aboutsummaryrefslogtreecommitdiffhomepage
path: root/plugins/extraction/common.ml
blob: 135d3fc7cd516d6730870574c42d759ef6dd1cb3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2012     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

open Pp
open Util
open Names
open Namegen
open Nameops
open Libnames
open Globnames
open Table
open Miniml
open Mlutil

let string_of_id id =
  let s = Names.Id.to_string id in
  for i = 0 to String.length s - 2 do
    if s.[i] == '_' && s.[i+1] == '_' then warning_id s
  done;
  Unicode.ascii_of_ident s

let is_mp_bound = function MPbound _ -> true | _ -> false

(*s Some pretty-print utility functions. *)

let pp_par par st = if par then str "(" ++ st ++ str ")" else st

(** [pp_apply] : a head part applied to arguments, possibly with parenthesis *)

let pp_apply st par args = match args with
  | [] -> st
  | _  -> hov 2 (pp_par par (st ++ spc () ++ prlist_with_sep spc identity args))

(** Same as [pp_apply], but with also protection of the head by parenthesis *)

let pp_apply2 st par args =
  let par' = not (List.is_empty args) || par in
  pp_apply (pp_par par' st) par args

let pr_binding = function
  | [] -> mt ()
  | l  -> str " " ++ prlist_with_sep (fun () -> str " ") pr_id l

let pp_tuple_light f = function
  | [] -> mt ()
  | [x] -> f true x
  | l ->
      pp_par true (prlist_with_sep (fun () -> str "," ++ spc ()) (f false) l)

let pp_tuple f = function
  | [] -> mt ()
  | [x] -> f x
  | l -> pp_par true (prlist_with_sep (fun () -> str "," ++ spc ()) f l)

let pp_boxed_tuple f = function
  | [] -> mt ()
  | [x] -> f x
  | l -> pp_par true (hov 0 (prlist_with_sep (fun () -> str "," ++ spc ()) f l))

(** By default, in module Format, you can do horizontal placing of blocks
    even if they include newlines, as long as the number of chars in the
    blocks is less that a line length. To avoid this awkward situation,
    we attach a big virtual size to [fnl] newlines. *)

let fnl () = stras (1000000,"") ++ fnl ()

let fnl2 () = fnl () ++ fnl ()

let space_if = function true -> str " " | false -> mt ()

let is_digit = function
  | '0'..'9' -> true
  | _ -> false

let begins_with_CoqXX s =
  let n = String.length s in
  n >= 4 && s.[0] == 'C' && s.[1] == 'o' && s.[2] == 'q' &&
  let i = ref 3 in
  try while !i < n do
    if s.[!i] == '_' then i:=n (*Stop*)
    else if is_digit s.[!i] then incr i
    else raise Not_found
  done; true
  with Not_found -> false

let unquote s =
  if lang () != Scheme then s
  else
    let s = String.copy s in
    for i=0 to String.length s - 1 do if s.[i] == '\'' then s.[i] <- '~' done;
    s

let rec qualify delim = function
  | [] -> assert false
  | [s] -> s
  | ""::l -> qualify delim l
  | s::l -> s^delim^(qualify delim l)

let dottify = qualify "."
let pseudo_qualify = qualify "__"

(*s Uppercase/lowercase renamings. *)

let is_upper s = match s.[0] with 'A' .. 'Z' -> true | _ -> false
let is_lower s = match s.[0] with 'a' .. 'z' | '_' -> true | _ -> false

let lowercase_id id = Id.of_string (String.uncapitalize (string_of_id id))
let uppercase_id id =
  let s = string_of_id id in
  assert (not (String.is_empty s));
  if s.[0] == '_' then Id.of_string ("Coq_"^s)
  else Id.of_string (String.capitalize s)

type kind = Term | Type | Cons | Mod

module KOrd =
struct
  type t = kind * string
  let compare (k1, s1) (k2, s2) =
    let c = Pervasives.compare k1 k2 (** OK *) in
    if c = 0 then String.compare s1 s2
    else c
end

module KMap = Map.Make(KOrd)

let upperkind = function
  | Type -> lang () == Haskell
  | Term -> false
  | Cons | Mod -> true

let kindcase_id k id =
  if upperkind k then uppercase_id id else lowercase_id id

