aboutsummaryrefslogtreecommitdiffhomepage
path: root/parsing/cLexer.ml4
blob: d7e3751fd7751d218e31d9a4cb7e2547c25c2295 (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
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2017     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

open Pp
open Util
open Tok

(** Location utilities  *)
let ploc_file_of_coq_file = function
| Loc.ToplevelInput -> ""
| Loc.InFile f -> f

let coq_file_of_ploc_file s =
  if s = "" then Loc.ToplevelInput else Loc.InFile s

let from_coqloc fname line_nb bol_pos bp ep =
  Ploc.make_loc (ploc_file_of_coq_file fname) line_nb bol_pos (bp, ep) ""

let to_coqloc loc =
  { Loc.fname = coq_file_of_ploc_file (Ploc.file_name loc);
    Loc.line_nb = Ploc.line_nb loc;
    Loc.bol_pos = Ploc.bol_pos loc;
    Loc.bp = Ploc.first_pos loc;
    Loc.ep = Ploc.last_pos loc;
    Loc.line_nb_last = Ploc.line_nb_last loc;
    Loc.bol_pos_last = Ploc.bol_pos_last loc; }

let (!@) = to_coqloc

(* Dictionaries: trees annotated with string options, each node being a map
   from chars to dictionaries (the subtrees). A trie, in other words. *)

module CharOrd = struct type t = char let compare : char -> char -> int = compare end
module CharMap = Map.Make (CharOrd)

type ttree = {
  node : string option;
  branch : ttree CharMap.t }

let empty_ttree = { node = None; branch = CharMap.empty }

let ttree_add ttree str =
  let rec insert tt i =
    if i == String.length str then
      {node = Some str; branch = tt.branch}
    else
      let c = str.[i] in
      let br =
        match try Some (CharMap.find c tt.branch) with Not_found -> None with
          | Some tt' ->
              CharMap.add c (insert tt' (i + 1)) (CharMap.remove c tt.branch)
          | None ->
              let tt' = {node = None; branch = CharMap.empty} in
              CharMap.add c (insert tt' (i + 1)) tt.branch
      in
      { node = tt.node; branch = br }
  in
  insert ttree 0

(* Search a string in a dictionary: raises [Not_found]
   if the word is not present. *)

let ttree_find ttree str =
  let rec proc_rec tt i =
    if i == String.length str then tt
    else proc_rec (CharMap.find str.[i] tt.branch) (i+1)
  in
  proc_rec ttree 0

(* Removes a string from a dictionary: returns an equal dictionary
   if the word not present. *)
let ttree_remove ttree str =
  let rec remove tt i =
    if i == String.length str then
      {node = None; branch = tt.branch}
    else
      let c = str.[i] in
      let br =
        match try Some (CharMap.find c tt.branch) with Not_found -> None with
          | Some tt' ->
              CharMap.add c (remove tt' (i + 1)) (CharMap.remove c tt.branch)
          | None -> tt.branch
      in
      { node = tt.node; branch = br }
  in
  remove ttree 0

let ttree_elements ttree =
  let rec elts tt accu =
    let accu = match tt.node with
    | None -> accu
    | Some s -> CString.Set.add s accu
    in
    CharMap.fold (fun _ tt accu -> elts tt accu) tt.branch accu
  in
  elts ttree CString.Set.empty

(* Errors occurring while lexing (explained as "Lexer error: ...") *)

module Error = struct

  type t =
    | Illegal_character
    | Unterminated_comment
    | Unterminated_string
    | Undefined_token
    | Bad_token of string

  exception E of t

  let to_string x =
    "Syntax Error: Lexer: " ^
      (match x with
         | Illegal_character -> "Illegal character"
         | Unterminated_comment -> "Unterminated comment"
         | Unterminated_string -> "Unterminated string"
         | Undefined_token -> "Undefined token"
         | Bad_token tok -> Format.sprintf "Bad token %S" tok)

end
open Error

let err loc str = Loc.raise ~loc:(to_coqloc loc) (Error.E str)

let bad_token str = raise (Error.E (Bad_token str))

