path: root/plugins/funind/indfun.ml

open Util
open Names
open Term
open Pp
open Indfun_common
open Libnames
open Rawterm
open Declarations

let is_rec_info scheme_info =
  let test_branche min acc (_,_,br) =
    acc || (
      let new_branche =
	it_mkProd_or_LetIn mkProp (fst (decompose_prod_assum br)) in
      let free_rels_in_br = Termops.free_rels new_branche in
      let max = min + scheme_info.Tactics.npredicates in
      Util.Intset.exists (fun i -> i >= min && i< max) free_rels_in_br
    )
  in
  Util.list_fold_left_i test_branche 1 false (List.rev scheme_info.Tactics.branches)


let choose_dest_or_ind scheme_info =
    if is_rec_info scheme_info
    then Tactics.new_induct false
    else Tactics.new_destruct false


let functional_induction with_clean c princl pat =
  Dumpglob.pause ();
  let res = let f,args = decompose_app c in
	      fun g ->
		let princ,bindings, princ_type =
		  match princl with
	| None -> (* No principle is given let's find the good one *)
	    begin
	      match kind_of_term f with
		| Const c' ->
		    let princ_option =
		      let finfo = (* we first try to find out a graph on f *)
			try find_Function_infos c'
			with Not_found ->
			  errorlabstrm "" (str "Cannot find induction information on "++
					     Printer.pr_lconstr (mkConst c') )
		      in
		      match Tacticals.elimination_sort_of_goal g with
			| InProp -> finfo.prop_lemma
			| InSet -> finfo.rec_lemma
			| InType -> finfo.rect_lemma
		    in
		    let princ =  (* then we get the principle *)
		      try mkConst (Option.get princ_option )
		      with Option.IsNone ->
			(*i If there is not default lemma defined then,
			  we cross our finger and try to find a lemma named f_ind
			  (or f_rec, f_rect) i*)
			let princ_name =
			  Indrec.make_elimination_ident
			    (id_of_label (con_label c'))
			    (Tacticals.elimination_sort_of_goal g)
			in
			try
			  mkConst(const_of_id princ_name )
			with Not_found -> (* This one is neither defined ! *)
			  errorlabstrm "" (str "Cannot find induction principle for "
					   ++Printer.pr_lconstr (mkConst c') )
		    in
		    (princ,Rawterm.NoBindings, Tacmach.pf_type_of g princ)
		| _ -> raise (UserError("",str "functional induction must be used with a function" ))

	    end
	| Some ((princ,binding)) ->
	    princ,binding,Tacmach.pf_type_of g princ
    in
    let princ_infos = Tactics.compute_elim_sig princ_type in
    let args_as_induction_constr =
      let c_list =
	if princ_infos.Tactics.farg_in_concl
	then [c] else []
      in
      List.map (fun c -> Tacexpr.ElimOnConstr (c,NoBindings)) (args@c_list)
    in
    let princ' = Some (princ,bindings) in
    let princ_vars =
      List.fold_right
	(fun a acc ->
	  try Idset.add (destVar a) acc
	  with _ -> acc
	)
	args
	Idset.empty
    in
    let old_idl = List.fold_right Idset.add (Tacmach.pf_ids_of_hyps g) Idset.empty in
    let old_idl = Idset.diff old_idl princ_vars in
    let subst_and_reduce g =
      if with_clean
      then
	let idl =
	  map_succeed
	    (fun id ->
	       if Idset.mem id old_idl then failwith "subst_and_reduce";
	       id
	    )
	    (Tacmach.pf_ids_of_hyps g)
	in
	let flag =
	  Rawterm.Cbv
	    {Rawterm.all_flags
	     with Rawterm.rDelta = false;
	    }
	in
	Tacticals.tclTHEN
	  (Tacticals.tclMAP (fun id -> Tacticals.tclTRY (Equality.subst_gen (do_rewrite_dependent ()) [id])) idl )
	  (Hiddentac.h_reduce flag Tacticals.allHypsAndConcl)
	  g
      else Tacticals.tclIDTAC g

