theory Lexer

begin

fun 

  mkeps :: "rexp \<Rightarrow> val"

where

  "mkeps(ONE) = Void"

| "mkeps(SEQ r1 r2) = Seq (mkeps r1) (mkeps r2)"

| "mkeps(ALT r1 r2) = (if nullable(r1) then Left (mkeps r1) else Right (mkeps r2))"

| "mkeps(STAR r) = Stars []"

fun injval :: "rexp \<Rightarrow> char \<Rightarrow> val \<Rightarrow> val"

where

  "injval (CHAR d) c Void = Char d"

| "injval (ALT r1 r2) c (Left v1) = Left(injval r1 c v1)"

| "injval (ALT r1 r2) c (Right v2) = Right(injval r2 c v2)"

| "injval (SEQ r1 r2) c (Seq v1 v2) = Seq (injval r1 c v1) v2"

| "injval (SEQ r1 r2) c (Left (Seq v1 v2)) = Seq (injval r1 c v1) v2"

| "injval (SEQ r1 r2) c (Right v2) = Seq (mkeps r1) (injval r2 c v2)"

| "injval (STAR r) c (Seq v (Stars vs)) = Stars ((injval r c v) # vs)" 

lemma mkeps_nullable:

  assumes "nullable(r)" 

  shows "\<turnstile> mkeps r : r"

using assms

by (induct rule: nullable.induct) 

   (auto intro: Prf.intros)

lemma mkeps_flat:

  assumes "nullable(r)" 

  shows "flat (mkeps r) = []"

using assms

by (induct rule: nullable.induct) (auto)

lemma Prf_injval:

  assumes "\<turnstile> v : der c r" 

  shows "\<turnstile> (injval r c v) : r"

using assms

apply(induct r arbitrary: c v rule: rexp.induct)

apply(auto intro!: Prf.intros mkeps_nullable elim!: Prf_elims split: if_splits)

done

lemma Prf_injval_flat:

  assumes "\<turnstile> v : der c r" 

  shows "flat (injval r c v) = c # (flat v)"

using assms

apply(induct arbitrary: v rule: der.induct)

apply(auto elim!: Prf_elims intro: mkeps_flat split: if_splits)

done

lemma Posix_mkeps:

  assumes "nullable r"

  shows "[] \<in> r \<rightarrow> mkeps r"

using assms

apply(induct r rule: nullable.induct)

apply(auto intro: Posix.intros simp add: nullable_correctness Sequ_def)

apply(subst append.simps(1)[symmetric])

apply(rule Posix.intros)

apply(auto)

done

lemma Posix_injval:

  assumes "s \<in> (der c r) \<rightarrow> v"

  shows "(c # s) \<in> r \<rightarrow> (injval r c v)"

using assms

proof(induct r arbitrary: s v rule: rexp.induct)

  case ZERO

  have "s \<in> der c ZERO \<rightarrow> v" by fact

  then have "s \<in> ZERO \<rightarrow> v" by simp

  then have "False" by cases

  then show "(c # s) \<in> ZERO \<rightarrow> (injval ZERO c v)" by simp

next

  case ONE

  have "s \<in> der c ONE \<rightarrow> v" by fact

  then have "s \<in> ZERO \<rightarrow> v" by simp

  then have "False" by cases

  then show "(c # s) \<in> ONE \<rightarrow> (injval ONE c v)" by simp

next 

  case (CHAR d)

  consider (eq) "c = d" | (ineq) "c \<noteq> d" by blast

  then show "(c # s) \<in> (CHAR d) \<rightarrow> (injval (CHAR d) c v)"

  proof (cases)

    case eq

    have "s \<in> der c (CHAR d) \<rightarrow> v" by fact

    then have "s \<in> ONE \<rightarrow> v" using eq by simp

    then have eqs: "s = [] \<and> v = Void" by cases simp

    show "(c # s) \<in> CHAR d \<rightarrow> injval (CHAR d) c v" using eq eqs 

    by (auto intro: Posix.intros)

