1docstrip(n) Literate programming tool docstrip(n)
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6
8 docstrip - Docstrip style source code extraction
9
11 package require Tcl 8.4
12 package require docstrip ?1.2?
14 docstrip::extract text terminals ?option value ...?
16 docstrip::sourcefrom filename terminals ?option value ...?
18_________________________________________________________________
20
22 Docstrip is a tool created to support a brand of Literate Programming.
23 It is most common in the (La)TeX community, where it is being used for
24 pretty much everything from the LaTeX core and up, but there is nothing
25 about docstrip which prevents using it for other types of software.
26 In short, the basic principle of literate programming is that program
28 source should primarily be written and structured to suit the develop‐
29 ers (and advanced users who want to peek "under the hood"), not to suit
30 the whims of a compiler or corresponding source code consumer. This
31 means literate sources often need some kind of "translation" to an
32 illiterate form that dumb software can understand. The docstrip Tcl
33 package handles this translation.
34 Even for those who do not whole-hartedly subscribe to the philosophy
36 behind literate programming, docstrip can bring greater clarity to in
37 particular:
38 · programs employing non-obvious mathematics
40 · projects where separate pieces of code, perhaps in different
42 languages, need to be closely coordinated.
43 The first is by providing access to much more powerful typographical
45 features for source code comments than are possible in plain text. The
46 second is because all the separate pieces of code can be kept next to
47 each other in the same source file.
48 The way it works is that the programmer edits directly only one or sev‐
50 eral "master" source code files, from which docstrip generates the more
51 traditional "source" files compilers or the like would expect. The mas‐
52 ter sources typically contain a large amount of documentation of the
53 code, sometimes even in places where the code consumers would not allow
54 any comments. The etymology of "docstrip" is that this documentation
55 was stripped away (although "code extraction" might be a better
56 description, as it has always been a matter of copying selected pieces
57 of the master source rather than deleting text from it). The docstrip
58 Tcl package contains a reimplementation of the basic extraction func‐
59 tionality from the docstrip program, and thus makes it possible for a
60 Tcl interpreter to read and interpret the master source files directly.
61 Readers who are not previously familiar with docstrip but want to know
63 more about it may consult the following sources.
64 [1] The tclldoc package and class, http://tug.org/tex-ar‐
66 chive/macros/latex/contrib/tclldoc/.
67 [2] The DocStrip utility, http://tug.org/tex-ar‐
69 chive/macros/latex/base/docstrip.dtx.
70 [3] The doc and shortvrb Packages, http://tug.org/tex-ar‐
72 chive/macros/latex/base/doc.dtx.
73 [4] Chapter 14 of The LaTeX Companion (second edition), Addison-Wes‐
75 ley, 2004; ISBN 0-201-36299-6.
76
78 The basic unit docstrip operates on are the lines of a master source
79 file. Extraction consists of selecting some of these lines to be copied
80 from input text to output text. The basic distinction is that between
81 code lines (which are copied and do not begin with a percent character)
82 and comment lines (which begin with a percent character and are not
83 copied).
84 docstrip::extract [join {
86 {% comment}
87 {% more comment !"#$%&/(}
88 {some command}
89 { % blah $blah "Not a comment."}
90 {% abc; this is comment}
91 {# def; this is code}
92 {ghi}
93 {% jkl}
94 } \n] {}
95 returns the same sequence of lines as
97 join {
99 {some command}
100 { % blah $blah "Not a comment."}
101 {# def; this is code}
102 {ghi} ""
103 } \n
104 It does not matter to docstrip what format is used for the documenta‐
106 tion in the comment lines, but in order to do better than plain text
107 comments, one typically uses some markup language. Most commonly LaTeX
108 is used, as that is a very established standard and also provides the
109 best support for mathematical formulae, but the docstrip::util package
110 also gives some support for doctools-like markup.
111 Besides the basic code and comment lines, there are also guard lines,
113 which begin with the two characters '%<', and meta-comment lines, which
114 begin with the two characters ´%%'. Within guard lines there is fur‐
115 thermore the distinction between verbatim guard lines, which begin with
116 '%<<', and ordinary guard lines, where the '%<' is not followed by
117 another '<'. The last category is by far the most common.
