]> matita.cs.unibo.it Git - helm.git/blobdiff - components/tactics/discriminationTactics.ml
- tactics:
[helm.git] / components / tactics / discriminationTactics.ml
index 42da52bd60101f2c996fbc1eaed08cd0973006bf..ebf7728449dad2d03de6b08744529171c667ae34 100644 (file)
 
 let debug_print = fun _ -> ()
 
-let rec injection_tac ~term =
+(* term ha tipo t1=t2; funziona solo se t1 e t2 hanno in testa costruttori
+diversi *)
+
+let discriminate_tac ~term =
+ let module C = Cic in
+ let module U = UriManager in
+ let module P = PrimitiveTactics in
+ let module T = Tacticals in
+ let true_URI =
+  match LibraryObjects.true_URI () with
+     Some uri -> uri
+   | None -> raise (ProofEngineTypes.Fail (lazy "You need to register the default \"true\" definition first. Please use the \"default\" command")) in
+ let false_URI =
+  match LibraryObjects.false_URI () with
+     Some uri -> uri
+   | None -> raise (ProofEngineTypes.Fail (lazy "You need to register the default \"false\" definition first. Please use the \"default\" command")) in
+ let fail msg = raise (ProofEngineTypes.Fail (lazy ("Discriminate: " ^ msg))) in
+ let find_discriminating_consno t1 t2 =
+   let rec aux t1 t2 =
+     match t1, t2 with
+     | C.MutConstruct _, C.MutConstruct _ when t1 = t2 -> None
+     | C.Appl ((C.MutConstruct _ as constr1) :: args1),
+       C.Appl ((C.MutConstruct _ as constr2) :: args2)
+       when constr1 = constr2 ->
+         let rec aux_list l1 l2 =
+           match l1, l2 with
+           | [], [] -> None
+           | hd1 :: tl1, hd2 :: tl2 ->
+               (match aux hd1 hd2 with
+               | None -> aux_list tl1 tl2
+               | Some _ as res -> res)
+           | _ -> (* same constructor applied to a different number of args *)
+               assert false
+         in
+         aux_list args1 args2
+     | ((C.MutConstruct (_,_,consno1,subst1)),
+       (C.MutConstruct (_,_,consno2,subst2)))
+     | ((C.MutConstruct (_,_,consno1,subst1)),
+       (C.Appl ((C.MutConstruct (_,_,consno2,subst2)) :: _)))
+     | ((C.Appl ((C.MutConstruct (_,_,consno1,subst1)) :: _)),
+       (C.MutConstruct (_,_,consno2,subst2)))
+     | ((C.Appl ((C.MutConstruct (_,_,consno1,subst1)) :: _)),
+       (C.Appl ((C.MutConstruct (_,_,consno2,subst2)) :: _)))
+       when (consno1 <> consno2) || (subst1 <> subst2) ->
+         Some consno2
+     | _ -> fail "not a discriminable equality"
+   in
+   aux t1 t2
+ in
+ let mk_branches_and_outtype turi typeno consno context args =
+    (* a list of "True" except for the element in position consno which
+     * is "False" *)
+    match fst (CicEnvironment.get_obj CicUniv.empty_ugraph turi) with
+    | C.InductiveDefinition (ind_type_list,_,paramsno,_)  ->
+        let _,_,rty,constructor_list = List.nth ind_type_list typeno in 
+        let false_constr_id,_ = List.nth constructor_list (consno - 1) in
+        let branches =
+         List.map 
+           (fun (id,cty) ->
+             (* dubbio: e' corretto ridurre in questo context ??? *)
+             let red_ty = CicReduction.whd context cty in
+             let rec aux t k =
+               match t with
+               | C.Prod (_,_,target) when (k <= paramsno) ->
+                   CicSubstitution.subst (List.nth args (k-1))
+                     (aux target (k+1))
+               | C.Prod (binder,source,target) when (k > paramsno) ->
+                   C.Lambda (binder, source, (aux target (k+1)))
+               | _ -> 
+                   if (id = false_constr_id)
+                   then (C.MutInd(false_URI,0,[]))
+                   else (C.MutInd(true_URI,0,[]))
+             in
+             (CicSubstitution.lift 1 (aux red_ty 1)))
+           constructor_list in
+        let outtype =
+         let seed = ref 0 in
+         let rec mk_lambdas rev_left_args =
+          function
+             0, args, C.Prod (_,so,ta) ->
+              C.Lambda
+               (C.Name (incr seed; "x" ^ string_of_int !seed),
+               so,
+               mk_lambdas rev_left_args (0,args,ta))
+           | 0, args, C.Sort _ ->
+              let rec mk_rels =
+               function
+                  0 -> []
+                | n -> C.Rel n :: mk_rels (n - 1) in
+              let argsno = List.length args in
+               C.Lambda
+                (C.Name "x",
+                 (if argsno + List.length rev_left_args > 0 then
+                   C.Appl
+                    (C.MutInd (turi, typeno, []) ::
+                     (List.map
+                      (CicSubstitution.lift (argsno + 1))
+                      (List.rev rev_left_args)) @
+                     mk_rels argsno)
+                  else
+                   C.MutInd (turi,typeno,[])),
+                 C.Sort C.Prop)
+           | 0, _, _ -> assert false (* seriously screwed up *)
+           | n, he::tl, C.Prod (_,_,ta) ->
+              mk_lambdas (he::rev_left_args)(n-1,tl,CicSubstitution.subst he ta)
+           | n,_,_ ->
+              assert false (* we should probably reduce in some context *)
+         in
