X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fcomponents%2Fng_tactics%2FnTacStatus.ml;h=e7d5bb3b532ee1eac2b6fdcee560ad8b58cb61c2;hb=ccf5878f2a2ec7f952f140e162391708a740517b;hp=545e5603bd3cb895b1cd05c2ecaa4ab2b0ebdeba;hpb=aefcb5f4e531c0318b7f495956c28eab971a4aa1;p=helm.git

diff --git a/helm/software/components/ng_tactics/nTacStatus.ml b/helm/software/components/ng_tactics/nTacStatus.ml
index 545e5603b..e7d5bb3b5 100644
--- a/helm/software/components/ng_tactics/nTacStatus.ml
+++ b/helm/software/components/ng_tactics/nTacStatus.ml
@@ -11,183 +11,292 @@
 
 (* $Id: nCic.ml 9058 2008-10-13 17:42:30Z tassi $ *)
 
-exception Error of string lazy_t
-let fail msg = raise (Error msg)
+let debug = ref false;;
+let pp x = 
+ if !debug then prerr_endline (Lazy.force x) else ()
+;;
+
+exception Error of string lazy_t * exn option
+let fail ?exn msg = raise (Error (msg,exn))
 
-type lowtac_status = {
-        pstatus : NCic.obj;
-        lstatus : LexiconEngine.status
-}
+module NRef = NReference
 
-type lowtactic = lowtac_status -> int -> lowtac_status 
+let wrap fname f x =
+  try f x 
+  with 
+  | MultiPassDisambiguator.DisambiguationError _ 
+  | NCicRefiner.RefineFailure _ 
+  | NCicUnification.UnificationFailure _ 
+  | NCicTypeChecker.TypeCheckerFailure _ 
+  | NCicMetaSubst.MetaSubstFailure _ as exn -> fail ~exn (lazy fname)
+;;
 
-type tac_status = {
-        gstatus : Continuationals.Stack.t; 
-        istatus : lowtac_status;
-} 
+class type g_pstatus =
+ object
+  inherit NEstatus.g_status
+  method obj: NCic.obj
+ end
 
-type tactic = tac_status -> tac_status
+class pstatus =
+ fun (o: NCic.obj) ->
+ object (self)
+   inherit NEstatus.status
+   val obj = o
+   method obj = obj
+   method set_obj o = {< obj = o >}
+   method set_pstatus : 'status. #g_pstatus as 'status -> 'self
+   = fun o -> (self#set_estatus o)#set_obj o#obj
+  end
 
 type tactic_term = CicNotationPt.term Disambiguate.disambiguator_input
 type tactic_pattern = GrafiteAst.npattern Disambiguate.disambiguator_input
 