    in
    Tacticals.tclTHEN
      (choose_dest_or_ind
	 princ_infos
	 args_as_induction_constr
	 princ'
	 (None,pat)
         None)
      subst_and_reduce
      g
  in
    Dumpglob.continue ();
    res




type annot =
    Struct of identifier
  | Wf of Topconstr.constr_expr * identifier option * Topconstr.constr_expr list
  | Mes of Topconstr.constr_expr * identifier option * Topconstr.constr_expr list


type newfixpoint_expr =
    identifier * annot * Topconstr.local_binder list * Topconstr.constr_expr * Topconstr.constr_expr

let rec abstract_rawconstr c = function
  | [] -> c
  | Topconstr.LocalRawDef (x,b)::bl -> Topconstr.mkLetInC(x,b,abstract_rawconstr c bl)
  | Topconstr.LocalRawAssum (idl,k,t)::bl ->
      List.fold_right (fun x b -> Topconstr.mkLambdaC([x],k,t,b)) idl
        (abstract_rawconstr c bl)

let interp_casted_constr_with_implicits sigma env impls c  =
(*   Constrintern.interp_rawconstr_with_implicits sigma env [] impls c *)
  Constrintern.intern_gen false sigma env ~impls
    ~allow_patvar:false  ~ltacvars:([],[]) c


(*
   Construct a fixpoint as a Rawterm
   and not as a constr
*)
let build_newrecursive
(lnameargsardef)  =
  let env0 = Global.env()
  and sigma = Evd.empty
  in
  let (rec_sign,rec_impls) =
    List.fold_left
      (fun (env,impls) ((_,recname),_,bl,arityc,_) ->
        let arityc = Topconstr.prod_constr_expr arityc bl in
        let arity = Constrintern.interp_type sigma env0 arityc in
	let impl = Constrintern.compute_internalization_data env0 Constrintern.Recursive arity [] in
        (Environ.push_named (recname,None,arity) env, (recname, impl) :: impls))
      (env0,[]) lnameargsardef in
  let recdef =
    (* Declare local notations *)
    let fs = States.freeze() in
    let def =
      try
	List.map
	  (fun (_,_,bl,_,def)  ->
             let def = abstract_rawconstr def bl in
             interp_casted_constr_with_implicits
	       sigma rec_sign rec_impls def
	  )
          lnameargsardef
	with e ->
	States.unfreeze fs; raise e in
    States.unfreeze fs; def
  in
  recdef,rec_impls


let compute_annot (name,annot,args,types,body) =
  let names = List.map snd (Topconstr.names_of_local_assums args) in
  match annot with
    | None ->
        if List.length names > 1 then
          user_err_loc
            (dummy_loc,"Function",
             Pp.str "the recursive argument needs to be specified");
        let new_annot = (id_of_name (List.hd names)) in
	(name,Struct new_annot,args,types,body)
    | Some r -> (name,r,args,types,body)


(* Checks whether or not the mutual bloc is recursive *)
let rec is_rec names =
  let names = List.fold_right Idset.add names Idset.empty in
  let check_id id names =  Idset.mem id names in
  let rec lookup names = function
    | RVar(_,id) -> check_id id names
    | RRef _ | REvar _ | RPatVar _ | RSort _ |  RHole _ | RDynamic _ -> false
    | RCast(_,b,_) -> lookup names b
    | RRec _ -> error "RRec not handled"
    | RIf(_,b,_,lhs,rhs) ->
	(lookup names b) || (lookup names lhs) || (lookup names rhs)
    | RLetIn(_,na,t,b) | RLambda(_,na,_,t,b) | RProd(_,na,_,t,b)  ->
	lookup names t || lookup (Nameops.name_fold Idset.remove na names) b
    | RLetTuple(_,nal,_,t,b) -> lookup names t ||
	lookup
	  (List.fold_left
	     (fun acc na -> Nameops.name_fold Idset.remove na acc)
	     names
	     nal
	  )
	  b
    | RApp(_,f,args) -> List.exists (lookup names) (f::args)
    | RCases(_,_,_,el,brl) ->
	List.exists (fun (e,_) -> lookup names e) el ||
	  List.exists (lookup_br names) brl
  and lookup_br names (_,idl,_,rt) =
    let new_names = List.fold_right Idset.remove idl names in
    lookup new_names rt
  in
  lookup names

