--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/AFP-Submission/Regular_Exp.thy Tue May 24 11:36:21 2016 +0100
@@ -0,0 +1,160 @@
+(* Author: Tobias Nipkow *)
+
+section "Regular expressions"
+
+theory Regular_Exp
+imports Regular_Set
+begin
+
+datatype (atoms: 'a) rexp =
+ is_Zero: Zero |
+ is_One: One |
+ Atom 'a |
+ Plus "('a rexp)" "('a rexp)" |
+ Times "('a rexp)" "('a rexp)" |
+ Star "('a rexp)"
+
+primrec lang :: "'a rexp => 'a lang" where
+"lang Zero = {}" |
+"lang One = {[]}" |
+"lang (Atom a) = {[a]}" |
+"lang (Plus r s) = (lang r) Un (lang s)" |
+"lang (Times r s) = conc (lang r) (lang s)" |
+"lang (Star r) = star(lang r)"
+
+primrec nullable :: "'a rexp \<Rightarrow> bool" where
+"nullable Zero = False" |
+"nullable One = True" |
+"nullable (Atom c) = False" |
+"nullable (Plus r1 r2) = (nullable r1 \<or> nullable r2)" |
+"nullable (Times r1 r2) = (nullable r1 \<and> nullable r2)" |
+"nullable (Star r) = True"
+
+lemma nullable_iff: "nullable r \<longleftrightarrow> [] \<in> lang r"
+by (induct r) (auto simp add: conc_def split: if_splits)
+
+text{* Composition on rhs usually complicates matters: *}
+lemma map_map_rexp:
+ "map_rexp f (map_rexp g r) = map_rexp (\<lambda>r. f (g r)) r"
+ unfolding rexp.map_comp o_def ..
+
+lemma map_rexp_ident[simp]: "map_rexp (\<lambda>x. x) = (\<lambda>r. r)"
+ unfolding id_def[symmetric] fun_eq_iff rexp.map_id id_apply by (intro allI refl)
+
+lemma atoms_lang: "w : lang r \<Longrightarrow> set w \<subseteq> atoms r"
+proof(induction r arbitrary: w)
+ case Times thus ?case by fastforce
+next
+ case Star thus ?case by (fastforce simp add: star_conv_concat)
+qed auto
+
+lemma lang_eq_ext: "(lang r = lang s) =
+ (\<forall>w \<in> lists(atoms r \<union> atoms s). w \<in> lang r \<longleftrightarrow> w \<in> lang s)"
+ by (auto simp: atoms_lang[unfolded subset_iff])
+
+lemma lang_eq_ext_Nil_fold_Deriv:
+ fixes r s
+ defines "\<BB> \<equiv> {(fold Deriv w (lang r), fold Deriv w (lang s))| w. w\<in>lists (atoms r \<union> atoms s)}"
+ shows "lang r = lang s \<longleftrightarrow> (\<forall>(K, L) \<in> \<BB>. [] \<in> K \<longleftrightarrow> [] \<in> L)"
+ unfolding lang_eq_ext \<BB>_def by (subst (1 2) in_fold_Deriv[of "[]", simplified, symmetric]) auto
+
+
+subsection {* Term ordering *}
+
+instantiation rexp :: (order) "{order}"
+begin
+
+fun le_rexp :: "('a::order) rexp \<Rightarrow> ('a::order) rexp \<Rightarrow> bool"
+where
+ "le_rexp Zero _ = True"
+| "le_rexp _ Zero = False"
+| "le_rexp One _ = True"
+| "le_rexp _ One = False"
+| "le_rexp (Atom a) (Atom b) = (a <= b)"
+| "le_rexp (Atom _) _ = True"
+| "le_rexp _ (Atom _) = False"
+| "le_rexp (Star r) (Star s) = le_rexp r s"
+| "le_rexp (Star _) _ = True"
+| "le_rexp _ (Star _) = False"
+| "le_rexp (Plus r r') (Plus s s') =
+ (if r = s then le_rexp r' s' else le_rexp r s)"
+| "le_rexp (Plus _ _) _ = True"
+| "le_rexp _ (Plus _ _) = False"
+| "le_rexp (Times r r') (Times s s') =
+ (if r = s then le_rexp r' s' else le_rexp r s)"
+
+(* The class instance stuff is by Dmitriy Traytel *)
+
+definition less_eq_rexp where "r \<le> s \<equiv> le_rexp r s"