  next

    case ineq

    have "s \<in> der c (CHAR d) \<rightarrow> v" by fact

    then have "s \<in> ZERO \<rightarrow> v" using ineq by simp

    then have "False" by cases

    then show "(c # s) \<in> CHAR d \<rightarrow> injval (CHAR d) c v" by simp

  qed

next

  case (ALT r1 r2)

  have IH1: "\<And>s v. s \<in> der c r1 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r1 \<rightarrow> injval r1 c v" by fact

  have IH2: "\<And>s v. s \<in> der c r2 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r2 \<rightarrow> injval r2 c v" by fact

  have "s \<in> der c (ALT r1 r2) \<rightarrow> v" by fact

  then have "s \<in> ALT (der c r1) (der c r2) \<rightarrow> v" by simp

  then consider (left) v' where "v = Left v'" "s \<in> der c r1 \<rightarrow> v'" 

              | (right) v' where "v = Right v'" "s \<notin> L (der c r1)" "s \<in> der c r2 \<rightarrow> v'" 

              by cases auto

  then show "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c v"

  proof (cases)

    case left

    have "s \<in> der c r1 \<rightarrow> v'" by fact

    then have "(c # s) \<in> r1 \<rightarrow> injval r1 c v'" using IH1 by simp

    then have "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c (Left v')" by (auto intro: Posix.intros)

    then show "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c v" using left by simp

  next 

    case right

    have "s \<notin> L (der c r1)" by fact

    then have "c # s \<notin> L r1" by (simp add: der_correctness Der_def)

    moreover 

    have "s \<in> der c r2 \<rightarrow> v'" by fact

    then have "(c # s) \<in> r2 \<rightarrow> injval r2 c v'" using IH2 by simp

    ultimately have "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c (Right v')" 

      by (auto intro: Posix.intros)

    then show "(c # s) \<in> ALT r1 r2 \<rightarrow> injval (ALT r1 r2) c v" using right by simp

  qed

next

  case (SEQ r1 r2)

  have IH1: "\<And>s v. s \<in> der c r1 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r1 \<rightarrow> injval r1 c v" by fact

  have IH2: "\<And>s v. s \<in> der c r2 \<rightarrow> v \<Longrightarrow> (c # s) \<in> r2 \<rightarrow> injval r2 c v" by fact

  have "s \<in> der c (SEQ r1 r2) \<rightarrow> v" by fact

  then consider 

        (left_nullable) v1 v2 s1 s2 where 

        "v = Left (Seq v1 v2)"  "s = s1 @ s2" 

        "s1 \<in> der c r1 \<rightarrow> v1" "s2 \<in> r2 \<rightarrow> v2" "nullable r1" 

        "\<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)"

      | (right_nullable) v1 s1 s2 where 

        "v = Right v1" "s = s1 @ s2"  

        "s \<in> der c r2 \<rightarrow> v1" "nullable r1" "s1 @ s2 \<notin> L (SEQ (der c r1) r2)"

      | (not_nullable) v1 v2 s1 s2 where

        "v = Seq v1 v2" "s = s1 @ s2" 

        "s1 \<in> der c r1 \<rightarrow> v1" "s2 \<in> r2 \<rightarrow> v2" "\<not>nullable r1" 

        "\<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 (force split: if_splits elim!: Posix_elims simp add: Sequ_def der_correctness Der_def)   

  then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" 

    proof (cases)

      case left_nullable

      have "s1 \<in> der c r1 \<rightarrow> v1" by fact

      then have "(c # s1) \<in> r1 \<rightarrow> injval r1 c v1" using IH1 by simp

      moreover

      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

      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)

      ultimately have "((c # s1) @ s2) \<in> SEQ r1 r2 \<rightarrow> Seq (injval r1 c v1) v2" using left_nullable by (rule_tac Posix.intros)

      then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" using left_nullable by simp

    next

      case right_nullable

      have "nullable r1" by fact

      then have "[] \<in> r1 \<rightarrow> (mkeps r1)" by (rule Posix_mkeps)

      moreover

      have "s \<in> der c r2 \<rightarrow> v1" by fact

      then have "(c # s) \<in> r2 \<rightarrow> (injval r2 c v1)" using IH2 by simp

      moreover

      have "s1 @ s2 \<notin> L (SEQ (der c r1) r2)" by fact

      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

        by(auto simp add: der_correctness Der_def append_eq_Cons_conv Sequ_def)