+          mk_lambdas [] (paramsno, args, rty)
+        in
+         branches, outtype 
+    | _ -> assert false
+ in
+ let discriminate'_tac ~term status = 
+  let (proof, goal) = status in
+  let _,metasenv,_,_ = proof in
+  let _,context,_ = CicUtil.lookup_meta goal metasenv in
+  let termty,_ = 
+    CicTypeChecker.type_of_aux' metasenv context term CicUniv.empty_ugraph
+  in
+  match termty with
+   | C.Appl [(C.MutInd (equri, 0, [])) ; tty ; t1 ; t2]
+     when LibraryObjects.is_eq_URI equri ->
+      let turi,typeno,exp_named_subst,args = 
+        match tty with
+        | (C.MutInd (turi,typeno,exp_named_subst)) ->
+            turi,typeno,exp_named_subst,[]
+        | (C.Appl (C.MutInd (turi,typeno,exp_named_subst)::args)) ->
+            turi,typeno,exp_named_subst,args
+        | _ -> fail "not a discriminable equality"
+      in
+      let consno =
+        match find_discriminating_consno t1 t2 with
+        | Some consno -> consno
+        | None -> fail "discriminating terms are structurally equal"
+      in
+      let branches,outtype =
+       mk_branches_and_outtype turi typeno consno context args
+      in
+      ProofEngineTypes.apply_tactic
+       (T.then_
+         ~start:(EliminationTactics.elim_type_tac (C.MutInd (false_URI, 0, [])))
+         ~continuation:
+           (T.then_
+             ~start:
+               (ReductionTactics.change_tac 
+                 ~pattern:(ProofEngineTypes.conclusion_pattern None)
+                 (fun _ m u ->
+                   C.Appl [
+                     C.Lambda ( C.Name "x", tty,
+                       C.MutCase (turi, typeno, outtype, (C.Rel 1), branches));
+                     t2 ],
+                   m, u))
+             ~continuation:
+               (T.then_
+                 ~start:
+                   (EqualityTactics.rewrite_simpl_tac
+                     ~direction:`RightToLeft
+                     ~pattern:(ProofEngineTypes.conclusion_pattern None)
+                     term [])
+                 ~continuation:
+                   (IntroductionTactics.constructor_tac ~n:1)))) status
+    | _ -> fail "not an equality"
+  in
+  ProofEngineTypes.mk_tactic (discriminate'_tac ~term)
+;;
+
+let rec injection_tac ~first_time ~term ~liftno ~continuation =
  let injection_tac ~term status = 
   let (proof, goal) = status in
   let module C = Cic in
@@ -36,64 +203,101 @@ let rec injection_tac ~term =
   let module T = Tacticals in
   let _,metasenv,_,_ = proof in
   let _,context,_ = CicUtil.lookup_meta goal metasenv in
+  let term = CicSubstitution.lift liftno term in
   let termty,_ = (* TASSI: FIXME *)
     CicTypeChecker.type_of_aux' metasenv context term CicUniv.empty_ugraph
   in
     ProofEngineTypes.apply_tactic
-      (match termty with
-          (C.Appl [(C.MutInd (equri, 0, [])) ; tty ; t1 ; t2])
-             when LibraryObjects.is_eq_URI equri -> (
+     (match termty with
+         (C.Appl [(C.MutInd (equri, 0, [])) ; tty ; t1 ; t2])
+            when LibraryObjects.is_eq_URI equri ->
+          begin
            match tty with
               (C.MutInd (turi,typeno,exp_named_subst))
-            | (C.Appl (C.MutInd (turi,typeno,exp_named_subst)::_)) -> (
-                   match t1,t2 with
-                      ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
-                       (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
-                         when (uri1 = uri2) && (typeno1 = typeno2) && 
-                             (consno1 = consno2) && (exp_named_subst1 = exp_named_subst2) ->
-                       (* raise (ProofEngineTypes.Fail "Injection: nothing to do") ; *) T.id_tac
-                    | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::applist1)),
-                       (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::applist2)))
-                         when (uri1 = uri2) && (typeno1 = typeno2) && (consno1 = consno2) && (exp_named_subst1 = exp_named_subst2) ->
-                       let rec traverse_list i liftno l1 l2 =
-                         match l1,l2 with
-                            [],[] -> T.id_tac
-                          | hd1::tl1,hd2::tl2 -> 
-                             if
-                              fst
-                               (CicReduction.are_convertible ~metasenv
-                                 context hd1 hd2 CicUniv.empty_ugraph)
-                             then
-                              traverse_list (i+1) liftno tl1 tl2
-                             else
-                              T.then_ 
-                               ~start:
-                                 (injection1_tac ~i ~liftno
-                                   ~term:(CicSubstitution.lift liftno term))
-                               ~continuation:
-                                 (traverse_list (i+1) (liftno+1) tl1 tl2)
-                          | _ -> raise (ProofEngineTypes.Fail (lazy "Discriminate: i 2 termini hanno in testa lo stesso costruttore, ma applicato a un numero diverso di termini. possibile???"))