+definition less_rexp where "r < s \<equiv> le_rexp r s \<and> r \<noteq> s"
+
+lemma le_rexp_Zero: "le_rexp r Zero \<Longrightarrow> r = Zero"
+by (induction r) auto
+
+lemma le_rexp_refl: "le_rexp r r"
+by (induction r) auto
+
+lemma le_rexp_antisym: "\<lbrakk>le_rexp r s; le_rexp s r\<rbrakk> \<Longrightarrow> r = s"
+by (induction r s rule: le_rexp.induct) (auto dest: le_rexp_Zero)
+
+lemma le_rexp_trans: "\<lbrakk>le_rexp r s; le_rexp s t\<rbrakk> \<Longrightarrow> le_rexp r t"
+proof (induction r s arbitrary: t rule: le_rexp.induct)
+ fix v t assume "le_rexp (Atom v) t" thus "le_rexp One t" by (cases t) auto
+next
+ fix s1 s2 t assume "le_rexp (Plus s1 s2) t" thus "le_rexp One t" by (cases t) auto
+next
+ fix s1 s2 t assume "le_rexp (Times s1 s2) t" thus "le_rexp One t" by (cases t) auto
+next
+ fix s t assume "le_rexp (Star s) t" thus "le_rexp One t" by (cases t) auto
+next
+ fix v u t assume "le_rexp (Atom v) (Atom u)" "le_rexp (Atom u) t"
+ thus "le_rexp (Atom v) t" by (cases t) auto
+next
+ fix v s1 s2 t assume "le_rexp (Plus s1 s2) t" thus "le_rexp (Atom v) t" by (cases t) auto
+next
+ fix v s1 s2 t assume "le_rexp (Times s1 s2) t" thus "le_rexp (Atom v) t" by (cases t) auto
+next
+ fix v s t assume "le_rexp (Star s) t" thus "le_rexp (Atom v) t" by (cases t) auto
+next
+ fix r s t
+ assume IH: "\<And>t. le_rexp r s \<Longrightarrow> le_rexp s t \<Longrightarrow> le_rexp r t"
+ and "le_rexp (Star r) (Star s)" "le_rexp (Star s) t"
+ thus "le_rexp (Star r) t" by (cases t) auto
+next
+ fix r s1 s2 t assume "le_rexp (Plus s1 s2) t" thus "le_rexp (Star r) t" by (cases t) auto
+next
+ fix r s1 s2 t assume "le_rexp (Times s1 s2) t" thus "le_rexp (Star r) t" by (cases t) auto
+next
+ fix r1 r2 s1 s2 t
+ assume "\<And>t. r1 = s1 \<Longrightarrow> le_rexp r2 s2 \<Longrightarrow> le_rexp s2 t \<Longrightarrow> le_rexp r2 t"
+ "\<And>t. r1 \<noteq> s1 \<Longrightarrow> le_rexp r1 s1 \<Longrightarrow> le_rexp s1 t \<Longrightarrow> le_rexp r1 t"
+ "le_rexp (Plus r1 r2) (Plus s1 s2)" "le_rexp (Plus s1 s2) t"
+ thus "le_rexp (Plus r1 r2) t" by (cases t) (auto split: split_if_asm intro: le_rexp_antisym)
+next
+ fix r1 r2 s1 s2 t assume "le_rexp (Times s1 s2) t" thus "le_rexp (Plus r1 r2) t" by (cases t) auto
+next
+ fix r1 r2 s1 s2 t
+ assume "\<And>t. r1 = s1 \<Longrightarrow> le_rexp r2 s2 \<Longrightarrow> le_rexp s2 t \<Longrightarrow> le_rexp r2 t"
+ "\<And>t. r1 \<noteq> s1 \<Longrightarrow> le_rexp r1 s1 \<Longrightarrow> le_rexp s1 t \<Longrightarrow> le_rexp r1 t"
+ "le_rexp (Times r1 r2) (Times s1 s2)" "le_rexp (Times s1 s2) t"
+ thus "le_rexp (Times r1 r2) t" by (cases t) (auto split: split_if_asm intro: le_rexp_antisym)
+qed auto
+
+instance proof
+qed (auto simp add: less_eq_rexp_def less_rexp_def
+ intro: le_rexp_refl le_rexp_antisym le_rexp_trans)
+
+end
+
+instantiation rexp :: (linorder) "{linorder}"
+begin
+
+lemma le_rexp_total: "le_rexp (r :: 'a :: linorder rexp) s \<or> le_rexp s r"
+by (induction r s rule: le_rexp.induct) auto
+
+instance proof
+qed (unfold less_eq_rexp_def less_rexp_def, rule le_rexp_total)
+
+end
+
+end