(*s de Bruijn environments for programs *)

type env = Id.t list * Id.Set.t

(*s Generic renaming issues for local variable names. *)

let rec rename_id id avoid =
  if Id.Set.mem id avoid then rename_id (lift_subscript id) avoid else id

let rec rename_vars avoid = function
  | [] ->
      [], avoid
  | id :: idl when id == dummy_name ->
      (* we don't rename dummy binders *)
      let (idl', avoid') = rename_vars avoid idl in
      (id :: idl', avoid')
  | id :: idl ->
      let (idl, avoid) = rename_vars avoid idl in
      let id = rename_id (lowercase_id id) avoid in
      (id :: idl, Id.Set.add id avoid)

let rename_tvars avoid l =
  let rec rename avoid = function
    | [] -> [],avoid
    | id :: idl ->
	let id = rename_id (lowercase_id id) avoid in
	let idl, avoid = rename (Id.Set.add id avoid) idl in
	(id :: idl, avoid) in
  fst (rename avoid l)

let push_vars ids (db,avoid) =
  let ids',avoid' = rename_vars avoid ids in
  ids', (ids' @ db, avoid')

let get_db_name n (db,_) =
  let id = List.nth db (pred n) in
  if Id.equal id dummy_name then Id.of_string "__" else id


(*S Renamings of global objects. *)

(*s Tables of global renamings *)

let register_cleanup, do_cleanup =
  let funs = ref [] in
  (fun f -> funs:=f::!funs), (fun () -> List.iter (fun f -> f ()) !funs)

type phase = Pre | Impl | Intf

let set_phase, get_phase =
  let ph = ref Impl in ((:=) ph), (fun () -> !ph)

let set_keywords, get_keywords =
  let k = ref Id.Set.empty in
  ((:=) k), (fun () -> !k)

let add_global_ids, get_global_ids =
  let ids = ref Id.Set.empty in
  register_cleanup (fun () -> ids := get_keywords ());
  let add s = ids := Id.Set.add s !ids
  and get () = !ids
  in (add,get)

let empty_env () = [], get_global_ids ()

(* We might have built [global_reference] whose canonical part is
   inaccurate. We must hence compare only the user part,
   hence using a Hashtbl might be incorrect *)

let mktable_id autoclean =
  let m = ref Id.Map.empty in
  let clear () = m := Id.Map.empty in
  if autoclean then register_cleanup clear;
  (fun r v -> m := Id.Map.add r v !m), (fun r -> Id.Map.find r !m), clear

let mktable_ref autoclean =
  let m = ref Refmap'.empty in
  let clear () = m := Refmap'.empty in
  if autoclean then register_cleanup clear;
  (fun r v -> m := Refmap'.add r v !m), (fun r -> Refmap'.find r !m), clear

let mktable_modpath autoclean =
  let m = ref MPmap.empty in
  let clear () = m := MPmap.empty in
  if autoclean then register_cleanup clear;
  (fun r v -> m := MPmap.add r v !m), (fun r -> MPmap.find r !m), clear

(* A table recording objects in the first level of all MPfile *)

let add_mpfiles_content,get_mpfiles_content,clear_mpfiles_content =
  mktable_modpath false

let get_mpfiles_content mp =
  try get_mpfiles_content mp
  with Not_found -> failwith "get_mpfiles_content"

(*s The list of external modules that will be opened initially *)

let mpfiles_add, mpfiles_mem, mpfiles_list, mpfiles_clear =
  let m = ref MPset.empty in
  let add mp = m:=MPset.add mp !m
  and mem mp = MPset.mem mp !m
  and list () = MPset.elements !m
  and clear () = m:=MPset.empty
  in
  register_cleanup clear;
  (add,mem,list,clear)

(*s List of module parameters that we should alpha-rename *)

let params_ren_add, params_ren_mem =
  let m = ref MPset.empty in
  let add mp = m:=MPset.add mp !m
  and mem mp = MPset.mem mp !m
  and clear () = m:=MPset.empty
  in
  register_cleanup clear;
  (add,mem)

(*s table indicating the visible horizon at a precise moment,
    i.e. the stack of structures we are inside.

