author  bulwahn 
Fri, 27 Jan 2012 10:31:30 +0100  
changeset 46343  6d9535e52915 
parent 41310  65631ca437c9 
child 47025  b2b8ae61d6ad 
permissions  rwrr 
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(* Title: LCF/LCF.thy 
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Author: Tobias Nipkow 
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Copyright 1992 University of Cambridge 
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*) 

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header {* LCF on top of FirstOrder Logic *} 
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theory LCF 
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imports FOL 

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begin 

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text {* This theory is based on Lawrence Paulson's book Logic and Computation. *} 
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subsection {* Natural Deduction Rules for LCF *} 
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classes cpo < "term" 

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default_sort cpo 
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typedecl tr 

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typedecl void 

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typedecl ('a,'b) prod (infixl "*" 6) 
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typedecl ('a,'b) sum (infixl "+" 5) 

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arities 
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"fun" :: (cpo, cpo) cpo 
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prod :: (cpo, cpo) cpo 
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sum :: (cpo, cpo) cpo 

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tr :: cpo 
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void :: cpo 

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consts 

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UU :: "'a" 
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TT :: "tr" 
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FF :: "tr" 

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FIX :: "('a => 'a) => 'a" 
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FST :: "'a*'b => 'a" 

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SND :: "'a*'b => 'b" 

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INL :: "'a => 'a+'b" 
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INR :: "'b => 'a+'b" 

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WHEN :: "['a=>'c, 'b=>'c, 'a+'b] => 'c" 

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adm :: "('a => o) => o" 
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VOID :: "void" ("'(')") 

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PAIR :: "['a,'b] => 'a*'b" ("(1<_,/_>)" [0,0] 100) 

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COND :: "[tr,'a,'a] => 'a" ("(_ =>/ (_ / _))" [60,60,60] 60) 

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less :: "['a,'a] => o" (infixl "<<" 50) 
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axioms 

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(** DOMAIN THEORY **) 
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eq_def: "x=y == x << y & y << x" 
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less_trans: "[ x << y; y << z ] ==> x << z" 
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less_ext: "(ALL x. f(x) << g(x)) ==> f << g" 
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mono: "[ f << g; x << y ] ==> f(x) << g(y)" 
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minimal: "UU << x" 
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FIX_eq: "f(FIX(f)) = FIX(f)" 
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(** TR **) 

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tr_cases: "p=UU  p=TT  p=FF" 
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not_TT_less_FF: "~ TT << FF" 
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not_FF_less_TT: "~ FF << TT" 

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not_TT_less_UU: "~ TT << UU" 

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not_FF_less_UU: "~ FF << UU" 

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COND_UU: "UU => x  y = UU" 
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COND_TT: "TT => x  y = x" 

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COND_FF: "FF => x  y = y" 

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(** PAIRS **) 

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surj_pairing: "<FST(z),SND(z)> = z" 
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FST: "FST(<x,y>) = x" 
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SND: "SND(<x,y>) = y" 

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(*** STRICT SUM ***) 

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INL_DEF: "~x=UU ==> ~INL(x)=UU" 
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INR_DEF: "~x=UU ==> ~INR(x)=UU" 

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INL_STRICT: "INL(UU) = UU" 
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INR_STRICT: "INR(UU) = UU" 

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WHEN_UU: "WHEN(f,g,UU) = UU" 
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WHEN_INL: "~x=UU ==> WHEN(f,g,INL(x)) = f(x)" 

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WHEN_INR: "~x=UU ==> WHEN(f,g,INR(x)) = g(x)" 

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SUM_EXHAUSTION: 
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"z = UU  (EX x. ~x=UU & z = INL(x))  (EX y. ~y=UU & z = INR(y))" 
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(** VOID **) 

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void_cases: "(x::void) = UU" 
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(** INDUCTION **) 

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induct: "[ adm(P); P(UU); ALL x. P(x) > P(f(x)) ] ==> P(FIX(f))" 
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(** Admissibility / Chain Completeness **) 

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(* All rules can be found on pages 199200 of Larry's LCF book. 

