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-(************************************************************************)
-(* 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 *)
-(************************************************************************)
-
-(* Certification of Imperative Programs / Jean-Christophe Filliātre *)
-
-(* $Id: Exchange.v,v 1.1.2.1 2004/07/16 19:30:16 herbelin Exp $ *)
-
-(****************************************************************************)
-(* Exchange of two elements in an array *)
-(* Definition and properties *)
-(****************************************************************************)
-
-Require ProgInt.
-Require Arrays.
-
-Set Implicit Arguments.
-
-(* Definition *)
-
-Inductive exchange [n:Z; A:Set; t,t':(array n A); i,j:Z] : Prop :=
- exchange_c :
- `0<=i<n` -> `0<=j<n` ->
- (#t[i] = #t'[j]) ->
- (#t[j] = #t'[i]) ->
- ((k:Z)`0<=k<n` -> `k<>i` -> `k<>j` -> #t[k] = #t'[k]) ->
- (exchange t t' i j).
-
-(* Properties about exchanges *)
-
-Lemma exchange_1 : (n:Z)(A:Set)(t:(array n A))
- (i,j:Z) `0<=i<n` -> `0<=j<n` ->
- (access (store (store t i #t[j]) j #t[i]) i) = #t[j].
-Proof.
-Intros n A t i j H_i H_j.
-Case (dec_eq j i).
-Intro eq_i_j. Rewrite eq_i_j.
-Auto with datatypes.
-Intro not_j_i.
-Rewrite (store_def_2 (store t i #t[j]) #t[i] H_j H_i not_j_i).
-Auto with datatypes.
-Save.
-
-Hints Resolve exchange_1 : v62 datatypes.
-
-
-Lemma exchange_proof :
- (n:Z)(A:Set)(t:(array n A))
- (i,j:Z) `0<=i<n` -> `0<=j<n` ->
- (exchange (store (store t i (access t j)) j (access t i)) t i j).
-Proof.
-Intros n A t i j H_i H_j.
-Apply exchange_c; Auto with datatypes.
-Intros k H_k not_k_i not_k_j.
-Cut ~j=k; Auto with datatypes. Intro not_j_k.
-Rewrite (store_def_2 (store t i (access t j)) (access t i) H_j H_k not_j_k).
-Auto with datatypes.
-Save.
-
-Hints Resolve exchange_proof : v62 datatypes.
-
-
-Lemma exchange_sym :
- (n:Z)(A:Set)(t,t':(array n A))(i,j:Z)
- (exchange t t' i j) -> (exchange t' t i j).
-Proof.
-Intros n A t t' i j H1.
-Elim H1. Clear H1. Intros.
-Constructor 1; Auto with datatypes.
-Intros. Rewrite (H3 k); Auto with datatypes.
-Save.
-
-Hints Resolve exchange_sym : v62 datatypes.
-
-
-Lemma exchange_id :
- (n:Z)(A:Set)(t,t':(array n A))(i,j:Z)
- (exchange t t' i j) ->
- i=j ->
- (k:Z) `0 <= k < n` -> (access t k)=(access t' k).
-Proof.
-Intros n A t t' i j Hex Heq k Hk.
-Elim Hex. Clear Hex. Intros.
-Rewrite Heq in H1. Rewrite Heq in H2.
-Case (Z_eq_dec k j).
- Intro Heq'. Rewrite Heq'. Assumption.
- Intro Hnoteq. Apply (H3 k); Auto with datatypes. Rewrite Heq. Assumption.
-Save.
-
-Hints Resolve exchange_id : v62 datatypes.