(* Update a loc without allocating an intermediate pair *)
let set_loc_pos loc bp ep =
  Ploc.sub loc (bp - Ploc.first_pos loc) (ep - bp)

(* Increase line number by 1 and update position of beginning of line *)
let bump_loc_line loc bol_pos =
  Ploc.make_loc (Ploc.file_name loc) (Ploc.line_nb loc + 1) bol_pos
		(Ploc.first_pos loc, Ploc.last_pos loc) (Ploc.comment loc)

(* Same as [bump_loc_line], but for the last line in location *)
(* For an obscure reason, camlp5 does not give an easy way to set line_nb_stop,
   so we have to resort to a hack merging two locations. *)
(* Warning: [bump_loc_line_last] changes the end position. You may need to call
   [set_loc_pos] to fix it. *)
let bump_loc_line_last loc bol_pos =
  let loc' =
    Ploc.make_loc (Ploc.file_name loc) (Ploc.line_nb_last loc + 1) bol_pos
		  (Ploc.first_pos loc + 1, Ploc.last_pos loc + 1) (Ploc.comment loc)
  in
  Ploc.encl loc loc'

(* For some reason, the [Ploc.after] function of Camlp5 does not update line
   numbers, so we define our own function that does it. *)
let after loc =
  let line_nb = Ploc.line_nb_last loc in
  let bol_pos = Ploc.bol_pos_last loc in
  Ploc.make_loc (Ploc.file_name loc) line_nb bol_pos
		(Ploc.last_pos loc, Ploc.last_pos loc) (Ploc.comment loc)

(** Lexer conventions on tokens *)

type token_kind =
  | Utf8Token of (Unicode.status * int)
  | AsciiChar
  | EmptyStream

let error_utf8 loc cs =
  let bp = Stream.count cs in
  Stream.junk cs; (* consume the char to avoid read it and fail again *)
  let loc = set_loc_pos loc bp (bp+1) in
  err loc Illegal_character

let utf8_char_size loc cs = function
  (* Utf8 leading byte *)
  | '\x00'..'\x7F' -> 1
  | '\xC0'..'\xDF' -> 2
  | '\xE0'..'\xEF' -> 3
  | '\xF0'..'\xF7' -> 4
  | _ (* '\x80'..\xBF'|'\xF8'..'\xFF' *) -> error_utf8 loc cs

let njunk n = Util.repeat n Stream.junk

let check_utf8_trailing_byte loc cs c =
  if not (Int.equal (Char.code c land 0xC0) 0x80) then error_utf8 loc cs

(* Recognize utf8 blocks (of length less than 4 bytes) *)
(* but don't certify full utf8 compliance (e.g. no emptyness check) *)
let lookup_utf8_tail loc c cs =
  let c1 = Char.code c in
  if Int.equal (c1 land 0x40) 0 || Int.equal (c1 land 0x38) 0x38 then error_utf8 loc cs
  else
    let n, unicode =
      if Int.equal (c1 land 0x20) 0 then
      match Stream.npeek 2 cs with
      | [_;c2] ->
          check_utf8_trailing_byte loc cs c2;
          2, (c1 land 0x1F) lsl 6 + (Char.code c2 land 0x3F)
      | _ -> error_utf8 loc cs
      else if Int.equal (c1 land 0x10) 0 then
      match Stream.npeek 3 cs with
      | [_;c2;c3] ->
          check_utf8_trailing_byte loc cs c2;
	  check_utf8_trailing_byte loc cs c3;
          3, (c1 land 0x0F) lsl 12 + (Char.code c2 land 0x3F) lsl 6 +
          (Char.code c3 land 0x3F)
      | _ -> error_utf8 loc cs
      else match Stream.npeek 4 cs with
      | [_;c2;c3;c4] ->
          check_utf8_trailing_byte loc cs c2;
	  check_utf8_trailing_byte loc cs c3;
          check_utf8_trailing_byte loc cs c4;
          4, (c1 land 0x07) lsl 18 + (Char.code c2 land 0x3F) lsl 12 +
          (Char.code c3 land 0x3F) lsl 6 + (Char.code c4 land 0x3F)
      | _ -> error_utf8 loc cs
    in
    Utf8Token (Unicode.classify unicode, n)