-                       in traverse_list 1 0 applist1 applist2
-                    | ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
-                       (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
-                    | ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
-                       (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::_)))
-                    | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::_)),
-                       (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
-                    | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::_)),
-                       (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::_)))
-                         when (consno1 <> consno2) || (exp_named_subst1 <> exp_named_subst2) ->
-                       raise (ProofEngineTypes.Fail (lazy "Injection: not a projectable equality but a discriminable one"))
-                    | _ -> raise (ProofEngineTypes.Fail (lazy "Injection: not a projectable equality"))
-                   )
-            | _ -> raise (ProofEngineTypes.Fail (lazy "Injection: not a projectable equality"))
-           )
-        | _ -> raise (ProofEngineTypes.Fail (lazy "Injection: not an equation"))
-      ) status
+            | (C.Appl (C.MutInd (turi,typeno,exp_named_subst)::_)) ->
+               begin
+                match t1,t2 with
+                   ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
+                    (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
+                      when (uri1 = uri2) && (typeno1 = typeno2) && 
+                           (consno1 = consno2) &&
+                    (exp_named_subst1 = exp_named_subst2)
+                   ->
+                    if first_time then
+                     raise
+                      (ProofEngineTypes.Fail (lazy "Injection: nothing to do"))
+                    else
+                     continuation ~liftno
+                 | C.Appl
+                    ((C.MutConstruct
+                       (uri1,typeno1,consno1,exp_named_subst1))::applist1),
+                   C.Appl
+                    ((C.MutConstruct
+                       (uri2,typeno2,consno2,exp_named_subst2))::applist2)
+                      when (uri1 = uri2) && (typeno1 = typeno2) &&
+                       (consno1 = consno2) &&
+                       (exp_named_subst1 = exp_named_subst2)
+                    ->
+                     let rec traverse_list i l1 l2 =
+                       match l1,l2 with
+                          [],[] ->
+                           if first_time then
+                            continuation
+                           else
+                            (match term with
+                                C.Rel n ->
+                                 (match List.nth context (n-1) with
+                                     Some (C.Name id,_) ->
+                                      fun ~liftno ->
+                                       T.then_
+                                        ~start:
+                                          (ProofEngineStructuralRules.clear
+                                            ~hyps:[id])
+                                        ~continuation:(continuation ~liftno)
+                                   | _ -> assert false)
+                              | _ -> assert false)
+                        | hd1::tl1,hd2::tl2 -> 
+                           if
+                            fst
+                             (CicReduction.are_convertible ~metasenv
+                               context hd1 hd2 CicUniv.empty_ugraph)
+                           then
+                            traverse_list (i+1) tl1 tl2
+                           else
+                            injection1_tac ~i ~term
+                             ~continuation:(traverse_list (i+1) tl1 tl2)
+                        | _ -> assert false (* i 2 termini hanno in testa lo stesso costruttore, ma applicato a un numero diverso di termini *)
+                     in
+                      traverse_list 1 applist1 applist2 ~liftno
+                 | ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
+                    (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
+                 | ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
+                    (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::_)))
+                 | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::_)),
+                    (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
+                 | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::_)),
+                    (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::_)))
+                      when (consno1 <> consno2) || (exp_named_subst1 <> exp_named_subst2) ->
+                    discriminate_tac ~term
