
diff -r 85766e408c66 -r 42ffaca7c85e thys/Paper/Paper.thy
--- a/thys/Paper/Paper.thy	Mon May 16 15:20:23 2016 +0100
+++ b/thys/Paper/Paper.thy	Tue May 17 03:47:33 2016 +0100
@@ -54,7 +54,7 @@
   F_SEQ ("F\<^bsub>Seq\<^esub> _ _") and
   simp_SEQ ("simp\<^bsub>Seq\<^esub> _ _" [1000, 1000] 1) and
   simp_ALT ("simp\<^bsub>Alt\<^esub> _ _" [1000, 1000] 1) and
-  slexer ("lexer\<^sup>+ _ _" [78,78] 77) and
+  slexer ("lexer\<^sup>+" 1000) and
 
   ValOrd ("_ >\<^bsub>_\<^esub> _" [77,77,77] 77) and
   ValOrdEq ("_ \<ge>\<^bsub>_\<^esub> _" [77,77,77] 77)
@@ -653,7 +653,7 @@
    We can prove that given a string @{term s} and regular expression @{term
    r}, the POSIX value @{term v} is uniquely determined by @{term "s \<in> r \<rightarrow> v"}.
 
-  \begin{theorem}
+  \begin{theorem}\label{posixdeterm}
   @{thm[mode=IfThen] Posix_determ(1)[of _ _ "v\<^sub>1" "v\<^sub>2"]}
   \end{theorem}
 
@@ -778,7 +778,7 @@
   the null value @{term "None"} iff the string is not in the language of the regular expression,
   and returning a unique POSIX value iff the string \emph{is} in the language):
 
-  \begin{theorem}\mbox{}\smallskip\\
+  \begin{theorem}\mbox{}\smallskip\\\label{lexercorrect}
   \begin{tabular}{ll}
   (1) & @{thm (lhs) lexer_correct_None} if and only if @{thm (rhs) lexer_correct_None}\\
   (2) & @{thm (lhs) lexer_correct_Some} if and only if @{thm (rhs) lexer_correct_Some}\\
@@ -928,26 +928,61 @@
   is then recursively called with the simplified derivative, but before
   we inject the character @{term c} into the value @{term v}, we need to rectify
   @{term v} (that is construct @{term "f\<^sub>r v"}). Before we can establish the correctness
-  of @{const "slexer"}, we need to show that simplification preserves the language
-  and the relation between simplification and our posix definition:
+  of @{term "slexer"}, we need to show that simplification preserves the language
+  and simplification preserves our POSIX relation once the value is rectified
+  (recall @{const "simp"} generates a regular expression, rectification function pair):
 
-  \begin{lemma}\mbox{}\smallskip\\
+  \begin{lemma}\mbox{}\smallskip\\\label{slexeraux}
   \begin{tabular}{ll}
   (1) & @{thm L_fst_simp[symmetric]}\\
   (2) & @{thm[mode=IfThen] Posix_simp}
   \end{tabular}
   \end{lemma}
 
-  \noindent
-  We can now prove that
+  \begin{proof}
+  Both are by induction on @{text r}. There is no interesting case for the
+  first statement. For the second statement of interest are the @{term "r = SEQ r\<^sub>1 r\<^sub>2"}
+  and @{term "r = ALT r\<^sub>1 r\<^sub>2"} cases.
+  
+  \end{proof}
+
+  \noindent We can now prove relatively straightforwardly that the
+  optimised lexer produce the expected result:
 
   \begin{theorem}
   @{thm slexer_correctness}
   \end{theorem}
 
-  \noindent
-  holds but for lack of space refer the reader to our mechanisation for details.
+  \begin{proof} By induction on @{term s} generalising over @{term
+  r}. The case @{term "[]"} is trivial. For the cons-case suppose the
+  string is of the form @{term "c # s"}. By induction hypothesis we
+  know @{term "slexer r s = lexer r s"} holds for all @{term r} (in
+  particular for @{term "r"} being the derivative @{term "der c
+  r"}). Let @{term "r\<^sub>s"} be the simplified derivative regular expression, @{term
+  "fst (simp (der c r))"}, and @{term "f\<^sub>r"} be the rectification
+  function, @{term "snd (simp (der c r))"}.  We distinguish the cases
+  whether (*) @{term "s \<in> L (der c r)"} or not. In the first case we
+  have by Thm~\ref{lexercorrect}(2) a value @{term "v"} so that @{term
+  "lexer (der c r) s = Some v"} and @{term "s \<in> der c r \<rightarrow> v"} hold.
+  By Lem~\ref{slexeraux}(1) we can also infer from~(*) that @{term "s
+  \<in> L r\<^sub>s"} holds.  Hence we know by Thm~\ref{lexercorrect}(2) that
+  there exists a @{term "v'"} with @{term "lexer r\<^sub>s s = Some v'"} and
+  @{term "s \<in> r\<^sub>s \<rightarrow> v'"}. From the latter we know by
+  Lem~\ref{slexeraux}(2) that @{term "s \<in> der c r \<rightarrow> (f\<^sub>r v')"} holds.
+  By the uniqueness of the POSIX relation (Thm~\ref{posixdeterm}) we
+  can infer that @{term v} is equal to @{term "f\<^sub>r v'"}---that is the 
+  rectification function applied to @{term "v'"}
+  produces the original @{term "v"}.  Now the case follows by the
+  definitions of @{const lexer} and @{const slexer}.
 
+  In the second case where @{term "s \<notin> L (der c r)"} we have that
+  @{term "lexer (der c r) s = None"} by Thm~\ref{lexercorrect}(1).  We
+  also know by Lem~\ref{slexeraux}(1) that @{term "s \<notin> L r\<^sub>s"}. Hence
+  @{term "lexer r\<^sub>s s = None"} by Thm~\ref{lexercorrect}(1) and
+  by IH then also @{term "slexer r\<^sub>s s = None"}. With this we can
+  conclude in this case too.\qed   
+
+  \end{proof} 
 *}
 
 section {* The Correctness Argument by Sulzmann and Lu\label{argu} *}




