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1 | =head1 NAME |
2 | |
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3 | version::Internals - Perl extension for Version Objects |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | Overloaded version objects for all modern versions of Perl. This documents |
8 | the internal data representation and underlying code for version.pm. See |
9 | L<version.pod> for daily usage. This document is only useful for users |
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10 | interested in the gory details. |
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11 | |
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12 | =head1 WHAT IS A VERSION? |
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13 | |
14 | For the purposes of this module, a version "number" is a sequence of |
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15 | positive integer values separated by one or more decimal points and |
16 | optionally a single underscore. This corresponds to what Perl itself |
17 | uses for a version, as well as extending the "version as number" that |
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18 | is discussed in the various editions of the Camel book. |
19 | |
20 | There are actually two distinct kinds of version objects: |
21 | |
22 | =over 4 |
23 | |
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24 | =item Decimal Versions |
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25 | |
26 | Any version which "looks like a number", see L<Decimal Versions>. This |
27 | also includes versions with a single decimal point and a single embedded |
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28 | underscore, see L<Alpha Versions>, even though these must be quoted |
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29 | to preserve the underscore formatting. |
30 | |
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31 | =item Dotted-Decimal Versions |
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32 | |
33 | Also referred to as "Dotted-Integer", these contains more than one decimal |
34 | point and may have an optional embedded underscore, see L<Dotted-Decimal |
35 | Versions>. This is what is commonly used in most open source software as |
36 | the "external" version (the one used as part of the tag or tarfile name). |
37 | A leading 'v' character is now required and will warn if it missing. |
38 | |
39 | =back |
40 | |
41 | Both of these methods will produce similar version objects, in that |
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42 | the default stringification will yield the version L<Normal Form> only |
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43 | if required: |
44 | |
45 | $v = version->new(1.002); # 1.002, but compares like 1.2.0 |
46 | $v = version->new(1.002003); # 1.002003 |
47 | $v2 = version->new("v1.2.3"); # v1.2.3 |
48 | |
49 | In specific, version numbers initialized as L<Decimal Versions> will |
50 | stringify as they were originally created (i.e. the same string that was |
51 | passed to C<new()>. Version numbers initialized as L<Dotted-Decimal Versions> |
52 | will be stringified as L<Normal Form>. |
53 | |
54 | =head2 Decimal Versions |
55 | |
56 | These correspond to historical versions of Perl itself prior to 5.6.0, |
57 | as well as all other modules which follow the Camel rules for the |
58 | $VERSION scalar. A Decimal version is initialized with what looks like |
59 | a floating point number. Leading zeros B<are> significant and trailing |
60 | zeros are implied so that a minimum of three places is maintained |
61 | between subversions. What this means is that any subversion (digits |
62 | to the right of the decimal place) that contains less than three digits |
63 | will have trailing zeros added to make up the difference, but only for |
64 | purposes of comparison with other version objects. For example: |
65 | |
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66 | # Prints Equivalent to |
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67 | $v = version->new( 1.2); # 1.2 v1.200.0 |
68 | $v = version->new( 1.02); # 1.02 v1.20.0 |
69 | $v = version->new( 1.002); # 1.002 v1.2.0 |
70 | $v = version->new( 1.0023); # 1.0023 v1.2.300 |
71 | $v = version->new( 1.00203); # 1.00203 v1.2.30 |
72 | $v = version->new( 1.002003); # 1.002003 v1.2.3 |
73 | |
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74 | All of the preceding examples are true whether or not the input value is |
75 | quoted. The important feature is that the input value contains only a |
76 | single decimal. See also L<Alpha Versions>. |
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77 | |
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78 | IMPORTANT NOTE: As shown above, if your Decimal version contains more |