+                    (*raise (ProofEngineTypes.Fail (lazy "Injection: not a projectable equality but a discriminable one"))*)
+                 | _ ->
+                   if first_time then
+                    raise (ProofEngineTypes.Fail (lazy "Injection: not a projectable equality"))
+                   else
+                    continuation ~liftno 
+               end
+            | _ ->
+              if first_time then
+               raise (ProofEngineTypes.Fail (lazy "Injection: not a projectable equality"))
+              else
+               continuation ~liftno 
+           end
+       | _ -> raise (ProofEngineTypes.Fail (lazy "Injection: not an equation"))
+     ) status
  in 
   ProofEngineTypes.mk_tactic (injection_tac ~term)
 
-and injection1_tac ~term ~i ~liftno 
+and injection1_tac ~term ~i ~liftno ~continuation =
  let injection1_tac ~term ~i status =
   let (proof, goal) = status in
   (* precondizione: t1 e t2 hanno in testa lo stesso costruttore ma differiscono (o potrebbero differire?) nell'i-esimo parametro del costruttore *)
@@ -102,10 +306,12 @@ and injection1_tac ~term ~i ~liftno =
    let module U = UriManager in
    let module P = PrimitiveTactics in
    let module T = Tacticals in
+   let term = CicSubstitution.lift liftno term in
    let _,metasenv,_,_ = proof in
    let _,context,_ = CicUtil.lookup_meta goal metasenv in
    let termty,_ = (* TASSI: FIXME *)
-     CicTypeChecker.type_of_aux' metasenv context term CicUniv.empty_ugraph in
+     CicTypeChecker.type_of_aux' metasenv context term CicUniv.empty_ugraph
+   in
      match termty with (* an equality *)
          (C.Appl [(C.MutInd (equri, 0, [])) ; tty ; t1 ; t2])
              when LibraryObjects.is_eq_URI equri -> (
@@ -151,12 +357,6 @@ and injection1_tac ~term ~i ~liftno =
                                in
                                 C.Lambda (binder',source,(aux target (k+1)))
                             | _ ->
-if id = i_constr_id then (
-prerr_endline ("k= " ^ string_of_int k);
-prerr_endline ("paramsno= " ^ string_of_int paramsno);
-prerr_endline ("nr_param_constr " ^ string_of_int (k - 1 - paramsno));
-prerr_endline ("rel= " ^ string_of_int (k - i));
-);
                                let nr_param_constr = k - 1 - paramsno in
                                 if id = i_constr_id
                                  then C.Rel (k - i)
@@ -208,64 +408,59 @@ prerr_endline ("rel= " ^ string_of_int (k - i));
                 in
                 ProofEngineTypes.apply_tactic   
                  (T.thens 
-                  ~start:(P.cut_tac (C.Appl [(C.MutInd (equri,0,[])) ; tty' ; t1' ; t2']))
-                  ~continuations:[
-                    T.then_ 
-                     ~start:T.id_tac (*(injection_tac ~term:(C.Rel 1))*)
-                     ~continuation:T.id_tac (* !!! qui devo anche fare clear di term tranne al primo passaggio *) 
-                    ;
-                    T.then_ 
-                     ~start:(ProofEngineTypes.mk_tactic 
-                       (fun status ->    
-                         let (proof, goal) = status in
-                         let _,metasenv,_,_ = proof in
-                          let _,context,gty =
-                           CicUtil.lookup_meta goal metasenv
-                          in
-                           let new_t1' = 
-                            match gty with 
-                               (C.Appl (C.MutInd (_,_,_)::arglist)) -> 
-                                List.nth arglist 1
-                             | _ ->
-                               raise
-                                (ProofEngineTypes.Fail
-                                  (lazy
-                                    "Injection: goal after cut is not correct"))
-                           in
-let aaa =
-                            ProofEngineTypes.apply_tactic 
-                            (ReductionTactics.change_tac
-                               ~pattern:(ProofEngineTypes.conclusion_pattern
-                                (Some new_t1'))
-                               (fun _ m u ->
-let xxx =
-                                 C.Appl [
-                                  C.Lambda
-                                   (C.Name "x",
-                                     tty,
-                                     C.MutCase
-                                      (turi,typeno,outtype,C.Rel 1,patterns)) ;
-                                  t1]
-in
-prerr_endline ("i=" ^ string_of_int i ^ "; liftno=" ^ string_of_int liftno);
-prerr_endline ("XXX: " ^ CicPp.ppterm xxx);
-prerr_endline ("WITH: " ^ CicPp.ppterm new_t1');
-xxx,
-                                 m, u))
-                        status
-in
-prerr_endline "OK";
-aaa
-                       ))
-                     ~continuation:
-                       (T.then_
-                         ~start:
-                           (EqualityTactics.rewrite_simpl_tac
-                             ~direction:`LeftToRight
-                             ~pattern:(ProofEngineTypes.conclusion_pattern None)
-                             term)
-                         ~continuation:EqualityTactics.reflexivity_tac
-                       )
+                  ~start:
+                    (P.cut_tac
+                     (C.Appl [C.MutInd (equri,0,[]) ; tty' ; t1' ; t2']))
+                  ~continuations:
+                    [ injection_tac ~first_time:false ~liftno:0
+                       ~term:(C.Rel 1)
+                       (* here I need to lift all the continuations by 1;
+                          since I am setting back liftno to 0, I actually
+                          need to lift all the continuations by liftno + 1 *)
+                       ~continuation:
+                         (fun ~liftno:x ->
+                           continuation ~liftno:(liftno + 1 + x)) ;
+                      T.then_ 
+                       ~start:(ProofEngineTypes.mk_tactic 
+                         (fun status ->    
+                           let (proof, goal) = status in
+                           let _,metasenv,_,_ = proof in
+                            let _,context,gty =
+                             CicUtil.lookup_meta goal metasenv
+                            in
+                             let new_t1' = 
+                              match gty with 
+                                 (C.Appl (C.MutInd (_,_,_)::arglist)) -> 
+                                  List.nth arglist 1
+                               | _ ->
+                                 raise
+                                  (ProofEngineTypes.Fail
+                                    (lazy
+                                      "Injection: goal after cut is not correct"))
+                             in
+                              ProofEngineTypes.apply_tactic 
+                              (ReductionTactics.change_tac
+                                 ~pattern:(ProofEngineTypes.conclusion_pattern
+                                  (Some new_t1'))
+                                 (fun _ m u ->
+                                   C.Appl [
+                                    C.Lambda
+                                     (C.Name "x",
+                                       tty,
+                                       C.MutCase
+                                        (turi,typeno,outtype,C.Rel 1,patterns)) ;
+                                    t1],
+                                   m, u))
+                          status
+                         ))
+                       ~continuation:
+                         (T.then_
+                           ~start:
+                             (EqualityTactics.rewrite_simpl_tac
+                               ~direction:`LeftToRight
+                               ~pattern:(ProofEngineTypes.conclusion_pattern None)
+                               term [])
+                           ~continuation:EqualityTactics.reflexivity_tac)
                    ])     
                   status
             | _ -> raise (ProofEngineTypes.Fail (lazy "Injection: not an equality over elements of an inductive type"))
@@ -275,307 +470,9 @@ aaa
   ProofEngineTypes.mk_tactic (injection1_tac ~term ~i)
 ;;
 
-exception TwoDifferentSubtermsFound of int 
-
-(* term ha tipo t1=t2; funziona solo se t1 e t2 hanno in testa costruttori
-diversi *)
-
-let discriminate'_tac ~term =
- let module C = Cic in
- let module U = UriManager in
- let module P = PrimitiveTactics in
- let module T = Tacticals in
- let true_URI =
-  match LibraryObjects.true_URI () with
-     Some uri -> uri
-   | None -> raise (ProofEngineTypes.Fail (lazy "You need to register the default \"true\" definition first. Please use the \"default\" command")) in
- let false_URI =
-  match LibraryObjects.false_URI () with
-     Some uri -> uri
-   | None -> raise (ProofEngineTypes.Fail (lazy "You need to register the default \"false\" definition first. Please use the \"default\" command")) in
- let fail msg = raise (ProofEngineTypes.Fail (lazy ("Discriminate: " ^ msg))) in
- let find_discriminating_consno t1 t2 =
-   let rec aux t1 t2 =
-     match t1, t2 with
-     | C.MutConstruct _, C.MutConstruct _ when t1 = t2 -> None
-     | C.Appl ((C.MutConstruct _ as constr1) :: args1),
-       C.Appl ((C.MutConstruct _ as constr2) :: args2)
-       when constr1 = constr2 ->
-         let rec aux_list l1 l2 =
-           match l1, l2 with
-           | [], [] -> None
-           | hd1 :: tl1, hd2 :: tl2 ->
-               (match aux hd1 hd2 with
-               | None -> aux_list tl1 tl2
-               | Some _ as res -> res)
-           | _ -> (* same constructor applied to a different number of args *)
-               assert false
-         in