let rec local_binders_length = function
  (* Assume that no `{ ... } contexts occur *)
  | [] -> 0
  | Topconstr.LocalRawDef _::bl -> 1 + local_binders_length bl
  | Topconstr.LocalRawAssum (idl,_,_)::bl -> List.length idl + local_binders_length bl

let prepare_body (name,annot,args,types,body) rt =
  let n = local_binders_length args in
(*   Pp.msgnl (str "nb lambda to chop : " ++ str (string_of_int n) ++ fnl () ++Printer.pr_rawconstr rt); *)
  let fun_args,rt' = chop_rlambda_n n rt in
  (fun_args,rt')


let derive_inversion fix_names =
  try
    (* we first transform the fix_names identifier into their corresponding constant *)
    let fix_names_as_constant =
      List.map (fun id -> destConst (Tacinterp.constr_of_id (Global.env ()) id)) fix_names
    in
    (*
       Then we check that the graphs have been defined
       If one of the graphs haven't been defined
       we do nothing
    *)
    List.iter (fun c -> ignore (find_Function_infos c)) fix_names_as_constant ;
    try
      Invfun.derive_correctness
	Functional_principles_types.make_scheme
	functional_induction
	fix_names_as_constant
	(*i The next call to mk_rel_id is valid since we have just construct the graph
	  Ensures by : register_built
	  i*)
	(List.map
	   (fun id -> destInd (Tacinterp.constr_of_id (Global.env ()) (mk_rel_id id)))
	   fix_names
	)
    with e ->
      msg_warning
	(str "Cannot built inversion information" ++
	   if do_observe () then Cerrors.explain_exn e else mt ())
  with _ -> ()

let warning_error names e =
  let e_explain e =
    match e with
      | ToShow e -> spc () ++ Cerrors.explain_exn e
      | _ -> if do_observe () then (spc () ++ Cerrors.explain_exn e) else mt ()
  in
  match e with
    | Building_graph e ->
	Pp.msg_warning
	  (str "Cannot define graph(s) for " ++
	     h 1 (prlist_with_sep (fun _ -> str","++spc ()) Ppconstr.pr_id names) ++
	     e_explain e)
    | Defining_principle e ->
	Pp.msg_warning
	  (str "Cannot define principle(s) for "++
	     h 1 (prlist_with_sep (fun _ -> str","++spc ()) Ppconstr.pr_id names) ++
	     e_explain e)
    | _ -> anomaly ""

let error_error names e =
  let e_explain e =
    match e with
      | ToShow e -> spc () ++ Cerrors.explain_exn e
      | _ -> if do_observe () then (spc () ++ Cerrors.explain_exn e) else mt ()
  in
  match e with
    | Building_graph e ->
	errorlabstrm ""
	  (str "Cannot define graph(s) for " ++
	     h 1 (prlist_with_sep (fun _ -> str","++spc ()) Ppconstr.pr_id names) ++
	     e_explain e)
    | _ -> anomaly ""

let generate_principle  on_error
    is_general do_built fix_rec_l recdefs  interactive_proof
    (continue_proof : int -> Names.constant array -> Term.constr array -> int ->
      Tacmach.tactic) : unit =
  let names = List.map (function ((_, name),_,_,_,_) -> name) fix_rec_l in
  let fun_bodies = List.map2 prepare_body fix_rec_l recdefs in
  let funs_args = List.map fst fun_bodies in
  let funs_types =  List.map (function (_,_,_,types,_) -> types) fix_rec_l in
  try
    (* We then register the Inductive graphs of the functions  *)
    Rawterm_to_relation.build_inductive names funs_args funs_types recdefs;
    if do_built
    then
      begin
	(*i The next call to mk_rel_id is valid since we have just construct the graph
	   Ensures by : do_built
	i*)
	let f_R_mut = Ident (dummy_loc,mk_rel_id (List.nth names 0)) in
	let ind_kn =
	  fst (locate_with_msg
		 (pr_reference f_R_mut++str ": Not an inductive type!")
		 locate_ind
		 f_R_mut)
	in
	let fname_kn (fname,_,_,_,_) =
	  let f_ref = Ident fname in
	  locate_with_msg
	    (pr_reference f_ref++str ": Not an inductive type!")
	    locate_constant
	    f_ref
	in
	let funs_kn = Array.of_list (List.map fname_kn fix_rec_l) in
	let _ =
	  list_map_i
	    (fun i x ->
	       let princ = destConst (Indrec.lookup_eliminator (ind_kn,i) (InProp)) in
	       let princ_type = Typeops.type_of_constant (Global.env()) princ
	       in
	       Functional_principles_types.generate_functional_principle
		 interactive_proof
		 princ_type
		 None
		 None
		 funs_kn
		 i
		 (continue_proof  0 [|funs_kn.(i)|])
	    )
	    0
	    fix_rec_l
	in
	Array.iter (add_Function is_general) funs_kn;
	()
      end
  with e ->
    on_error names e

