summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/source/latex/l3kernel/l3bootstrap.dtx
blob: 1fb3ac9454f8a17bba32cbabfe7f64ec646502fe (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
% \iffalse meta-comment
%
%% File: l3bootstrap.dtx Copyright (C) 2011-2012 The LaTeX3 project
%%
%% It may be distributed and/or modified under the conditions of the
%% LaTeX Project Public License (LPPL), either version 1.3c of this
%% license or (at your option) any later version.  The latest version
%% of this license is in the file
%%
%%    http://www.latex-project.org/lppl.txt
%%
%% This file is part of the "l3kernel bundle" (The Work in LPPL)
%% and all files in that bundle must be distributed together.
%%
%% The released version of this bundle is available from CTAN.
%%
%% -----------------------------------------------------------------------
%%
%% The development version of the bundle can be found at
%%
%%    http://www.latex-project.org/svnroot/experimental/trunk/
%%
%% for those people who are interested.
%%
%%%%%%%%%%%
%% NOTE: %%
%%%%%%%%%%%
%%
%%   Snapshots taken from the repository represent work in progress and may
%%   not work or may contain conflicting material!  We therefore ask
%%   people _not_ to put them into distributions, archives, etc. without
%%   prior consultation with the LaTeX3 Project.
%%
%% -----------------------------------------------------------------------
%
%<*driver|package>
% \begin{macro}{\GetIdInfo}
% \begin{macro}[aux]{\GetIdInfoAuxI, \GetIdInfoAuxII, \GetIdInfoAuxIII}
%   The idea here is to extract out the information needed from a standard
%   \textsc{svn} \texttt{Id} line, but without a line that will get
%   changed when the file is checked in. Hence the fact that there is
%   not a line which includes both a dollar sign and the \texttt{Id}
%   keyword together!
%    \begin{macrocode}
\protected\def\GetIdInfo
  {%
    \begingroup
      \catcode 32 = 10 %
      \GetIdInfoAuxI
  }
%    \end{macrocode}
%   A first check for a completely empty \textsc{svn} field. If that is
%   not the case, there is a second case when a file created using
%   \texttt{svn cp} but has not been checked in. That leaves a special
%   marker \texttt{-1} version, which has no further data. Dealing correctly
%   with that is the reason for the space in the line to use
%   \cs{GetIdInforAuxII}.
%    \begin{macrocode}
\protected\def\GetIdInfoAuxI$#1$#2%
  {%
    \def\tempa{#1}%
    \def\tempb{Id}%
    \ifx\tempa\tempb
      \def\tempa
        {%
          \endgroup
          \def\ExplFileDate{9999/12/31}%
          \def\ExplFileDescription{#2}%
          \def\ExplFileName{[unknown name]}%
          \def\ExplFileExtension{[unknown extension]}%
          \def\ExplFileVersion{999}%
        }%
    \else
      \def\tempa
        {%
          \endgroup
          \def\ExplFileDescription{#2}%
          \GetIdInfoAuxII$#1 $%
        }%
    \fi
    \tempa
  }
%    \end{macrocode}
%   Here, |#1| is |Id|, |#2| is the file name, |#3| is the extension,
%   |#4| is the version, |#5| is the check in date and |#6| is the check in
%   time and user, plus some trailing spaces. If |#4| is the marker |-1| value
%   then |#5| and |#6| will be empty.
%    \begin{macrocode}
\protected\def\GetIdInfoAuxII$#1 #2.#3 #4 #5 #6$%
  {%
    \def\ExplFileName{#2}%
    \def\ExplFileExtension{#3}%
    \def\ExplFileVersion{#4}%
    \begingroup
      \def\tempa{#4}%
      \def\tempb{-1}%
      \ifx\tempa\tempb
        \def\tempa
          {%
            \endgroup
            \def\ExplFileDate{0000/00/00}%
          }%
      \else
        \def\tempa
          {%
            \endgroup
            \GetIdInfoAuxIII$#5$%
          }%
      \fi
      \tempa
  }
%    \end{macrocode}
%   Convert an \textsc{svn}-style date into a \LaTeX{}-style one.
