 2001 +0200 @@ -1,6 +1,7 @@ % \begin{isabellebody}% \def\isabellecontext{Trie}% +\isamarkupfalse% % \begin{isamarkuptext}% To minimize running time, each node of a trie should contain an array that maps @@ -9,7 +10,9 @@ list of (letter,trie) pairs. Abstracting over the alphabet \isa{{\isacharprime}a} and the values \isa{{\isacharprime}v} we define a trie as follows:% \end{isamarkuptext}% -\isacommand{datatype}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie\ {\isacharequal}\ Trie\ \ {\isachardoublequote}{\isacharprime}v\ option{\isachardoublequote}\ \ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a\ {\isacharasterisk}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie{\isacharparenright}list{\isachardoublequote}% +\isamarkuptrue% +\isacommand{datatype}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie\ {\isacharequal}\ Trie\ \ {\isachardoublequote}{\isacharprime}v\ option{\isachardoublequote}\ \ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a\ {\isacharasterisk}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie{\isacharparenright}list{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptext}% \noindent \index{datatypes!and nested recursion}% @@ -18,50 +21,67 @@ which is fine because products are datatypes as well. We define two selector functions:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{consts}\ value\ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie\ {\isasymRightarrow}\ {\isacharprime}v\ option{\isachardoublequote}\isanewline \ \ \ \ \ \ \ alist\ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie\ {\isasymRightarrow}\ {\isacharparenleft}{\isacharprime}a\ {\isacharasterisk}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie{\isacharparenright}list{\isachardoublequote}\isanewline +\isamarkupfalse% \isacommand{primrec}\ {\isachardoublequote}value{\isacharparenleft}Trie\ ov\ al{\isacharparenright}\ {\isacharequal}\ ov{\isachardoublequote}\isanewline -\isacommand{primrec}\ {\isachardoublequote}alist{\isacharparenleft}Trie\ ov\ al{\isacharparenright}\ {\isacharequal}\ al{\isachardoublequote}% +\isamarkupfalse% +\isacommand{primrec}\ {\isachardoublequote}alist{\isacharparenleft}Trie\ ov\ al{\isacharparenright}\ {\isacharequal}\ al{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptext}% \noindent Association lists come with a generic lookup function. Its result involves type \isa{option} because a lookup can fail:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{consts}\ \ \ assoc\ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isacharprime}key\ {\isacharasterisk}\ {\isacharprime}val{\isacharparenright}list\ {\isasymRightarrow}\ {\isacharprime}key\ {\isasymRightarrow}\ {\isacharprime}val\ option{\isachardoublequote}\isanewline +\isamarkupfalse% \isacommand{primrec}\ {\isachardoublequote}assoc\ {\isacharbrackleft}{\isacharbrackright}\ x\ {\isacharequal}\ None{\isachardoublequote}\isanewline \ \ \ \ \ \ \ \ {\isachardoublequote}assoc\ {\isacharparenleft}p{\isacharhash}ps{\isacharparenright}\ x\ {\isacharequal}\isanewline -\ \ \ \ \ \ \ \ \ \ \ {\isacharparenleft}let\ {\isacharparenleft}a{\isacharcomma}b{\isacharparenright}\ {\isacharequal}\ p\ in\ if\ a{\isacharequal}x\ then\ Some\ b\ else\ assoc\ ps\ x{\isacharparenright}{\isachardoublequote}% +\ \ \ \ \ \ \ \ \ \ \ {\isacharparenleft}let\ {\isacharparenleft}a{\isacharcomma}b{\isacharparenright}\ {\isacharequal}\ p\ in\ if\ a{\isacharequal}x\ then\ Some\ b\ else\ assoc\ ps\ x{\isacharparenright}{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptext}% Now we can define the lookup function for tries. It descends into the trie examining the letters of the search string one by one. As recursion on lists is simpler than on tries, let us express this as primitive recursion on the search string argument:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{consts}\ \ \ lookup\ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie\ {\isasymRightarrow}\ {\isacharprime}a\ list\ {\isasymRightarrow}\ {\isacharprime}v\ option{\isachardoublequote}\isanewline +\isamarkupfalse% \isacommand{primrec}\ {\isachardoublequote}lookup\ t\ {\isacharbrackleft}{\isacharbrackright}\ {\isacharequal}\ value\ t{\isachardoublequote}\isanewline \ \ \ \ \ \ \ \ {\isachardoublequote}lookup\ t\ {\isacharparenleft}a{\isacharhash}as{\isacharparenright}\ {\isacharequal}\ {\isacharparenleft}case\ assoc\ {\isacharparenleft}alist\ t{\isacharparenright}\ a\ of\isanewline \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ None\ {\isasymRightarrow}\ None\isanewline -\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ {\isacharbar}\ Some\ at\ {\isasymRightarrow}\ lookup\ at\ as{\isacharparenright}{\isachardoublequote}% +\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ {\isacharbar}\ Some\ at\ {\isasymRightarrow}\ lookup\ at\ as{\isacharparenright}{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptext}% As a first simple property we prove that looking up a string in the empty trie \isa{Trie\ None\ {\isacharbrackleft}{\isacharbrackright}} always returns \isa{None}. The proof merely distinguishes the two cases whether the search string is