let lookup_utf8 loc cs =
  match Stream.peek cs with
    | Some ('\x00'..'\x7F') -> AsciiChar
    | Some ('\x80'..'\xFF' as c) -> lookup_utf8_tail loc c cs
    | None -> EmptyStream

let unlocated f x = f x
  (** FIXME: should we still unloc the exception? *)
(*   try f x with Loc.Exc_located (_, exc) -> raise exc *)

let check_keyword str =
  let rec loop_symb = parser
    | [< ' (' ' | '\n' | '\r' | '\t' | '"') >] -> bad_token str
    | [< s >] ->
        match unlocated lookup_utf8 Ploc.dummy s with
        | Utf8Token (_,n) -> njunk n s; loop_symb s
        | AsciiChar -> Stream.junk s; loop_symb s
        | EmptyStream -> ()
  in
  loop_symb (Stream.of_string str)

let check_ident str =
  let rec loop_id intail = parser
    | [< ' ('a'..'z' | 'A'..'Z' | '_'); s >] ->
        loop_id true s
    | [< ' ('0'..'9' | ''') when intail; s >] ->
        loop_id true s
    | [< s >] ->
        match unlocated lookup_utf8 Ploc.dummy s with
        | Utf8Token (st, n) when not intail && Unicode.is_valid_ident_initial st -> njunk n s; loop_id true s
        | Utf8Token (st, n) when intail && Unicode.is_valid_ident_trailing st ->
          njunk n s;
          loop_id true s
        | EmptyStream -> ()
        | Utf8Token _ | AsciiChar -> bad_token str
  in
  loop_id false (Stream.of_string str)

let is_ident str =
  try let _ = check_ident str in true with Error.E _ -> false

(* Keyword and symbol dictionary *)
let token_tree = ref empty_ttree

let is_keyword s =
  try match (ttree_find !token_tree s).node with None -> false | Some _ -> true
  with Not_found -> false

let add_keyword str =
  if not (is_keyword str) then
    begin
      check_keyword str;
      token_tree := ttree_add !token_tree str
    end

let remove_keyword str =
  token_tree := ttree_remove !token_tree str

let keywords () = ttree_elements !token_tree

(* Freeze and unfreeze the state of the lexer *)
type keyword_state = ttree

let get_keyword_state () = !token_tree
let set_keyword_state tt = (token_tree := tt)

(* The string buffering machinery *)

let buff = ref (Bytes.create 80)

let store len x =
  let open Bytes in
  if len >= length !buff then
    buff := cat !buff (create (length !buff));
  set !buff len x;
  succ len

let rec nstore n len cs =
  if n>0 then nstore (n-1) (store len (Stream.next cs)) cs else len

let get_buff len = Bytes.sub_string !buff 0 len

(* The classical lexer: idents, numbers, quoted strings, comments *)

let warn_unrecognized_unicode =
  CWarnings.create ~name:"unrecognized-unicode" ~category:"parsing"
         (fun (u,id) ->
          strbrk (Printf.sprintf "Not considering unicode character \"%s\" of unknown \
                                  lexical status as part of identifier \"%s\"." u id))

let rec ident_tail loc len = parser
  | [< ' ('a'..'z' | 'A'..'Z' | '0'..'9' | ''' | '_' as c); s >] ->
      ident_tail loc (store len c) s
  | [< s >] ->
      match lookup_utf8 loc s with
      | Utf8Token (st, n) when Unicode.is_valid_ident_trailing st ->
          ident_tail loc (nstore n len s) s
      | Utf8Token (st, n) when Unicode.is_unknown st ->
          let id = get_buff len in
          let u = String.concat "" (List.map (String.make 1) (Stream.npeek n s)) in
          warn_unrecognized_unicode ~loc:!@loc (u,id); len
      | _ -> len

let rec number len = parser
  | [< ' ('0'..'9' as c); s >] -> number (store len c) s
  | [< >] -> len

let warn_comment_terminator_in_string =
  CWarnings.create ~name:"comment-terminator-in-string" ~category:"parsing"
         (fun () ->
          (strbrk
             "Not interpreting \"*)\" as the end of current \
              non-terminated comment because it occurs in a \
              non-terminated string of the comment."))