%    \begin{macrocode}
\protected\def\GetIdInfoAuxIII$#1-#2-#3$%
  {%
    \def\ExplFileDate{#1/#2/#3}%
  }
%    \end{macrocode}
% \end{macro}
% \end{macro}
\GetIdInfo$Id: l3bootstrap.dtx 3986 2012-07-15 19:23:51Z joseph $
  {L3 Bootstrap code}
%</driver|package>
%<*driver>
\documentclass[full]{l3doc}
\begin{document}
  \DocInput{\jobname.dtx}
\end{document}
%</driver>
% \fi
%
% \title{^^A
%   The \pkg{l3bootstrap} package\\ Bootstrap code^^A
%   \thanks{This file describes v\ExplFileVersion,
%     last revised \ExplFileDate.}^^A
% }
%
% \author{^^A
%  The \LaTeX3 Project\thanks
%    {^^A
%      E-mail:
%        \href{mailto:latex-team@latex-project.org}
%          {latex-team@latex-project.org}^^A
%    }^^A
% }
%
% \date{Released \ExplFileDate}
%
% \maketitle
%
% \begin{documentation}
%
% \section{Using the \LaTeX3 modules}
%
% The modules documented in \file{source3} are designed to be used on top of
% \LaTeXe{} and are loaded all as one with the usual |\usepackage{expl3}| or
% |\RequirePackage{expl3}| instructions. These modules will also form the
% basis of the \LaTeX3 format, but work in this area is incomplete and not
% included in this documentation at present.
%
% As the modules use a coding syntax different from standard
% \LaTeXe{} it provides a few functions for setting it up.
%
% \begin{function}[updated = 2011-08-13]{\ExplSyntaxOn, \ExplSyntaxOff}
%   \begin{syntax}
%     \cs{ExplSyntaxOn} \meta{code} \cs{ExplSyntaxOff}
%   \end{syntax}
%   The \cs{ExplSyntaxOn} function switches to a category code
%   r{\'e}gime in which spaces are ignored and in which the colon (|:|)
%   and underscore (|_|) are treated as \enquote{letters}, thus allowing
%   access to the names of code functions and variables. Within this
%   environment, |~| is used to input a space. The \cs{ExplSyntaxOff}
%   reverts to the document category code r{\'e}gime.
% \end{function}
%
% \begin{function}{\ProvidesExplPackage, \ProvidesExplClass, \ProvidesExplFile}
%   \begin{syntax}
%     |\RequirePackage{expl3}| \\
%     \cs{ProvidesExplPackage} \Arg{package} \Arg{date} \Arg{version} \Arg{description}
%   \end{syntax}
%   These functions act broadly in the same way as the \LaTeXe{} kernel
%   functions \cs{ProvidesPackage}, \cs{ProvidesClass} and
%   \cs{ProvidesFile}. However, they also implicitly switch
%   \cs{ExplSyntaxOn} for the remainder of the code with the file. At the
%   end of the file, \cs{ExplSyntaxOff} will be called to reverse this.
%   (This is the same concept as \LaTeXe{} provides in turning on
%   \tn{makeatletter} within package and class code.)
% \end{function}
%
% \begin{function}[updated = 2012-06-04]{\GetIdInfo}
%   \begin{syntax}
%     |\RequirePackage{l3names}|
%     \cs{GetIdInfo} |$Id:| \meta{SVN info field} |$| \Arg{description}
%   \end{syntax}
%   Extracts all information from a SVN field. Spaces are not
%   ignored in these fields. The information pieces are stored in
%   separate control sequences with \cs{ExplFileName} for the part of the
%   file name leading up to the period, \cs{ExplFileDate} for date,
%   \cs{ExplFileVersion} for version and \cs{ExplFileDescription} for the
%   description.
% \end{function}
%
% To summarize: Every single package using this syntax should identify
% itself using one of the above methods. Special care is taken so that
% every package or class file loaded with \tn{RequirePackage} or alike
% are loaded with usual \LaTeXe{} category codes and the \LaTeX3 category code
% scheme is reloaded when needed afterwards. See implementation for
% details. If you use the \cs{GetIdInfo} command you can use the
% information when loading a package with
% \begin{verbatim}
%   \ProvidesExplPackage{\ExplFileName}
%     {\ExplFileDate}{\ExplFileVersion}{\ExplFileDescription}
% \end{verbatim}
% 
% \subsection{Internal functions and variables}
% 
% \begin{function}{\__expl_package_check:}
%   \begin{syntax}
%     \cs{__expl_package_check:}
%   \end{syntax}
%   Used to ensure that all parts of \pkg{expl3} are loaded together
%   (\emph{i.e.}~as part of \pkg{expl3}). Issues an error if a kernel package
%   is loaded independently of the bundle.
