X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fcomponents%2Fng_tactics%2Fdeclarative.ml;h=3a700ba961d28583bb89bb1c4e0d2c6a8e9b7984;hb=3fab56d1663ba3d5aeb9207612279e0bb0edbb8c;hp=ac521186a4db80d0c6190d9b39c4ba547406a718;hpb=dd627e471392375ca7b6dad78a931a8682e06dbe;p=helm.git

diff --git a/matita/components/ng_tactics/declarative.ml b/matita/components/ng_tactics/declarative.ml
index ac521186a..3a700ba96 100644
--- a/matita/components/ng_tactics/declarative.ml
+++ b/matita/components/ng_tactics/declarative.ml
@@ -1,14 +1,14 @@
 (* Copyright (C) 2019, HELM Team.
- * 
+ *
  * This file is part of HELM, an Hypertextual, Electronic
  * Library of Mathematics, developed at the Computer Science
  * Department, University of Bologna, Italy.
- * 
+ *
  * HELM is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version 2
  * of the License, or (at your option) any later version.
- * 
+ *
  * HELM is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ -18,327 +18,445 @@
  * along with HELM; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  * MA  02111-1307, USA.
- * 
+ *
  * For details, see the HELM World-Wide-Web page,
  * http://cs.unibo.it/helm/.
- *)
+*)
 
+open Continuationals.Stack
 module Ast = NotationPt
 open NTactics
 open NTacStatus
 
 type just = [ `Term of NTacStatus.tactic_term | `Auto of NnAuto.auto_params ]
 
-let mk_just =
-    function
-          `Auto (l,params) -> distribute_tac (fun status goal -> NnAuto.auto_lowtac
-          ~params:(l,params) status goal)
-        | `Term t -> apply_tac t
+let mk_just status goal =
+  function
+    `Auto (l,params) -> NnAuto.auto_lowtac ~params:(l,params) status goal
+  | `Term t -> apply_tac t
 
 exception NotAProduct
 exception FirstTypeWrong
 exception NotEquivalentTypes
 
+let extract_first_goal_from_status status =
+  let s = status#stack in
+  match s with
+  | [] -> fail (lazy "There's nothing to prove")
+  | (g1, _, k, tag1) :: tl ->
+    let goals = filter_open g1 in
+    let (loc::tl) = goals in 
+    let goal = goal_of_loc (loc) in
+    goal ;;
+  (*
+  let (_,_,metasenv,_,_) = status#obj in
+  match metasenv with
+  | [] -> fail (lazy "There's nothing to prove")
+  | (hd,_) :: tl -> hd
+  *)
+
 let extract_conclusion_type status goal =
-    let gty = get_goalty status goal in
-    let ctx = ctx_of gty in
-    let status,gty = term_of_cic_term status gty ctx in
-    gty
+  let gty = get_goalty status goal in
+  let ctx = ctx_of gty in
+  let status,gty = term_of_cic_term status gty ctx in
+  gty
 ;;
 
 let same_type_as_conclusion ty t status goal =
-    let gty = get_goalty status goal in
-    let ctx = ctx_of gty in
-    let status,cicterm = disambiguate status ctx ty `XTNone (*(`XTSome (mk_cic_term ctx t))*) in
-    let (_,_,metasenv,subst,_) = status#obj in
-    let status,ty = term_of_cic_term status cicterm ctx in
-    if NCicReduction.alpha_eq status metasenv subst ctx t ty then
-        true
-    else
-        false
+  let gty = get_goalty status goal in
+  let ctx = ctx_of gty in
+  let status,cicterm = disambiguate status ctx ty `XTNone (*(`XTSome (mk_cic_term ctx t))*) in
+  let (_,_,metasenv,subst,_) = status#obj in
+  let status,ty = term_of_cic_term status cicterm ctx in
+  if NCicReduction.alpha_eq status metasenv subst ctx t ty then
+    true
+  else
+    false
 ;;
 
 let are_convertible ty1 ty2 status goal =
-    let gty = get_goalty status goal in
-    let ctx = ctx_of gty in
-    let status,cicterm1 = disambiguate status ctx ty1 `XTNone (*(`XTSome (mk_cic_term ctx t))*) in
-    let status,cicterm2 = disambiguate status ctx ty2 `XTNone (*(`XTSome (mk_cic_term ctx t))*) in
-    NTacStatus.are_convertible status ctx cicterm1 cicterm2
+  let gty = get_goalty status goal in
+  let ctx = ctx_of gty in
+  let status,cicterm1 = disambiguate status ctx ty1 `XTNone (*(`XTSome (mk_cic_term ctx t))*) in
+  let status,cicterm2 = disambiguate status ctx ty2 `XTNone (*(`XTSome (mk_cic_term ctx t))*) in
+  NTacStatus.are_convertible status ctx cicterm1 cicterm2
 
