src/HOL/Sum.ML
author clasohm
Tue Jan 30 15:24:36 1996 +0100 (1996-01-30)
changeset 1465 5d7a7e439cec
parent 1264 3eb91524b938
child 1515 4ed79ebab64d
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(*  Title:      HOL/Sum.ML
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1991  University of Cambridge
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For Sum.thy.  The disjoint sum of two types
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*)
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open Sum;
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(** Inl_Rep and Inr_Rep: Representations of the constructors **)
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(*This counts as a non-emptiness result for admitting 'a+'b as a type*)
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goalw Sum.thy [Sum_def] "Inl_Rep(a) : Sum";
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by (EVERY1 [rtac CollectI, rtac disjI1, rtac exI, rtac refl]);
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qed "Inl_RepI";
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goalw Sum.thy [Sum_def] "Inr_Rep(b) : Sum";
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by (EVERY1 [rtac CollectI, rtac disjI2, rtac exI, rtac refl]);
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qed "Inr_RepI";
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goal Sum.thy "inj_onto Abs_Sum Sum";
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by (rtac inj_onto_inverseI 1);
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by (etac Abs_Sum_inverse 1);
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qed "inj_onto_Abs_Sum";
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(** Distinctness of Inl and Inr **)
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goalw Sum.thy [Inl_Rep_def, Inr_Rep_def] "Inl_Rep(a) ~= Inr_Rep(b)";
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by (EVERY1 [rtac notI,
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            etac (fun_cong RS fun_cong RS fun_cong RS iffE), 
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            rtac (notE RS ccontr),  etac (mp RS conjunct2), 
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            REPEAT o (ares_tac [refl,conjI]) ]);
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qed "Inl_Rep_not_Inr_Rep";
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goalw Sum.thy [Inl_def,Inr_def] "Inl(a) ~= Inr(b)";
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by (rtac (inj_onto_Abs_Sum RS inj_onto_contraD) 1);
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by (rtac Inl_Rep_not_Inr_Rep 1);
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by (rtac Inl_RepI 1);
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by (rtac Inr_RepI 1);
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qed "Inl_not_Inr";
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bind_thm ("Inl_neq_Inr", (Inl_not_Inr RS notE));
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val Inr_neq_Inl = sym RS Inl_neq_Inr;
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goal Sum.thy "(Inl(a)=Inr(b)) = False";
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by (simp_tac (!simpset addsimps [Inl_not_Inr]) 1);
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qed "Inl_Inr_eq";
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goal Sum.thy "(Inr(b)=Inl(a))  =  False";
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by (simp_tac (!simpset addsimps [Inl_not_Inr RS not_sym]) 1);
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qed "Inr_Inl_eq";
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(** Injectiveness of Inl and Inr **)
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val [major] = goalw Sum.thy [Inl_Rep_def] "Inl_Rep(a) = Inl_Rep(c) ==> a=c";
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by (rtac (major RS fun_cong RS fun_cong RS fun_cong RS iffE) 1);
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by (fast_tac HOL_cs 1);
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qed "Inl_Rep_inject";
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val [major] = goalw Sum.thy [Inr_Rep_def] "Inr_Rep(b) = Inr_Rep(d) ==> b=d";
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by (rtac (major RS fun_cong RS fun_cong RS fun_cong RS iffE) 1);
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by (fast_tac HOL_cs 1);
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qed "Inr_Rep_inject";
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goalw Sum.thy [Inl_def] "inj(Inl)";
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by (rtac injI 1);
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by (etac (inj_onto_Abs_Sum RS inj_ontoD RS Inl_Rep_inject) 1);
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by (rtac Inl_RepI 1);
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by (rtac Inl_RepI 1);
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qed "inj_Inl";
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val Inl_inject = inj_Inl RS injD;
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goalw Sum.thy [Inr_def] "inj(Inr)";
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by (rtac injI 1);
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by (etac (inj_onto_Abs_Sum RS inj_ontoD RS Inr_Rep_inject) 1);
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by (rtac Inr_RepI 1);
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by (rtac Inr_RepI 1);
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qed "inj_Inr";
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val Inr_inject = inj_Inr RS injD;
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goal Sum.thy "(Inl(x)=Inl(y)) = (x=y)";
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by (fast_tac (HOL_cs addSEs [Inl_inject]) 1);
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qed "Inl_eq";
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goal Sum.thy "(Inr(x)=Inr(y)) = (x=y)";
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by (fast_tac (HOL_cs addSEs [Inr_inject]) 1);
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qed "Inr_eq";
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(*** Rules for the disjoint sum of two SETS ***)
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(** Introduction rules for the injections **)
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goalw Sum.thy [sum_def] "!!a A B. a : A ==> Inl(a) : A plus B";
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by (REPEAT (ares_tac [UnI1,imageI] 1));
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qed "InlI";
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goalw Sum.thy [sum_def] "!!b A B. b : B ==> Inr(b) : A plus B";
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by (REPEAT (ares_tac [UnI2,imageI] 1));
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qed "InrI";
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(** Elimination rules **)
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val major::prems = goalw Sum.thy [sum_def]
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    "[| u: A plus B;  \
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\       !!x. [| x:A;  u=Inl(x) |] ==> P; \