  - The sequence of [mp] parts should have the following form:
  a [MPfile] at the beginning, and then more and more [MPdot]
  over this [MPfile], or [MPbound] when inside the type of a
  module parameter.

  - the [params] are the [MPbound] when [mp] is a functor,
    the innermost [MPbound] coming first in the list.

  - The [content] part is used to record all the names already
  seen at this level.
*)

type visible_layer = { mp : module_path;
		       params : module_path list;
		       mutable content : Label.t KMap.t; }

let pop_visible, push_visible, get_visible =
  let vis = ref [] in
  register_cleanup (fun () -> vis := []);
  let pop () =
    match !vis with
      | [] -> assert false
      | v :: vl ->
	  vis := vl;
	  (* we save the 1st-level-content of MPfile for later use *)
	  if get_phase () == Impl && modular () && is_modfile v.mp
	  then add_mpfiles_content v.mp v.content
  and push mp mps =
    vis := { mp = mp; params = mps; content = KMap.empty } :: !vis
  and get () = !vis
  in (pop,push,get)

let get_visible_mps () = List.map (function v -> v.mp) (get_visible ())
let top_visible () = match get_visible () with [] -> assert false | v::_ -> v
let top_visible_mp () = (top_visible ()).mp
let add_visible ks l =
  let visible = top_visible () in
  visible.content <- KMap.add ks l visible.content

(* table of local module wrappers used to provide non-ambiguous names *)

module DupOrd =
struct
  type t = ModPath.t * Label.t
  let compare (mp1, l1) (mp2, l2) =
    let c = Label.compare l1 l2 in
    if Int.equal c 0 then ModPath.compare mp1 mp2 else c
end

module DupMap = Map.Make(DupOrd)

let add_duplicate, check_duplicate =
  let index = ref 0 and dups = ref DupMap.empty in
  register_cleanup (fun () -> index := 0; dups := DupMap.empty);
  let add mp l =
     incr index;
     let ren = "Coq__" ^ string_of_int !index in
     dups := DupMap.add (mp,l) ren !dups
  and check mp l = DupMap.find (mp, l) !dups
  in (add,check)

type reset_kind = AllButExternal | Everything

let reset_renaming_tables flag =
  do_cleanup ();
  if flag == Everything then clear_mpfiles_content ()

(*S Renaming functions *)

(* This function creates from [id] a correct uppercase/lowercase identifier.
   This is done by adding a [Coq_] or [coq_] prefix. To avoid potential clashes
   with previous [Coq_id] variable, these prefixes are duplicated if already
   existing. *)

let modular_rename k id =
  let s = string_of_id id in
  let prefix,is_ok =
    if upperkind k then "Coq_",is_upper else "coq_",is_lower
  in
  if not (is_ok s) ||
    (Id.Set.mem id (get_keywords ())) ||
    (String.length s >= 4 && String.equal (String.sub s 0 4) prefix)
  then prefix ^ s
  else s

(*s For monolithic extraction, first-level modules might have to be renamed
    with unique numbers *)

let modfstlev_rename =
  let add_prefixes,get_prefixes,_ = mktable_id true in
  fun l ->
    let coqid = Id.of_string "Coq" in
    let id = Label.to_id l in
    try
      let coqset = get_prefixes id in
      let nextcoq = next_ident_away coqid coqset in
      add_prefixes id (nextcoq::coqset);
      (string_of_id nextcoq)^"_"^(string_of_id id)
    with Not_found ->
      let s = string_of_id id in
      if is_lower s || begins_with_CoqXX s then
	(add_prefixes id [coqid]; "Coq_"^s)
      else
	(add_prefixes id []; s)