 (* LCF-like tactic that checks whether the conclusion of the sequent of the given goal is a product, checks that
-the type of the conclusion's bound variable is the same as t1 and then uses an exact_tac with
-\lambda id: t1. ?. If a t2 is given it checks that t1 ~_{\beta} t2 and uses and exact_tac with \lambda id: t2. ?
+   the type of the conclusion's bound variable is the same as t1 and then uses an exact_tac with
+   \lambda id: t1. ?. If a t2 is given it checks that t1 ~_{\beta} t2 and uses and exact_tac with \lambda id: t2. ?
 *)
 let lambda_abstract_tac id t1 t2 status goal =
-    match extract_conclusion_type status goal with
-    | NCic.Prod (_,t,_) -> 
-        if same_type_as_conclusion t1 t status goal then
-            match t2 with
-            | None -> 
-                    let (_,_,t1) = t1 in
-                    exec (exact_tac ("",0,(Ast.Binder (`Lambda,(Ast.Ident (id,None),Some t1),Ast.Implicit
-                    `JustOne)))) status goal
-
-            | Some t2 -> 
-                let status,res = are_convertible t1 t2 status goal in
-                if res then
-                let (_,_,t2) = t2 in
-                    exec (exact_tac ("",0,(Ast.Binder (`Lambda,(Ast.Ident (id,None),Some t2),Ast.Implicit
-                    `JustOne)))) status goal
-                else
-                    raise NotEquivalentTypes
+  match extract_conclusion_type status goal with
+  | NCic.Prod (_,t,_) ->
+    if same_type_as_conclusion t1 t status goal then
+      match t2 with
+      | None ->
+        let (_,_,t1) = t1 in
+        exact_tac ("",0,(Ast.Binder (`Lambda,(Ast.Ident (id,None),Some t1),Ast.Implicit
+                                       `JustOne))) (*status*)
+      | Some t2 ->
+        let status,res = are_convertible t1 t2 status goal in
+        if res then
+          let (_,_,t2) = t2 in
+          exact_tac ("",0,(Ast.Binder (`Lambda,(Ast.Ident (id,None),Some t2),Ast.Implicit
+                                         `JustOne))) (*status*)
         else
-            raise FirstTypeWrong
-    | _ -> raise NotAProduct
+          raise NotEquivalentTypes
+    else
+      raise FirstTypeWrong
+  | _ -> raise NotAProduct
 
-let assume name ty eqty =
-    distribute_tac (fun status goal ->
-        try lambda_abstract_tac name ty eqty status goal
-        with
-        | NotAProduct -> fail (lazy "You can't assume without an universal quantification")
-        | FirstTypeWrong ->  fail (lazy "The assumed type is wrong")
-        | NotEquivalentTypes -> fail (lazy "The two given types are not equivalent")
-     )
+let assume name ty eqty (*status*) =
+(*   let goal = extract_first_goal_from_status status in *)
+  distribute_tac (fun status goal -> 
+    try exec (lambda_abstract_tac name ty eqty status goal) status goal
+    with
+    | NotAProduct -> fail (lazy "You can't assume without an universal quantification")
+    | FirstTypeWrong ->  fail (lazy "The assumed type is wrong")
+    | NotEquivalentTypes -> fail (lazy "The two given types are not equivalent")
+  )
 ;;
 
