1Text::WordDiff(3) User Contributed Perl Documentation Text::WordDiff(3)
2
6 Text::WordDiff - Track changes between documents
7
9 use Text::WordDiff;
10 my $diff = word_diff 'file1.txt', 'file2.txt', { STYLE => 'HTML' };
12 my $diff = word_diff \$string1, \$string2, { STYLE => 'ANSIColor' };
13 my $diff = word_diff \*FH1, \*FH2; \%options;
14 my $diff = word_diff \&reader1, \&reader2;
15 my $diff = word_diff \@records1, \@records2;
16 # May also mix input types:
18 my $diff = word_diff \@records1, 'file_B.txt';
19
21 This module is a variation on the lovely Text::Diff module. Rather
22 than generating traditional line-oriented diffs, however, it generates
23 word-oriented diffs. This can be useful for tracking changes in
24 narrative documents or documents with very long lines. To diff source
25 code, one is still best off using Text::Diff. But if you want to see
26 how a short story changed from one version to the next, this module
27 will do the job very nicely.
28 What is a Word?
30 I'm glad you asked! Well, sort of. It's a really hard question to
31 answer. I consulted a number of sources, but really just did my best to
32 punt on the question by reformulating it as, "How do I split text up
33 into individual words?" The short answer is to split on word
34 boundaries. However, every word has two boundaries, one at the
35 beginning and one at the end. So splitting on "/\b/" didn't work so
36 well. What I really wanted to do was to split on the beginning of every
37 word. Fortunately, _Mastering Regular Expressions_ has a recipe for
38 that: "/(?<!\w)(?=\w)/". I've borrowed this regular expression for use
39 in Perls before 5.6.x, but go for the Unicode variant in 5.6.0 and
40 newer: "/(?<!\p{IsWord})(?=\p{IsWord})/". With either of these regular
41 expressions, this sentence, for example, would be split up into the
42 following tokens:
43 my @words = (
45 'With ',
46 'either ',
47 'of ',
48 'these ',
49 'regular ',
50 "expressions,\n",
51 'this ',
52 'sentence, ',
53 'for ',
54 'example, ',
55 'would ',
56 'be ',
57 'split ',
58 'up ',
59 'into ',
60 'the ',
61 'following ',
62 'tokens:'
63 );
64 Note that this allows the tokens to include any spacing or punctuation
66 after each word. So it's not just comparing words, but word-like
67 tokens. This makes sense to me, at least, as the diff is between these
68 tokens, and thus leads to a nice word-and-space-and-punctation type
69 diff. It's not unlike what a word processor might do (although a lot of
70 them are character-based, but that seemed a bit extreme--feel free to
71 dupe this module into Text::CharDiff!).
72 Now, I acknowledge that there are localization issues with this
74 approach. In particular, it will fail with Chinese, Japanese, and
75 Korean text, as these languages don't put non-word characters between
76 words. Ideally, Test::WordDiff would then split on every charaters
77 (since a single character often equals a word), but such is not the
78 case when the "utf8" flag is set on a string. For example, This simple
79 script:
80 use strict;
82 use utf8;
83 use Data::Dumper;
84 my $string = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX';
85 my @tokens = split /(?<!\p{IsWord})(?=\p{IsWord})/msx, $string;
86 print Dumper \@tokens;
87 Outputs:
89 $VAR1 = [
91 "\x{bf08}\x{bf09}\x{bf18}\x{bf19}\x{bf1b}\x{bf1c}\x{bf1d}\x{bf40}\x{bf41}\x{bf44}\x{bf48}\x{bf50}\x{bf51}\x{bf55}\x{bf94}\x{bfb0}\x{bfc5}\x{bfcc}\x{bfcd}\x{bfd0}\x{bfd4}\x{bfdc}\x{bfdf}\x{bfe1}\x{c03c}\x{c051}\x{c058}\x{c05c}\x{c060}\x{c068}\x{c069}\x{c090}"
92 ];
93 Not so useful. It seems to be less of a problem if the "use utf8;" line
95 is commented out, in which case we get:
96 $VAR1 = [
98 'X',
99 'X',
100 'X',
101 'X',
102 'X',
103 'X',
104 'X',
105 'X',
106 'X',
107 'X',
108 'X',
109 'X',
110 'X',
111 'X',
112 'X',
113 'X',
114 'X',
115 'X',
116 'X',
117 'X',
118 'X',
119 'X',
120 'X',
121 'X',
122 '?',
123 '?X',
124 'X',
125 'X',
126 'X',
127 'X',
128 'X',
129 'X'
130 ];
131 Someone whose more familiar with non-space-using languages will have to
133 explain to me how I might be able to duplicate this pattern within the
134 scope of "use utf8;", seing as it may very well be important to have it
135 on in order to ensure proper character semantics.