(* If the string being lexed is in a comment, [comm_level] is Some i with i the
   current level of comments nesting. Otherwise, [comm_level] is None. *)
let rec string loc ~comm_level bp len = parser
  | [< ''"'; esc=(parser [<''"' >] -> true | [< >] -> false); s >] ->
      if esc then string loc ~comm_level bp (store len '"') s else (loc, len)
  | [< ''('; s >] ->
      (parser
      | [< ''*'; s >] ->
        let comm_level = Option.map succ comm_level in
            string loc ~comm_level
              bp (store (store len '(') '*')
              s
        | [< >] ->
            string loc ~comm_level bp (store len '(') s) s
  | [< ''*'; s >] ->
      (parser
        | [< '')'; s >] ->
            let () = match comm_level with
            | Some 0 ->
	       warn_comment_terminator_in_string ~loc:!@loc ()
            | _ -> ()
            in
            let comm_level = Option.map pred comm_level in
            string loc ~comm_level bp (store (store len '*') ')') s
        | [< >] ->
            string loc ~comm_level bp (store len '*') s) s
  | [< ''\n' as c; s >] ep ->
     (* If we are parsing a comment, the string if not part of a token so we
     update the first line of the location. Otherwise, we update the last
     line. *)
     let loc =
       if Option.has_some comm_level then bump_loc_line loc ep
       else bump_loc_line_last loc ep
     in
     string loc ~comm_level bp (store len c) s
  | [< 'c; s >] -> string loc ~comm_level bp (store len c) s
  | [< _ = Stream.empty >] ep ->
     let loc = set_loc_pos loc bp ep in
     err loc Unterminated_string

(* To associate locations to a file name *)
let current_file = ref Loc.ToplevelInput

(* Utilities for comments in beautify *)
let comment_begin = ref None
let comm_loc bp = match !comment_begin with
| None -> comment_begin := Some bp
| _ -> ()

let comments = ref []
let current_comment = Buffer.create 8192
let between_commands = ref true

(* The state of the lexer visible from outside *)
type lexer_state = int option * string * bool * ((int * int) * string) list * Loc.source

let init_lexer_state f = (None,"",true,[],f)
let set_lexer_state (o,s,b,c,f) =
  comment_begin := o;
  Buffer.clear current_comment; Buffer.add_string current_comment s;
  between_commands := b;
  comments := c;
  current_file := f
let get_lexer_state () =
  (!comment_begin, Buffer.contents current_comment, !between_commands, !comments, !current_file)
let release_lexer_state = get_lexer_state
let drop_lexer_state () =
    set_lexer_state (init_lexer_state Loc.ToplevelInput)

let get_comment_state (_,_,_,c,_) = c

let real_push_char c = Buffer.add_char current_comment c

(* Add a char if it is between two commands, if it is a newline or
   if the last char is not a space itself. *)
let push_char c =
  if
    !between_commands || List.mem c ['\n';'\r'] ||
    (List.mem c [' ';'\t']&&
     (Int.equal (Buffer.length current_comment) 0 ||
      not (let s = Buffer.contents current_comment in
           List.mem s.[String.length s - 1] [' ';'\t';'\n';'\r'])))
  then
    real_push_char c

let push_string s = Buffer.add_string current_comment s

let null_comment s =
  let rec null i =
    i<0 || (List.mem s.[i] [' ';'\t';'\n';'\r'] && null (i-1)) in
  null (String.length s - 1)