let register_struct is_rec fixpoint_exprl =
  match fixpoint_exprl with
    | [((_,fname),_,bl,ret_type,body),_] when not is_rec ->
	let ce,imps =
	  Command.interp_definition
	    (Flags.boxed_definitions ()) bl None body (Some ret_type)
	in
	Command.declare_definition
	  fname (Decl_kinds.Global,Decl_kinds.Definition)
	  ce imps (fun _ _ -> ())
    | _ ->
        let fixpoint_exprl =
          List.map (fun ((name,annot,bl,types,body),ntn) ->
            ((name,annot,bl,types,Some body),ntn)) fixpoint_exprl in
	Command.do_fixpoint fixpoint_exprl (Flags.boxed_definitions())

let generate_correction_proof_wf f_ref tcc_lemma_ref
    is_mes functional_ref eq_ref rec_arg_num rec_arg_type nb_args relation
    (_: int) (_:Names.constant array) (_:Term.constr array) (_:int) : Tacmach.tactic =
  Functional_principles_proofs.prove_principle_for_gen
    (f_ref,functional_ref,eq_ref)
    tcc_lemma_ref is_mes  rec_arg_num rec_arg_type relation


let register_wf ?(is_mes=false) fname rec_impls wf_rel_expr wf_arg using_lemmas args ret_type body
    pre_hook
    =
  let type_of_f = Topconstr.prod_constr_expr ret_type args in
  let rec_arg_num =
    let names =
      List.map
	snd
	(Topconstr.names_of_local_assums args)
    in
    match wf_arg with
      | None ->
	  if List.length names = 1 then 1
	  else error "Recursive argument must be specified"
      | Some wf_arg ->
	  list_index (Name wf_arg) names
  in
  let unbounded_eq =
    let f_app_args =
      Topconstr.CAppExpl
	(dummy_loc,
	 (None,(Ident (dummy_loc,fname))) ,
	 (List.map
	    (function
	       | _,Anonymous -> assert false
	       | _,Name e -> (Topconstr.mkIdentC e)
	    )
	    (Topconstr.names_of_local_assums args)
	 )
	)
    in
    Topconstr.CApp (dummy_loc,(None,Topconstr.mkRefC (Qualid (dummy_loc,(qualid_of_string "Logic.eq")))),
		    [(f_app_args,None);(body,None)])
  in
  let eq = Topconstr.prod_constr_expr unbounded_eq args in
  let hook f_ref tcc_lemma_ref functional_ref eq_ref rec_arg_num rec_arg_type
      nb_args relation =
    try
      pre_hook
	(generate_correction_proof_wf f_ref tcc_lemma_ref is_mes
	   functional_ref eq_ref rec_arg_num rec_arg_type nb_args relation
	);
      derive_inversion [fname]
    with e ->
      (* No proof done *)
      ()
  in
  Recdef.recursive_definition
    is_mes fname rec_impls
    type_of_f
    wf_rel_expr
    rec_arg_num
    eq
    hook
    using_lemmas