      ultimately have "([] @ (c # s)) \<in> SEQ r1 r2 \<rightarrow> Seq (mkeps r1) (injval r2 c v1)"

      by(rule Posix.intros)

      then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" using right_nullable by simp

    next

      case not_nullable

      have "s1 \<in> der c r1 \<rightarrow> v1" by fact

      then have "(c # s1) \<in> r1 \<rightarrow> injval r1 c v1" using IH1 by simp

      moreover

      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

      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)

      ultimately have "((c # s1) @ s2) \<in> SEQ r1 r2 \<rightarrow> Seq (injval r1 c v1) v2" using not_nullable 

        by (rule_tac Posix.intros) (simp_all) 

      then show "(c # s) \<in> SEQ r1 r2 \<rightarrow> injval (SEQ r1 r2) c v" using not_nullable by simp

    qed

next

  case (STAR r)

  have IH: "\<And>s v. s \<in> der c r \<rightarrow> v \<Longrightarrow> (c # s) \<in> r \<rightarrow> injval r c v" by fact

  have "s \<in> der c (STAR r) \<rightarrow> v" by fact

  then consider

      (cons) v1 vs s1 s2 where 

        "v = Seq v1 (Stars vs)" "s = s1 @ s2" 

        "s1 \<in> der c r \<rightarrow> v1" "s2 \<in> (STAR r) \<rightarrow> (Stars vs)"

        "\<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))" 

        apply(auto elim!: Posix_elims(1-5) simp add: der_correctness Der_def intro: Posix.intros)

        apply(rotate_tac 3)

        apply(erule_tac Posix_elims(6))

        apply (simp add: Posix.intros(6))

        using Posix.intros(7) by blast

    then show "(c # s) \<in> STAR r \<rightarrow> injval (STAR r) c v" 

    proof (cases)

      case cons

          have "s1 \<in> der c r \<rightarrow> v1" by fact

          then have "(c # s1) \<in> r \<rightarrow> injval r c v1" using IH by simp

        moreover

          have "s2 \<in> STAR r \<rightarrow> Stars vs" by fact

        moreover 

          have "(c # s1) \<in> r \<rightarrow> injval r c v1" by fact 

          then have "flat (injval r c v1) = (c # s1)" by (rule Posix1)

          then have "flat (injval r c v1) \<noteq> []" by simp

        moreover 

          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

          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))" 

            by (simp add: der_correctness Der_def)

        ultimately 

        have "((c # s1) @ s2) \<in> STAR r \<rightarrow> Stars (injval r c v1 # vs)" by (rule Posix.intros)

        then show "(c # s) \<in> STAR r \<rightarrow> injval (STAR r) c v" using cons by(simp)

    qed

qed

lemma lexer_correct_None:

  shows "s \<notin> L r \<longleftrightarrow> lexer r s = None"

apply(induct s arbitrary: r)

apply(simp add: nullable_correctness)

apply(drule_tac x="der a r" in meta_spec)

apply(auto simp add: der_correctness Der_def)

done

lemma lexer_correct_Some:

  shows "s \<in> L r \<longleftrightarrow> (\<exists>v. lexer r s = Some(v) \<and> s \<in> r \<rightarrow> v)"

apply(induct s arbitrary: r)

apply(auto simp add: Posix_mkeps nullable_correctness)[1]

apply(drule_tac x="der a r" in meta_spec)

apply(simp add: der_correctness Der_def)

apply(rule iffI)

apply(auto intro: Posix_injval simp add: Posix1(1))

done 

lemma lexer_correctness:

  shows "(lexer r s = Some v) \<longleftrightarrow> s \<in> r \<rightarrow> v"

  and   "(lexer r s = None) \<longleftrightarrow> \<not>(\<exists>v. s \<in> r \<rightarrow> v)"

using Posix1(1) Posix_determ lexer_correct_None lexer_correct_Some apply fastforce

using Posix1(1) lexer_correct_None lexer_correct_Some by blast

end