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Note that "easiness" of types is not taken into account 

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because it cannot be expressed schematically; flatness could be. *) 

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adm_less: "adm(%x. t(x) << u(x))" 
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adm_not_less: "adm(%x.~ t(x) << u)" 

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adm_not_free: "adm(%x. A)" 

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adm_subst: "adm(P) ==> adm(%x. P(t(x)))" 

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adm_conj: "[ adm(P); adm(Q) ] ==> adm(%x. P(x)&Q(x))" 

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adm_disj: "[ adm(P); adm(Q) ] ==> adm(%x. P(x)Q(x))" 

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adm_imp: "[ adm(%x.~P(x)); adm(Q) ] ==> adm(%x. P(x)>Q(x))" 

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adm_all: "(!!y. adm(P(y))) ==> adm(%x. ALL y. P(y,x))" 

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lemma eq_imp_less1: "x = y ==> x << y" 

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by (simp add: eq_def) 

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lemma eq_imp_less2: "x = y ==> y << x" 

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by (simp add: eq_def) 

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lemma less_refl [simp]: "x << x" 

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apply (rule eq_imp_less1) 

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apply (rule refl) 

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done 

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lemma less_anti_sym: "[ x << y; y << x ] ==> x=y" 

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by (simp add: eq_def) 

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lemma ext: "(!!x::'a::cpo. f(x)=(g(x)::'b::cpo)) ==> (%x. f(x))=(%x. g(x))" 

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apply (rule less_anti_sym) 

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apply (rule less_ext) 

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apply simp 

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apply simp 

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done 

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lemma cong: "[ f=g; x=y ] ==> f(x)=g(y)" 

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by simp 

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lemma less_ap_term: "x << y ==> f(x) << f(y)" 

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by (rule less_refl [THEN mono]) 

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lemma less_ap_thm: "f << g ==> f(x) << g(x)" 

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by (rule less_refl [THEN [2] mono]) 

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lemma ap_term: "(x::'a::cpo) = y ==> (f(x)::'b::cpo) = f(y)" 

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apply (rule cong [OF refl]) 

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apply simp 

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done 

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lemma ap_thm: "f = g ==> f(x) = g(x)" 

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apply (erule cong) 

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apply (rule refl) 

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done 

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lemma UU_abs: "(%x::'a::cpo. UU) = UU" 

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apply (rule less_anti_sym) 

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prefer 2 

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apply (rule minimal) 

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apply (rule less_ext) 

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apply (rule allI) 

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apply (rule minimal) 

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done 

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lemma UU_app: "UU(x) = UU" 

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by (rule UU_abs [symmetric, THEN ap_thm]) 

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lemma less_UU: "x << UU ==> x=UU" 

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apply (rule less_anti_sym) 

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apply assumption 

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apply (rule minimal) 

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done 

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lemma tr_induct: "[ P(UU); P(TT); P(FF) ] ==> ALL b. P(b)" 
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apply (rule allI) 

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apply (rule mp) 

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apply (rule_tac [2] p = b in tr_cases) 

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apply blast 

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done 

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lemma Contrapos: "~ B ==> (A ==> B) ==> ~A" 

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by blast 

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lemma not_less_imp_not_eq1: "~ x << y \<Longrightarrow> x \<noteq> y" 

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apply (erule Contrapos) 

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apply simp 

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done 

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lemma not_less_imp_not_eq2: "~ y << x \<Longrightarrow> x \<noteq> y" 

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apply (erule Contrapos) 

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apply simp 

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done 

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lemma not_UU_eq_TT: "UU \<noteq> TT" 

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by (rule not_less_imp_not_eq2) (rule not_TT_less_UU) 

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lemma not_UU_eq_FF: "UU \<noteq> FF" 

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by (rule not_less_imp_not_eq2) (rule not_FF_less_UU) 

