From: Enrico Tassi <enrico.tassi@inria.fr>
Date: Mon, 31 Jan 2005 17:18:55 +0000 (+0000)
Subject: added delift
X-Git-Tag: V_0_1_0~83
X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=commitdiff_plain;h=3c9c376401844c389d682ba835845443105e4b1a;p=helm.git

added delift
---

diff --git a/helm/ocaml/cic_proof_checking/cicSubstitution.ml b/helm/ocaml/cic_proof_checking/cicSubstitution.ml
index 431fa4b50..cd9773160 100644
--- a/helm/ocaml/cic_proof_checking/cicSubstitution.ml
+++ b/helm/ocaml/cic_proof_checking/cicSubstitution.ml
@@ -104,6 +104,81 @@ let lift n t =
    lift_from 1 n t
 ;;
 
+(* delifts a term t of n levels strating from k, that is changes (Rel m)
+ * to (Rel (m - n)) when m > (k + n). if k <= m < k + n delift fails
+ *)
+let delift_from k n =
+ let rec liftaux k =
+  let module C = Cic in
+   function
+      C.Rel m ->
+       if m < k then
+        C.Rel m
+       else if m < k + n then
+         (failwith "delifting this term whould capture free variables")
+       else
+        C.Rel (m - n)
+    | C.Var (uri,exp_named_subst) ->
+       let exp_named_subst' = 
+        List.map (function (uri,t) -> (uri,liftaux k t)) exp_named_subst
+       in
+        C.Var (uri,exp_named_subst')
+    | C.Meta (i,l) ->
+       let l' =
+        List.map
+         (function
+             None -> None
+           | Some t -> Some (liftaux k t)
+         ) l
+       in
+        C.Meta(i,l')
+    | C.Sort _ as t -> t
+    | C.Implicit _ as t -> t
+    | C.Cast (te,ty) -> C.Cast (liftaux k te, liftaux k ty)
+    | C.Prod (n,s,t) -> C.Prod (n, liftaux k s, liftaux (k+1) t)
+    | C.Lambda (n,s,t) -> C.Lambda (n, liftaux k s, liftaux (k+1) t)
+    | C.LetIn (n,s,t) -> C.LetIn (n, liftaux k s, liftaux (k+1) t)
+    | C.Appl l -> C.Appl (List.map (liftaux k) l)
+    | C.Const (uri,exp_named_subst) ->
+       let exp_named_subst' = 
+        List.map (function (uri,t) -> (uri,liftaux k t)) exp_named_subst
+       in
+        C.Const (uri,exp_named_subst')
+    | C.MutInd (uri,tyno,exp_named_subst) ->
+       let exp_named_subst' = 
+        List.map (function (uri,t) -> (uri,liftaux k t)) exp_named_subst
+       in
+        C.MutInd (uri,tyno,exp_named_subst')
+    | C.MutConstruct (uri,tyno,consno,exp_named_subst) ->
+       let exp_named_subst' = 
+        List.map (function (uri,t) -> (uri,liftaux k t)) exp_named_subst
+       in
+        C.MutConstruct (uri,tyno,consno,exp_named_subst')
+    | C.MutCase (sp,i,outty,t,pl) ->
+       C.MutCase (sp, i, liftaux k outty, liftaux k t,
+        List.map (liftaux k) pl)
+    | C.Fix (i, fl) ->
+       let len = List.length fl in
+       let liftedfl =
+        List.map
+         (fun (name, i, ty, bo) -> (name, i, liftaux k ty, liftaux (k+len) bo))
+          fl
+       in
+        C.Fix (i, liftedfl)
+    | C.CoFix (i, fl) ->
+       let len = List.length fl in
+       let liftedfl =
+        List.map
+         (fun (name, ty, bo) -> (name, liftaux k ty, liftaux (k+len) bo))
+          fl
+       in
+        C.CoFix (i, liftedfl)
+ in
+ liftaux k
+
+let delift n t =
+  delift_from 1 n t
+ 
 let subst arg =
  let rec substaux k =
   let module C = Cic in
diff --git a/helm/ocaml/cic_proof_checking/cicSubstitution.mli b/helm/ocaml/cic_proof_checking/cicSubstitution.mli
index 9083212ae..1f0705881 100644
--- a/helm/ocaml/cic_proof_checking/cicSubstitution.mli
+++ b/helm/ocaml/cic_proof_checking/cicSubstitution.mli
@@ -33,6 +33,12 @@ exception ReferenceToInductiveDefinition;;
 (* lifts [t] of [n] *)
 val lift : int -> Cic.term -> Cic.term
 
+(** delifts t of n
+ *  @raise Failure s
+ *)
+val delift : int -> Cic.term -> Cic.term
+ 
+
 (* lift from n t *)
 (* as lift but lifts only indexes >= from *)
 val lift_from: int -> int -> Cic.term -> Cic.term