-let suppose t1 id t2 =
-    distribute_tac (fun status goal ->
-        try lambda_abstract_tac id t1 t2 status goal
-        with
-        | NotAProduct -> fail (lazy "You can't suppose without a logical implication")
-        | FirstTypeWrong ->  fail (lazy "The supposed proposition is different from the premise")
-        | NotEquivalentTypes -> fail (lazy "The two given propositions are not equivalent")
-     )
+let suppose t1 id t2 (*status*) =
+(*   let goal = extract_first_goal_from_status status in *)
+  distribute_tac (fun status goal ->
+    try exec (lambda_abstract_tac id t1 t2 status goal) status goal
+    with
+    | NotAProduct -> fail (lazy "You can't suppose without a logical implication")
+    | FirstTypeWrong ->  fail (lazy "The supposed proposition is different from the premise")
+    | NotEquivalentTypes -> fail (lazy "The two given propositions are not equivalent")
+  )
 ;;
 
 let assert_tac t1 t2 status goal continuation =
-    let t = extract_conclusion_type status goal in
-    if same_type_as_conclusion t1 t status goal then
-        match t2 with
-        | None -> exec continuation status goal
-        | Some t2 ->
-            let status,res = are_convertible t1 t2 status goal in
-            if res then
-                exec continuation status goal
-            else
-                raise NotEquivalentTypes
+  let t = extract_conclusion_type status goal in
+  if same_type_as_conclusion t1 t status goal then
+    match t2 with
+    | None -> continuation
+    | Some t2 ->
+      let status,res = are_convertible t1 t2 status goal in
+      if res then continuation
+      else
+        raise NotEquivalentTypes
+  else
+    raise FirstTypeWrong
+
+let mustdot status =
+  let s = status#stack in
+  match s with
+  | [] -> fail (lazy "No goals to dot")
+  | (_, _, k, _) :: tl ->
+    if List.length k > 0 then
+      true
     else
-        raise FirstTypeWrong
+      false
 
-let we_need_to_prove t id t1 =
-    distribute_tac (fun status goal ->
-        match id with
-        | None -> 
-            (
-                match t1 with
-                | None ->  (* We need to prove t *)
-                    (
-                    try
-                        assert_tac t None status goal id_tac
-                    with
-                    | FirstTypeWrong -> fail (lazy "The given proposition is not the same as the conclusion")
-                    )
-                | Some t1 -> (* We need to prove t or equivalently t1 *)
-                    (
-                        try
-                            assert_tac t (Some t1) status goal (change_tac ~where:("",0,(None,[],Some Ast.UserInput)) ~with_what:t1)
-                        with
-                        | FirstTypeWrong -> fail (lazy "The given proposition is not the same as the conclusion")
-                        | NotEquivalentTypes -> fail (lazy "The given propositions are not equivalent")
-                    )
-            )
-        | Some id -> 
-            (
-                match t1 with
-                | None -> (* We need to prove t (id) *)
-                    exec (block_tac [cut_tac t; branch_tac ~force:false; shift_tac; intro_tac id;
-                    (*merge_tac*)]) status goal
-                | Some t1 -> (* We need to prove t (id) or equivalently t1 *)
-                    exec (block_tac [cut_tac t; branch_tac ~force:false; change_tac ~where:("",0,(None,[],Some Ast.UserInput))
-                    ~with_what:t1; shift_tac; intro_tac id; merge_tac]) status goal
-            )
-    )
+let bydone just status =
+  let goal = extract_first_goal_from_status status in
+  let mustdot = mustdot status in
+(*
+  let goal,mustdot =
+    let s = status#stack in
+    match s with
+    | [] -> fail (lazy "Invalid use of done")
+    | (g1, _, k, tag1) :: tl ->
+      let goals = filter_open g1 in
+      let (loc::tl) = goals in 
+      let goal = goal_of_loc (loc) in
+      if List.length k > 0 then
+        goal,true
+      else
+        goal,false
+  in
+
+   *)
+(*
+      let goals = filter_open g1 in
+      let (loc::tl) = goals in 
+      let goal = goal_of_loc (loc) in
+      if tag1 == `BranchTag then
+        if List.length (shift_goals s) > 0 then (* must simply shift *)
+          (
+            prerr_endline (pp status#stack); 
+            prerr_endline "Head goals:";
+            List.map (fun goal -> prerr_endline (string_of_int goal)) (head_goals status#stack);
+            prerr_endline "Shift goals:";
+            List.map (fun goal -> prerr_endline (string_of_int goal)) (shift_goals status#stack);
+            prerr_endline "Open goals:";
+            List.map (fun goal -> prerr_endline (string_of_int goal)) (open_goals status#stack);
+            if tag2 == `BranchTag && g2 <> [] then 
+              goal,true,false,false
+            else if tag2 == `BranchTag then
+              goal,false,true,true
+            else
+              goal,false,true,false
+          )
+        else
+          (
+           if tag2 == `BranchTag then
+              goal,false,true,true
+            else
+              goal,false,true,false
+          )
+      else
+        goal,false,false,false (* It's a strange situation, there's is an underlying level on the
+                                  stack but the current one was not created by a branch? Should be
+                                  an error *)
+    | (g, _, _, tag) :: [] ->
+      let (loc::tl) = filter_open g in 
+      let goal = goal_of_loc (loc) in
+      if tag == `BranchTag then
+(*         let goals = filter_open g in *)
+          goal,false,true,false
+      else
+        goal,false,false,false 
+  in
+   *)
+  let l = [mk_just status goal just] in
+  let l =
+    if mustdot then List.append l [dot_tac] else l
+  in
+  (*
+  let l =
+    if mustmerge then List.append l [merge_tac] else l
+  in
+  let l =
+    if mustmergetwice then List.append l [merge_tac]  else l
+  in 
+     *)
+    block_tac l status
+(*
+  let (_,_,metasenv,subst,_) = status#obj in
+  let goal,last =
+    match metasenv with
+    | [] -> fail (lazy "There's nothing to prove")
+    | (_,_) :: (hd,_) :: tl -> hd,false
+    | (hd,_) :: tl -> hd,true
+  in
+  if last then
+    mk_just status goal just status
+  else
+    block_tac [ mk_just status goal just; shift_tac ] status
+*)
 ;;
 
