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Diffstat (limited to 'theories7/Logic/Eqdep_dec.v')
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diff --git a/theories7/Logic/Eqdep_dec.v b/theories7/Logic/Eqdep_dec.v deleted file mode 100644 index 959395e3..00000000 --- a/theories7/Logic/Eqdep_dec.v +++ /dev/null @@ -1,149 +0,0 @@ -(************************************************************************) -(* v * The Coq Proof Assistant / The Coq Development Team *) -(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *) -(* \VV/ **************************************************************) -(* // * This file is distributed under the terms of the *) -(* * GNU Lesser General Public License Version 2.1 *) -(************************************************************************) - -(*i $Id: Eqdep_dec.v,v 1.1.2.1 2004/07/16 19:31:29 herbelin Exp $ i*) - -(** We prove that there is only one proof of [x=x], i.e [(refl_equal ? x)]. - This holds if the equality upon the set of [x] is decidable. - A corollary of this theorem is the equality of the right projections - of two equal dependent pairs. - - Author: Thomas Kleymann |<tms@dcs.ed.ac.uk>| in Lego - adapted to Coq by B. Barras - - Credit: Proofs up to [K_dec] follows an outline by Michael Hedberg -*) - - -(** We need some dependent elimination schemes *) - -Set Implicit Arguments. - - (** Bijection between [eq] and [eqT] *) - Definition eq2eqT: (A:Set)(x,y:A)x=y->x==y := - [A,x,_,eqxy]<[y:A]x==y>Cases eqxy of refl_equal => (refl_eqT ? x) end. - - Definition eqT2eq: (A:Set)(x,y:A)x==y->x=y := - [A,x,_,eqTxy]<[y:A]x=y>Cases eqTxy of refl_eqT => (refl_equal ? x) end. - - Lemma eq_eqT_bij: (A:Set)(x,y:A)(p:x=y)p==(eqT2eq (eq2eqT p)). -Intros. -Case p; Reflexivity. -Qed. - - Lemma eqT_eq_bij: (A:Set)(x,y:A)(p:x==y)p==(eq2eqT (eqT2eq p)). -Intros. -Case p; Reflexivity. -Qed. - - -Section DecidableEqDep. - - Variable A: Type. - - Local comp [x,y,y':A]: x==y->x==y'->y==y' := - [eq1,eq2](eqT_ind ? ? [a]a==y' eq2 ? eq1). - - Remark trans_sym_eqT: (x,y:A)(u:x==y)(comp u u)==(refl_eqT ? y). -Intros. -Case u; Trivial. -Qed. - - - - Variable eq_dec: (x,y:A) x==y \/ ~x==y. - - Variable x: A. - - - Local nu [y:A]: x==y->x==y := - [u]Cases (eq_dec x y) of - (or_introl eqxy) => eqxy - | (or_intror neqxy) => (False_ind ? (neqxy u)) - end. - - Local nu_constant : (y:A)(u,v:x==y) (nu u)==(nu v). -Intros. -Unfold nu. -Case (eq_dec x y); Intros. -Reflexivity. - -Case n; Trivial. -Qed. - - - Local nu_inv [y:A]: x==y->x==y := [v](comp (nu (refl_eqT ? x)) v). - - - Remark nu_left_inv : (y:A)(u:x==y) (nu_inv (nu u))==u. -Intros. -Case u; Unfold nu_inv. -Apply trans_sym_eqT. -Qed. - - - Theorem eq_proofs_unicity: (y:A)(p1,p2:x==y) p1==p2. -Intros. -Elim nu_left_inv with u:=p1. -Elim nu_left_inv with u:=p2. -Elim nu_constant with y p1 p2. -Reflexivity. -Qed. - - Theorem K_dec: (P:x==x->Prop)(P (refl_eqT ? x)) -> (p:x==x)(P p). -Intros. -Elim eq_proofs_unicity with x (refl_eqT ? x) p. -Trivial. -Qed. - - - (** The corollary *) - - Local proj: (P:A->Prop)(ExT P)->(P x)->(P x) := - [P,exP,def]Cases exP of - (exT_intro x' prf) => - Cases (eq_dec x' x) of - (or_introl eqprf) => (eqT_ind ? x' P prf x eqprf) - | _ => def - end - end. - - - Theorem inj_right_pair: (P:A->Prop)(y,y':(P x)) - (exT_intro ? P x y)==(exT_intro ? P x y') -> y==y'. -Intros. -Cut (proj (exT_intro A P x y) y)==(proj (exT_intro A P x y') y). -Simpl. -Case (eq_dec x x). -Intro e. -Elim e using K_dec; Trivial. - -Intros. -Case n; Trivial. - -Case H. -Reflexivity. -Qed. - -End DecidableEqDep. - - (** We deduce the [K] axiom for (decidable) Set *) - Theorem K_dec_set: (A:Set)((x,y:A){x=y}+{~x=y}) - ->(x:A)(P: x=x->Prop)(P (refl_equal ? x)) - ->(p:x=x)(P p). -Intros. -Rewrite eq_eqT_bij. -Elim (eq2eqT p) using K_dec. -Intros. -Case (H x0 y); Intros. -Elim e; Left ; Reflexivity. - -Right ; Red; Intro neq; Apply n; Elim neq; Reflexivity. - -Trivial. -Qed. |