136 However, if my word tokenization approach is just too naive, and you
138 decide that you need to take a different approach (maybe use
139 Lingua::ZH::Toke or similar module), you can still use this module;
140 you'll just have to tokenize your strings into words yourself, and pass
141 them to word_diff() as array references:
142 word_diff \@my_words1, \@my_words2;
144
146 word_diff() takes two arguments from which to draw input and an
147 optional hash reference of options to control its output. The first two
148 arguments contain the data to be diffed, and each may be in the form of
149 any of the following (that is, they can be in two different formats):
150 · String
152 A bare scalar will be assumed to be a file name. The file will be
154 opened and split up into words. word_diff() will also "stat" the
155 file to get the last modified time for use in the header, unless
156 the relevant option ("MTIME_A" or "MTIME_B") has been specified
157 explicitly.
158 · Scalar Reference
160 A scalar reference will be assumed to refer to a string. That
162 string will be split up into words.
163 · Array Reference
165 An array reference will be assumed to be a list of words.
167 · File Handle
169 A glob or IO::Handle-derived object will be read from and split up
171 into its constituent words.
172 The optional hash reference may contain the following options.
174 Additional options may be specified by the formattting class; see the
175 specific class for details.
176 · STYLE
178 "ANSIColor", "HTML" or an object or class name for a class
180 providing "file_header()", "hunk_header()", "same_items()",
181 "delete_items()", "insert_items()", "hunk_footer()" and
182 "file_footer()" methods. Defaults to "ANSIColor" for nice display
183 of diffs in an ANSI Color-supporting terminal.
184 If the package indicated by the "STYLE" has no "new()" method,
186 "word_diff()" will load it automatically (lazy loading). It will
187 then instantiate an object of that class, passing in the options
188 hash reference with which the formatting class can initialize the
189 object.
190 Styles may be specified as class names ("STYLE => "My::Foo""), in
192 which case they will be instantiated by calling the "new()"
193 construcctor and passing in the options hash reference, or as
194 objects ("STYLE => My::Foo->new").
195 The simplest way to implement your own formatting style is to
197 create a new class that inherits from Text::WordDiff::Base, wherein
198 the "new()" method is already provided, and the "file_header()"
199 returns a Unified diff-style header. All of the other formatting
200 methods simply return empty strings, and are therefore ripe for
201 overriding.
202 · FILENAME_A, MTIME_A, FILENAME_B, MTIME_B
204 The name of the file and the modification time "files" in epoch
206 seconds. Unless a defined value is specified for these options,
207 they will be filled in for each file when word_diff() is passed a
208 filename. If a filename is not passed in and "FILENAME_A" and
209 "FILENAME_B" are not defined, the header will not be printed by the
210 base formatting base class.
211 · OUTPUT
213 The method by which diff output should be, well, output. Examples
215 and their equivalent subroutines:
216 OUTPUT => \*FOOHANDLE, # like: sub { print FOOHANDLE shift() }
218 OUTPUT => \$output, # like: sub { $output .= shift }
219 OUTPUT => \@output, # like: sub { push @output, shift }
220 OUTPUT => sub { $output .= shift },
221 If "OUTPUT" is not defined, word_diff() will simply return the diff
223 as a string. If "OUTPUT" is a code reference, it will be called
224 once with the file header, once for each hunk body, and once for
225 each piece of content. If "OUTPUT" is an IO::Handle-derived object,
226 output will be sent to that handle.
227 · FILENAME_PREFIX_A, FILENAME_PREFIX_B
229 The string to print before the filename in the header. Defaults are
231 "---", "+++".