let comment_stop ep =
  let current_s = Buffer.contents current_comment in
  (if !Flags.beautify && Buffer.length current_comment > 0 &&
    (!between_commands || not(null_comment current_s)) then
    let bp = match !comment_begin with
        Some bp -> bp
      | None ->
          Feedback.msg_notice
            (str "No begin location for comment '"
             ++ str current_s ++str"' ending at  "
             ++ int ep);
          ep-1 in
    comments := ((bp,ep),current_s) :: !comments);
  Buffer.clear current_comment;
  comment_begin := None;
  between_commands := false

let rec comment loc bp = parser bp2
  | [< ''(';
       loc = (parser
              | [< ''*'; s >] -> push_string "(*"; comment loc bp s
              | [< >] -> push_string "("; loc );
       s >] -> comment loc bp s
  | [< ''*';
       loc = parser
         | [< '')' >] -> push_string "*)"; loc
         | [< s >] -> real_push_char '*'; comment loc bp s >] -> loc
  | [< ''"'; s >] ->
      let loc, len = string loc ~comm_level:(Some 0) bp2 0 s in
      push_string "\""; push_string (get_buff len); push_string "\"";
      comment loc bp s
  | [< _ = Stream.empty >] ep ->
      let loc = set_loc_pos loc bp ep in
      err loc Unterminated_comment
  | [< ''\n' as z; s >] ep -> real_push_char z; comment (bump_loc_line loc ep) bp s
  | [< 'z; s >] -> real_push_char z; comment loc bp s

(* Parse a special token, using the [token_tree] *)

(* Peek as much utf-8 lexemes as possible *)
(* and retain the longest valid special token obtained *)
let rec progress_further loc last nj tt cs =
  try progress_from_byte loc last nj tt cs (List.nth (Stream.npeek (nj+1) cs) nj)
  with Failure _ -> last

and update_longest_valid_token loc last nj tt cs =
  match tt.node with
  | Some _ as last' ->
    stream_njunk nj cs;
    progress_further loc last' 0 tt cs
  | None ->
    progress_further loc last nj tt cs

(* nj is the number of char peeked since last valid token *)
(* n the number of char in utf8 block *)
and progress_utf8 loc last nj n c tt cs =
  try
    let tt = CharMap.find c tt.branch in
    if Int.equal n 1 then
      update_longest_valid_token loc last (nj+n) tt cs
    else
      match Util.List.skipn (nj+1) (Stream.npeek (nj+n) cs) with
      | l when Int.equal (List.length l) (n - 1) ->
         List.iter (check_utf8_trailing_byte loc cs) l;
         let tt = List.fold_left (fun tt c -> CharMap.find c tt.branch) tt l in
         update_longest_valid_token loc last (nj+n) tt cs
      | _ ->
          error_utf8 loc cs
  with Not_found ->
    last

and progress_from_byte loc last nj tt cs c =
  progress_utf8 loc last nj (utf8_char_size loc cs c) c tt cs

let find_keyword loc id s =
  let tt = ttree_find !token_tree id in
  match progress_further loc tt.node 0 tt s with
  | None -> raise Not_found
  | Some c -> KEYWORD c

let process_sequence loc bp c cs =
  let rec aux n cs =
    match Stream.peek cs with
    | Some c' when c == c' -> Stream.junk cs; aux (n+1) cs
    | _ -> BULLET (String.make n c), set_loc_pos loc bp (Stream.count cs)
  in
  aux 1 cs

(* Must be a special token *)
let process_chars loc bp c cs =
  let t = progress_from_byte loc None (-1) !token_tree cs c in
  let ep = Stream.count cs in
  match t with
    | Some t -> (KEYWORD t, set_loc_pos loc bp ep)
    | None ->
        let ep' = bp + utf8_char_size loc cs c in
        njunk (ep' - ep) cs;
	let loc = set_loc_pos loc bp ep' in
        err loc Undefined_token