-let by_just_we_proved just ty id ty' = 
-    distribute_tac (fun status goal -> 
-        let just = mk_just just in
-            match id with
-            | None ->
-                (match ty' with
-                     | None -> (* just we proved P done *)
-                        (
-                            try
-                                assert_tac ty None status goal just
-                            with
-                            | FirstTypeWrong -> fail (lazy "The given proposition is not the same as the conclusion")
-                            | NotEquivalentTypes -> fail (lazy "The given propositions are not equivalent")
-                        )
-                     | Some ty' -> (* just we proved P that is equivalent to P' done *)
-                        (
-                            try
-                                assert_tac ty' (Some ty) status goal (block_tac [change_tac
-                                ~where:("",0,(None,[],Some Ast.UserInput)) ~with_what:ty; just])
-                            with
-                            | FirstTypeWrong -> fail (lazy "The second proposition is not the same as the conclusion")
-                            | NotEquivalentTypes -> fail (lazy "The given propositions are not equivalent")
-                        )
-                 )
-            | Some id ->
-                (
-                    match ty' with
-                    | None -> exec (block_tac [cut_tac ty; branch_tac; just; shift_tac; intro_tac
-                    id; merge_tac ]) status goal
-                    | Some ty' -> exec (block_tac [cut_tac ty; branch_tac; just; shift_tac; intro_tac
-                    id; change_tac ~where:("",0,(None,[id,Ast.UserInput],None))
-                    ~with_what:ty'; merge_tac]) status goal
-                )
+let we_need_to_prove t id t1 status =
+  let goal = extract_first_goal_from_status status in
+  match id with
+  | None ->
+    (
+      match t1 with
+      | None ->  (* We need to prove t *)
+        (
+          try assert_tac t None status goal (id_tac status)
+          with
+          | FirstTypeWrong -> fail (lazy "The given proposition is not the same as the conclusion")
+        )
+      | Some t1 -> (* We need to prove t or equivalently t1 *)
+        (
+          try assert_tac t (Some t1) status goal (change_tac ~where:("",0,(None,[],Some
+                                                                             Ast.UserInput)) ~with_what:t1 status)
+          with
+          | FirstTypeWrong -> fail (lazy "The given proposition is not the same as the conclusion")
+          | NotEquivalentTypes -> fail (lazy "The given propositions are not equivalent")
+        )
+    )
+  | Some id ->
+    (
+      match t1 with
+      (* We need to prove t (id) *)
+      | None -> block_tac [cut_tac t; branch_tac; shift_tac; intro_tac id; merge_tac;
+                           dot_tac
+                          ] status
+      (* We need to prove t (id) or equivalently t1 *)
+      | Some t1 ->  block_tac [cut_tac t; branch_tac ; change_tac ~where:("",0,(None,[],Some
+                                                                                  Ast.UserInput))
+                                 ~with_what:t1; shift_tac; intro_tac id; merge_tac;
+                               dot_tac
+                              ]
+                      status
     )
 ;;
 
