src/ZF/Constructible/Datatype_absolute.thy
author wenzelm
Tue Jul 16 18:46:59 2002 +0200 (2002-07-16)
changeset 13382 b37764a46b16
parent 13363 c26eeb000470
child 13385 31df66ca0780
permissions -rw-r--r--
adapted locales;
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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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constdefs
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  iterates_MH :: "[i=>o, [i,i]=>o, i, i, i, i] => o"
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   "iterates_MH(M,isF,v,n,g,z) ==
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        is_nat_case(M, v, \<lambda>m u. \<exists>gm[M]. fun_apply(M,g,m,gm) & isF(gm,u),
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                    n, z)"
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  iterates_replacement :: "[i=>o, [i,i]=>o, i] => o"
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   "iterates_replacement(M,isF,v) ==
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      \<forall>n[M]. n\<in>nat --> 
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         wfrec_replacement(M, iterates_MH(M,isF,v), Memrel(succ(n)))"
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lemma (in M_axioms) iterates_MH_abs:
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  "[| relativize1(M,isF,F); M(n); M(g); M(z) |] 
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   ==> iterates_MH(M,isF,v,n,g,z) <-> z = nat_case(v, \<lambda>m. F(g`m), n)"
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by (simp add: nat_case_abs [of _ "\<lambda>m. F(g ` m)"]
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              relativize1_def iterates_MH_def)  
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lemma (in M_axioms) iterates_imp_wfrec_replacement:
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  "[|relativize1(M,isF,F); n \<in> nat; iterates_replacement(M,isF,v)|] 
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   ==> wfrec_replacement(M, \<lambda>n f z. z = nat_case(v, \<lambda>m. F(f`m), n), 
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                       Memrel(succ(n)))" 
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by (simp add: iterates_replacement_def iterates_MH_abs)
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theorem (in M_trancl) iterates_abs:
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  "[| iterates_replacement(M,isF,v); relativize1(M,isF,F);
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      n \<in> nat; M(v); M(z); \<forall>x[M]. M(F(x)) |] 
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   ==> is_wfrec(M, iterates_MH(M,isF,v), Memrel(succ(n)), n, z) <->
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       z = iterates(F,n,v)" 
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apply (frule iterates_imp_wfrec_replacement, assumption+)
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apply (simp add: wf_Memrel trans_Memrel relation_Memrel nat_into_M
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                 relativize2_def iterates_MH_abs 
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                 iterates_nat_def recursor_def transrec_def 
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                 eclose_sing_Ord_eq nat_into_M
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         trans_wfrec_abs [of _ _ _ _ "\<lambda>n g. nat_case(v, \<lambda>m. F(g`m), n)"])
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done
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lemma (in M_wfrank) iterates_closed [intro,simp]:
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  "[| iterates_replacement(M,isF,v); relativize1(M,isF,F);
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      n \<in> nat; M(v); \<forall>x[M]. M(F(x)) |] 
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   ==> M(iterates(F,n,v))"
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apply (frule iterates_imp_wfrec_replacement, assumption+)
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apply (simp add: wf_Memrel trans_Memrel relation_Memrel nat_into_M
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                 relativize2_def iterates_MH_abs 
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                 iterates_nat_def recursor_def transrec_def 
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                 eclose_sing_Ord_eq nat_into_M
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         trans_wfrec_closed [of _ _ _ "\<lambda>n g. nat_case(v, \<lambda>m. F(g`m), n)"])
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done
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constdefs
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  is_list_functor :: "[i=>o,i,i,i] => o"
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    "is_list_functor(M,A,X,Z) == 
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        \<exists>n1[M]. \<exists>AX[M]. 
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         number1(M,n1) & cartprod(M,A,X,AX) & is_sum(M,n1,AX,Z)"
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lemma (in M_axioms) list_functor_abs [simp]: 
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     "[| M(A); M(X); M(Z) |] ==> is_list_functor(M,A,X,Z) <-> (Z = {0} + A*X)"
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by (simp add: is_list_functor_def singleton_0 nat_into_M)
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locale (open) M_datatypes = M_wfrank +
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 assumes list_replacement1: 
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   "M(A) ==> iterates_replacement(M, is_list_functor(M,A), 0)"
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  and list_replacement2: 
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   "M(A) ==> strong_replacement(M, 
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         \<lambda>n y. n\<in>nat & 
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               (\<exists>sn[M]. \<exists>msn[M]. successor(M,n,sn) & membership(M,sn,msn) &
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               is_wfrec(M, iterates_MH(M,is_list_functor(M,A), 0), 
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                        msn, n, y)))"
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lemma (in M_datatypes) list_replacement2': 
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  "M(A) ==> strong_replacement(M, \<lambda>n y. n\<in>nat & y = (\<lambda>X. {0} + A * X)^n (0))"
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apply (insert list_replacement2 [of A]) 
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apply (rule strong_replacement_cong [THEN iffD1])  
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apply (rule conj_cong [OF iff_refl iterates_abs [of "is_list_functor(M,A)"]]) 
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apply (simp_all add: list_replacement1 relativize1_def) 
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done
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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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apply (insert list_replacement1)
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by  (simp add: RepFun_closed2 list_eq_Union 
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               list_replacement2' relativize1_def
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               iterates_closed [of "is_list_functor(M,A)"])
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end