 let pp_tac_status status = 
-  prerr_endline (NCicPp.ppobj status.istatus.pstatus)
-;;
-
-let pp_lowtac_status status = 
-  prerr_endline "--------------------------------------------";
-  prerr_endline (NCicPp.ppobj status.pstatus)
-;;
-
-type cic_term = NCic.conjecture (* name, context, term *)
-let ctx_of (_,c,_) = c ;;
-
-let relocate status destination (name,source,t as orig) =
- if source == destination then status, orig else
-  let rec lcp j i = function
-    | (n1, t1)::cl1, (n2, t2)::cl2 ->
-        if n1 = n2 && t1 = t2 then
-          NCic.Rel i :: lcp (j-1) (i-1) (cl1,cl2)
-        else
-          HExtlib.mk_list (NCic.Appl 
-            [NCic.Sort NCic.Prop; NCic.Sort NCic.Prop]) j
-    | _::_, [] -> 
-          HExtlib.mk_list (NCic.Appl 
-            [NCic.Sort NCic.Prop; NCic.Sort NCic.Prop]) j
-    | _ -> []
-  in
-  let lc = 
-    lcp (List.length destination) (List.length source) 
-      (List.rev destination, List.rev source)
-  in
-  let lc = (0,NCic.Ctx (List.rev lc)) in
-  let u, d, metasenv, subst, o = status.pstatus in 
-  let db = NCicUnifHint.db () in (* XXX fixme *)
-  let (metasenv, subst), t =
-    NCicMetaSubst.delift 
-       ~unify:(fun m s c t1 t2 -> 
-         try Some (NCicUnification.unify db m s c t1 t2)
-         with 
-          | NCicUnification.UnificationFailure _ 
-          | NCicUnification.Uncertain _ -> None) 
-     metasenv subst source 0 lc t
-  in
-  let status = { status with pstatus = u, d, metasenv, subst, o } in
-  status, (name, destination, t)
+  prerr_endline (NCicPp.ppobj status#obj);
+  prerr_endline ("STACK:\n" ^ Continuationals.Stack.pp status#stack)
+;;
+
+type cic_term = NCic.context * NCic.term
+let ctx_of (c,_) = c ;;
+let mk_cic_term c t = c,t ;;
+
+let ppterm status t =
+ let uri,height,metasenv,subst,obj = status#obj in
+ let context,t = t in
+  NCicPp.ppterm ~metasenv ~subst ~context t
+;;
+
+let ppcontext status c =
+ let uri,height,metasenv,subst,obj = status#obj in
+  NCicPp.ppcontext ~metasenv ~subst c
+;;
+
+let ppterm_and_context status t =
+ let uri,height,metasenv,subst,obj = status#obj in
+ let context,t = t in
+  NCicPp.ppcontext ~metasenv ~subst context ^ "\n ⊢ "^ 
+  NCicPp.ppterm ~metasenv ~subst ~context t
+;;
+
+let relocate status destination (source,t as orig) =
+ pp(lazy("relocate:\n" ^ ppterm_and_context status orig));
+ pp(lazy("relocate in:\n" ^ ppcontext status destination));
+ let rc = 
+   if source == destination then status, orig else
+    let _, _, metasenv, subst, _ = status#obj in
+    let rec compute_ops ctx = function (* destination, source *)
+      | (n1, NCic.Decl t1 as e)::cl1 as ex, (n2, NCic.Decl t2)::cl2 ->
+          if n1 = n2 && 
+             NCicReduction.are_convertible ctx ~subst ~metasenv t1 t2 then
+            compute_ops (e::ctx) (cl1,cl2)
+          else
+            [ `Delift ctx; `Lift (List.rev ex) ]
+      | (n1, NCic.Def (b1,t1) as e)::cl1 as ex, (n2, NCic.Def (b2,t2))::cl2 ->
+          if n1 = n2 && 
+             NCicReduction.are_convertible ctx ~subst ~metasenv t1 t2 &&
+             NCicReduction.are_convertible ctx ~subst ~metasenv b1 b2 then
+            compute_ops (e::ctx) (cl1,cl2)
+          else
+            [ `Delift ctx; `Lift (List.rev ex) ]
+      | (n1, NCic.Def (b1,t1) as e)::cl1 as ex, (n2, NCic.Decl t2)::cl2 ->
+          if n1 = n2 && 
+             NCicReduction.are_convertible ctx ~subst ~metasenv t1 t2 then
+            compute_ops (e::ctx) (cl1,cl2)
+          else
+            [ `Delift ctx; `Lift (List.rev ex) ]
+      | (n1, NCic.Decl _)::cl1 as ex, (n2, NCic.Def _)::cl2 -> 
+            [ `Delift ctx; `Lift (List.rev ex) ]
+      | _::_ as ex, [] -> [ `Lift (List.rev ex) ]
+      | [], _::_ -> [ `Delift ctx ]
+      | [],[] -> []
+    in
+    let ops = compute_ops [] (List.rev destination, List.rev source) in
+    let rec mk_irl i j = if i > j then [] else NCic.Rel i :: mk_irl (i+1) j in
+    List.fold_left 
+     (fun (status, (source,t)) -> function 
+      | `Lift extra_ctx -> 
+           let len = List.length extra_ctx in
+           status, (extra_ctx@source, NCicSubstitution.lift len t)
+      | `Delift ctx -> 
+            let len_ctx = List.length ctx in
+            let irl = mk_irl 1 (List.length ctx) in
+            let lc = List.length source - len_ctx, NCic.Ctx irl in
+            let u, d, metasenv, subst, o = status#obj in
+            pp(lazy("delifting as " ^ 
+              NCicPp.ppterm ~metasenv ~subst ~context:source 
+               (NCic.Meta (0,lc))));
+            let (metasenv, subst), t =
+              NCicMetaSubst.delift 
+                 ~unify:(fun m s c t1 t2 -> 
+                   try Some (NCicUnification.unify status m s c t1 t2)
+                   with 
+                    | NCicUnification.UnificationFailure _ 
+                    | NCicUnification.Uncertain _ -> None) 
+               metasenv subst source 0 lc t
+            in
+            let status = status#set_obj (u, d, metasenv, subst, o) in
+            status, (ctx,t))
+       (status,orig) ops
+ in
+ pp(lazy("relocated: " ^ ppterm (fst rc) (snd rc)));
+ rc
 ;;
+let relocate a b c = wrap "relocate" (relocate a b) c;;
 