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\       !!y. [| y:B;  u=Inr(y) |] ==> P \
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\    |] ==> P";
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by (rtac (major RS UnE) 1);
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by (REPEAT (rtac refl 1
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     ORELSE eresolve_tac (prems@[imageE,ssubst]) 1));
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qed "plusE";
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val sum_cs = set_cs addSIs [InlI, InrI] 
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                    addSEs [plusE, Inl_neq_Inr, Inr_neq_Inl]
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                    addSDs [Inl_inject, Inr_inject];
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(** sum_case -- the selection operator for sums **)
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goalw Sum.thy [sum_case_def] "sum_case f g (Inl x) = f(x)";
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by (fast_tac (sum_cs addIs [select_equality]) 1);
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qed "sum_case_Inl";
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goalw Sum.thy [sum_case_def] "sum_case f g (Inr x) = g(x)";
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by (fast_tac (sum_cs addIs [select_equality]) 1);
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qed "sum_case_Inr";
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(** Exhaustion rule for sums -- a degenerate form of induction **)
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val prems = goalw Sum.thy [Inl_def,Inr_def]
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    "[| !!x::'a. s = Inl(x) ==> P;  !!y::'b. s = Inr(y) ==> P \
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\    |] ==> P";
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by (rtac (rewrite_rule [Sum_def] Rep_Sum RS CollectE) 1);
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by (REPEAT (eresolve_tac [disjE,exE] 1
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     ORELSE EVERY1 [resolve_tac prems, 
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                    etac subst,
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                    rtac (Rep_Sum_inverse RS sym)]));
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qed "sumE";
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goal Sum.thy "sum_case (%x::'a. f(Inl x)) (%y::'b. f(Inr y)) s = f(s)";
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by (EVERY1 [res_inst_tac [("s","s")] sumE, 
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            etac ssubst, rtac sum_case_Inl,
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            etac ssubst, rtac sum_case_Inr]);
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qed "surjective_sum";
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goal Sum.thy "R(sum_case f g s) = \
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\             ((! x. s = Inl(x) --> R(f(x))) & (! y. s = Inr(y) --> R(g(y))))";
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by (rtac sumE 1);
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by (etac ssubst 1);
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by (stac sum_case_Inl 1);
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by (fast_tac (set_cs addSEs [make_elim Inl_inject, Inl_neq_Inr]) 1);
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by (etac ssubst 1);
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by (stac sum_case_Inr 1);
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by (fast_tac (set_cs addSEs [make_elim Inr_inject, Inr_neq_Inl]) 1);
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qed "expand_sum_case";
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Addsimps [Inl_eq, Inr_eq, Inl_Inr_eq, Inr_Inl_eq,  sum_case_Inl, sum_case_Inr];
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(*Prevents simplification of f and g: much faster*)
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qed_goal "sum_case_weak_cong" Sum.thy
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  "s=t ==> sum_case f g s = sum_case f g t"
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  (fn [prem] => [rtac (prem RS arg_cong) 1]);
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(** Rules for the Part primitive **)
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goalw Sum.thy [Part_def]
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    "!!a b A h. [| a : A;  a=h(b) |] ==> a : Part A h";
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by (fast_tac set_cs 1);
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qed "Part_eqI";
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val PartI = refl RSN (2,Part_eqI);
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val major::prems = goalw Sum.thy [Part_def]
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    "[| a : Part A h;  !!z. [| a : A;  a=h(z) |] ==> P  \
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\    |] ==> P";
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by (rtac (major RS IntE) 1);
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by (etac CollectE 1);
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by (etac exE 1);
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by (REPEAT (ares_tac prems 1));
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qed "PartE";
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goalw Sum.thy [Part_def] "Part A h <= A";
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by (rtac Int_lower1 1);
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qed "Part_subset";
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goal Sum.thy "!!A B. A<=B ==> Part A h <= Part B h";
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by (fast_tac (set_cs addSIs [PartI] addSEs [PartE]) 1);
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qed "Part_mono";
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goalw Sum.thy [Part_def] "!!a. a : Part A h ==> a : A";
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by (etac IntD1 1);
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qed "PartD1";
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goal Sum.thy "Part A (%x.x) = A";
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by (fast_tac (set_cs addIs [PartI,equalityI] addSEs [PartE]) 1);
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qed "Part_id";
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goal Sum.thy "Part (A Int B) h = (Part A h) Int (Part B h)";
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by (fast_tac (set_cs addIs [PartI,equalityI] addSEs [PartE]) 1);
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qed "Part_Int";
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(*For inductive definitions*)
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goal Sum.thy "Part (A Int {x.P x}) h = (Part A h) Int {x.P x}";
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by (fast_tac (set_cs addIs [PartI,equalityI] addSEs [PartE]) 1);
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qed "Part_Collect";