-         aux_list args1 args2
-     | ((C.MutConstruct (_,_,consno1,subst1)),
-       (C.MutConstruct (_,_,consno2,subst2)))
-     | ((C.MutConstruct (_,_,consno1,subst1)),
-       (C.Appl ((C.MutConstruct (_,_,consno2,subst2)) :: _)))
-     | ((C.Appl ((C.MutConstruct (_,_,consno1,subst1)) :: _)),
-       (C.MutConstruct (_,_,consno2,subst2)))
-     | ((C.Appl ((C.MutConstruct (_,_,consno1,subst1)) :: _)),
-       (C.Appl ((C.MutConstruct (_,_,consno2,subst2)) :: _)))
-       when (consno1 <> consno2) || (subst1 <> subst2) ->
-         Some consno2
-     | _ -> fail "not a discriminable equality"
-   in
-   aux t1 t2
- in
- let mk_pattern turi typeno consno context left_args =
-    (* a list of "True" except for the element in position consno which
-     * is "False" *)
-    match fst (CicEnvironment.get_obj CicUniv.empty_ugraph turi) with
-    | C.InductiveDefinition (ind_type_list,_,nr_ind_params,_)  ->
-        let _,_,_,constructor_list = List.nth ind_type_list typeno in 
-        let false_constr_id,_ = List.nth constructor_list (consno - 1) in
-        List.map 
-          (fun (id,cty) ->
-            (* dubbio: e' corretto ridurre in questo context ??? *)
-            let red_ty = CicReduction.whd context cty in
-            let rec aux t k =
-              match t with
-              | C.Prod (_,_,target) when (k <= nr_ind_params) ->
-                  CicSubstitution.subst (List.nth left_args (k-1))
-                    (aux target (k+1))
-              | C.Prod (binder,source,target) when (k > nr_ind_params) ->
-                  C.Lambda (binder, source, (aux target (k+1)))
-              | _ -> 
-                  if (id = false_constr_id)
-                  then (C.MutInd(false_URI,0,[]))
-                  else (C.MutInd(true_URI,0,[]))
-            in
-            (CicSubstitution.lift 1 (aux red_ty 1)))
-          constructor_list
-    | _ -> (* object is not an inductive definition *)
-        assert false
- in
- let discriminate'_tac ~term status = 
-  let (proof, goal) = status in
-  let _,metasenv,_,_ = proof in
-  let _,context,_ = CicUtil.lookup_meta goal metasenv in
-  let termty,_ = 
-    CicTypeChecker.type_of_aux' metasenv context term CicUniv.empty_ugraph
-  in
-  match termty with
-  | (C.Appl [(C.MutInd (equri, 0, [])) ; tty ; t1 ; t2])
-    when LibraryObjects.is_eq_URI equri ->
-      let turi,typeno,exp_named_subst,left_args = 
-        match tty with
-        | (C.MutInd (turi,typeno,exp_named_subst)) ->
-            turi,typeno,exp_named_subst,[]
-        | (C.Appl (C.MutInd (turi,typeno,exp_named_subst)::left_args)) ->
-            turi,typeno,exp_named_subst,left_args
-        | _ -> fail "not a discriminable equality"
-      in
-      let consno =
-        match find_discriminating_consno t1 t2 with
-        | Some consno -> consno
-        | None -> fail "discriminating terms are structurally equal"
-      in
-      let pattern = mk_pattern turi typeno consno context left_args in
-      let (proof',goals') = 
-        ProofEngineTypes.apply_tactic 
-          (EliminationTactics.elim_type_tac
-            (C.MutInd (false_URI, 0, [])))
-          status 
-      in
-      (match goals' with
-      | [goal'] -> 
-          let _,metasenv',_,_ = proof' in
-          let _,context',gty' = CicUtil.lookup_meta goal' metasenv' in
-          ProofEngineTypes.apply_tactic
-            (T.then_
-              ~start:
-                (ReductionTactics.change_tac 
-                  ~pattern:(ProofEngineTypes.conclusion_pattern (Some gty'))
-                  (fun _ m u ->
-                    C.Appl [
-                      C.Lambda ( C.Name "x", tty,
-                        C.MutCase (turi, typeno,
-                          (C.Lambda ((C.Name "x"),
-                           (CicSubstitution.lift 1 tty),
-                           (C.Sort C.Prop))),
-                          (C.Rel 1), pattern));
-                      t2 ], m, u))
-              ~continuation:
-                (T.then_
-                  ~start:
-                    (EqualityTactics.rewrite_simpl_tac
-                      ~direction:`RightToLeft
-                      ~pattern:(ProofEngineTypes.conclusion_pattern None)
-                      term)
-                  ~continuation:
-                    (IntroductionTactics.constructor_tac ~n:1)))
-            (proof',goal')
-      | [] -> fail "ElimType False left no goals"
-      | _ -> fail "ElimType False left more than one goal")
-    | _ -> fail "not an equality"
-  in
-  ProofEngineTypes.mk_tactic (discriminate'_tac ~term)
-
-let discriminate_tac ~term = 
- let discriminate_tac ~term status =
-  ProofEngineTypes.apply_tactic 
-  (Tacticals.then_
-    ~start:(* (injection_tac ~term) *) Tacticals.id_tac
-    ~continuation:(discriminate'_tac ~term)) (* NOOO!!! non term ma una (qualunque) delle nuove hyp introdotte da inject *)
-   status