% \end{function}
%
% \begin{variable}{\l__kernel_expl_bool}
%   A boolean which records the current code syntax status: \texttt{true} if
%   currently inside a code environment. This variable should only be
%   set by \cs{ExplSyntaxOn}/\cs{ExplSyntaxOff}.
% \end{variable}
%
% \end{documentation}
%
% \begin{implementation}
%
% \section{\pkg{l3bootstrap} implementation}
%
%    \begin{macrocode}
%<*initex|package>
%<@@=expl>
%    \end{macrocode}
%
% \subsection{Format-specific code}
%
% The very first thing to do is to bootstrap the \IniTeX{} system so
% that everything else will actually work. \TeX{} does not start with
% some pretty basic character codes set up.
%    \begin{macrocode}
%<*initex>
\catcode `\{ = 1 \relax
\catcode `\} = 2 \relax
\catcode `\# = 6 \relax
\catcode `\^ = 7 \relax
%</initex>
%    \end{macrocode}
%
% Tab characters should not show up in the code, but to be on the
% safe side.
%    \begin{macrocode}
%<*initex>
\catcode `\^^I = 10 \relax
%</initex>
%    \end{macrocode}
%
% For \LuaTeX{} the extra primitives need to be enabled before
% they can be used. No \tn{ifdefined} yet, so do it the old-fashioned
% way. The primitive \tn{strcmp} is simulated using some \Lua{}
% code, which currently has to be applied to every job as the \Lua{}
% code is not part of the format. Thanks to Taco Hoekwater for this
% code. The odd \tn{csname} business is needed so that the later
% deletion code will work.
%    \begin{macrocode}
%<*initex>
\begingroup\expandafter\expandafter\expandafter\endgroup
\expandafter\ifx\csname directlua\endcsname\relax
\else
  \directlua
    {
      tex.enableprimitives('',tex.extraprimitives ())
      lua.bytecode[1] = function ()
        function strcmp (A, B)
          if A == B then
            tex.write("0")
          elseif A < B then
            tex.write("-1")
          else
            tex.write("1")
          end
        end
      end
      lua.bytecode[1]()
    }
  \everyjob\expandafter
    {\csname\detokenize{luatex_directlua:D}\endcsname{lua.bytecode[1]()}}
  \long\edef\pdfstrcmp#1#2%
     {%
       \expandafter\noexpand\csname\detokenize{luatex_directlua:D}\endcsname
         {%
           strcmp%
             (%
               "\noexpand\luaescapestring{#1}",%
               "\noexpand\luaescapestring{#2}"%
             )%
         }%
     }
\fi
%</initex>
%    \end{macrocode}
%
% \subsection{Package-specific code part one}
%
% The package starts by identifying itself: the information itself is
% taken from the SVN |Id| string at the start of the source file.
%    \begin{macrocode}
%<*package>
\ProvidesPackage{l3bootstrap}
  [%
    \ExplFileDate\space v\ExplFileVersion\space
    L3 Experimental bootstrap code%
  ]
%</package>
%    \end{macrocode}
%
% For \LuaTeX{} the functionality of the \tn{pdfstrcmp} primitive
% needs to be provided: the \pkg{pdftexmcds} package is used to
% do this if necessary. At present, there is also a need to deal
% with some low-level allocation stuff that could usefully be added
% to \texttt{lualatex.ini}. As it is currently not, load Heiko
% Oberdiek's \pkg{luatex} package instead.
%    \begin{macrocode}
%<*package>
\def\@tempa%
  {%
    \def\@tempa{}%
    \RequirePackage{luatex}%
    \RequirePackage{pdftexcmds}%
    \let\pdfstrcmp\pdf@strcmp
  }
\begingroup\expandafter\expandafter\expandafter\endgroup
\expandafter\ifx\csname directlua\endcsname\relax
\else
  \expandafter\@tempa
\fi
%</package>
%    \end{macrocode}
%    
% \subsection{The \tn{pdfstrcmp} primitive in \XeTeX{}}
%
% Only \pdfTeX{} has a primitive called \tn{pdfstrcmp}. The \XeTeX{}
% version is just \tn{strcmp}, so there is some shuffling to do.