 let term_of_cic_term s t c = 
-  let s, (_,_,t) = relocate s c t in
+  let s, (_,t) = relocate s c t in
   s, t
 ;;
 
-type ast_term = string * int * CicNotationPt.term
-
-let disambiguate (status : lowtac_status) (t : ast_term)  
-                 (ty : cic_term option) context =
+let disambiguate status context t ty =
  let status, expty = 
    match ty with 
    | None -> status, None 
    | Some ty -> 
-       let status, (_,_,x) = relocate status context ty in status, Some x 
+       let status, (_,x) = relocate status context ty in status, Some x 
  in
- let uri,height,metasenv,subst,obj = status.pstatus in
- let metasenv, subst, lexicon_status, t = 
-   GrafiteDisambiguate.disambiguate_nterm expty
-    status.lstatus context metasenv subst t 
+ let uri,height,metasenv,subst,obj = status#obj in
+ let metasenv, subst, status, t = 
+   GrafiteDisambiguate.disambiguate_nterm expty status context metasenv subst t 
  in
  let new_pstatus = uri,height,metasenv,subst,obj in
- { lstatus = lexicon_status; pstatus = new_pstatus }, (None, context, t) 
+  status#set_obj new_pstatus, (context, t) 
 ;;
+let disambiguate a b c d = wrap "disambiguate" (disambiguate a b c) d;;
 
 let typeof status ctx t =
-  let status, (_,_,t) = relocate status ctx t in
-  let _,_,metasenv,subst,_ = status.pstatus in
+  let status, (_,t) = relocate status ctx t in
+  let _,_,metasenv,subst,_ = status#obj in
   let ty = NCicTypeChecker.typeof ~subst ~metasenv ctx t in
-  status, (None, ctx, ty)
+  status, (ctx, ty)
+;;
+let typeof a b c = wrap "typeof" (typeof a b) c;;
+
+let saturate status ?delta (ctx,t) =
+  let n,h,metasenv,subst,k = status#obj in
+  let t,metasenv,args = NCicMetaSubst.saturate ?delta metasenv subst ctx t 0 in
+  let status = status#set_obj (n,h,metasenv,subst,k) in
+  status, (ctx,t), List.map (fun x -> ctx,x) args
 ;;
+let saturate a ?delta b = wrap "saturate" (saturate a ?delta) b;;
   
 let whd status ?delta ctx t =
-  let status, (name,_,t) = relocate status ctx t in
-  let _,_,_,subst,_ = status.pstatus in
+  let status, (_,t) = relocate status ctx t in
+  let _,_,_,subst,_ = status#obj in
   let t = NCicReduction.whd ~subst ?delta ctx t in
-  status, (name, ctx, t)
+  status, (ctx, t)
+;;
+  
+let normalize status ?delta ctx t =
+  let status, (_,t) = relocate status ctx t in
+  let _,_,_,subst,_ = status#obj in
+  let t = NCicTacReduction.normalize ~subst ?delta ctx t in
+  status, (ctx, t)
 ;;
   