232 · DIFF_OPTS
234 A hash reference to be passed as the options to
236 "Algorithm::Diff->new". See Algorithm::Diff for details on
237 available options.
238
240 Text::WordDiff comes with two formatting classes:
241 Text::WordDiff::ANSIColor
243 This is the default formatting class. It emits a header and then
244 the diff content, with deleted text in bodfaced red and inserted
245 text in boldfaced green.
246 Text::WordDiff::HTML
248 Specify "STYLE => 'HTML'" to take advantage of this formatting
249 class. It outputs the diff content as XHTML, with deleted text in
250 "<del>" elements and inserted text in "<ins>" elements.
251 To implement your own formatting class, simply inherit from
253 Text::WordDiff::Base and override its methods as necssary. By default,
254 only the "file_header()" formatting method returns a value. All others
255 simply return empty strings, and are therefore ripe for overriding:
256 package My::WordDiff::Format;
258 use base 'Text::WordDiff::Base';
259 sub file_footer { return "End of diff\n"; }
261 The methods supplied by the base class are:
263 "new()"
265 Constructs and returns a new formatting object. It takes a single
266 hash reference as its argument, and uses it to construct the
267 object. The nice thing about this is that if you want to support
268 other options in your formatting class, you can just use them in
269 the formatting object constructed by the Text::WordDiff::Base class
270 and document that they can be passed as part of the options hash
271 refernce to word_diff().
272 "file_header()"
274 Called once for a single call to "word_diff()", this method outputs
275 the header for the whole diff. This is the only formatting method
276 in the base class that returns anything other than an empty string.
277 It collects the filenames from "filname_a()" and "filename_b()"
278 and, if they're defined, uses the relevant prefixes and
279 modification times to return a unified diff-style header.
280 "hunk_header()"
282 This method is called for each diff hunk. It should output any
283 necessary header for the hunk.
284 "same_items()"
286 This method is called for items that have not changed between the
287 two sequnces being compared. The unchanged items will be passed as
288 a list to the method.
289 "delete_items"
291 This method is called for items in the first sequence that are not
292 present in the second sequcne. The deleted items will be passed as
293 a list to the method.
294 "insert_items"
296 This method is called for items in the second sequence that are not
297 present in the first sequcne. The inserted items will be passed as
298 a list to the method.
299 "hunk_footer"
301 This method is called at the end of a hunk. It should output any
302 necessary content to close out the hunk.
303 "file_footer()"
305 This method is called once when the whole diff has been procssed.
306 It should output any necessary content to close out the diff file.
307 "filename_a"
309 This accessor returns the value specified for the "FILENAME_A"
310 option to word_diff().
311 "filename_b"
313 This accessor returns the value specified for the "FILENAME_B"
314 option to word_diff().
315 "mtime_a"
317 This accessor returns the value specified for the "MTIME_A" option
318 to word_diff().
319 "mtime_b"
321 This accessor returns the value specified for the "MTIME_B" option
322 to word_diff().
323 "filename_prefix_a"
325 This accessor returns the value specified for the
326 "FILENAME_PREFIX_A" option to word_diff().
327 "filename_prefix_b"
329 This accessor returns the value specified for the
330 "FILENAME_PREFIX_B" option to word_diff().
331
333 Text::Diff
334 Inspired the interface and implementation of this module. Thanks
335 Barry!
336 Text::ParagraphDiff
338 A module that attempts to diff paragraphs and the words in them.
339 Algorithm::Diff
341 The module that makes this all possible.
342
344 This module is stored in an open repository at the following address:
345 https://svn.kineticode.com/Text-WordDiff/trunk/
347 <https://svn.kineticode.com/Text-WordDiff/trunk/>
348 Patches against Text::WordDiff are welcome. Please send bug reports to
350 <bug-text-worddiff@rt.cpan.org>.
351
353 David Wheeler <david@kineticode.com>
354
356 Copyright (c) 2005-2008 David Wheeler. Some Rights Reserved.
357 This module is free software; you can redistribute it and/or modify it
359 under the same terms as Perl itself.
360perl v5.12.0 2010-05-07 Text::WordDiff(3)