src/ZF/Constructible/Datatype_absolute.thy
author paulson
Thu Jul 11 13:43:24 2002 +0200 (2002-07-11)
changeset 13348 374d05460db4
parent 13339 0f89104dd377
child 13350 626b79677dfa
permissions -rw-r--r--
Separation/Replacement up to M_wfrank!
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header {*Absoluteness Properties for Recursive Datatypes*}
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theory Datatype_absolute = Formula + WF_absolute:
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subsection{*The lfp of a continuous function can be expressed as a union*}
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constdefs
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  contin :: "[i=>i]=>o"
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   "contin(h) == (\<forall>A. A\<noteq>0 --> h(\<Union>A) = (\<Union>X\<in>A. h(X)))"
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lemma bnd_mono_iterates_subset: "[|bnd_mono(D, h); n \<in> nat|] ==> h^n (0) <= D"
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apply (induct_tac n) 
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 apply (simp_all add: bnd_mono_def, blast) 
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done
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lemma contin_iterates_eq: 
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    "contin(h) \<Longrightarrow> h(\<Union>n\<in>nat. h^n (0)) = (\<Union>n\<in>nat. h^n (0))"
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apply (simp add: contin_def) 
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apply (rule trans) 
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apply (rule equalityI) 
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 apply (simp_all add: UN_subset_iff) 
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 apply safe
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 apply (erule_tac [2] natE) 
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  apply (rule_tac a="succ(x)" in UN_I) 
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   apply simp_all 
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apply blast 
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done
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lemma lfp_subset_Union:
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     "[|bnd_mono(D, h); contin(h)|] ==> lfp(D,h) <= (\<Union>n\<in>nat. h^n(0))"
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apply (rule lfp_lowerbound) 
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 apply (simp add: contin_iterates_eq) 
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apply (simp add: contin_def bnd_mono_iterates_subset UN_subset_iff) 
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done
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lemma Union_subset_lfp:
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     "bnd_mono(D,h) ==> (\<Union>n\<in>nat. h^n(0)) <= lfp(D,h)"
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apply (simp add: UN_subset_iff)
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apply (rule ballI)  
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apply (induct_tac n, simp_all) 
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apply (rule subset_trans [of _ "h(lfp(D,h))"])
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 apply (blast dest: bnd_monoD2 [OF _ _ lfp_subset] )  
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apply (erule lfp_lemma2) 
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done
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lemma lfp_eq_Union:
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     "[|bnd_mono(D, h); contin(h)|] ==> lfp(D,h) = (\<Union>n\<in>nat. h^n(0))"
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by (blast del: subsetI 
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          intro: lfp_subset_Union Union_subset_lfp)
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subsection {*lists without univ*}
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lemmas datatype_univs = A_into_univ Inl_in_univ Inr_in_univ 
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                        Pair_in_univ zero_in_univ
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lemma list_fun_bnd_mono: "bnd_mono(univ(A), \<lambda>X. {0} + A*X)"
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apply (rule bnd_monoI)
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 apply (intro subset_refl zero_subset_univ A_subset_univ 
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	      sum_subset_univ Sigma_subset_univ) 
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 apply (blast intro!: subset_refl sum_mono Sigma_mono del: subsetI)
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done
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lemma list_fun_contin: "contin(\<lambda>X. {0} + A*X)"
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by (simp add: contin_def, blast)
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text{*Re-expresses lists using sum and product*}
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lemma list_eq_lfp2: "list(A) = lfp(univ(A), \<lambda>X. {0} + A*X)"
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apply (simp add: list_def) 
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apply (rule equalityI) 
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 apply (rule lfp_lowerbound) 
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  prefer 2 apply (rule lfp_subset)
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 apply (clarify, subst lfp_unfold [OF list_fun_bnd_mono])
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 apply (simp add: Nil_def Cons_def)
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 apply blast 
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txt{*Opposite inclusion*}
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apply (rule lfp_lowerbound) 
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 prefer 2 apply (rule lfp_subset) 
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apply (clarify, subst lfp_unfold [OF list.bnd_mono]) 
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apply (simp add: Nil_def Cons_def)