 let unify status ctx a b =
-  let status, (_,_,a) = relocate status ctx a in
-  let status, (_,_,b) = relocate status ctx b in
-  let n,h,metasenv,subst,o = status.pstatus in
-  let metasenv, subst = 
-    NCicUnification.unify (NCicUnifHint.db ()) metasenv subst ctx a b
-  in
-  { status with pstatus = n,h,metasenv,subst,o }
+  let status, (_,a) = relocate status ctx a in
+  let status, (_,b) = relocate status ctx b in
+  let n,h,metasenv,subst,o = status#obj in
+  let metasenv, subst = NCicUnification.unify status metasenv subst ctx a b in
+   status#set_obj (n,h,metasenv,subst,o)
+;;
+let unify a b c d = wrap "unify" (unify a b c) d;;
+
+let fix_sorts status (ctx,t) =
+ let f () =
+  let name,height,metasenv,subst,obj = status#obj in
+  let metasenv, t = 
+    NCicUnification.fix_sorts metasenv subst t in
+  let status = status#set_obj (name,height,metasenv,subst,obj) in
+   status, (ctx,t)
+ in
+  wrap "fix_sorts" f ()
 ;;
 
 let refine status ctx term expty =
-  let status, (nt,_,term) = relocate status ctx term in
-  let status, ne, expty = 
-    match expty with None -> status, None, None 
+  let status, (_,term) = relocate status ctx term in
+  let status, expty = 
+    match expty with
+      None -> status, None 
     | Some e -> 
-        let status, (n,_, e) = relocate status ctx e in status, n, Some e
+        let status, (_, e) = relocate status ctx e in status, Some e
   in
-  let name,height,metasenv,subst,obj = status.pstatus in
-  let db = NCicUnifHint.db () in (* XXX fixme *)
-  let coercion_db = NCicCoercion.db () in
-  let look_for_coercion = NCicCoercion.look_for_coercion coercion_db in
-  let metasenv, subst, t, ty = 
-   NCicRefiner.typeof db ~look_for_coercion metasenv subst ctx term expty
+  let name,height,metasenv,subst,obj = status#obj in
+  let metasenv,subst,t,ty = 
+   NCicRefiner.typeof status metasenv subst ctx term expty
   in
-  { status with pstatus = name,height,metasenv,subst,obj }, 
-  (nt,ctx,t), (ne,ctx,ty)
+   status#set_obj (name,height,metasenv,subst,obj), (ctx,t), (ctx,ty)
 ;;
+let refine a b c d = wrap "refine" (refine a b c) d;;
 
-let get_goalty (status : lowtac_status) (g : int) =
- let _,_,metasenv,_,_ = status.pstatus in
- List.assoc g metasenv
+let get_goalty status g =
+ let _,_,metasenv,_,_ = status#obj in
+ try
+   let _, ctx, ty = NCicUtils.lookup_meta g metasenv in
+   ctx, ty
+ with NCicUtils.Meta_not_found _ as exn -> fail ~exn (lazy "get_goalty")
 ;;
 
-let instantiate status i t =
- let (gname, context, _ as gty) = get_goalty status i in
- let status, (_,_,t), (_,_,ty) = 
-   refine status (ctx_of gty) t (Some gty) 
- in
+let get_subst status =
+  let _,_,_,subst,_ = status#obj in subst
+;;
 
- let name,height,metasenv,subst,obj = status.pstatus in
+let to_subst status i entry =
+ let name,height,metasenv,subst,obj = status#obj in
  let metasenv = List.filter (fun j,_ -> j <> i) metasenv in
- let subst = (i, (gname, context, t, ty)) :: subst in
- { status with pstatus = (name,height,metasenv,subst,obj) }
+ let subst = (i, entry) :: subst in
+  status#set_obj (name,height,metasenv,subst,obj)
+;;
+
+let instantiate status ?refine:(dorefine=true) i t =
+ let _,_,metasenv,_,_ = status#obj in
+ let gname, context, gty = List.assoc i metasenv in
+  if dorefine then
+   let status, (_,t), (_,ty) = refine status context t (Some (context,gty)) in
+    to_subst status i (gname,context,t,ty)
+  else
+   let status,(_,ty) = typeof status context t in
+    to_subst status i (gname,context,snd t,ty)
+;;
+
+let instantiate_with_ast status i t =
+ let _,_,metasenv,_,_ = status#obj in
+ let gname, context, gty = List.assoc i metasenv in
+ let ggty = mk_cic_term context gty in
+ let status, (_,t) = disambiguate status context t (Some ggty) in
+  to_subst status i (gname,context,t,gty)
 ;;
 
