let assume id t =
 Tacticals.then_
  ~start:
    (Tactics.intros ~howmany:1
      ~mk_fresh_name_callback:(fun _ _ _ ~typ -> Cic.Name id) ())
  ~continuation:
    (Tactics.change ~pattern:(None,[id,Cic.Implicit (Some `Hole)],None)
     (fun _ metasenv ugraph -> t,metasenv,ugraph))
;;

let suppose t id =
 Tacticals.then_
   ~start:
       (Tactics.intros ~howmany:1
             ~mk_fresh_name_callback:(fun _ _ _ ~typ -> Cic.Name id) ())
   ~continuation:
	    (Tactics.change ~pattern:(None,[id,Cic.Implicit (Some `Hole)],None)  
	      (fun _ metasenv ugraph -> t,metasenv,ugraph))
;;

let by_term_we_proved t ty id =
 Tacticals.thens
 ~start:
   (Tactics.cut ty
     ~mk_fresh_name_callback:(fun _ _ _  ~typ -> Cic.Name id))
 ~continuations:
   [ Tacticals.id_tac ; Tactics.apply t ]
;;

let bydone t =
   (Tactics.apply ~term:t)

;;

let we_need_to_prove t id =
 let aux status =
  let proof,goals =
   ProofEngineTypes.apply_tactic
    (Tactics.cut t
      ~mk_fresh_name_callback:(fun _ _ _  ~typ -> Cic.Name id))
    status
  in
   let goals' =
    match goals with
       [fst; snd] -> [snd; fst]
     | _ -> assert false
   in
    proof,goals'
 in
  ProofEngineTypes.mk_tactic aux
;;