thys3/src/Lexer.thy
changeset 496 f493a20feeb3
parent 495 f9cdc295ccf7
child 563 c92a41d9c4da
equal deleted inserted replaced
495:f9cdc295ccf7 496:f493a20feeb3
       
     1    
       
     2 theory Lexer
       
     3   imports PosixSpec 
       
     4 begin
       
     5 
       
     6 section {* The Lexer Functions by Sulzmann and Lu  (without simplification) *}
       
     7 
       
     8 fun 
       
     9   mkeps :: "rexp \<Rightarrow> val"
       
    10 where
       
    11   "mkeps(ONE) = Void"
       
    12 | "mkeps(SEQ r1 r2) = Seq (mkeps r1) (mkeps r2)"
       
    13 | "mkeps(ALT r1 r2) = (if nullable(r1) then Left (mkeps r1) else Right (mkeps r2))"
       
    14 | "mkeps(STAR r) = Stars []"
       
    15 
       
    16 fun injval :: "rexp \<Rightarrow> char \<Rightarrow> val \<Rightarrow> val"
       
    17 where
       
    18   "injval (CH d) c Void = Char d"
       
    19 | "injval (ALT r1 r2) c (Left v1) = Left(injval r1 c v1)"
       
    20 | "injval (ALT r1 r2) c (Right v2) = Right(injval r2 c v2)"
       
    21 | "injval (SEQ r1 r2) c (Seq v1 v2) = Seq (injval r1 c v1) v2"
       
    22 | "injval (SEQ r1 r2) c (Left (Seq v1 v2)) = Seq (injval r1 c v1) v2"
       
    23 | "injval (SEQ r1 r2) c (Right v2) = Seq (mkeps r1) (injval r2 c v2)"
       
    24 | "injval (STAR r) c (Seq v (Stars vs)) = Stars ((injval r c v) # vs)" 
       
    25 
       
    26 fun 
       
    27   lexer :: "rexp \<Rightarrow> string \<Rightarrow> val option"
       
    28 where
       
    29   "lexer r [] = (if nullable r then Some(mkeps r) else None)"
       
    30 | "lexer r (c#s) = (case (lexer (der c r) s) of  
       
    31                     None \<Rightarrow> None
       
    32                   | Some(v) \<Rightarrow> Some(injval r c v))"
       
    33 
       
    34 
       
    35 
       
    36 section {* Mkeps, Injval Properties *}
       
    37 
       
    38 lemma mkeps_nullable:
       
    39   assumes "nullable(r)" 
       
    40   shows "\<Turnstile> mkeps r : r"
       
    41 using assms
       
    42 by (induct rule: nullable.induct) 
       
    43    (auto intro: Prf.intros)
       
    44 
       
    45 lemma mkeps_flat:
       
    46   assumes "nullable(r)" 
       
    47   shows "flat (mkeps r) = []"
       
    48 using assms
       
    49 by (induct rule: nullable.induct) (auto)
       
    50 
       
    51 lemma Prf_injval_flat:
       
    52   assumes "\<Turnstile> v : der c r" 
       
    53   shows "flat (injval r c v) = c # (flat v)"
       
    54 using assms
       
    55 apply(induct c r arbitrary: v rule: der.induct)
       
    56 apply(auto elim!: Prf_elims intro: mkeps_flat split: if_splits)
       
    57 done
       
    58 
       
    59 lemma Prf_injval:
       
    60   assumes "\<Turnstile> v : der c r" 
       
    61   shows "\<Turnstile> (injval r c v) : r"
       
    62 using assms
       
    63 apply(induct r arbitrary: c v rule: rexp.induct)
       
    64 apply(auto intro!: Prf.intros mkeps_nullable elim!: Prf_elims split: if_splits)
       
    65 apply(simp add: Prf_injval_flat)
       
    66 done
       
    67 
       
    68 
       
    69 
       
    70 text {*
       
    71   Mkeps and injval produce, or preserve, Posix values.
       
    72 *}
       
    73 
       
    74 lemma Posix_mkeps:
       
    75   assumes "nullable r"
       
    76   shows "[] \<in> r \<rightarrow> mkeps r"
       