118 Ordinary guard lines conditions extraction of the code line(s) they
120 guard by the value of a boolean expression; the guarded block of code
121 lines will only be included if the expression evaluates to true. The
122 syntax of an ordinary guard line is one of
123 '%' '<' STARSLASH EXPRESSION '>'
125 '%' '<' PLUSMINUS EXPRESSION '>' CODE
126 where
128 STARSLASH ::= '*' | '/'
130 PLUSMINUS ::= '+' | '-' |
131 EXPRESSION ::= SECONDARY | SECONDARY ',' EXPRESSION
132 | SECONDARY '|' EXPRESSION
133 SECONDARY ::= PRIMARY | PRIMARY '&' SECONDARY
134 PRIMARY ::= TERMINAL | '!' PRIMARY | '(' EXPRESSION ')'
135 CODE ::= { any character except end-of-line }
136 Comma and vertical bar both denote 'or'. Ampersand denotes 'and'.
138 Exclamation mark denotes 'not'. A TERMINAL can be any nonempty string
139 of characters not containing '>', '&', '|', comma, '(', or ')',
140 although the docstrip manual is a bit restrictive and only guarantees
141 proper operation for strings of letters (although even the LaTeX core
142 sources make heavy use also of digits in TERMINALs). The second argu‐
143 ment of docstrip::extract is the list of those TERMINALs that should
144 count as having the value 'true'; all other TERMINALs count as being
145 'false' when guard expressions are evaluated.
146 In the case of a '%<*EXPRESSION>' guard, the lines guarded are all
148 lines up to the next '%</EXPRESSION>' guard with the same EXPRESSION
149 (compared as strings). The blocks of code delimited by such '*' and '/'
150 guard lines must be properly nested.
151 set text [join {
153 {begin}
154 {%<*foo>}
155 {1}
156 {%<*bar>}
157 {2}
158 {%</bar>}
159 {%<*!bar>}
160 {3}
161 {%</!bar>}
162 {4}
163 {%</foo>}
164 {5}
165 {%<*bar>}
166 {6}
167 {%</bar>}
168 {end}
169 } \n]
170 set res [docstrip::extract $text foo]
171 append res [docstrip::extract $text {foo bar}]
172 append res [docstrip::extract $text bar]
173 sets $res to the result of
175 join {
177 {begin}
178 {1}
179 {3}
180 {4}
181 {5}
182 {end}
183 {begin}
184 {1}
185 {2}
186 {4}
187 {5}
188 {6}
189 {end}
190 {begin}
191 {5}
192 {6}
193 {end} ""
194 } \n
195 In guard lines without a '*', '/', '+', or '-' modifier after the ´%<',
197 the guard applies only to the CODE following the '>' on that single
198 line. A '+' modifier is equivalent to no modifier. A '-' modifier is
199 like the case with no modifier, but the expression is implicitly
200 negated, i.e., the CODE of a '%<-' guard line is only included if the
201 expression evaluates to false.
202 Metacomment lines are "comment lines which should not be stripped
204 away", but be extracted like code lines; these are sometimes used for
205 copyright notices and similar material. The '%%' prefix is however not
206 kept, but substituted by the current -metaprefix, which is customarily
207 set to some "comment until end of line" character (or character
208 sequence) of the language of the code being extracted.
209 set text [join {
211 {begin}
212 {%<foo> foo}
213 {%<+foo>plusfoo}
214 {%<-foo>minusfoo}
215 {middle}
216 {%% some metacomment}
217 {%<*foo>}
218 {%%another metacomment}
219 {%</foo>}
220 {end}
221 } \n]
222 set res [docstrip::extract $text foo -metaprefix {# }]
223 append res [docstrip::extract $text bar -metaprefix {#}]
224 sets $res to the result of
226 join {
228 {begin}
229 { foo}
230 {plusfoo}
231 {middle}
232 {# some metacomment}
233 {# another metacomment}
234 {end}
235 {begin}
236 {minusfoo}
237 {middle}
238 {# some metacomment}
239 {end} ""
240 } \n
241 Verbatim guards can be used to force code line interpretation of a
243 block of lines even if some of them happen to look like any other type
244 of lines to docstrip. A verbatim guard has the form '%<<END-TAG' and
245 the verbatim block is terminated by the first line that is exactly
246 '%END-TAG'.
247 set text [join {
249 {begin}
250 {%<*myblock>}
251 {some stupid()}
252 { #computer<program>}
253 {%<<QQQ-98765}
254 {% These three lines are copied verbatim (including percents}
255 {%% even if -metaprefix is something different than %%).}
256 {%</myblock>}
257 {%QQQ-98765}
258 { using*strange@programming<language>}
259 {%</myblock>}
260 {end}
261 } \n]
262 set res [docstrip::extract $text myblock -metaprefix {# }]
263 append res [docstrip::extract $text {}]
264 sets $res to the result of
266 join {
268 {begin}
269 {some stupid()}
270 { #computer<program>}
271 {% These three lines are copied verbatim (including percents}
272 {%% even if -metaprefix is something different than %%).}
273 {%</myblock>}
274 { using*strange@programming<language>}
275 {end}
276 {begin}
277 {end} ""
278 } \n
279 The processing of verbatim guards takes place also inside blocks of
281 lines which due to some outer block guard will not be copied.