(* Parse what follows a dot *)

let parse_after_dot loc c bp =
  parser
  | [< ' ('a'..'z' | 'A'..'Z' | '_' as d); len = ident_tail loc (store 0 d); s >] ->
      let field = get_buff len in
      (try find_keyword loc ("."^field) s with Not_found -> FIELD field)
  | [< s >] ->
      match lookup_utf8 loc s with
      | Utf8Token (st, n) when Unicode.is_valid_ident_initial st ->
          let len = ident_tail loc (nstore n 0 s) s in
          let field = get_buff len in
          (try find_keyword loc ("."^field) s with Not_found -> FIELD field)
      | AsciiChar | Utf8Token _ | EmptyStream -> fst (process_chars loc bp c s)

(* Parse what follows a question mark *)

let parse_after_qmark loc bp s =
  match Stream.peek s with
    | Some ('a'..'z' | 'A'..'Z' | '_') -> LEFTQMARK
    | None -> KEYWORD "?"
    | _ ->
        match lookup_utf8 loc s with
          | Utf8Token (st, _) when Unicode.is_valid_ident_initial st -> LEFTQMARK
          | AsciiChar | Utf8Token _ | EmptyStream ->
            fst (process_chars loc bp '?' s)

let blank_or_eof cs =
  match Stream.peek cs with
    | None -> true
    | Some (' ' | '\t' | '\n' |'\r') -> true
    | _ -> false

(* Parse a token in a char stream *)

let rec next_token loc = parser bp
  | [< ''\n' as c; s >] ep ->
      comm_loc bp; push_char c; next_token (bump_loc_line loc ep) s
  | [< '' ' | '\t' | '\r' as c; s >] ->
      comm_loc bp; push_char c; next_token loc s
  | [< ''.' as c; t = parse_after_dot loc c bp; s >] ep ->
      comment_stop bp;
      (* We enforce that "." should either be part of a larger keyword,
         for instance ".(", or followed by a blank or eof. *)
      let () = match t with
      | KEYWORD ("." | "...") ->
        if not (blank_or_eof s) then
	  err (set_loc_pos loc bp (ep+1)) Undefined_token;
	between_commands := true;
      | _ -> ()
      in
      (t, set_loc_pos loc bp ep)
  | [< ' ('-'|'+'|'*' as c); s >] ->
      let t,new_between_commands =
        if !between_commands then process_sequence loc bp c s, true
        else process_chars loc bp c s,false
      in
      comment_stop bp; between_commands := new_between_commands; t
  | [< ''?'; s >] ep ->
      let t = parse_after_qmark loc bp s in
      comment_stop bp; (t, set_loc_pos loc bp ep)
  | [< ' ('a'..'z' | 'A'..'Z' | '_' as c);
       len = ident_tail loc (store 0 c); s >] ep ->
      let id = get_buff len in
      comment_stop bp;
      (try find_keyword loc id s with Not_found -> IDENT id), set_loc_pos loc bp ep
  | [< ' ('0'..'9' as c); len = number (store 0 c) >] ep ->
      comment_stop bp;
      (INT (get_buff len), set_loc_pos loc bp ep)
  | [< ''\"'; (loc,len) = string loc ~comm_level:None bp 0 >] ep ->
      comment_stop bp;
      (STRING (get_buff len), set_loc_pos loc bp ep)
  | [< ' ('(' as c);
      t = parser
        | [< ''*'; s >] ->
            comm_loc bp;
            push_string "(*";
            let loc = comment loc bp s in next_token loc s
        | [< t = process_chars loc bp c >] -> comment_stop bp; t >] ->
      t
  | [< ' ('{' | '}' as c); s >] ep ->
      let t,new_between_commands =
        if !between_commands then (KEYWORD (String.make 1 c), set_loc_pos loc bp ep), true
        else process_chars loc bp c s, false
      in
      comment_stop bp; between_commands := new_between_commands; t
  | [< s >] ->
      match lookup_utf8 loc s with
        | Utf8Token (st, n) when Unicode.is_valid_ident_initial st ->
            let len = ident_tail loc (nstore n 0 s) s in
            let id = get_buff len in
            let ep = Stream.count s in
            comment_stop bp;
            (try find_keyword loc id s with Not_found -> IDENT id), set_loc_pos loc bp ep
        | AsciiChar | Utf8Token _ ->
            let t = process_chars loc bp (Stream.next s) s in
            comment_stop bp; t
        | EmptyStream ->
            comment_stop bp; (EOI, set_loc_pos loc bp (bp+1))