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apply (blast intro: datatype_univs
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             dest: lfp_subset [THEN subsetD])
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done
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text{*Re-expresses lists using "iterates", no univ.*}
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lemma list_eq_Union:
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     "list(A) = (\<Union>n\<in>nat. (\<lambda>X. {0} + A*X) ^ n (0))"
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by (simp add: list_eq_lfp2 lfp_eq_Union list_fun_bnd_mono list_fun_contin)
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subsection {*Absoluteness for "Iterates"*}
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lemma (in M_trancl) iterates_relativize:
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  "[|n \<in> nat; M(v); \<forall>x[M]. M(F(x));
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     strong_replacement(M, 
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       \<lambda>x z. \<exists>y[M]. \<exists>g[M]. pair(M, x, y, z) &
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              is_recfun (Memrel(succ(n)), x,
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                         \<lambda>n f. nat_case(v, \<lambda>m. F(f`m), n), g) &
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              y = nat_case(v, \<lambda>m. F(g`m), x))|] 
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   ==> iterates(F,n,v) = z <-> 
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       (\<exists>g[M]. is_recfun(Memrel(succ(n)), n, 
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                             \<lambda>n g. nat_case(v, \<lambda>m. F(g`m), n), g) &
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            z = nat_case(v, \<lambda>m. F(g`m), n))"
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by (simp add: iterates_nat_def recursor_def transrec_def 
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              eclose_sing_Ord_eq trans_wfrec_relativize nat_into_M
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              wf_Memrel trans_Memrel relation_Memrel nat_case_closed)
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lemma (in M_wfrank) iterates_closed [intro,simp]:
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  "[|n \<in> nat; M(v); \<forall>x[M]. M(F(x));
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     strong_replacement(M, 
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       \<lambda>x z. \<exists>y[M]. \<exists>g[M]. pair(M, x, y, z) &
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              is_recfun (Memrel(succ(n)), x,
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                         \<lambda>n f. nat_case(v, \<lambda>m. F(f`m), n), g) &
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              y = nat_case(v, \<lambda>m. F(g`m), x))|] 
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   ==> M(iterates(F,n,v))"
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by (simp add: iterates_nat_def recursor_def transrec_def 
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              eclose_sing_Ord_eq trans_wfrec_closed nat_into_M
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              wf_Memrel trans_Memrel relation_Memrel nat_case_closed)
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locale M_datatypes = M_wfrank +
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(*THEY NEED RELATIVIZATION*)
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  assumes list_replacement1: 
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	   "[|M(A); n \<in> nat|] ==> 
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	    strong_replacement(M, 
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	      \<lambda>x z. \<exists>y[M]. \<exists>g[M]. \<exists>sucn[M]. \<exists>memr[M]. 
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                     pair(M,x,y,z) & successor(M,n,sucn) & 
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                     membership(M,sucn,memr) &
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		     is_recfun (memr, x,
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				\<lambda>n f. nat_case(0, \<lambda>m. {0} + A \<times> f`m, n), g) &
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		     y = nat_case(0, \<lambda>m. {0} + A \<times> g`m, x))"
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      and list_replacement2: 
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           "M(A) ==> strong_replacement(M, \<lambda>x y. y = (\<lambda>X. {0} + A \<times> X)^x (0))"
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lemma (in M_datatypes) list_replacement1':
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  "[|M(A); n \<in> nat|]
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   ==> strong_replacement
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	  (M, \<lambda>x y. \<exists>z[M]. y = \<langle>x,z\<rangle> &
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               (\<exists>g[M]. is_recfun (Memrel(succ(n)), x,
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		          \<lambda>n f. nat_case(0, \<lambda>m. {0} + A \<times> f`m, n), g) &
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 	       z = nat_case(0, \<lambda>m. {0} + A \<times> g ` m, x)))"
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by (insert list_replacement1, simp add: nat_into_M) 
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lemma (in M_datatypes) list_replacement2': 
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  "M(A) ==> strong_replacement(M, \<lambda>x y. y = (\<lambda>X. {0} + A \<times> X)^x (0))"
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by (insert list_replacement2, simp add: nat_into_M) 
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lemma (in M_datatypes) list_closed [intro,simp]:
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     "M(A) ==> M(list(A))"
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by (simp add: list_eq_Union list_replacement1' list_replacement2')
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end