diff -r 6ceb8d38bc9e -r 35fcab3da1b7 src/HOL/Lambda/ParRed.thy --- a/src/HOL/Lambda/ParRed.thy Tue Sep 07 11:51:53 2010 +0200 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,115 +0,0 @@ -(* Title: HOL/Lambda/ParRed.thy - Author: Tobias Nipkow - Copyright 1995 TU Muenchen - -Properties of => and "cd", in particular the diamond property of => and -confluence of beta. -*) - -header {* Parallel reduction and a complete developments *} - -theory ParRed imports Lambda Commutation begin - - -subsection {* Parallel reduction *} - -inductive par_beta :: "[dB, dB] => bool" (infixl "=>" 50) - where - var [simp, intro!]: "Var n => Var n" - | abs [simp, intro!]: "s => t ==> Abs s => Abs t" - | app [simp, intro!]: "[| s => s'; t => t' |] ==> s \ t => s' \ t'" - | beta [simp, intro!]: "[| s => s'; t => t' |] ==> (Abs s) \ t => s'[t'/0]" - -inductive_cases par_beta_cases [elim!]: - "Var n => t" - "Abs s => Abs t" - "(Abs s) \ t => u" - "s \ t => u" - "Abs s => t" - - -subsection {* Inclusions *} - -text {* @{text "beta \ par_beta \ beta^*"} \medskip *} - -lemma par_beta_varL [simp]: - "(Var n => t) = (t = Var n)" - by blast - -lemma par_beta_refl [simp]: "t => t" (* par_beta_refl [intro!] causes search to blow up *) - by (induct t) simp_all - -lemma beta_subset_par_beta: "beta <= par_beta" - apply (rule predicate2I) - apply (erule beta.induct) - apply (blast intro!: par_beta_refl)+ - done - -lemma par_beta_subset_beta: "par_beta <= beta^**" - apply (rule predicate2I) - apply (erule par_beta.induct) - apply blast - apply (blast del: rtranclp.rtrancl_refl intro: rtranclp.rtrancl_into_rtrancl)+ - -- {* @{thm[source] rtrancl_refl} complicates the proof by increasing the branching factor *} - done - - -subsection {* Misc properties of @{text "par_beta"} *} - -lemma par_beta_lift [simp]: - "t => t' \ lift t n => lift t' n" - by (induct t arbitrary: t' n) fastsimp+ - -lemma par_beta_subst: - "s => s' \ t => t' \ t[s/n] => t'[s'/n]" - apply (induct t arbitrary: s s' t' n) - apply (simp add: subst_Var) - apply (erule par_beta_cases) - apply simp - apply (simp add: subst_subst [symmetric]) - apply (fastsimp intro!: par_beta_lift) - apply fastsimp - done - - -subsection {* Confluence (directly) *} - -lemma diamond_par_beta: "diamond par_beta" - apply (unfold diamond_def commute_def square_def) - apply (rule impI [THEN allI [THEN allI]]) - apply (erule par_beta.induct) - apply (blast intro!: par_beta_subst)+ - done - - -subsection {* Complete developments *} - -fun - "cd" :: "dB => dB" -where - "cd (Var n) = Var n" -| "cd (Var n \ t) = Var n \ cd t" -| "cd ((s1 \ s2) \ t) = cd (s1 \ s2) \ cd t" -| "cd (Abs u \ t) = (cd u)[cd t/0]" -| "cd (Abs s) = Abs (cd s)" - -lemma par_beta_cd: "s => t \ t => cd s" - apply (induct s arbitrary: t rule: cd.induct) - apply auto - apply (fast intro!: par_beta_subst) - done - - -subsection {* Confluence (via complete developments) *} - -lemma diamond_par_beta2: "diamond par_beta" - apply (unfold diamond_def commute_def square_def) - apply (blast intro: par_beta_cd) - done - -theorem beta_confluent: "confluent beta" - apply (rule diamond_par_beta2 diamond_to_confluence - par_beta_subset_beta beta_subset_par_beta)+ - done - -end