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1%D \module
2%D   [       file=catc-sym,
3%D        version=1997.01.03, % moved code
4%D          title=\CONTEXT\ Catcode Macros,
5%D       subtitle=Some Handy Constants,
6%D         author=Hans Hagen,
7%D           date=\currentdate,
8%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
9%C
10%C This module is part of the \CONTEXT\ macro||package and is
11%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
12%C details.
13
14%D We want to have access to the raw alternatives of the special characters. We
15%D use a \type {\xdef} instead of \type {\let} because we need an expandable token
16%D in a \type {\write}.
17
18\bgroup
19
20\catcode`B=\begingroupcatcode
21\catcode`E=\endgroupcatcode
22\catcode`.=\escapecatcode
23
24.catcode `.{ 12 .xdef .letterleftbrace        B.string{E
25.catcode `.} 12 .xdef .letterrightbrace       B.string}E
26.catcode `.& 12 .xdef .letterampersand        B.string&E
27.catcode `.< 12 .xdef .letterless             B.string<E
28.catcode `.> 12 .xdef .lettermore             B.string>E
29.catcode `.# 12 .xdef .letterhash             B.string#E
30.catcode `." 12 .xdef .letterdoublequote      B.string"E
31.catcode `.' 12 .xdef .lettersinglequote      B.string'E
32.catcode `.$ 12 .xdef .letterdollar           B.string$E
33.catcode `.% 12 .xdef .letterpercent          B.string%E
34.catcode `.^ 12 .xdef .letterhat              B.string^E
35.catcode `._ 12 .xdef .letterunderscore       B.string_E
36.catcode `.| 12 .xdef .letterbar              B.string|E
37.catcode `.~ 12 .xdef .lettertilde            B.string~E
38.catcode `.\ 12 .xdef .letterbackslash        B.string\E
39.catcode `./ 12 .xdef .letterslash            B.string/E
40.catcode `.? 12 .xdef .letterquestionmark     B.string?E
41.catcode `.! 12 .xdef .letterexclamationmark  B.string!E
42.catcode `.@ 12 .xdef .letterat               B.string@E
43.catcode `.: 12 .xdef .lettercolon            B.string:E
44
45.catcode `.( 12 .xdef .letterleftparenthesis  B.string(E
46.catcode `.) 12 .xdef .letterrightparenthesis B.string)E
47.catcode `.[ 12 .xdef .letterleftbracket      B.string[E
48.catcode `.] 12 .xdef .letterrightbracket     B.string]E
49
50         .global .let .letterescape     .letterbackslash
51         .global .let .letterbgroup     .letterleftbrace
52         .global .let .letteregroup     .letterrightbrace
53         .global .let .letteropenbrace  .letterleftbrace
54         .global .let .letterclosebrace .letterrightbrace
55
56.egroup
57
58\bgroup
59
60\catcode`_=\lettercatcode
61
62%xdef\_n_u_l_{\expandafter\string\Uchar1} % nul(l)
63%xdef\_s_o_h_{\expandafter\string\Uchar1} % start of header       ^^^^0001
64\xdef\_s_t_x_{\expandafter\string\Uchar2} % start of text         ^^^^0002
65\xdef\_e_t_x_{\expandafter\string\Uchar3} % end of text           ^^^^0003
66\xdef\_e_o_t_{\expandafter\string\Uchar4} % end of transmission   ^^^^0004
67%xdef\_e_n_q_{\expandafter\string\Uchar5} % enquiry
68%xdef\_a_c_k_{\expandafter\string\Uchar6} % aknowledgement
69
70\egroup
71
72%D \macros
73%D   {uncatcodespecials,setnaturalcatcodes,setnormalcatcodes,
74%D    uncatcodecharacters,uncatcodeallcharacters,
75%D    uncatcodespacetokens}
76%D
77%D The following macros are more or less replaced by switching
78%D to a catcode table (which we simulate in \MKII) but we keep
79%D them for convenience and compatibility. Some old engine code
80%D has been removed.
81
82\protected\def\uncatcodespecials     {\setcatcodetable\nilcatcodes \uncatcodespacetokens}
83\protected\def\setnaturalcatcodes    {\setcatcodetable\nilcatcodes}
84\protected\def\setnormalcatcodes     {\setcatcodetable\ctxcatcodes} % maybe \texcatcodes
\protected\def\uncatcodecharacters   {\setcatcodetable\nilcatcodes} % was fast version, gone now
\protected\def\uncatcodeallcharacters{\setcatcodetable\nilcatcodes} % was slow one, with restore
87
88\protected\def\uncatcodespacetokens
89  {\catcode\spaceasciicode    \spacecatcode
90   \catcode\tabasciicode      \spacecatcode
91   \catcode\formfeedasciicode \endoflinecatcode
92   \catcode\endoflineasciicode\endoflinecatcode
93   \catcode\delasciicode      \ignorecatcode}
94
95%D \macros
96%D   {setverbosecharacter,setverbosecscharacters}
97%D
98%D Next follows a definition that lets some shortcuts expand to
99%D themselves. This macro is meant for \POSTSCRIPT\ and \PDF\
100%D code passed on to the backend.