    77 using assms
       
    78 apply(induct r rule: nullable.induct)
       
    79 apply(auto intro: Posix.intros simp add: nullable_correctness Sequ_def)
       
    80 apply(subst append.simps(1)[symmetric])
       
    81 apply(rule Posix.intros)
       
    82 apply(auto)
       
    83 done
       
    84 
       
    85 lemma Posix_injval:
       
    86   assumes "s \<in> (der c r) \<rightarrow> v"
       
    87   shows "(c # s) \<in> r \<rightarrow> (injval r c v)"
       
    88 using assms
       
    89 proof(induct r arbitrary: s v rule: rexp.induct)
       
    90   case ZERO
       
    91   have "s \<in> der c ZERO \<rightarrow> v" by fact
       
    92   then have "s \<in> ZERO \<rightarrow> v" by simp
       
    93   then have "False" by cases
       
    94   then show "(c # s) \<in> ZERO \<rightarrow> (injval ZERO c v)" by simp
       
    95 next
       
    96   case ONE
       
    97   have "s \<in> der c ONE \<rightarrow> v" by fact
       
    98   then have "s \<in> ZERO \<rightarrow> v" by simp
       
    99   then have "False" by cases
       
   100   then show "(c # s) \<in> ONE \<rightarrow> (injval ONE c v)" by simp
       
   101 next 
       
   102   case (CH d)
       
   103   consider (eq) "c = d" | (ineq) "c \<noteq> d" by blast
       
   104   then show "(c # s) \<in> (CH d) \<rightarrow> (injval (CH d) c v)"
       
   105   proof (cases)
       
   106     case eq
       
   107     have "s \<in> der c (CH d) \<rightarrow> v" by fact
       
   108     then have "s \<in> ONE \<rightarrow> v" using eq by simp
       
   109     then have eqs: "s = [] \<and> v = Void" by cases simp
       
   110     show "(c # s) \<in> CH d \<rightarrow> injval (CH d) c v" using eq eqs 
       
   111     by (auto intro: Posix.intros)
       
   112   next
       
   113     case ineq
       
   114     have "s \<in> der c (CH d) \<rightarrow> v" by fact
       
   115     then have "s \<in> ZERO \<rightarrow> v" using ineq by simp
       
   116     then have "False" by cases
       
   117     then show "(c # s) \<in> CH d \<rightarrow> injval (CH d) c v" by simp
       
   118   qed
       
   119 next
       
   120   case (ALT r1 r2)
       
   121   have IH1: "\<And>s v. s \<in> der c r1 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r1 \<rightarrow> injval r1 c v" by fact
       
   122   have IH2: "\<And>s v. s \<in> der c r2 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r2 \<rightarrow> injval r2 c v" by fact
       
   123   have "s \<in> der c (ALT r1 r2) \<rightarrow> v" by fact
       
   124   then have "s \<in> ALT (der c r1) (der c r2) \<rightarrow> v" by simp
       
   125   then consider (left) v' where "v = Left v'" "s \<in> der c r1 \<rightarrow> v'" 
       
   126               | (right) v' where "v = Right v'" "s \<notin> L (der c r1)" "s \<in> der c r2 \<rightarrow> v'" 
       
   127               by cases auto
       
   128   then show "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c v"
       
   129   proof (cases)
       
   130     case left
       
   131     have "s \<in> der c r1 \<rightarrow> v'" by fact
       
   132     then have "(c # s) \<in> r1 \<rightarrow> injval r1 c v'" using IH1 by simp
       
   133     then have "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c (Left v')" by (auto intro: Posix.intros)
       
   134     then show "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c v" using left by simp
       
   135   next 
       
   136     case right
       
   137     have "s \<notin> L (der c r1)" by fact
       
   138     then have "c # s \<notin> L r1" by (simp add: der_correctness Der_def)
       
   139     moreover 
       
   140     have "s \<in> der c r2 \<rightarrow> v'" by fact
       
   141     then have "(c # s) \<in> r2 \<rightarrow> injval r2 c v'" using IH2 by simp
       
   142     ultimately have "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c (Right v')" 
       
   143       by (auto intro: Posix.intros)
       
   144     then show "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c v" using right by simp
       