79 | than 3 significant digits after the decimal place, it will be split on |
80 | each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need |
81 | to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation. |
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82 | Any trailing zeros are ignored for mathematical comparison purposes. |
83 | |
84 | =head2 Dotted-Decimal Versions |
85 | |
86 | These are the newest form of versions, and correspond to Perl's own |
87 | version style beginning with 5.6.0. Starting with Perl 5.10.0, |
88 | and most likely Perl 6, this is likely to be the preferred form. This |
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89 | method normally requires that the input parameter be quoted, although |
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90 | Perl's after 5.8.1 can use v-strings as a special form of quoting, but |
91 | this is highly discouraged. |
92 | |
93 | Unlike L<Decimal Versions>, Dotted-Decimal Versions have more than |
94 | a single decimal point, e.g.: |
95 | |
96 | # Prints |
97 | $v = version->new( "v1.200"); # v1.200.0 |
98 | $v = version->new("v1.20.0"); # v1.20.0 |
99 | $v = qv("v1.2.3"); # v1.2.3 |
100 | $v = qv("1.2.3"); # v1.2.3 |
101 | $v = qv("1.20"); # v1.20.0 |
102 | |
103 | In general, Dotted-Decimal Versions permit the greatest amount of freedom |
104 | to specify a version, whereas Decimal Versions enforce a certain |
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105 | uniformity. |
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106 | |
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107 | Just like L<Decimal Versions>, Dotted-Decimal Versions can be used as |
108 | L<Alpha Versions>. |
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109 | |
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110 | =head2 Alpha Versions |
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111 | |
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112 | For module authors using CPAN, the convention has been to note unstable |
113 | releases with an underscore in the version string. (See L<CPAN>.) version.pm |
114 | follows this convention and alpha releases will test as being newer than the |
115 | more recent stable release, and less than the next stable release. Only the |
116 | last element may be separated by an underscore: |
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117 | |
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118 | # Declaring |
119 | use version 0.77; our $VERSION = version->declare("v1.2_3"); |
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120 | |
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121 | # Parsing |
122 | $v1 = version->parse("v1.2_3"); |
123 | $v1 = version->parse("1.002_003"); |
124 | |
125 | Note that you B<must> quote the version when writing an alpha Decimal version. |
126 | The stringified form of Decimal versions will always be the same string that |
127 | was used to initialize the version object. |
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128 | |
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129 | =head2 Regular Expressions for Version Parsing |
130 | |
131 | A formalized definition of the legal forms for version strings is |
132 | included in the main F<version.pm> file. Primitives are included for |
133 | common elements, although they are scoped to the file so they are useful |
134 | for reference purposes only. There are two publicly accessible scalars |
135 | that can be used in other code (not exported): |
136 | |
137 | =over 4 |
138 | |
139 | =item C<$version::LAX> |
140 | |
141 | This regexp covers all of the legal forms allowed under the current |
142 | version string parser. This is not to say that all of these forms |
143 | are recommended, and some of them can only be used when quoted. |
144 | |
145 | For dotted decimals: |
146 | |
147 | v1.2 |
148 | 1.2345.6 |
149 | v1.23_4 |
150 | |
151 | The leading 'v' is optional if two or more decimals appear. If only |
152 | a single decimal is included, then the leading 'v' is required to |
153 | trigger the dotted-decimal parsing. A leading zero is permitted, |
154 | though not recommended except when quoted, because of the risk that |
155 | Perl will treat the number as octal. A trailing underscore plus one |
156 | or more digits denotes an alpha or development release (and must be |
157 | quoted to be parsed properly). |
158 | |
159 | For decimal versions: |
160 | |
161 | 1 |
162 | 1.2345 |
163 | 1.2345_01 |
164 | |
165 | an integer portion, an optional decimal point, and optionally one or |
166 | more digits to the right of the decimal are all required. A trailing |
167 | underscore is permitted and a leading zero is permitted. Just like |
168 | the lax dotted-decimal version, quoting the values is required for |
169 | alpha/development forms to be parsed correctly. |