(*s Creating renaming for a [module_path] : first, the real function ... *)

let rec mp_renaming_fun mp = match mp with
  | _ when not (modular ()) && at_toplevel mp -> [""]
  | MPdot (mp,l) ->
      let lmp = mp_renaming mp in
      let mp = match lmp with
      | [""] -> modfstlev_rename l
      | _ -> modular_rename Mod (Label.to_id l)
      in
      mp ::lmp
  | MPbound mbid ->
      let s = modular_rename Mod (MBId.to_id mbid) in
      if not (params_ren_mem mp) then [s]
      else let i,_,_ = MBId.repr mbid in [s^"__"^string_of_int i]
  | MPfile _ ->
      assert (modular ()); (* see [at_toplevel] above *)
      assert (get_phase () == Pre);
      let current_mpfile = (List.last (get_visible ())).mp in
      if not (ModPath.equal mp current_mpfile) then mpfiles_add mp;
      [string_of_modfile mp]

(* ... and its version using a cache *)

and mp_renaming =
  let add,get,_ = mktable_modpath true in
  fun x ->
    try if is_mp_bound (base_mp x) then raise Not_found; get x
    with Not_found -> let y = mp_renaming_fun x in add x y; y

(*s Renamings creation for a [global_reference]: we build its fully-qualified
    name in a [string list] form (head is the short name). *)

let ref_renaming_fun (k,r) =
  let mp = modpath_of_r r in
  let l = mp_renaming mp in
  let l = if lang () != Ocaml && not (modular ()) then [""] else l in
  let s =
    let idg = safe_basename_of_global r in
    match l with
    | [""] -> (* this happens only at toplevel of the monolithic case *)
      let globs = Id.Set.elements (get_global_ids ()) in
      let id = next_ident_away (kindcase_id k idg) globs in
      string_of_id id
    | _ -> modular_rename k idg
  in
  add_global_ids (Id.of_string s);
  s::l

(* Cached version of the last function *)

let ref_renaming =
  let add,get,_ = mktable_ref true in
  fun ((k,r) as x) ->
    try if is_mp_bound (base_mp (modpath_of_r r)) then raise Not_found; get r
    with Not_found -> let y = ref_renaming_fun x in add r y; y

(* [visible_clash mp0 (k,s)] checks if [mp0-s] of kind [k]
   can be printed as [s] in the current context of visible
   modules. More precisely, we check if there exists a
   visible [mp] that contains [s].
   The verification stops if we encounter [mp=mp0]. *)

let rec clash mem mp0 ks = function
  | [] -> false
  | mp :: _ when ModPath.equal mp mp0 -> false
  | mp :: _ when mem mp ks -> true
  | _ :: mpl -> clash mem mp0 ks mpl

let mpfiles_clash mp0 ks =
  clash (fun mp k -> KMap.mem k (get_mpfiles_content mp)) mp0 ks
    (List.rev (mpfiles_list ()))

let rec params_lookup mp0 ks = function
  | [] -> false
  | param :: _ when ModPath.equal mp0 param -> true
  | param :: params ->
      let () = match ks with
      | (Mod, mp) when String.equal (List.hd (mp_renaming param)) mp -> params_ren_add param
      | _ -> ()
      in
      params_lookup mp0 ks params

let visible_clash mp0 ks =
  let rec clash = function
    | [] -> false
    | v :: _ when ModPath.equal v.mp mp0 -> false
    | v :: vis ->
	let b = KMap.mem ks v.content in
	if b && not (is_mp_bound mp0) then true
	else begin
	  if b then params_ren_add mp0;
	  if params_lookup mp0 ks v.params then false
	  else clash vis
	end
  in clash (get_visible ())