-let thesisbecomes t1 t2 = we_need_to_prove t1 None t2 ;;
+let by_just_we_proved just ty id ty' (*status*) =
+  distribute_tac (fun status goal ->
+    let wrappedjust = just in
+    let just = mk_just status goal just in
+    match id with
+    | None ->
+      (match ty' with
+       | None -> (* just we proved P done *)
+         (
+           try
+             assert_tac ty None status goal (exec (bydone wrappedjust) status goal)
+           with
+           | FirstTypeWrong -> fail (lazy "The given proposition is not the same as the conclusion")
+           | NotEquivalentTypes -> fail (lazy "The given propositions are not equivalent")
+         )
+       | Some ty' -> (* just we proved P that is equivalent to P' done *)
+         (
+           try
+             assert_tac ty' (Some ty) status goal (exec (block_tac [change_tac
+                                                                ~where:("",0,(None,[],Some Ast.UserInput)) ~with_what:ty; bydone
+                                                                wrappedjust]) status goal)
+           with
+           | FirstTypeWrong -> fail (lazy "The second proposition is not the same as the conclusion")
+           | NotEquivalentTypes -> fail (lazy "The given propositions are not equivalent")
+         )
+      )
+    | Some id ->
+      (
+        match ty' with
+        | None -> exec (block_tac [cut_tac ty; branch_tac; just; shift_tac; intro_tac
+                               id; merge_tac ]) status goal
+        | Some ty' -> exec (block_tac [cut_tac ty; branch_tac; just; shift_tac; intro_tac
+                                   id; change_tac ~where:("",0,(None,[id,Ast.UserInput],None))
+                                   ~with_what:ty'; merge_tac]) status goal
+      )
+  )
+;;
 
-let bydone just =
-    mk_just just
+let thesisbecomes t1 t2 status = we_need_to_prove t1 None t2 status
 ;;
 
-let existselim just id1 t1 t2 id2 =
+let existselim just id1 t1 t2 id2 (*status*) =
+  distribute_tac (fun status goal ->
     let (_,_,t1) = t1 in
     let (_,_,t2) = t2 in
-    let just = mk_just just in
-    block_tac [
-        cut_tac ("",0,(Ast.Appl [Ast.Ident ("ex",None); t1; Ast.Binder (`Lambda,(Ast.Ident
-        (id1,None), Some t1),t2)])); 
-        branch_tac ~force:false;
-        just; 
-        shift_tac; 
-        case1_tac "_";
-        intros_tac ~names_ref:(ref []) [id1;id2]; 
-        merge_tac
-    ]
+    let just = mk_just status goal just in
+    exec (block_tac [
+      cut_tac ("",0,(Ast.Appl [Ast.Ident ("ex",None); t1; Ast.Binder (`Lambda,(Ast.Ident
+                                                                                 (id1,None), Some t1),t2)]));
+      branch_tac ~force:false;
+      just;
+      shift_tac;
+      case1_tac "_";
+      intros_tac ~names_ref:(ref []) [id1;id2];
+      merge_tac
+    ]) status goal
+  )
+;;
 
-let andelim just t1 id1 t2 id2 = 
+let andelim just t1 id1 t2 id2 (*status*) =
+(*   let goal = extract_first_goal_from_status status in *)
+  distribute_tac (fun status goal ->
     let (_,_,t1) = t1 in
     let (_,_,t2) = t2 in
-    let just = mk_just just in
-    block_tac [
-        cut_tac ("",0,(Ast.Appl [Ast.Ident ("And",None); t1 ; t2])); 
-        branch_tac ~force:false;
-        just; 
-        shift_tac; 
-        case1_tac "_";
-        intros_tac ~names_ref:(ref []) [id1;id2]; 
-        merge_tac
-    ]
+    let just = mk_just status goal just in
+    exec (block_tac [
+      cut_tac ("",0,(Ast.Appl [Ast.Ident ("And",None); t1 ; t2]));
+      branch_tac ~force:false;
+      just;
+      shift_tac;
+      case1_tac "_";
+      intros_tac ~names_ref:(ref []) [id1;id2];
+      merge_tac
+    ]) status goal
+  )
 ;;
 