let register_mes fname rec_impls wf_mes_expr wf_arg using_lemmas args ret_type body =
  let wf_arg_type,wf_arg =
    match wf_arg with
      | None ->
	  begin
	    match args with
	      | [Topconstr.LocalRawAssum ([(_,Name x)],k,t)] -> t,x
	      | _ -> error "Recursive argument must be specified"
	  end
      | Some wf_args ->
	  try
	    match
	      List.find
		(function
		   | Topconstr.LocalRawAssum(l,k,t) ->
		       List.exists
			 (function (_,Name id) -> id =  wf_args | _ -> false)
			 l
		   | _ -> false
		)
		args
	    with
	      | Topconstr.LocalRawAssum(_,k,t)  ->	    t,wf_args
	      | _ -> assert false
	  with Not_found -> assert false
  in
  let ltof =
    let make_dir l = make_dirpath (List.map id_of_string (List.rev l)) in
    Libnames.Qualid (dummy_loc,Libnames.qualid_of_path
      (Libnames.make_path (make_dir ["Arith";"Wf_nat"]) (id_of_string "ltof")))
  in
  let fun_from_mes =
    let applied_mes =
      Topconstr.mkAppC(wf_mes_expr,[Topconstr.mkIdentC wf_arg])    in
    Topconstr.mkLambdaC ([(dummy_loc,Name wf_arg)],Topconstr.default_binder_kind,wf_arg_type,applied_mes)
  in
  let wf_rel_from_mes =
    Topconstr.mkAppC(Topconstr.mkRefC  ltof,[wf_arg_type;fun_from_mes])
  in
  register_wf ~is_mes:true fname rec_impls wf_rel_from_mes (Some wf_arg)
    using_lemmas args ret_type body


let do_generate_principle on_error register_built interactive_proof fixpoint_exprl  =
  let recdefs,rec_impls = build_newrecursive fixpoint_exprl in
  let _is_struct =
    match fixpoint_exprl with
      | [(((_,name),Some (Wf (wf_rel,wf_x,using_lemmas)),args,types,body))] ->
	  let pre_hook =
	    generate_principle
	      on_error
	      true
	      register_built
	      fixpoint_exprl
	      recdefs
	      true
	  in
	  if register_built
	  then register_wf name rec_impls wf_rel wf_x using_lemmas args types body pre_hook;
	  false
      | [(((_,name),Some (Mes (wf_mes,wf_x,using_lemmas)),args,types,body))] ->
	  let pre_hook =
	    generate_principle
	      on_error
	      true
	      register_built
	      fixpoint_exprl
	      recdefs
	      true
	  in
	  if register_built
	  then register_mes name rec_impls wf_mes wf_x using_lemmas args types body pre_hook;
	  true
      | _ ->
	  let fix_names =
	    List.map (function ((_,name),_,_,_,_) -> name) fixpoint_exprl
	  in
	  let is_one_rec = is_rec fix_names  in
	  let old_fixpoint_exprl =
	    List.map
	      (function
		 | (name,Some (Struct id),args,types,body),_ ->
		     let annot =
		       try Some (dummy_loc, id), Topconstr.CStructRec
		       with Not_found ->
			 raise (UserError("",str "Cannot find argument " ++
					    Ppconstr.pr_id id))
		     in
		     (name,annot,args,types,body),([]:Vernacexpr.decl_notation list)
		 | (name,None,args,types,body),recdef ->
		     let names =  (Topconstr.names_of_local_assums args) in
		     if  is_one_rec recdef  && List.length names > 1 then
		       user_err_loc
			 (dummy_loc,"Function",
			  Pp.str "the recursive argument needs to be specified in Function")
		     else
		       let loc, na = List.hd names in
			 (name,(Some (loc, Nameops.out_name na), Topconstr.CStructRec),args,types,body),
		     ([]:Vernacexpr.decl_notation list)
		 | (_,Some (Wf _),_,_,_),_ | (_,Some (Mes _),_,_,_),_->
		     error
		       ("Cannot use mutual definition with well-founded recursion or measure")
	      )
	      (List.combine fixpoint_exprl recdefs)
	  in
	  (* ok all the expressions are structural *)
	  let fix_names =
	    List.map (function ((_,name),_,_,_,_) -> name) fixpoint_exprl
	  in
	  let is_rec = List.exists (is_rec fix_names) recdefs in
	  if register_built then register_struct is_rec old_fixpoint_exprl;
	  generate_principle
	    on_error
	    false
	    register_built
	    fixpoint_exprl
	    recdefs
	    interactive_proof
	    (Functional_principles_proofs.prove_princ_for_struct interactive_proof);
	  if register_built then derive_inversion fix_names;
	  true;
  in
  ()