(* Same, but with verbose output (and mp0 shouldn't be a MPbound) *)

let visible_clash_dbg mp0 ks =
  let rec clash = function
    | [] -> None
    | v :: _ when ModPath.equal v.mp mp0 -> None
    | v :: vis ->
	try Some (v.mp,KMap.find ks v.content)
	with Not_found ->
	  if params_lookup mp0 ks v.params then None
	  else clash vis
  in clash (get_visible ())

(* After the 1st pass, we can decide which modules will be opened initially *)

let opened_libraries () =
  if not (modular ()) then []
  else
    let used_files = mpfiles_list () in
    let used_ks = List.map (fun mp -> Mod,string_of_modfile mp) used_files in
    (* By default, we open all used files. Ambiguities will be resolved later
       by using qualified names. Nonetheless, we don't open any file A that
       contains an immediate submodule A.B hiding another file B : otherwise,
       after such an open, there's no unambiguous way to refer to objects of B. *)
    let to_open =
      List.filter
	(fun mp ->
	   not (List.exists (fun k -> KMap.mem k (get_mpfiles_content mp)) used_ks))
	used_files
    in
    mpfiles_clear ();
    List.iter mpfiles_add to_open;
    mpfiles_list ()

(*s On-the-fly qualification issues for both monolithic or modular extraction. *)

(* [pp_ocaml_gen] below is a function that factorize the printing of both
   [global_reference] and module names for ocaml. When [k=Mod] then [olab=None],
   otherwise it contains the label of the reference to print.
   [rls] is the string list giving the qualified name, short name at the end. *)

(* In Coq, we can qualify [M.t] even if we are inside [M], but in Ocaml we
   cannot do that. So, if [t] gets hidden and we need a long name for it,
   we duplicate the _definition_ of t in a Coq__XXX module, and similarly
   for a sub-module [M.N] *)

let pp_duplicate k' prefix mp rls olab =
  let rls', lbl =
    if k' != Mod then
      (* Here rls=[s], the ref to print is <prefix>.<s>, and olab<>None *)
      rls, Option.get olab
    else
      (* Here rls=s::rls', we search the label for s inside mp *)
      List.tl rls, get_nth_label_mp (mp_length mp - mp_length prefix) mp
  in
  try dottify (check_duplicate prefix lbl :: rls')
  with Not_found ->
    assert (get_phase () == Pre); (* otherwise it's too late *)
    add_duplicate prefix lbl; dottify rls

let fstlev_ks k = function
  | [] -> assert false
  | [s] -> k,s
  | s::_ -> Mod,s

(* [pp_ocaml_local] : [mp] has something in common with [top_visible ()]
   but isn't equal to it *)

let pp_ocaml_local k prefix mp rls olab =
  (* what is the largest prefix of [mp] that belongs to [visible]? *)
  assert (k != Mod || not (ModPath.equal mp prefix)); (* mp as whole module isn't in itself *)
  let rls' = List.skipn (mp_length prefix) rls in
  let k's = fstlev_ks k rls' in
  (* Reference r / module path mp is of the form [<prefix>.s.<...>]. *)
  if not (visible_clash prefix k's) then dottify rls'
  else pp_duplicate (fst k's) prefix mp rls' olab

(* [pp_ocaml_bound] : [mp] starts with a [MPbound], and we are not inside
   (i.e. we are not printing the type of the module parameter) *)

let pp_ocaml_bound base rls =
  (* clash with a MPbound will be detected and fixed by renaming this MPbound *)
  if get_phase () == Pre then ignore (visible_clash base (Mod,List.hd rls));
  dottify rls