-let mk_meta status ?name ctx bo_or_ty =
+let mk_meta status ?(attrs=[]) ctx bo_or_ty kind =
   match bo_or_ty with
   | `Decl ty ->
-      let status, (_,_,ty) = relocate status ctx ty in
-      let n,h,metasenv,subst,o = status.pstatus in
+      let status, (_,ty) = relocate status ctx ty in
+      let n,h,metasenv,subst,o = status#obj in
       let metasenv, _, instance, _ = 
-        NCicMetaSubst.mk_meta ?name metasenv ctx (`WithType ty)
+        NCicMetaSubst.mk_meta ~attrs metasenv ctx ~with_type:ty kind
       in
-      let status = { status with pstatus = n,h,metasenv,subst,o } in
-      status, (None,ctx,instance)
+      let status = status#set_obj (n,h,metasenv,subst,o) in
+      status, (ctx,instance)
   | `Def bo ->
-      let status, (_,_,bo_ as bo) = relocate status ctx bo in
-      let status, (_,_,ty) = typeof status ctx bo in
-      let n,h,metasenv,subst,o = status.pstatus in
+      let status, (_,bo_ as bo) = relocate status ctx bo in
+      let status, (_,ty) = typeof status ctx bo in
+      let n,h,metasenv,subst,o = status#obj in
       let metasenv, metano, instance, _ = 
-        NCicMetaSubst.mk_meta ?name metasenv ctx (`WithType ty) in
+        NCicMetaSubst.mk_meta ~attrs metasenv ctx ~with_type:ty kind in
+      let attrs,_,_ = NCicUtils.lookup_meta metano metasenv in
       let metasenv = List.filter (fun j,_ -> j <> metano) metasenv in
-      let subst = (metano, (name, ctx, bo_, ty)) :: subst in
-      let status = { status with pstatus = n,h,metasenv,subst,o } in
-      status, (None,ctx,instance)
+      let subst = (metano, (attrs, ctx, bo_, ty)) :: subst in
+      let status = status#set_obj (n,h,metasenv,subst,o) in
+      status, (ctx,instance)
 ;;
 
-let mk_in_scope status t = 
-  mk_meta status ~name:NCicMetaSubst.in_scope_tag (ctx_of t) (`Def t)
+let mk_in_scope status t =
+  mk_meta status ~attrs:[`InScope] (ctx_of t) (`Def t) `IsTerm
 ;;
 
 let mk_out_scope n status t = 
-  mk_meta status ~name:(NCicMetaSubst.out_scope_tag n) (ctx_of t) (`Def t)
+  mk_meta status ~attrs:[`OutScope n] (ctx_of t) (`Def t) `IsTerm
 ;;
 