open Topconstr
let rec add_args id new_args b =
  match b with
  | CRef r ->
      begin      match r with
	| Libnames.Ident(loc,fname) when fname = id ->
	    CAppExpl(dummy_loc,(None,r),new_args)
	| _ -> b
      end
  | CFix  _  | CCoFix _ -> anomaly "add_args : todo"
  | CArrow(loc,b1,b2) ->
      CArrow(loc,add_args id new_args  b1, add_args id new_args b2)
  | CProdN(loc,nal,b1) ->
      CProdN(loc,
	     List.map (fun (nal,k,b2) -> (nal,k,add_args id new_args b2)) nal,
	     add_args id new_args  b1)
  | CLambdaN(loc,nal,b1) ->
      CLambdaN(loc,
	       List.map (fun (nal,k,b2) -> (nal,k,add_args id new_args  b2)) nal,
	       add_args id new_args  b1)
  | CLetIn(loc,na,b1,b2) ->
      CLetIn(loc,na,add_args id new_args b1,add_args id new_args b2)
  | CAppExpl(loc,(pf,r),exprl) ->
      begin
	match r with
	| Libnames.Ident(loc,fname) when fname = id ->
	    CAppExpl(loc,(pf,r),new_args@(List.map (add_args id new_args) exprl))
	| _ -> CAppExpl(loc,(pf,r),List.map (add_args id new_args) exprl)
      end
  | CApp(loc,(pf,b),bl) ->
      CApp(loc,(pf,add_args id new_args b),
	   List.map (fun (e,o) -> add_args id new_args e,o) bl)
  | CCases(loc,sty,b_option,cel,cal) ->
      CCases(loc,sty,Option.map (add_args id new_args) b_option,
	     List.map (fun (b,(na,b_option)) ->
			 add_args id new_args b,
			 (na,Option.map (add_args id new_args) b_option)) cel,
	     List.map (fun (loc,cpl,e) -> (loc,cpl,add_args id new_args e)) cal
	    )
  | CLetTuple(loc,nal,(na,b_option),b1,b2) ->
      CLetTuple(loc,nal,(na,Option.map (add_args id new_args) b_option),
		add_args id new_args b1,
		add_args id new_args b2
	       )

  | CIf(loc,b1,(na,b_option),b2,b3) ->
      CIf(loc,add_args id new_args b1,
	  (na,Option.map (add_args id new_args) b_option),
	  add_args id new_args b2,
	  add_args id new_args b3
	 )
  | CHole _ -> b
  | CPatVar _ -> b
  | CEvar _ -> b
  | CSort _ -> b
  | CCast(loc,b1,CastConv(ck,b2))  ->
      CCast(loc,add_args id new_args b1,CastConv(ck,add_args id new_args b2))
  | CCast(loc,b1,CastCoerce) ->
      CCast(loc,add_args id new_args b1,CastCoerce)
  | CRecord (loc, w, pars) ->
      CRecord (loc,
	       (match w with Some w -> Some (add_args id new_args w) | _ -> None),
	       List.map (fun (e,o) -> e, add_args id new_args o) pars)
  | CNotation _ -> anomaly "add_args : CNotation"
  | CGeneralization _ -> anomaly "add_args : CGeneralization"
  | CPrim _ -> b
  | CDelimiters _ -> anomaly "add_args : CDelimiters"
  | CDynamic _ -> anomaly "add_args : CDynamic"
exception Stop of  Topconstr.constr_expr