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lemma not_TT_eq_UU: "TT \<noteq> UU" 

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by (rule not_less_imp_not_eq1) (rule not_TT_less_UU) 

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lemma not_TT_eq_FF: "TT \<noteq> FF" 

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by (rule not_less_imp_not_eq1) (rule not_TT_less_FF) 

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lemma not_FF_eq_UU: "FF \<noteq> UU" 

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by (rule not_less_imp_not_eq1) (rule not_FF_less_UU) 

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lemma not_FF_eq_TT: "FF \<noteq> TT" 

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by (rule not_less_imp_not_eq1) (rule not_FF_less_TT) 

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lemma COND_cases_iff [rule_format]: 

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"ALL b. P(b=>xy) <> (b=UU>P(UU)) & (b=TT>P(x)) & (b=FF>P(y))" 

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apply (insert not_UU_eq_TT not_UU_eq_FF not_TT_eq_UU 

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not_TT_eq_FF not_FF_eq_UU not_FF_eq_TT) 

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apply (rule tr_induct) 

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apply (simplesubst COND_UU) 

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apply blast 

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apply (simplesubst COND_TT) 

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apply blast 

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apply (simplesubst COND_FF) 

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apply blast 

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done 

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lemma COND_cases: 

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"[ x = UU > P(UU); x = TT > P(xa); x = FF > P(y) ] ==> P(x => xa  y)" 

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apply (rule COND_cases_iff [THEN iffD2]) 

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apply blast 

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done 

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lemmas [simp] = 

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minimal 

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UU_app 

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UU_app [THEN ap_thm] 

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UU_app [THEN ap_thm, THEN ap_thm] 

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not_TT_less_FF not_FF_less_TT not_TT_less_UU not_FF_less_UU not_UU_eq_TT 

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not_UU_eq_FF not_TT_eq_UU not_TT_eq_FF not_FF_eq_UU not_FF_eq_TT 

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COND_UU COND_TT COND_FF 

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surj_pairing FST SND 

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subsection {* Ordered pairs and products *} 

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lemma expand_all_PROD: "(ALL p. P(p)) <> (ALL x y. P(<x,y>))" 
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apply (rule iffI) 

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apply blast 

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apply (rule allI) 

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apply (rule surj_pairing [THEN subst]) 

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apply blast 

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done 

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lemma PROD_less: "(p::'a*'b) << q <> FST(p) << FST(q) & SND(p) << SND(q)" 

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apply (rule iffI) 

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apply (rule conjI) 

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apply (erule less_ap_term) 

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apply (erule less_ap_term) 

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apply (erule conjE) 

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apply (rule surj_pairing [of p, THEN subst]) 

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apply (rule surj_pairing [of q, THEN subst]) 

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apply (rule mono, erule less_ap_term, assumption) 

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done 

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lemma PROD_eq: "p=q <> FST(p)=FST(q) & SND(p)=SND(q)" 

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apply (rule iffI) 

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apply simp 

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apply (unfold eq_def) 

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apply (simp add: PROD_less) 

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done 

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lemma PAIR_less [simp]: "<a,b> << <c,d> <> a<<c & b<<d" 

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by (simp add: PROD_less) 

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lemma PAIR_eq [simp]: "<a,b> = <c,d> <> a=c & b=d" 

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by (simp add: PROD_eq) 

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lemma UU_is_UU_UU [simp]: "<UU,UU> = UU" 

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by (rule less_UU) (simp add: PROD_less) 

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lemma FST_STRICT [simp]: "FST(UU) = UU" 

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apply (rule subst [OF UU_is_UU_UU]) 

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apply (simp del: UU_is_UU_UU) 

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done 

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lemma SND_STRICT [simp]: "SND(UU) = UU" 

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apply (rule subst [OF UU_is_UU_UU]) 

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apply (simp del: UU_is_UU_UU) 

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done 

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subsection {* Fixedpoint theory *} 