 (* the following unification problem will be driven by 
@@ -201,34 +310,36 @@ let mk_out_scope n status t =
  *  postprocess is called on the entire term after selection
  *)
 let select_term 
-  low_status ~found ~postprocess (name,context,term) (wanted,path) 
+  low_status ~found ~postprocess (context,term) (wanted,path) 
 =
   let is_found status ctx t wanted =
     (* we could lift wanted step-by-step *)
-    try true, unify status ctx (None, ctx, t) wanted
+    pp(lazy("is_found: "^ppterm status (ctx,t)));
+    try true, unify status ctx (ctx, t) wanted
     with 
-    | NCicUnification.UnificationFailure _ 
-    | NCicUnification.Uncertain _ -> false, status
+    | Error (_, Some (NCicUnification.UnificationFailure _))
+    | Error (_, Some (NCicUnification.Uncertain _)) -> false, status
   in
   let match_term status ctx (wanted : cic_term) t =
-    let rec aux ctx status t =
+    let rec aux ctx (status,already_found) t =
       let b, status = is_found status ctx t wanted in
       if b then
-         let status , (_,_,t) = found status (None, ctx, t) in 
-         status, t
+         let status , (_,t) = found status (ctx, t) in 
+         (status,true),t
       else
-        let _,_,_,subst,_ = status.pstatus in
+        let _,_,_,subst,_ = status#obj in
         match t with
         | NCic.Meta (i,lc) when List.mem_assoc i subst ->
             let _,_,t,_ = NCicUtils.lookup_subst i subst in
-            aux ctx status t
-        | NCic.Meta _ -> status, t
-        | _ ->      
-            NCicUntrusted.map_term_fold_a (fun e c -> e::c) ctx aux status t
+            aux ctx (status,already_found) t
+        | NCic.Meta _ -> (status,already_found),t
+        | _ ->
+          NCicUntrusted.map_term_fold_a (fun e c -> e::c) ctx aux
+           (status,already_found) t
      in 
-       aux ctx status t
+       aux ctx (status,false) t
   in 
-  let _,_,_,subst,_ = low_status.pstatus in
+  let _,_,_,subst,_ = low_status#obj in
   let rec select status ctx pat cic = 
     match pat, cic with
     | _, NCic.Meta (i,lc) when List.mem_assoc i subst ->
@@ -276,17 +387,23 @@ let select_term
     | NCic.Implicit `Hole, t -> 
         (match wanted with
         | Some wanted -> 
-             let status, wanted = disambiguate status wanted None ctx in
-             match_term status ctx wanted t
-        | None -> match_term status ctx (None,ctx,t) t)
+             let status', wanted = disambiguate status ctx wanted None in
+             pp(lazy("wanted: "^ppterm status' wanted));
+             let (status',found), t' = match_term status' ctx wanted t in
+              if found then status',t' else status,t
+        | None ->
+           let (status,_),t = match_term status ctx (ctx,t) t in
+            status,t)
     | NCic.Implicit _, t -> status, t
     | _,t -> 
         fail (lazy ("malformed pattern: " ^ NCicPp.ppterm ~metasenv:[]
           ~context:[] ~subst:[] pat ^ " against " ^ 
           NCicPp.ppterm ~metasenv:[] ~subst:[] ~context:[] t))
   in
+  pp(lazy ("select in: "^ppterm low_status (context,term)));
   let status, term = select low_status context path term in
-  let term = (name, context, term) in
+  let term = (context, term) in
+  pp(lazy ("postprocess: "^ppterm low_status term));
   postprocess status term
 ;;
 
@@ -294,9 +411,10 @@ let analyse_indty status ty =
  let status, reduct = whd status (ctx_of ty) ty in
  let ref, args =
   match reduct with
-   | _,_,NCic.Const ref -> ref, []
-   | _,_,NCic.Appl (NCic.Const ref :: args) -> ref, args
-   | _,_,_ -> fail (lazy ("not an inductive type")) in
+   | _,NCic.Const ref -> ref, []
+   | _,NCic.Appl (NCic.Const (NRef.Ref (_,(NRef.Ind _)) as ref) :: args) -> 
+         ref, args
+   | _,_ -> fail (lazy ("not an inductive type: " ^ ppterm status ty)) in
  let _,lno,tl,_,i = NCicEnvironment.get_checked_indtys ref in
  let _,_,_,cl = List.nth tl i in
  let consno = List.length cl in
@@ -304,4 +422,112 @@ let analyse_indty status ty =
  status, (ref, consno, left, right)
 ;;
 