%    \begin{macrocode}
\begingroup\expandafter\expandafter\expandafter\endgroup
  \expandafter\ifx\csname pdfstrcmp\endcsname\relax
  \let\pdfstrcmp\strcmp
\fi
%    \end{macrocode}
%    
% \subsection{Engine requirements}
%
% The code currently requires functionality equivalent to \tn{pdfstrcmp}
% in addition to \eTeX{}. The former is therefore used as a test for
% a suitable engine.
%    \begin{macrocode}
\begingroup\expandafter\expandafter\expandafter\endgroup
\expandafter\ifx\csname pdfstrcmp\endcsname\relax
%<*package>
  \PackageError{expl3}{Required primitives not found}
    {%
      LaTeX3 requires the e-TeX primitives and \string\pdfstrcmp.\MessageBreak
      \MessageBreak
      These are available in engine versions:\MessageBreak
      - pdfTeX 1.30\MessageBreak
      - XeTeX 0.9994\MessageBreak
      - LuaTeX 0.40\MessageBreak
      or later.\MessageBreak
      \MessageBreak
      Loading of expl3 will abort!%
    }
  \expandafter\endinput
%</package>
%<*initex>
  \newlinechar`\^^J\relax
  \errhelp{%
      LaTeX3 requires the e-TeX primitives and \pdfstrcmp.^^J%
      ^^J%
      These are available in engine versions:^^J%
      - pdfTeX 1.30^^J%
      - XeTeX 0.9994^^J%
      - LuaTeX 0.40^^J%
      or later.^^J%
      ^^J%
      For pdfTeX and XeTeX the '-etex' command-line switch is also
      needed.^^J%
       ^^J%
      Format building will abort!%
  }
  \errmessage{Required primitives not found}%
  \expandafter\end
%</initex>
\fi
%    \end{macrocode}
%
% \subsection{Package-specific code part two}
%
% \begin{macro}{\ExplSyntaxOff, \ExplSyntaxOn}
%   Experimental syntax switching is set up here for the package-loading
%   process.  These are redefined in \pkg{expl3} for the package and in
%   \pkg{l3final} for the format.
%    \begin{macrocode}
%<*package>
\protected\edef\ExplSyntaxOff
  {%
    \catcode   9 = \the\catcode   9\relax
    \catcode  32 = \the\catcode  32\relax
    \catcode  34 = \the\catcode  34\relax
    \catcode  38 = \the\catcode  38\relax
    \catcode  58 = \the\catcode  58\relax
    \catcode  94 = \the\catcode  94\relax
    \catcode  95 = \the\catcode  95\relax
    \catcode 124 = \the\catcode 124\relax
    \catcode 126 = \the\catcode 126\relax
    \endlinechar = \the\endlinechar\relax
    \chardef\csname\detokenize{l__kernel_expl_bool}\endcsname = 0 \relax
  }
\protected\edef\ExplSyntaxOn
  {
    \catcode 9   = 9  \relax
    \catcode 32  = 9  \relax
    \catcode 34  = 12 \relax
    \catcode 58  = 11 \relax
    \catcode 94  = 7  \relax
    \catcode 95  = 11 \relax
    \catcode 124 = 12 \relax
    \catcode 126 = 10 \relax
    \endlinechar = 32 \relax
    \chardef\csname\detokenize{l__kernel_expl_bool}\endcsname = 1 \relax
  }
%</package>
%    \end{macrocode}
% \end{macro}
%
% \begin{variable}{\l__kernel_expl_bool}
%   The status for experimental code syntax: this is off at present. This
%   code is used by both the package and the format.
%    \begin{macrocode}
\expandafter\chardef\csname\detokenize{l__kernel_expl_bool}\endcsname = 0 \relax
%    \end{macrocode}
%\end{variable}
%
% \subsection{Dealing with package-mode meta-data}
%
% \begin{macro}{\GetIdInfo}
%   This is implemented right at the start of \texttt{l3bootstrap.dtx}.