   145   qed
       
   146 next
       
   147   case (SEQ r1 r2)
       
   148   have IH1: "\<And>s v. s \<in> der c r1 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r1 \<rightarrow> injval r1 c v" by fact
       
   149   have IH2: "\<And>s v. s \<in> der c r2 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r2 \<rightarrow> injval r2 c v" by fact
       
   150   have "s \<in> der c (SEQ r1 r2) \<rightarrow> v" by fact
       
   151   then consider 
       
   152         (left_nullable) v1 v2 s1 s2 where 
       
   153         "v = Left (Seq v1 v2)"  "s = s1 @ s2" 
       
   154         "s1 \<in> der c r1 \<rightarrow> v1" "s2 \<in> r2 \<rightarrow> v2" "nullable r1" 
       
   155         "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> s1 @ s\<^sub>3 \<in> L (der c r1) \<and> s\<^sub>4 \<in> L r2)"
       
   156       | (right_nullable) v1 s1 s2 where 
       
   157         "v = Right v1" "s = s1 @ s2"  
       
   158         "s \<in> der c r2 \<rightarrow> v1" "nullable r1" "s1 @ s2 \<notin> L (SEQ (der c r1) r2)"
       
   159       | (not_nullable) v1 v2 s1 s2 where
       
   160         "v = Seq v1 v2" "s = s1 @ s2" 
       
   161         "s1 \<in> der c r1 \<rightarrow> v1" "s2 \<in> r2 \<rightarrow> v2" "\<not>nullable r1" 
       
   162         "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> s1 @ s\<^sub>3 \<in> L (der c r1) \<and> s\<^sub>4 \<in> L r2)"
       
   163         by (force split: if_splits elim!: Posix_elims simp add: Sequ_def der_correctness Der_def)   
       
   164   then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" 
       
   165     proof (cases)
       
   166       case left_nullable
       
   167       have "s1 \<in> der c r1 \<rightarrow> v1" by fact
       
   168       then have "(c # s1) \<in> r1 \<rightarrow> injval r1 c v1" using IH1 by simp
       
   169       moreover
       
   170       have "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> s1 @ s\<^sub>3 \<in> L (der c r1) \<and> s\<^sub>4 \<in> L r2)" by fact
       
   171       then have "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> (c # s1) @ s\<^sub>3 \<in> L r1 \<and> s\<^sub>4 \<in> L r2)" by (simp add: der_correctness Der_def)
       
   172       ultimately have "((c # s1) @ s2) \<in> SEQ r1 r2 \<rightarrow> Seq (injval r1 c v1) v2" using left_nullable by (rule_tac Posix.intros)
       
   173       then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" using left_nullable by simp
       
   174     next
       
   175       case right_nullable
       
   176       have "nullable r1" by fact
       
   177       then have "[] \<in> r1 \<rightarrow> (mkeps r1)" by (rule Posix_mkeps)
       
   178       moreover
       
   179       have "s \<in> der c r2 \<rightarrow> v1" by fact
       
   180       then have "(c # s) \<in> r2 \<rightarrow> (injval r2 c v1)" using IH2 by simp
       
   181       moreover
       
   182       have "s1 @ s2 \<notin> L (SEQ (der c r1) r2)" by fact
       
   183       then have "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = c # s \<and> [] @ s\<^sub>3 \<in> L r1 \<and> s\<^sub>4 \<in> L r2)" using right_nullable
       
   184         by(auto simp add: der_correctness Der_def append_eq_Cons_conv Sequ_def)
       
   185       ultimately have "([] @ (c # s)) \<in> SEQ r1 r2 \<rightarrow> Seq (mkeps r1) (injval r2 c v1)"
       
   186       by(rule Posix.intros)
       
   187       then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" using right_nullable by simp
       
   188     next
       
   189       case not_nullable
       
   190       have "s1 \<in> der c r1 \<rightarrow> v1" by fact
       
   191       then have "(c # s1) \<in> r1 \<rightarrow> injval r1 c v1" using IH1 by simp
       
   192       moreover
       
   193       have "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> s1 @ s\<^sub>3 \<in> L (der c r1) \<and> s\<^sub>4 \<in> L r2)" by fact
       