101
102\newtoks\everyverbosechacters
103
104\protected\def\setverbosecscharacter#1%
105  {\edef#1{\string#1}}
106
\protected\def\setverbosecscharacters
108  {\the\everyverbosechacters}
109
110\bgroup
111
112    % if used often we can move the code inline
113
114    \catcode\barasciicode  \activecatcode
115    \catcode\tildeasciicode\activecatcode
116
117    \global \everyverbosechacters =
118      {\setverbosecscharacter |\setverbosecscharacter ~% context specific
119       \setverbosecscharacter\|\setverbosecscharacter\~%
120       \setverbosecscharacter\:\setverbosecscharacter\;%
121       \setverbosecscharacter\+\setverbosecscharacter\-%
122       \setverbosecscharacter\[\setverbosecscharacter\]%
123       \setverbosecscharacter\.\setverbosecscharacter\\%
124       \setverbosecscharacter\)\setverbosecscharacter\(%
125       \setverbosecscharacter\0\setverbosecscharacter\1%
126       \setverbosecscharacter\2\setverbosecscharacter\3%
127       \setverbosecscharacter\4\setverbosecscharacter\5%
128       \setverbosecscharacter\6\setverbosecscharacter\7%
129       \setverbosecscharacter\8\setverbosecscharacter\9%
130       \setverbosecscharacter\n\setverbosecscharacter\s%
131       \setverbosecscharacter\/}
132
133\egroup
134
135%D (Inspired by a discussion on the \CONTEXT\ mailing list)
136%D
137%D In \TEX\ each character can have one of 16 catcodes. This way the
138%D backslash, dollar, ampersand, hash and some more characters get
139%D their  special meaning. If you want to process tokens under a
140%D certain catcode  regime, passing arguments can interfere badly.
141%D
142%D \startbuffer[a]
143%D \def\whatever#1{[#1]}
144%D \whatever{whatever \type {\whatever{you want}} $or$ not!}
145%D \stopbuffer
146%D
147%D \typebuffer[a]
148%D
149%D Here we pass an argument to \type {\whatever} but part of that
150%D argument is to be processed under a different catcode regime, i.e.\
151%D all characters that need to be typeset verbatim need to get
152%D the catcode that makes it a letter. This is what we get when we typeset
153%D the text verbatim:
154%D
155%D \starttyping
156%D whatever \type {\whatever{you want}} $or$ not!
157%D \stoptyping
158%D
159%D However, when passed to \type {\whatever} we get:
160%D
161%D \getbuffer[a]
162%D
163%D In \ETEX\ one can use  \type {\scantokens} to circumvent this problem.
164%D
165%D \startbuffer[b]
166%D \def\rescan#1{\scantokens{#1}}
167%D \def\whatever#1{[\rescan{#1}]}
168%D \whatever{whatever \type {\whatever{you want}} $or$ not!}
169%D \stopbuffer
170%D
171%D \getbuffer[b] \typebuffer[b]
172%D
173%D This time the \type {\whatever} call gives:
174%D
175%D \getbuffer[b]
176%D
177%D In this example, two spaces have crept in. The first one, after the
178%D macro name, is inserted by \TEX\ and cannot be avoided. The last space
179%D is inserted by \type {\scantokens}, and is the consequence of the fact
180%D that this macro mimics reading from a file. You can avoid the last
181%D space by a slightly different definition:
182%D
183%D \startbuffer[c]
184%D \def\rescan#1{\scantokens{#1\ignorespaces}}
185%D \def\whatever#1{[\rescan{#1}]}
186%D \whatever{whatever \type {\whatever{you want}} $or$ not!}
187%D \stopbuffer
188%D
189%D \typebuffer[c]
190%D
191%D Unfortunately we still keep the first space, but at least it's better than
192%D a failure:
193%D
194%D \getbuffer[c]
195
196\def\rescan           #1{\scantokens{#1\ignorespaces}}
197\def\rescanwithsetup#1#2{\begingroup\directsetup{#1}\scantokens{#2\ignorespaces}\endgroup}
198
199\ifx\scantextokens\undefined \else
200    \def\rescan           #1{\scantextokens{#1}}
201    \def\rescanwithsetup#1#2{\begingroup\directsetup{#1}\scantextokens{#2}\endgroup}
202\fi
203
204\endinput
205