src/ZF/Finite.ML
author clasohm
Tue Jan 30 13:42:57 1996 +0100 (1996-01-30)
changeset 1461 6bcb44e4d6e5
parent 803 4c8333ab3eae
child 1956 589af052bcd4
permissions -rw-r--r--
expanded tabs
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(*  Title:      ZF/Finite.ML
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1994  University of Cambridge
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Finite powerset operator; finite function space
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prove X:Fin(A) ==> |X| < nat
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prove:  b: Fin(A) ==> inj(b,b)<=surj(b,b)
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*)
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open Finite;
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(*** Finite powerset operator ***)
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goalw Finite.thy Fin.defs "!!A B. A<=B ==> Fin(A) <= Fin(B)";
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by (rtac lfp_mono 1);
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by (REPEAT (rtac Fin.bnd_mono 1));
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by (REPEAT (ares_tac (Pow_mono::basic_monos) 1));
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qed "Fin_mono";
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(* A : Fin(B) ==> A <= B *)
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val FinD = Fin.dom_subset RS subsetD RS PowD;
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(** Induction on finite sets **)
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(*Discharging x~:y entails extra work*)
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val major::prems = goal Finite.thy 
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    "[| b: Fin(A);  \
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\       P(0);        \
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\       !!x y. [| x: A;  y: Fin(A);  x~:y;  P(y) |] ==> P(cons(x,y)) \
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\    |] ==> P(b)";
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by (rtac (major RS Fin.induct) 1);
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by (excluded_middle_tac "a:b" 2);
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by (etac (cons_absorb RS ssubst) 3 THEN assume_tac 3);      (*backtracking!*)
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by (REPEAT (ares_tac prems 1));
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qed "Fin_induct";
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(** Simplification for Fin **)
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val Fin_ss = arith_ss addsimps Fin.intrs;
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(*The union of two finite sets is finite.*)
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val major::prems = goal Finite.thy
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    "[| b: Fin(A);  c: Fin(A) |] ==> b Un c : Fin(A)";
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by (rtac (major RS Fin_induct) 1);
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by (ALLGOALS (asm_simp_tac (Fin_ss addsimps (prems@[Un_0, Un_cons]))));
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qed "Fin_UnI";
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(*The union of a set of finite sets is finite.*)
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val [major] = goal Finite.thy "C : Fin(Fin(A)) ==> Union(C) : Fin(A)";
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by (rtac (major RS Fin_induct) 1);
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by (ALLGOALS (asm_simp_tac (Fin_ss addsimps [Union_0, Union_cons, Fin_UnI])));
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qed "Fin_UnionI";
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(*Every subset of a finite set is finite.*)
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goal Finite.thy "!!b A. b: Fin(A) ==> ALL z. z<=b --> z: Fin(A)";
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by (etac Fin_induct 1);
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by (simp_tac (Fin_ss addsimps [subset_empty_iff]) 1);
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by (asm_simp_tac (ZF_ss addsimps subset_cons_iff::distrib_rews) 1);
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by (safe_tac ZF_cs);
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by (eres_inst_tac [("b","z")] (cons_Diff RS subst) 1);
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by (asm_simp_tac Fin_ss 1);
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qed "Fin_subset_lemma";
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goal Finite.thy "!!c b A. [| c<=b;  b: Fin(A) |] ==> c: Fin(A)";
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by (REPEAT (ares_tac [Fin_subset_lemma RS spec RS mp] 1));
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qed "Fin_subset";
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val major::prems = goal Finite.thy 
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    "[| c: Fin(A);  b: Fin(A);                                  \
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\       P(b);                                                   \
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\       !!x y. [| x: A;  y: Fin(A);  x:y;  P(y) |] ==> P(y-{x}) \
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\    |] ==> c<=b --> P(b-c)";
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by (rtac (major RS Fin_induct) 1);
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by (rtac (Diff_cons RS ssubst) 2);
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by (ALLGOALS (asm_simp_tac (Fin_ss addsimps (prems@[Diff_0, cons_subset_iff, 
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                                Diff_subset RS Fin_subset]))));
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qed "Fin_0_induct_lemma";
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val prems = goal Finite.thy 
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    "[| b: Fin(A);                                              \
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\       P(b);                                                   \
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\       !!x y. [| x: A;  y: Fin(A);  x:y;  P(y) |] ==> P(y-{x}) \
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\    |] ==> P(0)";
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by (rtac (Diff_cancel RS subst) 1);
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by (rtac (Fin_0_induct_lemma RS mp) 1);
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by (REPEAT (ares_tac (subset_refl::prems) 1));
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qed "Fin_0_induct";
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(*Functions from a finite ordinal*)
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val prems = goal Finite.thy "n: nat ==> n->A <= Fin(nat*A)";
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by (nat_ind_tac "n" prems 1);
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by (simp_tac (ZF_ss addsimps [Pi_empty1, Fin.emptyI, subset_iff, cons_iff]) 1);
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by (asm_simp_tac (ZF_ss addsimps [succ_def, mem_not_refl RS cons_fun_eq]) 1);
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by (fast_tac (ZF_cs addSIs [Fin.consI]) 1);
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qed "nat_fun_subset_Fin";
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(*** Finite function space ***)
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goalw Finite.thy FiniteFun.defs
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    "!!A B C D. [| A<=C;  B<=D |] ==> A -||> B  <=  C -||> D";
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by (rtac lfp_mono 1);
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by (REPEAT (rtac FiniteFun.bnd_mono 1));
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by (REPEAT (ares_tac (Fin_mono::Sigma_mono::basic_monos) 1));
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qed "FiniteFun_mono";
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goal Finite.thy "!!A B. A<=B ==> A -||> A  <=  B -||> B";
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by (REPEAT (ares_tac [FiniteFun_mono] 1));
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qed "FiniteFun_mono1";
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goal Finite.thy "!!h. h: A -||>B ==> h: domain(h) -> B";
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by (etac FiniteFun.induct 1);
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by (simp_tac (ZF_ss addsimps [empty_fun, domain_0]) 1);
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by (asm_simp_tac (ZF_ss addsimps [fun_extend3, domain_cons]) 1);
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qed "FiniteFun_is_fun";
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goal Finite.thy "!!h. h: A -||>B ==> domain(h) : Fin(A)";
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by (etac FiniteFun.induct 1);
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by (simp_tac (Fin_ss addsimps [domain_0]) 1);
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by (asm_simp_tac (Fin_ss addsimps [domain_cons]) 1);
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qed "FiniteFun_domain_Fin";
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bind_thm ("FiniteFun_apply_type", FiniteFun_is_fun RS apply_type);
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(*Every subset of a finite function is a finite function.*)
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goal Finite.thy "!!b A. b: A-||>B ==> ALL z. z<=b --> z: A-||>B";
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by (etac FiniteFun.induct 1);
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by (simp_tac (ZF_ss addsimps subset_empty_iff::FiniteFun.intrs) 1);
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by (asm_simp_tac (ZF_ss addsimps subset_cons_iff::distrib_rews) 1);
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by (safe_tac ZF_cs);
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by (eres_inst_tac [("b","z")] (cons_Diff RS subst) 1);
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by (dtac (spec RS mp) 1 THEN assume_tac 1);
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by (fast_tac (ZF_cs addSIs FiniteFun.intrs) 1);
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qed "FiniteFun_subset_lemma";
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goal Finite.thy "!!c b A. [| c<=b;  b: A-||>B |] ==> c: A-||>B";
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by (REPEAT (ares_tac [FiniteFun_subset_lemma RS spec RS mp] 1));
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qed "FiniteFun_subset";
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