   194       then have "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> (c # s1) @ s\<^sub>3 \<in> L r1 \<and> s\<^sub>4 \<in> L r2)" by (simp add: der_correctness Der_def)
       
   195       ultimately have "((c # s1) @ s2) \<in> SEQ r1 r2 \<rightarrow> Seq (injval r1 c v1) v2" using not_nullable 
       
   196         by (rule_tac Posix.intros) (simp_all) 
       
   197       then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" using not_nullable by simp
       
   198     qed
       
   199 next
       
   200   case (STAR r)
       
   201   have IH: "\<And>s v. s \<in> der c r \<rightarrow> v \<Longrightarrow> (c # s) \<in> r \<rightarrow> injval r c v" by fact
       
   202   have "s \<in> der c (STAR r) \<rightarrow> v" by fact
       
   203   then consider
       
   204       (cons) v1 vs s1 s2 where 
       
   205         "v = Seq v1 (Stars vs)" "s = s1 @ s2" 
       
   206         "s1 \<in> der c r \<rightarrow> v1" "s2 \<in> (STAR r) \<rightarrow> (Stars vs)"
       
   207         "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> s1 @ s\<^sub>3 \<in> L (der c r) \<and> s\<^sub>4 \<in> L (STAR r))" 
       
   208         apply(auto elim!: Posix_elims(1-5) simp add: der_correctness Der_def intro: Posix.intros)
       
   209         apply(rotate_tac 3)
       
   210         apply(erule_tac Posix_elims(6))
       
   211         apply (simp add: Posix.intros(6))
       
   212         using Posix.intros(7) by blast
       
   213     then show "(c # s) \<in> STAR r \<rightarrow> injval (STAR r) c v" 
       
   214     proof (cases)
       
   215       case cons
       
   216           have "s1 \<in> der c r \<rightarrow> v1" by fact
       
   217           then have "(c # s1) \<in> r \<rightarrow> injval r c v1" using IH by simp
       
   218         moreover
       
   219           have "s2 \<in> STAR r \<rightarrow> Stars vs" by fact
       
   220         moreover 
       
   221           have "(c # s1) \<in> r \<rightarrow> injval r c v1" by fact 
       
   222           then have "flat (injval r c v1) = (c # s1)" by (rule Posix1)
       
   223           then have "flat (injval r c v1) \<noteq> []" by simp
       
   224         moreover 
       
   225           have "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> s1 @ s\<^sub>3 \<in> L (der c r) \<and> s\<^sub>4 \<in> L (STAR r))" by fact
       
   226           then have "\<not> (\<exists>s\<^sub>3 s\<^sub>4. s\<^sub>3 \<noteq> [] \<and> s\<^sub>3 @ s\<^sub>4 = s2 \<and> (c # s1) @ s\<^sub>3 \<in> L r \<and> s\<^sub>4 \<in> L (STAR r))" 
       
   227             by (simp add: der_correctness Der_def)
       
   228         ultimately 
       
   229         have "((c # s1) @ s2) \<in> STAR r \<rightarrow> Stars (injval r c v1 # vs)" by (rule Posix.intros)
       
   230         then show "(c # s) \<in> STAR r \<rightarrow> injval (STAR r) c v" using cons by(simp)
       
   231     qed
       
   232 qed
       
   233 
       
   234 
       
   235 section {* Lexer Correctness *}
       
   236 
       
   237 
       
   238 lemma lexer_correct_None:
       
   239   shows "s \<notin> L r \<longleftrightarrow> lexer r s = None"
       
   240   apply(induct s arbitrary: r)
       
   241   apply(simp)
       
   242   apply(simp add: nullable_correctness)
       
   243   apply(simp)
       
   244   apply(drule_tac x="der a r" in meta_spec) 
       
   245   apply(auto)
       
   246   apply(auto simp add: der_correctness Der_def)
       
   247 done
       
   248 
       
   249 lemma lexer_correct_Some:
       
   250   shows "s \<in> L r \<longleftrightarrow> (\<exists>v. lexer r s = Some(v) \<and> s \<in> r \<rightarrow> v)"
       
   251   apply(induct s arbitrary : r)
       