(* [chop_n_arrow n t] chops the [n] first arrows in [t]
   Acts on Topconstr.constr_expr
*)
let rec chop_n_arrow n t =
  if n <= 0
  then t (* If we have already removed all the arrows then return the type *)
  else (* If not we check the form of [t] *)
    match t with
      | Topconstr.CArrow(_,_,t) ->  (* If we have an arrow, we discard it and recall [chop_n_arrow] *)
	  chop_n_arrow (n-1) t
      | Topconstr.CProdN(_,nal_ta',t') -> (* If we have a forall, to result are possible :
					     either we need to discard more than the number of arrows contained
					     in this product declaration then we just recall [chop_n_arrow] on
					     the remaining number of arrow to chop and [t'] we discard it and
					     recall [chop_n_arrow], either this product contains more arrows
					     than the number we need to chop and then we return the new type
					  *)
	  begin
	    try
	      let new_n =
		let rec aux (n:int) = function
		    [] -> n
		| (nal,k,t'')::nal_ta' ->
		    let nal_l = List.length nal in
		    if n >= nal_l
		    then
		      aux (n - nal_l) nal_ta'
		    else
		      let new_t' =
			Topconstr.CProdN(dummy_loc,
					((snd (list_chop n nal)),k,t'')::nal_ta',t')
		      in
		      raise (Stop new_t')
		in
		aux n nal_ta'
	    in
	      chop_n_arrow new_n t'
	    with Stop t -> t
	  end
      | _ -> anomaly "Not enough products"


let rec get_args b t : Topconstr.local_binder list *
    Topconstr.constr_expr * Topconstr.constr_expr =
  match b with
    | Topconstr.CLambdaN (loc, (nal_ta), b') ->
	begin
	  let n =
	    (List.fold_left (fun n (nal,_,_) ->
			       n+List.length nal) 0 nal_ta )
	  in
	  let nal_tas,b'',t'' = get_args b' (chop_n_arrow n t) in
	  (List.map (fun (nal,k,ta) ->
		       (Topconstr.LocalRawAssum (nal,k,ta))) nal_ta)@nal_tas, b'',t''
	end
    | _ -> [],b,t


let make_graph (f_ref:global_reference) =
 let c,c_body =
      match f_ref with
	| ConstRef c ->
	    begin try c,Global.lookup_constant c
	    with Not_found ->
	      raise (UserError ("",str "Cannot find " ++ Printer.pr_lconstr (mkConst c)) )
	    end
	| _ -> raise (UserError ("", str "Not a function reference") )

  in
   Dumpglob.pause ();
  (match c_body.const_body with
    | None -> error "Cannot build a graph over an axiom !"
    | Some b ->
	let env = Global.env () in
	let body = (force b) in
	let extern_body,extern_type =
	  with_full_print
	    (fun () ->
	       (Constrextern.extern_constr false env body,
		Constrextern.extern_type false env
                  (Typeops.type_of_constant_type env c_body.const_type)
	       )
	    )
	    ()
	in
	let (nal_tas,b,t)  = get_args extern_body extern_type in
	let expr_list =
	  match b with
	    | Topconstr.CFix(loc,l_id,fixexprl) ->
		let l =
		  List.map
		    (fun (id,(n,recexp),bl,t,b) ->
		       let loc, rec_id = Option.get n in
		       let new_args =
			 List.flatten
			   (List.map
			      (function
 				 | Topconstr.LocalRawDef (na,_)-> []
			      	 | Topconstr.LocalRawAssum (nal,_,_) ->
				     List.map
				       (fun (loc,n) ->
					  CRef(Libnames.Ident(loc, Nameops.out_name n)))
				       nal
			      )
			      nal_tas
			   )
		       in
		       let b' = add_args (snd id) new_args b in
		       (id, Some (Struct rec_id),nal_tas@bl,t,b')
		    )
		    fixexprl
		in
		l
	    | _ ->
		let id = id_of_label (con_label c) in
		[((dummy_loc,id),None,nal_tas,t,b)]
	in
	do_generate_principle error_error false false expr_list;
	(* We register the infos *)
	let mp,dp,_ = repr_con c in
	List.iter
	  (fun ((_,id),_,_,_,_) -> add_Function false (make_con mp dp (label_of_id id)))
	  expr_list);
  Dumpglob.continue ()


(* let make_graph _ = assert false	 *)

let do_generate_principle = do_generate_principle warning_error true