From 812e565e94b0e926c48614127d0672c4e04e2ce7 Mon Sep 17 00:00:00 2001
From: Claudio Sacerdoti Coen <claudio.sacerdoticoen@unibo.it>
Date: Fri, 20 Jan 2006 17:59:43 +0000
Subject: [PATCH] Yet another strategy for let...ins: a let-in is _NEVER_
 simplified. The user has to use unfold to zeta-expand it. (Thus, a let-in is
 more opaque than a constant in the environment.)

---
 helm/matita/tests/simpl.ma                 | 16 ++--------------
 helm/ocaml/tactics/proofEngineReduction.ml | 10 ++--------
 2 files changed, 4 insertions(+), 22 deletions(-)

diff --git a/helm/matita/tests/simpl.ma b/helm/matita/tests/simpl.ma
index 65e9d48a4..898122869 100644
--- a/helm/matita/tests/simpl.ma
+++ b/helm/matita/tests/simpl.ma
@@ -23,27 +23,15 @@ alias id "not" = "cic:/Coq/Init/Logic/not.con".
 alias id "nat" = "cic:/Coq/Init/Datatypes/nat.ind#xpointer(1/1)".
 alias id "plus_comm" = "cic:/Coq/Arith/Plus/plus_comm.con".
 
-theorem a : 
- \forall A:Set.
- \forall x,y : A.
- not (x = y) \to not(y = x).
-intros.
-unfold not. (* simplify. *)
-intro. apply H.
-symmetry.
-exact H1.
-qed.
-
 theorem t: let f \def \lambda x,y. x y in f (\lambda x.S x) O = S O.
- intros. simplify. change in \vdash (? ? (? %) ?) with O. 
+ intros. simplify. change in \vdash (? ? (? ? %) ?) with O. 
  reflexivity. qed.
- 
 
 theorem X: \forall x:nat. let myplus \def plus x in myplus (S O) = S x.
  intros. simplify. change in \vdash (? ? (% ?) ?) with (plus x).
 
 rewrite > plus_comm. reflexivity. qed.
- 
+
 theorem R: \forall x:nat. let uno \def x + O in S O + uno = 1 + x.
  intros. simplify.
   change in \vdash (? ? (? %) ?) with (x + O).
diff --git a/helm/ocaml/tactics/proofEngineReduction.ml b/helm/ocaml/tactics/proofEngineReduction.ml
index fca06f6f0..0dc4ce4ee 100644
--- a/helm/ocaml/tactics/proofEngineReduction.ml
+++ b/helm/ocaml/tactics/proofEngineReduction.ml
@@ -603,14 +603,8 @@ let simpl context =
   let module S = CicSubstitution in
    function
       C.Rel n as t ->
-       (try
-         match List.nth context (n-1) with
-            Some (_,C.Decl _) -> if l = [] then t else C.Appl (t::l)
-          | Some (_,C.Def (bo,_)) ->
-             try_delta_expansion context l t (S.lift n bo)
-	  | None -> raise RelToHiddenHypothesis
-        with
-         Failure _ -> assert false)
+       (* we never perform delta expansion automatically *)
+       if l = [] then t else C.Appl (t::l)
     | C.Var (uri,exp_named_subst) ->
        let exp_named_subst' =
         reduceaux_exp_named_subst context l exp_named_subst
-- 
2.39.2