   252   apply(simp only: lexer.simps)
       
   253   apply(simp)
       
   254   apply(simp add: nullable_correctness Posix_mkeps)
       
   255   apply(drule_tac x="der a r" in meta_spec)
       
   256   apply(simp (no_asm_use) add: der_correctness Der_def del: lexer.simps) 
       
   257   apply(simp del: lexer.simps)
       
   258   apply(simp only: lexer.simps)
       
   259   apply(case_tac "lexer (der a r) s = None")
       
   260    apply(auto)[1]
       
   261   apply(simp)
       
   262   apply(erule exE)
       
   263   apply(simp)
       
   264   apply(rule iffI)
       
   265   apply(simp add: Posix_injval)
       
   266   apply(simp add: Posix1(1))
       
   267 done 
       
   268 
       
   269 lemma lexer_correctness:
       
   270   shows "(lexer r s = Some v) \<longleftrightarrow> s \<in> r \<rightarrow> v"
       
   271   and   "(lexer r s = None) \<longleftrightarrow> \<not>(\<exists>v. s \<in> r \<rightarrow> v)"
       
   272 using Posix1(1) Posix_determ lexer_correct_None lexer_correct_Some apply fastforce
       
   273 using Posix1(1) lexer_correct_None lexer_correct_Some by blast
       
   274 
       
   275 
       
   276 subsection {* A slight reformulation of the lexer algorithm using stacked functions*}
       
   277 
       
   278 fun flex :: "rexp \<Rightarrow> (val \<Rightarrow> val) => string \<Rightarrow> (val \<Rightarrow> val)"
       
   279   where
       
   280   "flex r f [] = f"
       
   281 | "flex r f (c#s) = flex (der c r) (\<lambda>v. f (injval r c v)) s"  
       
   282 
       
   283 lemma flex_fun_apply:
       
   284   shows "g (flex r f s v) = flex r (g o f) s v"
       
   285   apply(induct s arbitrary: g f r v)
       
   286   apply(simp_all add: comp_def)
       
   287   by meson
       
   288 
       
   289 lemma flex_fun_apply2:
       
   290   shows "g (flex r id s v) = flex r g s v"
       
   291   by (simp add: flex_fun_apply)
       
   292 
       
   293 
       
   294 lemma flex_append:
       
   295   shows "flex r f (s1 @ s2) = flex (ders s1 r) (flex r f s1) s2"
       
   296   apply(induct s1 arbitrary: s2 r f)
       
   297   apply(simp_all)
       
   298   done  
       
   299 
       
   300 lemma lexer_flex:
       
   301   shows "lexer r s = (if nullable (ders s r) 
       
   302                       then Some(flex r id s (mkeps (ders s r))) else None)"
       
   303   apply(induct s arbitrary: r)
       
   304   apply(simp_all add: flex_fun_apply)
       
   305   done  
       
   306 
       
   307 lemma Posix_flex:
       
   308   assumes "s2 \<in> (ders s1 r) \<rightarrow> v"
       
   309   shows "(s1 @ s2) \<in> r \<rightarrow> flex r id s1 v"
       
   310   using assms
       
   311   apply(induct s1 arbitrary: r v s2)
       
   312   apply(simp)
       
   313   apply(simp)  
       
   314   apply(drule_tac x="der a r" in meta_spec)
       
   315   apply(drule_tac x="v" in meta_spec)
       
   316   apply(drule_tac x="s2" in meta_spec)
       
   317   apply(simp)
       
   318   using  Posix_injval
       
   319   apply(drule_tac Posix_injval)
       
   320   apply(subst (asm) (5) flex_fun_apply)
       
   321   apply(simp)
       
   322   done
       
   323 
       
   324 lemma injval_inj:
       
   325   assumes "\<Turnstile> a : (der c r)" "\<Turnstile> v : (der c r)" "injval r c a = injval r c v" 
       
   326   shows "a = v"
       
   327   using  assms
       
   328   apply(induct r arbitrary: a c v)
       
   329        apply(auto)
       
   330   using Prf_elims(1) apply blast
       
   331   using Prf_elims(1) apply blast
       
   332      apply(case_tac "c = x")
       
