(* Title: LCF/LCF.thy ID: $Id$ Author: Tobias Nipkow Copyright 1992 University of Cambridge *) header {* LCF on top of First-Order Logic *} theory LCF imports FOL begin text {* This theory is based on Lawrence Paulson's book Logic and Computation. *} subsection {* Natural Deduction Rules for LCF *} classes cpo < "term" defaultsort cpo typedecl tr typedecl void typedecl ('a,'b) "*" (infixl 6) typedecl ('a,'b) "+" (infixl 5) arities fun :: (cpo, cpo) cpo "*" :: (cpo, cpo) cpo "+" :: (cpo, cpo) cpo tr :: cpo void :: cpo consts UU :: "'a" TT :: "tr" FF :: "tr" FIX :: "('a => 'a) => 'a" FST :: "'a*'b => 'a" SND :: "'a*'b => 'b" INL :: "'a => 'a+'b" INR :: "'b => 'a+'b" WHEN :: "['a=>'c, 'b=>'c, 'a+'b] => 'c" adm :: "('a => o) => o" VOID :: "void" ("'(')") PAIR :: "['a,'b] => 'a*'b" ("(1<_,/_>)" [0,0] 100) COND :: "[tr,'a,'a] => 'a" ("(_ =>/ (_ |/ _))" [60,60,60] 60) less :: "['a,'a] => o" (infixl "<<" 50) axioms (** DOMAIN THEORY **) eq_def: "x=y == x << y & y << x" less_trans: "[| x << y; y << z |] ==> x << z" less_ext: "(ALL x. f(x) << g(x)) ==> f << g" mono: "[| f << g; x << y |] ==> f(x) << g(y)" minimal: "UU << x" FIX_eq: "f(FIX(f)) = FIX(f)" (** TR **) tr_cases: "p=UU | p=TT | p=FF" not_TT_less_FF: "~ TT << FF" not_FF_less_TT: "~ FF << TT" not_TT_less_UU: "~ TT << UU" not_FF_less_UU: "~ FF << UU" COND_UU: "UU => x | y = UU" COND_TT: "TT => x | y = x" COND_FF: "FF => x | y = y" (** PAIRS **) surj_pairing: " = z" FST: "FST() = x" SND: "SND() = y" (*** STRICT SUM ***) INL_DEF: "~x=UU ==> ~INL(x)=UU" INR_DEF: "~x=UU ==> ~INR(x)=UU" INL_STRICT: "INL(UU) = UU" INR_STRICT: "INR(UU) = UU" WHEN_UU: "WHEN(f,g,UU) = UU" WHEN_INL: "~x=UU ==> WHEN(f,g,INL(x)) = f(x)" WHEN_INR: "~x=UU ==> WHEN(f,g,INR(x)) = g(x)" SUM_EXHAUSTION: "z = UU | (EX x. ~x=UU & z = INL(x)) | (EX y. ~y=UU & z = INR(y))" (** VOID **) void_cases: "(x::void) = UU" (** INDUCTION **) induct: "[| adm(P); P(UU); ALL x. P(x) --> P(f(x)) |] ==> P(FIX(f))" (** Admissibility / Chain Completeness **) (* All rules can be found on pages 199--200 of Larry's LCF book. Note that "easiness" of types is not taken into account because it cannot be expressed schematically; flatness could be. *) adm_less: "adm(%x. t(x) << u(x))" adm_not_less: "adm(%x.~ t(x) << u)" adm_not_free: "adm(%x. A)" adm_subst: "adm(P) ==> adm(%x. P(t(x)))" adm_conj: "[| adm(P); adm(Q) |] ==> adm(%x. P(x)&Q(x))" adm_disj: "[| adm(P); adm(Q) |] ==> adm(%x. P(x)|Q(x))" adm_imp: "[| adm(%x.