(* (* Debug: uncomment this for tracing tokens seen by coq...*)
let next_token loc s =
  let (t,loc as r) = next_token loc s in
  Printf.eprintf "(line %i, %i-%i)[%s]\n%!" (Ploc.line_nb loc) (Ploc.first_pos loc) (Ploc.last_pos loc) (Tok.to_string t);
  r *)

(* Location table system for creating tables associating a token count
   to its location in a char stream (the source) *)

let locerr () = invalid_arg "Lexer: location function"

let loct_create () = Hashtbl.create 207

let loct_func loct i =
  try Hashtbl.find loct i with Not_found -> locerr ()

let loct_add loct i loc = Hashtbl.add loct i loc

(** {6 The lexer of Coq} *)

(** Note: removing a token.
   We do nothing because [remove_token] is called only when removing a grammar
   rule with [Grammar.delete_rule]. The latter command is called only when
   unfreezing the state of the grammar entries (see GRAMMAR summary, file
   env/metasyntax.ml). Therefore, instead of removing tokens one by one,
   we unfreeze the state of the lexer. This restores the behaviour of the
   lexer. B.B. *)

type te = Tok.t

(** Names of tokens, for this lexer, used in Grammar error messages *)

let token_text = function
  | ("", t) -> "'" ^ t ^ "'"
  | ("IDENT", "") -> "identifier"
  | ("IDENT", t) -> "'" ^ t ^ "'"
  | ("INT", "") -> "integer"
  | ("INT", s) -> "'" ^ s ^ "'"
  | ("STRING", "") -> "string"
  | ("EOI", "") -> "end of input"
  | (con, "") -> con
  | (con, prm) -> con ^ " \"" ^ prm ^ "\""

let func cs =
  let loct = loct_create () in
  let cur_loc = ref (from_coqloc !current_file 1 0 0 0) in
  let ts =
    Stream.from
      (fun i ->
         let (tok, loc) = next_token !cur_loc cs in
	 cur_loc := after loc;
         loct_add loct i loc; Some tok)
  in
  (ts, loct_func loct)

let lexer = {
  Token.tok_func = func;
  Token.tok_using =
    (fun pat -> match Tok.of_pattern pat with
       | KEYWORD s -> add_keyword s
       | _ -> ());
  Token.tok_removing = (fun _ -> ());
  Token.tok_match = Tok.match_pattern;
  Token.tok_comm = None;
  Token.tok_text = token_text }

(** Terminal symbols interpretation *)

let is_ident_not_keyword s =
  is_ident s && not (is_keyword s)

let is_number s =
  let rec aux i =
    Int.equal (String.length s) i ||
    match s.[i] with '0'..'9' -> aux (i+1) | _ -> false
  in aux 0

let strip s =
  let len =
    let rec loop i len =
      if Int.equal i (String.length s) then len
      else if s.[i] == ' ' then loop (i + 1) len
      else loop (i + 1) (len + 1)
    in
    loop 0 0
  in
  if len == String.length s then s
  else
    let s' = Bytes.create len in
    let rec loop i i' =
      if i == String.length s then s'
      else if s.[i] == ' ' then loop (i + 1) i'
      else begin Bytes.set s' i' s.[i]; loop (i + 1) (i' + 1) end
    in
    Bytes.to_string (loop 0 0)

let terminal s =
  let s = strip s in
  let () = match s with "" -> failwith "empty token." | _ -> () in
  if is_ident_not_keyword s then IDENT s
  else if is_number s then INT s
  else KEYWORD s