   333       apply(auto)
       
   334   using Prf_elims(4) apply auto[1]
       
   335   using Prf_elims(1) apply blast
       
   336     prefer 2
       
   337   apply (smt Prf_elims(3) injval.simps(2) injval.simps(3) val.distinct(25) val.inject(3) val.inject(4))
       
   338   apply(case_tac "nullable r1")
       
   339     apply(auto)
       
   340     apply(erule Prf_elims)
       
   341      apply(erule Prf_elims)
       
   342      apply(erule Prf_elims)
       
   343       apply(erule Prf_elims)
       
   344       apply(auto)
       
   345      apply (metis Prf_injval_flat list.distinct(1) mkeps_flat)
       
   346   apply(erule Prf_elims)
       
   347      apply(erule Prf_elims)
       
   348   apply(auto)
       
   349   using Prf_injval_flat mkeps_flat apply fastforce
       
   350   apply(erule Prf_elims)
       
   351      apply(erule Prf_elims)
       
   352    apply(auto)
       
   353   apply(erule Prf_elims)
       
   354      apply(erule Prf_elims)
       
   355   apply(auto)
       
   356    apply (smt Prf_elims(6) injval.simps(7) list.inject val.inject(5))
       
   357   by (smt Prf_elims(6) injval.simps(7) list.inject val.inject(5))
       
   358   
       
   359   
       
   360 
       
   361 lemma uu:
       
   362   assumes "(c # s) \<in> r \<rightarrow> injval r c v" "\<Turnstile> v : (der c r)"
       
   363   shows "s \<in> der c r \<rightarrow> v"
       
   364   using assms
       
   365   apply -
       
   366   apply(subgoal_tac "lexer r (c # s) = Some (injval r c v)")
       
   367   prefer 2
       
   368   using lexer_correctness(1) apply blast
       
   369   apply(simp add: )
       
   370   apply(case_tac  "lexer (der c r) s")
       
   371    apply(simp)
       
   372   apply(simp)
       
   373   apply(case_tac "s \<in> der c r \<rightarrow> a")
       
   374    prefer 2
       
   375    apply (simp add: lexer_correctness(1))
       
   376   apply(subgoal_tac "\<Turnstile> a : (der c r)")
       
   377    prefer 2
       
   378   using Posix_Prf apply blast
       
   379   using injval_inj by blast
       
   380   
       
   381 
       
   382 lemma Posix_flex2:
       
   383   assumes "(s1 @ s2) \<in> r \<rightarrow> flex r id s1 v" "\<Turnstile> v : ders s1 r"
       
   384   shows "s2 \<in> (ders s1 r) \<rightarrow> v"
       
   385   using assms
       
   386   apply(induct s1 arbitrary: r v s2 rule: rev_induct)
       
   387   apply(simp)
       
   388   apply(simp)  
       
   389   apply(drule_tac x="r" in meta_spec)
       
   390   apply(drule_tac x="injval (ders xs r) x v" in meta_spec)
       
   391   apply(drule_tac x="x#s2" in meta_spec)
       
   392   apply(simp add: flex_append ders_append)
       
   393   using Prf_injval uu by blast
       
   394 
       
   395 lemma Posix_flex3:
       
   396   assumes "s1 \<in> r \<rightarrow> flex r id s1 v" "\<Turnstile> v : ders s1 r"
       
   397   shows "[] \<in> (ders s1 r) \<rightarrow> v"
       
   398   using assms
       
   399   by (simp add: Posix_flex2)
       
   400 
       
   401 lemma flex_injval:
       
   402   shows "flex (der a r) (injval r a) s v = injval r a (flex (der a r) id s v)"
       
   403   by (simp add: flex_fun_apply)
       
   404   
       
   405 lemma Prf_flex:
       
   406   assumes "\<Turnstile> v : ders s r"
       
   407   shows "\<Turnstile> flex r id s v : r"
       
   408   using assms
       
   409   apply(induct s arbitrary: v r)
       
   410   apply(simp)
       
   411   apply(simp)
       
   412   by (simp add: Prf_injval flex_injval)
       
   413 
       
   414 
       
   415 unused_thms
       
   416 
       
   417 end