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lemma adm_eq: "adm(%x. t(x)=(u(x)::'a::cpo))" 
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apply (unfold eq_def) 

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apply (rule adm_conj adm_less)+ 

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done 

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lemma adm_not_not: "adm(P) ==> adm(%x.~~P(x))" 

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by simp 

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lemma not_eq_TT: "ALL p. ~p=TT <> (p=FF  p=UU)" 

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and not_eq_FF: "ALL p. ~p=FF <> (p=TT  p=UU)" 

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and not_eq_UU: "ALL p. ~p=UU <> (p=TT  p=FF)" 

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by (rule tr_induct, simp_all)+ 

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lemma adm_not_eq_tr: "ALL p::tr. adm(%x. ~t(x)=p)" 

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apply (rule tr_induct) 

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apply (simp_all add: not_eq_TT not_eq_FF not_eq_UU) 

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apply (rule adm_disj adm_eq)+ 

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done 

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lemmas adm_lemmas = 

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adm_not_free adm_eq adm_less adm_not_less 

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adm_not_eq_tr adm_conj adm_disj adm_imp adm_all 

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ML {* 

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fun induct_tac ctxt v i = 
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res_inst_tac ctxt [(("f", 0), v)] @{thm induct} i THEN 
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REPEAT (resolve_tac @{thms adm_lemmas} i) 
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*} 
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lemma least_FIX: "f(p) = p ==> FIX(f) << p" 

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apply (tactic {* induct_tac @{context} "f" 1 *}) 
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apply (rule minimal) 
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apply (intro strip) 

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apply (erule subst) 

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apply (erule less_ap_term) 

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done 

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lemma lfp_is_FIX: 

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assumes 1: "f(p) = p" 

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and 2: "ALL q. f(q)=q > p << q" 

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shows "p = FIX(f)" 

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apply (rule less_anti_sym) 

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apply (rule 2 [THEN spec, THEN mp]) 

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apply (rule FIX_eq) 

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apply (rule least_FIX) 

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apply (rule 1) 

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done 

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lemma FIX_pair: "<FIX(f),FIX(g)> = FIX(%p.<f(FST(p)),g(SND(p))>)" 

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apply (rule lfp_is_FIX) 

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apply (simp add: FIX_eq [of f] FIX_eq [of g]) 

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apply (intro strip) 

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apply (simp add: PROD_less) 

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apply (rule conjI) 

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apply (rule least_FIX) 

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apply (erule subst, rule FST [symmetric]) 

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apply (rule least_FIX) 

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apply (erule subst, rule SND [symmetric]) 

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done 

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lemma FIX1: "FIX(f) = FST(FIX(%p. <f(FST(p)),g(SND(p))>))" 

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by (rule FIX_pair [unfolded PROD_eq FST SND, THEN conjunct1]) 

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lemma FIX2: "FIX(g) = SND(FIX(%p. <f(FST(p)),g(SND(p))>))" 

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by (rule FIX_pair [unfolded PROD_eq FST SND, THEN conjunct2]) 

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lemma induct2: 

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assumes 1: "adm(%p. P(FST(p),SND(p)))" 

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and 2: "P(UU::'a,UU::'b)" 

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and 3: "ALL x y. P(x,y) > P(f(x),g(y))" 

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shows "P(FIX(f),FIX(g))" 

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apply (rule FIX1 [THEN ssubst, of _ f g]) 

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apply (rule FIX2 [THEN ssubst, of _ f g]) 

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apply (rule induct [where ?f = "%x. <f(FST(x)),g(SND(x))>"]) 
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apply (rule 1) 

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apply simp 
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apply (rule 2) 

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apply (simp add: expand_all_PROD) 

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apply (rule 3) 

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done 

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ML {* 

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fun induct2_tac ctxt (f, g) i = 
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res_inst_tac ctxt [(("f", 0), f), (("g", 0), g)] @{thm induct2} i THEN 
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REPEAT(resolve_tac @{thms adm_lemmas} i) 
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*} 
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end 