~P(x)); adm(Q) |] ==> adm(%x. P(x)-->Q(x))" adm_all: "(!!y. adm(P(y))) ==> adm(%x. ALL y. P(y,x))" lemma eq_imp_less1: "x = y ==> x << y" by (simp add: eq_def) lemma eq_imp_less2: "x = y ==> y << x" by (simp add: eq_def) lemma less_refl [simp]: "x << x" apply (rule eq_imp_less1) apply (rule refl) done lemma less_anti_sym: "[| x << y; y << x |] ==> x=y" by (simp add: eq_def) lemma ext: "(!!x::'a::cpo. f(x)=(g(x)::'b::cpo)) ==> (%x. f(x))=(%x. g(x))" apply (rule less_anti_sym) apply (rule less_ext) apply simp apply simp done lemma cong: "[| f=g; x=y |] ==> f(x)=g(y)" by simp lemma less_ap_term: "x << y ==> f(x) << f(y)" by (rule less_refl [THEN mono]) lemma less_ap_thm: "f << g ==> f(x) << g(x)" by (rule less_refl [THEN [2] mono]) lemma ap_term: "(x::'a::cpo) = y ==> (f(x)::'b::cpo) = f(y)" apply (rule cong [OF refl]) apply simp done lemma ap_thm: "f = g ==> f(x) = g(x)" apply (erule cong) apply (rule refl) done lemma UU_abs: "(%x::'a::cpo. UU) = UU" apply (rule less_anti_sym) prefer 2 apply (rule minimal) apply (rule less_ext) apply (rule allI) apply (rule minimal) done lemma UU_app: "UU(x) = UU" by (rule UU_abs [symmetric, THEN ap_thm]) lemma less_UU: "x << UU ==> x=UU" apply (rule less_anti_sym) apply assumption apply (rule minimal) done lemma tr_induct: "[| P(UU); P(TT); P(FF) |] ==> ALL b. P(b)" apply (rule allI) apply (rule mp) apply (rule_tac [2] p = b in tr_cases) apply blast done lemma Contrapos: "~ B ==> (A ==> B) ==> ~A" by blast lemma not_less_imp_not_eq1: "~ x << y \ x \ y" apply (erule Contrapos) apply simp done lemma not_less_imp_not_eq2: "~ y << x \ x \ y" apply (erule Contrapos) apply simp done lemma not_UU_eq_TT: "UU \ TT" by (rule not_less_imp_not_eq2) (rule not_TT_less_UU) lemma not_UU_eq_FF: "UU \ FF" by (rule not_less_imp_not_eq2) (rule not_FF_less_UU) lemma not_TT_eq_UU: "TT \ UU" by (rule not_less_imp_not_eq1) (rule not_TT_less_UU) lemma not_TT_eq_FF: "TT \ FF" by (rule not_less_imp_not_eq1) (rule not_TT_less_FF) lemma not_FF_eq_UU: "FF \ UU" by (rule not_less_imp_not_eq1) (rule not_FF_less_UU) lemma not_FF_eq_TT: "FF \ TT" by (rule not_less_imp_not_eq1) (rule not_FF_less_TT) lemma COND_cases_iff [rule_format]: "ALL b. P(b=>x|y) <-> (b=UU-->P(UU)) & (b=TT-->P(x)) & (b=FF-->P(y))" apply (insert not_UU_eq_TT not_UU_eq_FF not_TT_eq_UU not_TT_eq_FF not_FF_eq_UU not_FF_eq_TT) apply (rule tr_induct) apply (simplesubst COND_UU) apply blast apply (simplesubst COND_TT) apply blast apply (simplesubst COND_FF) apply blast done lemma COND_cases: "[| x = UU --> P(UU); x = TT --> P(xa); x = FF --> P(y) |] ==> P(x => xa | y)" apply (rule COND_cases_iff [THEN iffD2]) apply blast done lemmas [simp] = minimal UU_app UU_app [THEN ap_thm] UU_app [THEN ap_thm, THEN ap_thm] not_TT_less_FF not_FF_less_TT not_TT_less_UU not_FF_less_UU not_UU_eq_TT not_UU_eq_FF not_TT_eq_UU not_TT_eq_FF not_FF_eq_UU not_FF_eq_TT COND_UU COND_TT COND_FF surj_pairing FST SND subsection {* Ordered pairs and products *} lemma expand_all_PROD: "(ALL p. P(p)) <-> (ALL x y. P())" apply (rule iffI) apply blast apply (rule allI) apply (rule surj_pairing [THEN subst]) apply blast done lemma PROD_less: "(p::'a*'b) << q <-> FST(p) << FST(q) & SND(p) << SND(q)" apply (rule iffI) apply (rule conjI) apply (erule less_ap_term) apply (erule less_ap_term) apply (erule conjE) apply (rule surj_pairing [of p, THEN subst]) apply (rule surj_pairing [of q, THEN subst]) apply (rule mono, erule less_ap_term, assumption) done lemma PROD_eq: "p=q <-> FST(p)=FST(q) & SND(p)=SND(q)" apply (rule iffI) apply simp apply (unfold eq_def) apply (simp add: PROD_less) done lemma PAIR_less [simp]: " << <-> a< = <-> a=c & b=d" by (simp add: PROD_eq) lemma UU_is_UU_UU [simp]: " = UU" by (rule less_UU) (simp add: PROD_less) lemma FST_STRICT [simp]: "FST(UU) = UU" apply (rule subst [OF UU_is_UU_UU]) apply (simp del: UU_is_UU_UU) done lemma SND_STRICT [simp]: "SND(UU) = UU" apply (rule subst [OF UU_is_UU_UU]) apply (simp del: UU_is_UU_UU) done subsection {* Fixedpoint theory *} lemma adm_eq: "adm(%x. t(x)=(u(x)::'a::cpo))" apply (unfold eq_def) apply (rule adm_conj adm_less)+ done lemma adm_not_not: "adm(P) ==> adm(%x.~~P(x))" by simp lemma not_eq_TT: "ALL p. ~p=TT <-> (p=FF | p=UU)" and not_eq_FF: "ALL p. ~p=FF <-> (p=TT | p=UU)" and not_eq_UU: "ALL p. ~p=UU <-> (p=TT | p=FF)" by (rule tr_induct, simp_all)+ lemma adm_not_eq_tr: "ALL p::tr. adm(%x. ~t(x)=p)" apply (rule tr_induct) apply (simp_all add: not_eq_TT not_eq_FF not_eq_UU) apply (rule adm_disj adm_eq)+ done lemmas adm_lemmas = adm_not_free adm_eq adm_less adm_not_less adm_not_eq_tr adm_conj adm_disj adm_imp adm_all ML {* fun induct_tac v i = res_inst_tac[("f",v)] @{thm induct} i THEN REPEAT (resolve_tac @{thms adm_lemmas} i) *} lemma least_FIX: "f(p) = p ==> FIX(f) << p" apply (tactic {* induct_tac "f" 1 *}) apply (rule minimal) apply (intro strip) apply (erule subst) apply (erule less_ap_term) done lemma lfp_is_FIX: assumes 1: "f(p) = p" and 2: "ALL q. f(q)=q --> p << q" shows "p = FIX(f)" apply (rule less_anti_sym) apply (rule 2 [THEN spec, THEN mp]) apply (rule FIX_eq) apply (rule least_FIX) apply (rule 1) done lemma FIX_pair: " = FIX(%p.)" apply (rule lfp_is_FIX) apply (simp add: FIX_eq [of f] FIX_eq [of g]) apply (intro strip) apply (simp add: PROD_less) apply (rule conjI) apply (rule least_FIX) apply (erule subst, rule FST [symmetric]) apply (rule least_FIX) apply (erule subst, rule SND [symmetric]) done lemma FIX1: "FIX(f) = FST(FIX(%p. ))" by (rule FIX_pair [unfolded PROD_eq FST SND, THEN conjunct1]) lemma FIX2: "FIX(g) = SND(FIX(%p. ))" by (rule FIX_pair [unfolded PROD_eq FST SND, THEN conjunct2]) lemma induct2: assumes 1: "adm(%p. P(FST(p),SND(p)))" and 2: "P(UU::'a,UU::'b)" and 3: "ALL x y. P(x,y) --> P(f(x),g(y))" shows "P(FIX(f),FIX(g))" apply (rule FIX1 [THEN ssubst, of _ f g]) apply (rule FIX2 [THEN ssubst, of _ f g]) apply (rule induct [where ?f = "%x. "]) apply (rule 1) apply simp apply (rule 2) apply (simp add: expand_all_PROD) apply (rule 3) done ML {* fun induct2_tac (f,g) i = res_inst_tac[("f",f),("g",g)] @{thm induct2} i THEN REPEAT(resolve_tac @{thms adm_lemmas} i) *} end