- in
-  ProofEngineTypes.mk_tactic (discriminate_tac ~term)
-
-(* DISCRIMINTATE SENZA INJECTION 
-
-exception TwoDifferentSubtermsFound of (Cic.term * Cic.term * int) 
-
-let discriminate_tac ~term status =
-  let module C = Cic in
-  let module U = UriManager in
-  let module P = PrimitiveTactics in
-  let module T = Tacticals in
-  let (proof, goal) = status in
-   let _,metasenv,_,_ = proof in
-    let _,context,_ = CicUtil.lookup_meta goal metasenv in
-     let termty = (CicTypeChecker.type_of_aux' metasenv context term) in
-      match termty with
-         (C.Appl [(C.MutInd (equri, 0, [])) ; tty ; t1 ; t2]) 
-          when (U.eq equri (U.uri_of_string "cic:/Coq/Init/Logic/eq.ind")) 
-            or (U.eq equri (U.uri_of_string "cic:/Coq/Init/Logic_Type/eqT.ind")) -> (
-           match tty with
-              (C.MutInd (turi,typeno,exp_named_subst))
-            | (C.Appl (C.MutInd (turi,typeno,exp_named_subst)::_)) ->
-
-                let (t1',t2',consno2') = (* bruuutto: uso un eccezione per terminare con successo! buuu!! :-/ *)
-                 try
-                  let rec traverse t1 t2 =
-debug_print (lazy ("XXXX t1 " ^ CicPp.ppterm t1)) ;
-debug_print (lazy ("XXXX t2 " ^ CicPp.ppterm t2)) ;
-                   match t1,t2 with
-                      ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
-                       (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
-                         when (uri1 = uri2) && (typeno1 = typeno2) && (consno1 = consno2) && (exp_named_subst1 = exp_named_subst2) ->
-                       t1,t2,0
-                    | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::applist1)),
-                       (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::applist2))) 
-                         when (uri1 = uri2) && (typeno1 = typeno2) && (consno1 = consno2) && (exp_named_subst1 = exp_named_subst2) ->
-                       let rec traverse_list l1 l2 =
-                         match l1,l2 with
-                            [],[] -> t1,t2,0
-                          | hd1::tl1,hd2::tl2 -> traverse hd1 hd2; traverse_list tl1 tl2
-                          | _ -> raise (ProofEngineTypes.Fail "Discriminate: i 2 termini hanno in testa lo stesso costruttore, ma applicato a un numero diverso di termini. possibile???")
-                       in traverse_list applist1 applist2
-
-                    | ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
-                       (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
-                    | ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1)),
-                       (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::_)))
-                    | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::_)),
-                       (C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2)))
-                    | ((C.Appl ((C.MutConstruct (uri1,typeno1,consno1,exp_named_subst1))::_)),
-                       (C.Appl ((C.MutConstruct (uri2,typeno2,consno2,exp_named_subst2))::_)))
-                         when (consno1 <> consno2) || (exp_named_subst1 <> exp_named_subst2) ->
-                       raise (TwoDifferentSubtermsFound (t1,t2,consno2))
-                    | _ -> raise (ProofEngineTypes.Fail "Discriminate: not a discriminable equality")
-                  in traverse t1 t2
-                 with (TwoDifferentSubtermsFound (t1,t2,consno2)) -> (t1,t2,consno2)
-                in
-debug_print (lazy ("XXXX consno2' " ^ (string_of_int consno2'))) ;
-                 if consno2' = 0 
-                  then raise (ProofEngineTypes.Fail "Discriminate: Discriminating terms are structurally equal")
-                  else
-
-                   let pattern = 
-                     (* a list of "True" except for the element in position consno2' which is "False" *)
-                     match fst(CicEnvironment.get_obj turi 
-                                 CicUniv.empty_ugraph) with
-                        C.InductiveDefinition (ind_type_list,_,nr_ind_params)  ->
-debug_print (lazy ("XXXX nth " ^ (string_of_int (List.length ind_type_list)) ^ " " ^ (string_of_int typeno))) ;
-                         let _,_,_,constructor_list = (List.nth ind_type_list typeno) in 
-debug_print (lazy ("XXXX nth " ^ (string_of_int (List.length constructor_list)) ^ " " ^ (string_of_int consno2'))) ;
-                          let false_constr_id,_ = List.nth constructor_list (consno2' - 1) in
-debug_print (lazy "XXXX nth funzionano ") ;
-                           List.map 
-                            (function (id,cty) ->
-                              let red_ty = CicReduction.whd context cty in (* dubbio: e' corretto ridurre in questo context ??? *)
-                               let rec aux t k =
-                                match t with