(* [pp_ocaml_extern] : [mp] isn't local, it is defined in another [MPfile]. *)

let pp_ocaml_extern k base rls = match rls with
  | [] -> assert false
  | base_s :: rls' ->
      if (not (modular ())) (* Pseudo qualification with "" *)
	|| (List.is_empty rls')  (* Case of a file A.v used as a module later *)
	|| (not (mpfiles_mem base)) (* Module not opened *)
	|| (mpfiles_clash base (fstlev_ks k rls')) (* Conflict in opened files *)
	|| (visible_clash base (fstlev_ks k rls')) (* Local conflict *)
      then
	(* We need to fully qualify. Last clash situation is unsupported *)
	match visible_clash_dbg base (Mod,base_s) with
	  | None -> dottify rls
	  | Some (mp,l) -> error_module_clash base (MPdot (mp,l))
      else
	(* Standard situation : object in an opened file *)
	dottify rls'

(* [pp_ocaml_gen] : choosing between [pp_ocaml_extern] or [pp_ocaml_extern] *)

let pp_ocaml_gen k mp rls olab =
  match common_prefix_from_list mp (get_visible_mps ()) with
    | Some prefix -> pp_ocaml_local k prefix mp rls olab
    | None ->
	let base = base_mp mp in
	if is_mp_bound base then pp_ocaml_bound base rls
	else pp_ocaml_extern k base rls

(* For Haskell, things are simplier: we have removed (almost) all structures *)

let pp_haskell_gen k mp rls = match rls with
  | [] -> assert false
  | s::rls' ->
    let str = pseudo_qualify rls' in
    let str = if is_upper str && not (upperkind k) then ("_"^str) else str in
    let prf = if not (ModPath.equal (base_mp mp) (top_visible_mp ())) then s ^ "." else "" in
    prf ^ str

(* Main name printing function for a reference *)

let pp_global k r =
  let ls = ref_renaming (k,r) in
  assert (List.length ls > 1);
  let s = List.hd ls in
  let mp,_,l = repr_of_r r in
  if ModPath.equal mp (top_visible_mp ()) then
    (* simpliest situation: definition of r (or use in the same context) *)
    (* we update the visible environment *)
    (add_visible (k,s) l; unquote s)
  else
    let rls = List.rev ls in (* for what come next it's easier this way *)
    match lang () with
      | Scheme -> unquote s (* no modular Scheme extraction... *)
      | Haskell -> if modular () then pp_haskell_gen k mp rls else s
      | Ocaml -> pp_ocaml_gen k mp rls (Some l)

(* The next function is used only in Ocaml extraction...*)

let pp_module mp =
  let ls = mp_renaming mp in
  match mp with
    | MPdot (mp0,l) when ModPath.equal mp0 (top_visible_mp ()) ->
	(* simpliest situation: definition of mp (or use in the same context) *)
	(* we update the visible environment *)
	let s = List.hd ls in
	add_visible (Mod,s) l; s
    | _ -> pp_ocaml_gen Mod mp (List.rev ls) None

(** Special hack for constants of type Ascii.ascii : if an
    [Extract Inductive ascii => char] has been declared, then
    the constants are directly turned into chars *)

let mk_ind path s =
  MutInd.make2 (MPfile (dirpath_of_string path)) (Label.make s)

let ind_ascii = mk_ind "Coq.Strings.Ascii" "ascii"

let check_extract_ascii () =
  try
    let char_type = match lang () with
      | Ocaml -> "char"
      | Haskell -> "Char"
      | _ -> raise Not_found
    in
    String.equal (find_custom (IndRef (ind_ascii, 0))) (char_type)
  with Not_found -> false

let is_list_cons l =
 List.for_all (function MLcons (_,ConstructRef(_,_),[]) -> true | _ -> false) l

let is_native_char = function
  | MLcons(_,ConstructRef ((kn,0),1),l) ->
    MutInd.equal kn ind_ascii && check_extract_ascii () && is_list_cons l
  | _ -> false

let pp_native_char c =
  let rec cumul = function
    | [] -> 0
    | MLcons(_,ConstructRef(_,j),[])::l -> (2-j) + 2 * (cumul l)
    | _ -> assert false
  in
  let l = match c with MLcons(_,_,l) -> l | _ -> assert false in
  str ("'"^Char.escaped (Char.chr (cumul l))^"'")