+let type_of_tactic_term status ctx t =
+  let status,cicterm = disambiguate status ctx t `XTNone in
+  let (_,cicty) = typeof status ctx cicterm in
+  cicty
 
-
-let rewritingstep lhs rhs just last_step = fail (lazy "Not implemented");
- (*
- let aux ((proof,goal) as status) =
-  let (curi,metasenv,_subst,proofbo,proofty, attrs) = proof in
-  let _,context,gty = CicUtil.lookup_meta goal metasenv in
-  let eq,trans =
-   match LibraryObjects.eq_URI () with
-      None -> raise (ProofEngineTypes.Fail (lazy "You need to register the default equality first. Please use the \"default\" command"))
-    | Some uri ->
-      Cic.MutInd (uri,0,[]), Cic.Const (LibraryObjects.trans_eq_URI ~eq:uri,[])
-  in
-  let ty,_ =
-   CicTypeChecker.type_of_aux' metasenv context rhs CicUniv.oblivion_ugraph in
-  let just' =
-   match just with
+let rewritingstep lhs rhs just last_step status =
+  let goal = extract_first_goal_from_status status in
+  let cicgty = get_goalty status goal in
+  let ctx = ctx_of cicgty in
+  let _,gty = term_of_cic_term status cicgty ctx in
+  let cicty = type_of_tactic_term status ctx rhs in
+  let _,ty = term_of_cic_term status cicty ctx in
+  let just' = (* Extraction of the ""justification"" from the ad hoc justification *)
+    match just with
       `Auto (univ, params) ->
-        let params =
-         if not (List.exists (fun (k,_) -> k = "timeout") params) then
+      let params =
+        if not (List.mem_assoc "timeout" params) then
           ("timeout","3")::params
-         else params
-        in
-        let params' =
-         if not (List.exists (fun (k,_) -> k = "paramodulation") params) then
+        else params
+      in
+      let params' =
+        if not (List.mem_assoc "paramodulation" params) then
           ("paramodulation","1")::params
-         else params
-        in
-         if params = params' then
-          Tactics.auto ~dbd ~params:(univ, params) ~automation_cache
-         else
-          Tacticals.first
-           [Tactics.auto ~dbd ~params:(univ, params) ~automation_cache ;
-            Tactics.auto ~dbd ~params:(univ, params') ~automation_cache]
-    | `Term just -> Tactics.apply just
-    | `SolveWith term -> 
-                    Tactics.demodulate ~automation_cache ~dbd
-                    ~params:(Some [term],
-                      ["all","1";"steps","1"; "use_context","false"])
-    | `Proof ->
-        Tacticals.id_tac
+        else params
+      in
+      if params = params' then NnAuto.auto_lowtac ~params:(univ, params) status goal
+      else
+        first_tac [NnAuto.auto_lowtac ~params:(univ, params) status goal; NnAuto.auto_lowtac
+                     ~params:(univ, params') status goal]
+    | `Term just -> apply_tac just
+    | `SolveWith term -> NnAuto.demod_tac ~params:(Some [term], ["all","1";"steps","1"; "use_ctx","false"])
+    | `Proof -> id_tac
   in
-   let plhs,prhs,prepare =
+  let plhs,prhs,prepare =
     match lhs with
-       None ->
-        let plhs,prhs =
-         match gty with 
-            Cic.Appl [_;_;plhs;prhs] -> plhs,prhs
-          | _ -> assert false
-        in
-         plhs,prhs,
-          (fun continuation ->
-            ProofEngineTypes.apply_tactic continuation status)
-     | Some (None,lhs) ->
-        let plhs,prhs =
-         match gty with 
-            Cic.Appl [_;_;plhs;prhs] -> plhs,prhs
-          | _ -> assert false
-        in
-         (*CSC: manca check plhs convertibile con lhs *)
-         plhs,prhs,
-          (fun continuation ->
-            ProofEngineTypes.apply_tactic continuation status)
-     | Some (Some name,lhs) ->
-        let newmeta = CicMkImplicit.new_meta metasenv [] in
-        let irl =
-         CicMkImplicit.identity_relocation_list_for_metavariable context in
-        let plhs = lhs in
-        let prhs = Cic.Meta(newmeta,irl) in
-         plhs,prhs,