-let mk_cic_term c t = None,c,t ;;
+let apply_subst status ctx t =
+ let status, (_,t) = relocate status ctx t in
+ let _,_,_,subst,_ = status#obj in
+  status, (ctx, NCicUntrusted.apply_subst subst ctx t)
+;;
+
+let apply_subst_context status ~fix_projections ctx =
+ let _,_,_,subst,_ = status#obj in
+  NCicUntrusted.apply_subst_context ~fix_projections subst ctx
+;;
+
+let metas_of_term status (context,t) =
+ let _,_,_,subst,_ = status#obj in
+ NCicUntrusted.metas_of_term subst context t
+;;
+
+(* ============= move this elsewhere ====================*)
+
+class type ['stack] g_status =
+ object
+  inherit g_pstatus
+  method stack: 'stack
+ end
+
+class ['stack] status =
+ fun (o: NCic.obj) (s: 'stack) ->
+ object (self)
+   inherit (pstatus o)
+   val stack = s
+   method stack = stack
+   method set_stack s = {< stack = s >}
+   method set_status : 'status. 'stack #g_status as 'status -> 'self
+   = fun o -> (self#set_pstatus o)#set_stack o#stack
+  end
+
+class type lowtac_status = [unit] status
+
+type 'status lowtactic = #lowtac_status as 'status -> int -> 'status
+
+class type tac_status = [Continuationals.Stack.t] status
+
+type 'status tactic = #tac_status as 'status -> 'status
+
+module NCicInverseRelIndexable : Discrimination_tree.Indexable
+with type input = cic_term and type constant_name = NUri.uri = struct
+
+open Discrimination_tree
+
+type input = cic_term
+type constant_name = NUri.uri
+
+let ppelem = function
+  | Constant (uri,arity) -> 
+      "("^NUri.name_of_uri uri ^ "," ^ string_of_int arity^")"
+  | Bound (i,arity) -> 
+      "("^string_of_int i ^ "," ^ string_of_int arity^")"
+  | Variable -> "?"
+  | Proposition -> "Prop"
+  | Datatype -> "Type"
+  | Dead -> "Dead"
+;;
+
+let string_of_path l = String.concat "." (List.map ppelem l) ;;
+
+let path_string_of (ctx,t) =
+  let len_ctx = List.length ctx in
+  let rec aux arity = function
+    | NCic.Appl ((NCic.Meta _|NCic.Implicit _)::_) -> [Variable]
+    | NCic.Appl (NCic.Lambda _ :: _) -> [Variable] (* maybe we should b-reduce *)
+    | NCic.Appl [] -> assert false
+    | NCic.Appl (hd::tl) ->
+        aux (List.length tl) hd @ List.flatten (List.map (aux 0) tl) 
+    | NCic.Lambda _ | NCic.Prod _ -> [Variable]
+        (* I think we should CicSubstitution.subst Implicit t *)
+    | NCic.LetIn _ -> [Variable] (* z-reduce? *)
+    | NCic.Meta _ | NCic.Implicit _ -> assert (arity = 0); [Variable]
+    | NCic.Rel i -> [Bound (len_ctx - i, arity)]
+    | NCic.Sort (NCic.Prop) -> assert (arity=0); [Proposition]
+    | NCic.Sort _ -> assert (arity=0); [Datatype]
+    | NCic.Const (NReference.Ref (u,_)) -> [Constant (u, arity)]
+    | NCic.Match _ -> [Dead]
+  in 
+  let path = aux 0 t in
+(*   prerr_endline (string_of_path path); *)
+  path
+;;
+
+let compare e1 e2 =
+  match e1,e2 with
+  | Constant (u1,a1),Constant (u2,a2) -> 
+       let x = NUri.compare u1 u2 in
+       if x = 0 then Pervasives.compare a1 a2 else x
+  | e1,e2 -> Pervasives.compare e1 e2
+;;
+
+
+end
+
+module Ncic_termOT : Set.OrderedType with type t = cic_term =
+ struct
+   type t = cic_term
+   let compare = Pervasives.compare
+ end
+
+module Ncic_termSet : Set.S with type elt = cic_term = Set.Make(Ncic_termOT)
+
+module InvRelDiscriminationTree = 
+   Discrimination_tree.Make(NCicInverseRelIndexable)(Ncic_termSet)
+