empty or not:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{lemma}\ {\isacharbrackleft}simp{\isacharbrackright}{\isacharcolon}\ {\isachardoublequote}lookup\ {\isacharparenleft}Trie\ None\ {\isacharbrackleft}{\isacharbrackright}{\isacharparenright}\ as\ {\isacharequal}\ None{\isachardoublequote}\isanewline +\isamarkupfalse% \isacommand{apply}{\isacharparenleft}case{\isacharunderscore}tac\ as{\isacharcomma}\ simp{\isacharunderscore}all{\isacharparenright}\isanewline -\isacommand{done}% +\isamarkupfalse% +\isacommand{done}\isamarkupfalse% +% \begin{isamarkuptext}% Things begin to get interesting with the definition of an update function that adds a new (string,value) pair to a trie, overwriting the old value associated with that string:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{consts}\ update\ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie\ {\isasymRightarrow}\ {\isacharprime}a\ list\ {\isasymRightarrow}\ {\isacharprime}v\ {\isasymRightarrow}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}v{\isacharparenright}trie{\isachardoublequote}\isanewline +\isamarkupfalse% \isacommand{primrec}\isanewline \ \ {\isachardoublequote}update\ t\ {\isacharbrackleft}{\isacharbrackright}\ \ \ \ \ v\ {\isacharequal}\ Trie\ {\isacharparenleft}Some\ v{\isacharparenright}\ {\isacharparenleft}alist\ t{\isacharparenright}{\isachardoublequote}\isanewline \ \ {\isachardoublequote}update\ t\ {\isacharparenleft}a{\isacharhash}as{\isacharparenright}\ v\ {\isacharequal}\isanewline \ \ \ \ \ {\isacharparenleft}let\ tt\ {\isacharequal}\ {\isacharparenleft}case\ assoc\ {\isacharparenleft}alist\ t{\isacharparenright}\ a\ of\isanewline \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ None\ {\isasymRightarrow}\ Trie\ None\ {\isacharbrackleft}{\isacharbrackright}\ {\isacharbar}\ Some\ at\ {\isasymRightarrow}\ at{\isacharparenright}\isanewline -\ \ \ \ \ \ in\ Trie\ {\isacharparenleft}value\ t{\isacharparenright}\ {\isacharparenleft}{\isacharparenleft}a{\isacharcomma}update\ tt\ as\ v{\isacharparenright}\ {\isacharhash}\ alist\ t{\isacharparenright}{\isacharparenright}{\isachardoublequote}% +\ \ \ \ \ \ in\ Trie\ {\isacharparenleft}value\ t{\isacharparenright}\ {\isacharparenleft}{\isacharparenleft}a{\isacharcomma}update\ tt\ as\ v{\isacharparenright}\ {\isacharhash}\ alist\ t{\isacharparenright}{\isacharparenright}{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptext}% \noindent The base case is obvious. In the recursive case the subtrie @@ -75,7 +95,9 @@ expand all \isa{let}s and to split all \isa{case}-constructs over options:% \end{isamarkuptext}% -\isacommand{declare}\ Let{\isacharunderscore}def{\isacharbrackleft}simp{\isacharbrackright}\ option{\isachardot}split{\isacharbrackleft}split{\isacharbrackright}% +\isamarkuptrue% +\isacommand{declare}\ Let{\isacharunderscore}def{\isacharbrackleft}simp{\isacharbrackright}\ option{\isachardot}split{\isacharbrackleft}split{\isacharbrackright}\isamarkupfalse% +% \begin{isamarkuptext}% \noindent The reason becomes clear when looking (probably after a failed proof @@ -85,8 +107,10 @@ Our main goal is to prove the correct interaction of \isa{update} and \isa{lookup}:% \end{isamarkuptext}% +\isamarkuptrue% \isacommand{theorem}\ {\isachardoublequote}{\isasymforall}t\ v\ bs{\isachardot}\ lookup\ {\isacharparenleft}update\ t\ as\ v{\isacharparenright}\ bs\ {\isacharequal}\isanewline -\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ {\isacharparenleft}if\ as{\isacharequal}bs\ then\ Some\ v\ else\ lookup\ t\ bs{\isacharparenright}{\isachardoublequote}% +\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ {\isacharparenleft}if\ as{\isacharequal}bs\ then\ Some\ v\ else\ lookup\ t\ bs{\isacharparenright}{\isachardoublequote}\isamarkupfalse% +% \begin{isamarkuptxt}% \noindent Our plan is to induct on \isa{as}; hence the remaining variables are @@ -97,7 +121,9 @@ \isa{as} is instantiated. The start of the proof is conventional:% \end{isamarkuptxt}% -\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ as{\isacharcomma}\ auto{\isacharparenright}% +\isamarkuptrue% +\isacommand{apply}{\isacharparenleft}induct{\isacharunderscore}tac\ as{\isacharcomma}\ auto{\isacharparenright}\isamarkupfalse% +% \begin{isamarkuptxt}% \noindent Unfortunately, this time we are left with three intimidating looking subgoals: @@ -110,8 +136,11 @@ well now. It turns out that instead of induction, case distinction suffices:% \end{isamarkuptxt}% +\isamarkuptrue% \isacommand{apply}{\isacharparenleft}case{\isacharunderscore}tac{\isacharbrackleft}{\isacharbang}{\isacharbrackright}\ bs{\isacharcomma}\ auto{\isacharparenright}\isanewline -\isacommand{done}% +\isamarkupfalse% +\isacommand{done}\isamarkupfalse% +% \begin{isamarkuptext}% \noindent \index{subgoal numbering}% @@ -149,6 +178,42 @@ with \isa{{\isacharprime}a\ {\isasymRightarrow}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}\ {\isacharprime}v{\isacharparenright}\ trie\ option}. \end{exercise}% \end{isamarkuptext}% +\isamarkuptrue% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% +\isamarkupfalse% \end{isabellebody}% %%% Local Variables: %%% mode: latex