-                                   C.Prod (_,_,target) when (k <= nr_ind_params) ->
-                                    aux target (k+1)
-                                 | C.Prod (binder,source,target) when (k > nr_ind_params) -> 
-                                    C.Lambda (binder,source,(aux target (k+1)))
-                                 | _ -> 
-                                    if (id = false_constr_id)
-                                     then (C.MutInd (U.uri_of_string "cic:/Coq/Init/Logic/False.ind") 0 [])
-                                     else (C.MutInd (U.uri_of_string "cic:/Coq/Init/Logic/True.ind") 0 [])
-                               in aux red_ty 1
-                            ) 
-                            constructor_list
-                      | _ -> raise (ProofEngineTypes.Fail "Discriminate: object is not an Inductive Definition: it's imposible")
-                   in
-
-                    let (proof',goals') = 
-                     EliminationTactics.elim_type_tac 
-                      ~term:(C.MutInd (U.uri_of_string "cic:/Coq/Init/Logic/False.ind") 0 [] ) 
-                      status 
-                    in
-                     (match goals' with
-                         [goal'] -> 
-                          let _,metasenv',_,_ = proof' in
-                           let _,context',gty' =
-                             CicUtil.lookup_meta goal' metasenv'
-                           in
-                            T.then_
-                             ~start:
-                              (P.change_tac 
-                               ~what:gty' 
-                               ~with_what:
-                                (C.Appl [
-                                  C.Lambda (
-                                   C.Name "x", tty, 
-                                   C.MutCase (
-                                    turi, typeno,
-                                    (C.Lambda ((C.Name "x"),tty,(C.Sort C.Prop))),
-                                    (C.Rel 1), pattern
-                                   )
-                                  ); 
-                                  t2']
-                                )
-                              )
-                             ~continuation:
-                              (
-debug_print (lazy ("XXXX rewrite<-: " ^ CicPp.ppterm (CicTypeChecker.type_of_aux' metasenv' context' (C.Appl [(C.MutInd (equri,0,[])) ; tty ; t1' ; t2']))));
-debug_print (lazy ("XXXX rewrite<-: " ^ CicPp.ppterm (C.Appl [(C.MutInd (equri,0,[])) ; tty ; t1' ; t2']))) ;
-debug_print (lazy ("XXXX equri: " ^ U.string_of_uri equri)) ;
-debug_print (lazy ("XXXX tty : " ^ CicPp.ppterm tty)) ;
-debug_print (lazy ("XXXX tt1': " ^ CicPp.ppterm (CicTypeChecker.type_of_aux' metasenv' context' t1'))) ;
-debug_print (lazy ("XXXX tt2': " ^ CicPp.ppterm (CicTypeChecker.type_of_aux' metasenv' context' t2'))) ;
-if (CicTypeChecker.type_of_aux' metasenv' context' t1') <> tty then debug_print (lazy ("XXXX tt1': " ^ CicPp.ppterm (CicTypeChecker.type_of_aux' metasenv' context' t1'))) ;
-if (CicTypeChecker.type_of_aux' metasenv' context' t2') <> tty then debug_print (lazy ("XXXX tt2': " ^ CicPp.ppterm (CicTypeChecker.type_of_aux' metasenv' context' t2'))) ;
-if (CicTypeChecker.type_of_aux' metasenv' context' t1') <> (CicTypeChecker.type_of_aux' metasenv' context' t2') 
- then debug_print (lazy ("XXXX tt1': " ^ CicPp.ppterm (CicTypeChecker.type_of_aux'
- metasenv' context' t1'))) ; debug_print (lazy ("XXXX tt2': " ^ CicPp.ppterm (CicTypeChecker.type_of_aux' metasenv' context' t2'))) ;
-
-                               let termty' = ProofEngineReduction.replace_lifting ~equality:(==) ~what:t1 ~with_what:t1' ~where:termty in
-                                let termty'' = ProofEngineReduction.replace_lifting ~equality:(==) ~what:t2 ~with_what:t2' ~where:termty' in
-
-debug_print (lazy ("XXXX rewrite<- " ^ CicPp.ppterm term ^ " : " ^ CicPp.ppterm (CicTypeChecker.type_of_aux' metasenv' context' term)));
-                                 T.then_
-                                   ~start:(EqualityTactics.rewrite_back_simpl_tac ~term:term)
-                                   ~continuation:(IntroductionTactics.constructor_tac ~n:1) 
-                              )
-                             (proof',goal')
-                       | _ -> raise (ProofEngineTypes.Fail "Discriminate: ElimType False left more (or less) than one goal")
-                     )    
-            | _ -> raise (ProofEngineTypes.Fail "Discriminate: not a discriminable equality")
-           )
-       | _ -> raise (ProofEngineTypes.Fail "Discriminate: not an equality")
+(* destruct performs either injection or discriminate *)
+(* equivalent to Coq's "analyze equality"             *)
+let destruct_tac =
+ injection_tac
+  ~first_time:true ~liftno:0 ~continuation:(fun ~liftno -> Tacticals.id_tac)
 ;;
-
-*)
-
-
-