282 The final piece of docstrip syntax is that extraction stops at a line
284 that is exactly "\endinput"; this is often used to avoid copying random
285 whitespace at the end of a file. In the unlikely case that one wants
286 such a code line, one can protect it with a verbatim guard.
287
289 The package defines two commands.
290 docstrip::extract text terminals ?option value ...?
292 The extract command docstrips the text and returns the extracted
293 lines of code, as a string with each line terminated with a new‐
294 line. The terminals is the list of those guard expression termi‐
295 nals which should evaluate to true. The available options are:
296 -annotate lines
298 Requests the specified number of lines of annotation to
299 follow each extracted line in the result. Defaults to 0.
300 Annotation lines are mostly useful when the extracted
301 lines are to undergo some further transformation. A first
302 annotation line is a list of three elements: line type,
303 prefix removed in extraction, and prefix inserted in
304 extraction. The line type is one of: 'V' (verbatim), ´M'
305 (metacomment), '+' (+ or no modifier guard line), '-' (-
306 modifier guard line), '.' (normal line). A second annota‐
307 tion line is the source line number. A third annotation
308 line is the current stack of block guards. Requesting
309 more than three lines of annotation is currently not sup‐
310 ported.
311 -metaprefix string
313 The string by which the '%%' prefix of a metacomment line
314 will be replaced. Defaults to '%%'. For Tcl code this
315 would typically be '#'.
316 -onerror keyword
318 Controls what will be done when a format error in the
319 text being processed is detected. The settings are:
320 ignore Just ignore the error; continue as if nothing hap‐
322 pened.
323 puts Write an error message to stderr, then continue
325 processing.
326 throw Throw an error. ::errorCode is set to a list whose
328 first element is DOCSTRIP, second element is the
329 type of error, and third element is the line num‐
330 ber where the error is detected. This is the
331 default.
332 -trimlines boolean
334 Controls whether spaces at the end of a line should be
335 trimmed away before the line is processed. Defaults to
336 true.
337 It should be remarked that the terminals are often called "options" in
338 the context of the docstrip program, since these specify which optional
339 code fragments should be included.
340 docstrip::sourcefrom filename terminals ?option value ...?
342 The sourcefrom command is a docstripping emulation of source. It
343 opens the file filename, reads it, closes it, docstrips the con‐
344 tents as specified by the terminals, and evaluates the result in
345 the local context of the caller, during which time the info
346 script value will be the filename. The options are passed on to
347 fconfigure to configure the file before its contents are read.
348 The -metaprefix is set to '#', all other extract options have
349 their default values.
350
352 The file format (as described above) determines whether a master source
353 code file can be processed correctly by docstrip, but the usefulness of
354 the format is to no little part also dependent on that the code and
355 comment lines together constitute a well-formed document.
356 For a document format that does not require any non-Tcl software, see
358 the ddt2man command in the docstrip::util package. It is suggested that
359 files employing that document format are given the suffix ".ddt", to
360 distinguish them from the more traditional LaTeX-based ".dtx" files.
361 Master source files with ".dtx" extension are usually set up so that
363 they can be typeset directly by latex without any support from other
364 files. This is achieved by beginning the file with the lines
365 % \iffalse
367 %<*driver>
368 \documentclass{tclldoc}
369 \begin{document}
370 \DocInput{filename.dtx}
371 \end{document}
372 %</driver>
373 % \fi
374 or some variation thereof. The trick is that the file gets read twice.
376 With normal LaTeX reading rules, the first two lines are comments and
377 therefore ignored. The third line is the document preamble, the fourth
378 line begins the document body, and the sixth line ends the document, so
379 LaTeX stops there -- non-comments below that point in the file are
380 never subjected to the normal LaTeX reading rules. Before that, how‐
381 ever, the \DocInput command on the fifth line is processed, and that
382 does two things: it changes the interpretation of '%' from "comment" to
383 "ignored", and it inputs the file specified in the argument (which is
384 normally the name of the file the command is in). It is this second
385 time that the file is being read that the comments and code in it are
386 typeset.
387 The function of the \iffalse ... \fi is to skip lines two to seven on
389 this second time through; this is similar to the "if 0 { ... }" idiom
390 for block comments in Tcl code, and it is needed here because (amongst
391 other things) the \documentclass command may only be executed once. The
392 function of the <driver> guards is to prevent this short piece of LaTeX
393 code from being extracted by docstrip. The total effect is that the
394 file can function both as a LaTeX document and as a docstrip master
395 source code file.
396 It is not necessary to use the tclldoc document class, but that does
398 provide a number of features that are convenient for ".dtx" files con‐
399 taining Tcl code. More information on this matter can be found in the
400 references above.
401
403 docstrip_util
404
407 Copyright (c) 2003-2005 Lars Hellström <Lars dot Hellstrom at residenset dot net>
408docstrip 1.2 docstrip(n)