% \end{macro}
%
% \begin{macro}{\ProvidesExplPackage, \ProvidesExplClass, \ProvidesExplFile}
%   For other packages and classes building on this one it is convenient
%   not to need \cs{ExplSyntaxOn} each time.
%    \begin{macrocode}
%<*package>
\protected\def\ProvidesExplPackage#1#2#3#4%
  {%
    \ProvidesPackage{#1}[#2 v#3 #4]%
    \ExplSyntaxOn
  }
\protected\def\ProvidesExplClass#1#2#3#4%
  {%
    \ProvidesClass{#1}[#2 v#3 #4]%
    \ExplSyntaxOn
  }
\protected\def\ProvidesExplFile#1#2#3#4%
  {%
    \ProvidesFile{#1}[#2 v#3 #4]%
    \ExplSyntaxOn
  }
%</package>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@pushfilename, \@popfilename}
%   The idea here is to use \LaTeXe{}'s \tn{@pushfilename} and
%   \tn{@popfilename} to track the current syntax status. This can be
%   achieved by saving the current status flag at each push to a stack,
%   then recovering it at the pop stage and checking if the code
%   environment should still be active.
%    \begin{macrocode}
%<*package>
\edef\@pushfilename
  {%
    \edef\expandafter\noexpand
      \csname\detokenize{l_@@_status_stack_tl}\endcsname
      {%
        \noexpand\ifodd\expandafter\noexpand
          \csname\detokenize{l__kernel_expl_bool}\endcsname
          1%
        \noexpand\else
          0%
        \noexpand\fi
        \expandafter\noexpand
          \csname\detokenize{l_@@_status_stack_tl}\endcsname
      }%
    \ExplSyntaxOff
    \unexpanded\expandafter{\@pushfilename}%
  }
\edef\@popfilename
  {%
    \unexpanded\expandafter{\@popfilename}%
    \noexpand\if a\expandafter\noexpand\csname
      \detokenize{l_@@_status_stack_tl}\endcsname a%
      \ExplSyntaxOff
    \noexpand\else
      \noexpand\expandafter
        \expandafter\noexpand\csname
          \detokenize{@@_status_pop:w}\endcsname
          \expandafter\noexpand\csname
            \detokenize{l_@@_status_stack_tl}\endcsname
          \noexpand\@nil
   \noexpand\fi
  }
%</package>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\l_@@_status_stack_tl}
%   As \pkg{expl3} itself cannot be loaded with the code environment
%   already active, at the end of the package \cs{ExplSyntaxOff} can
%   safely be called.
%    \begin{macrocode}
%<*package>
\@namedef{\detokenize{l_@@_status_stack_tl}}{0}
%</package>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[aux]{\@@_status_pop:w}
%   The pop auxiliary function removes the first item from the stack,
%   saves the rest of the stack and then does the test. As
%   \cs{ExplSyntaxOff} is already defined as a protected macro, there
%   is no need for \tn{noexpand} here.
%    \begin{macrocode}
%<*package>
\expandafter\edef\csname\detokenize{@@_status_pop:w}\endcsname#1#2\@nil
  {%
    \def\expandafter\noexpand
      \csname\detokenize{l_@@_status_stack_tl}\endcsname{#2}%
    \noexpand\ifodd#1\space
      \noexpand\expandafter\noexpand\ExplSyntaxOn
    \noexpand\else
      \noexpand\expandafter\ExplSyntaxOff
    \noexpand\fi
  }
%</package>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[int]{\__expl_package_check:}
%   We want the \pkg{expl3} bundle to be loaded \enquote{as one};
%   this command is used to ensure that one of the |l3| packages isn't loaded
%   on its own.
%    \begin{macrocode}
%<*package>
\expandafter\protected\expandafter\def
  \csname\detokenize{__expl_package_check:}\endcsname
  {%
    \@ifpackageloaded{expl3}
      {}
      {%
        \PackageError{expl3}
          {Cannot load the expl3 modules separately}
          {%
            The expl3 modules cannot be loaded separately;\MessageBreak
            please \string\usepackage\string{expl3\string} instead.%
          }%
      }%
  }
%</package>
%    \end{macrocode}
% \end{macro}
%
% \subsection{The \LaTeX3 code environment}
%
% The code environment is now set up for the format: the package deals
% with this using \cs{ProvidesExplPackage}.