-          (fun continuation ->
-            let metasenv = (newmeta, context, ty)::metasenv in
-            let mk_fresh_name_callback =
-             fun metasenv context _ ~typ ->
-	      FreshNamesGenerator.mk_fresh_name ~subst:[] metasenv context
+      None -> (* = E2 *)
+      let plhs,prhs =
+        match gty with (* Extracting the lhs and rhs of the previous equality *)
+          NCic.Appl [_;_;plhs;prhs] -> plhs,prhs
+        | _ -> fail (lazy "You are not building an equaility chain")
+      in
+      plhs,prhs,
+      (fun continuation -> continuation status)
+    | Some (None,lhs) -> (* conclude *) 
+      let plhs,prhs =
+        match gty with
+          NCic.Appl [_;_;plhs;prhs] -> plhs,prhs
+        | _ -> fail (lazy "You are not building an equaility chain")
+      in
+      (*TODO*)
+      (*CSC: manca check plhs convertibile con lhs *)
+      plhs,prhs,
+      (fun continuation -> continuation status)
+    | Some (Some name,lhs) -> (* obtain *)
+      fail (lazy "Not implemented")
+        (*
+      let plhs = lhs in
+      let prhs = Cic.Meta(newmeta,irl) in
+      plhs,prhs,
+      (fun continuation ->
+         let metasenv = (newmeta, ctx, ty)::metasenv in
+         let mk_fresh_name_callback =
+           fun metasenv ctx _ ~typ ->
+             FreshNamesGenerator.mk_fresh_name ~subst:[] metasenv ctx
                (Cic.Name name) ~typ
-	    in
-            let proof = curi,metasenv,_subst,proofbo,proofty, attrs in
-            let proof,goals =
-             ProofEngineTypes.apply_tactic
-              (Tacticals.thens
+         in
+         let proof = curi,metasenv,_subst,proofbo,proofty, attrs in
+         let proof,goals =
+           ProofEngineTypes.apply_tactic
+             (Tacticals.thens
                 ~start:(Tactics.cut ~mk_fresh_name_callback
-                 (Cic.Appl [eq ; ty ; lhs ; prhs]))
+                          (Cic.Appl [eq ; ty ; lhs ; prhs]))
                 ~continuations:[Tacticals.id_tac ; continuation]) (proof,goal)
-            in
-             let goals =
-              match just,goals with
-                 `Proof, [g1;g2;g3] -> [g2;g3;newmeta;g1]
-               | _, [g1;g2] -> [g2;newmeta;g1]
-               | _, l -> 
-                 prerr_endline (String.concat "," (List.map string_of_int l));
-                 prerr_endline (CicMetaSubst.ppmetasenv [] metasenv);
-                 assert false
-             in
-              proof,goals)
-   in
-    let continuation =
-     if last_step then
+         in
+         let goals =
+           match just,goals with
+             `Proof, [g1;g2;g3] -> [g2;g3;newmeta;g1]
+           | _, [g1;g2] -> [g2;newmeta;g1]
+           | _, l ->
+             prerr_endline (String.concat "," (List.map string_of_int l));
+             prerr_endline (CicMetaSubst.ppmetasenv [] metasenv);
+             assert false
+         in
+         proof,goals)
+           *)
+  in
+  let continuation =
+    if last_step then
       (*CSC:manca controllo sul fatto che rhs sia convertibile con prhs*)
-      just'
-     else
-      Tacticals.thens
-       ~start:(Tactics.apply ~term:(Cic.Appl [trans;ty;plhs;rhs;prhs]))
-       ~continuations:[just' ; Tacticals.id_tac]
-    in
-     prepare continuation
- in
-  ProofEngineTypes.mk_tactic aux
+      let todo = [just'] in
+      let todo = if mustdot status then List.append todo [dot_tac] else todo
+      in
+        block_tac todo
+    else
+      let (_,_,rhs) = rhs in
+      block_tac [apply_tac ("",0,Ast.Appl [Ast.Ident ("trans_eq",None); Ast.NCic ty; Ast.NCic plhs;
+                                           rhs; Ast.NCic prhs]); branch_tac; just'; merge_tac]
+  in
+    prepare continuation
 ;;
-  *)
+
+let print_stack status = prerr_endline ("PRINT STACK: " ^ (pp status#stack)); id_tac status ;;
+
+(* vim: ts=2: sw=0: et:
+ * *)