%    \begin{macrocode}
%<*initex>
\catcode 9   = 9  \relax
\catcode 32  = 9  \relax
\catcode 34  = 12 \relax
\catcode 58  = 11 \relax
\catcode 94  = 7  \relax
\catcode 95  = 11 \relax
\catcode 124 = 12 \relax
\catcode 126 = 10 \relax
\endlinechar = 32 \relax
%</initex>
%    \end{macrocode}
%
% \begin{macro}{\ExplSyntaxOn, \ExplSyntaxOff}
%  The idea here is that multiple \cs{ExplSyntaxOn} calls are not
%  going to mess up category codes, and that multiple calls to
%  \cs{ExplSyntaxOff} are also not wasting time.
%    \begin{macrocode}
%<*initex>
\protected \def \ExplSyntaxOn
  {
    \bool_if:NF \l__kernel_expl_bool
      {
        \cs_set_protected_nopar:Npx \ExplSyntaxOff
          {
            \char_set_catcode:nn { 9 }   { \char_value_catcode:n { 9 } }
            \char_set_catcode:nn { 32 }  { \char_value_catcode:n { 32 } }
            \char_set_catcode:nn { 34 }  { \char_value_catcode:n { 34 } }
            \char_set_catcode:nn { 38 }  { \char_value_catcode:n { 38 } }
            \char_set_catcode:nn { 58 }  { \char_value_catcode:n { 58 } }
            \char_set_catcode:nn { 94 }  { \char_value_catcode:n { 94 } }
            \char_set_catcode:nn { 95 }  { \char_value_catcode:n { 95 } }
            \char_set_catcode:nn { 124 } { \char_value_catcode:n { 124 } }
            \char_set_catcode:nn { 126 } { \char_value_catcode:n { 126 } }
            \tex_endlinechar:D =
              \tex_the:D \tex_endlinechar:D \scan_stop:
            \bool_set_false:N \l__kernel_expl_bool
            \cs_set_protected_nopar:Npn \ExplSyntaxOff { }
          }
      }
    \char_set_catcode_ignore:n           { 9 }   % tab
    \char_set_catcode_ignore:n           { 32 }  % space
    \char_set_catcode_other:n            { 34 }  % double quote
    \char_set_catcode_alignment:n        { 38 }  % ampersand
    \char_set_catcode_letter:n           { 58 }  % colon
    \char_set_catcode_math_superscript:n { 94 }  % circumflex
    \char_set_catcode_letter:n           { 95 }  % underscore
    \char_set_catcode_other:n            { 124 } % pipe
    \char_set_catcode_space:n            { 126 } % tilde
    \tex_endlinechar:D = 32 \scan_stop:
    \bool_set_true:N \l__kernel_expl_bool
  }
\protected \def \ExplSyntaxOff { }
%</initex>
%    \end{macrocode}
% \end{macro}
%
% \begin{variable}{\l__kernel_expl_bool}
%   A flag to show the current syntax status.
%    \begin{macrocode}
%<*initex>
\chardef \l__kernel_expl_bool = 0 ~
%</initex>
%    \end{macrocode}
% \end{variable}
% 
% \subsection{Deprecated functions}
% 
% Deprecated 2012-06-19 for removal after 2012-12-31.
%
% \begin{macro}{\ExplSyntaxNamesOn, \ExplSyntaxNamesOff}
%   These can be set up early, as they are not used anywhere in the
%   package or format itself. Using an \tn{edef} here makes the
%   definitions that bit clearer later.
%    \begin{macrocode}
\protected\edef\ExplSyntaxNamesOn
  {%
    \expandafter\noexpand
      \csname\detokenize{char_set_catcode_letter:n}\endcsname{58}%
    \expandafter\noexpand
      \csname\detokenize{char_set_catcode_letter:n}\endcsname{95}%
  }
\protected\edef\ExplSyntaxNamesOff
  {%
    \expandafter\noexpand
      \csname\detokenize{char_set_catcode_other:n}\endcsname{58}%
    \expandafter\noexpand
      \csname\detokenize{char_set_catcode_math_subscript:n}\endcsname{95}%
  }
%    \end{macrocode}
% \end{macro}
%
%    \begin{macrocode}
%</initex|package>
%    \end{macrocode}
%
% \end{implementation}
%
% \PrintIndex