170 | |
171 | =item C<$version::STRICT> |
172 | |
173 | This regexp covers a much more limited set of formats and constitutes |
174 | the best practices for initializing version objects. Whether you choose |
175 | to employ decimal or dotted-decimal for is a personal preference however. |
176 | |
177 | =over 4 |
178 | |
179 | =item v1.234.5 |
180 | |
181 | For dotted-decimal versions, a leading 'v' is required, with three or |
182 | more sub-versions of no more than three digits. A leading 0 (zero) |
183 | before the first sub-version (in the above example, '1') is also |
184 | prohibited. |
185 | |
186 | =item 2.3456 |
187 | |
188 | For decimal versions, an integer portion (no leading 0), a decimal point, |
189 | and one or more digits to the right of the decimal are all required. |
190 | |
191 | =back |
192 | |
193 | =back |
194 | |
195 | Both of the provided scalars are already compiled as regular expressions |
196 | and do not contain either anchors or implicit groupings, so they can be |
197 | included in your own regular expressions freely. For example, consider |
198 | the following code: |
199 | |
200 | ($pkg, $ver) =~ / |
201 | ^[ \t]* |
202 | use [ \t]+($PKGNAME) |
203 | (?:[ \t]+($version::STRICT))? |
204 | [ \t]*; |
205 | /x; |
206 | |
207 | This would match a line of the form: |
208 | |
209 | use Foo::Bar::Baz v1.2.3; # legal only in Perl 5.8.1+ |
210 | |
211 | where C<$PKGNAME> is another regular expression that defines the legal |
212 | forms for package names. |
213 | |
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214 | =head1 IMPLEMENTATION DETAILS |
215 | |
216 | =head2 Equivalence between Decimal and Dotted-Decimal Versions |
217 | |
218 | When Perl 5.6.0 was released, the decision was made to provide a |
219 | transformation between the old-style decimal versions and new-style |
220 | dotted-decimal versions: |
221 | |
222 | 5.6.0 == 5.006000 |
223 | 5.005_04 == 5.5.40 |
224 | |
225 | The floating point number is taken and split first on the single decimal |
226 | place, then each group of three digits to the right of the decimal makes up |
227 | the next digit, and so on until the number of significant digits is exhausted, |
228 | B<plus> enough trailing zeros to reach the next multiple of three. |
229 | |
230 | This was the method that version.pm adopted as well. Some examples may be |
231 | helpful: |
232 | |
233 | equivalent |
234 | decimal zero-padded dotted-decimal |
235 | ------- ----------- -------------- |
236 | 1.2 1.200 v1.200.0 |
237 | 1.02 1.020 v1.20.0 |
238 | 1.002 1.002 v1.2.0 |
239 | 1.0023 1.002300 v1.2.300 |
240 | 1.00203 1.002030 v1.2.30 |
241 | 1.002003 1.002003 v1.2.3 |
242 | |
243 | =head2 Quoting Rules |
244 | |
245 | Because of the nature of the Perl parsing and tokenizing routines, |
246 | certain initialization values B<must> be quoted in order to correctly |
247 | parse as the intended version, especially when using the L<declare> or |
248 | L<qv> methods. While you do not have to quote decimal numbers when |
249 | creating version objects, it is always safe to quote B<all> initial values |
250 | when using version.pm methods, as this will ensure that what you type is |
251 | what is used. |
252 | |
253 | Additionally, if you quote your initializer, then the quoted value that goes |
254 | B<in> will be be exactly what comes B<out> when your $VERSION is printed |
255 | (stringified). If you do not quote your value, Perl's normal numeric handling |
256 | comes into play and you may not get back what you were expecting. |
257 | |
258 | If you use a mathematic formula that resolves to a floating point number, |
259 | you are dependent on Perl's conversion routines to yield the version you |
260 | expect. You are pretty safe by dividing by a power of 10, for example, |
261 | but other operations are not likely to be what you intend. For example: |
262 | |
263 | $VERSION = version->new((qw$Revision: 1.4)[1]/10); |
264 | print $VERSION; # yields 0.14 |
265 | $V2 = version->new(100/9); # Integer overflow in decimal number |
266 | print $V2; # yields something like 11.111.111.100 |
267 | |
268 | Perl 5.8.1 and beyond are able to automatically quote v-strings but |
269 | that is not possible in earlier versions of Perl. In other words: |
270 | |
271 | $version = version->new("v2.5.4"); # legal in all versions of Perl |
272 | $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1 |
273 | |
274 | =head2 What about v-strings? |
275 | |
276 | There are two ways to enter v-strings: a bare number with two or more |
277 | decimal points, or a bare number with one or more decimal points and a |
278 | leading 'v' character (also bare). For example: |
279 | |
280 | $vs1 = 1.2.3; # encoded as \1\2\3 |
281 | $vs2 = v1.2; # encoded as \1\2 |
282 | |
283 | However, the use of bare v-strings to initialize version objects is |
284 | B<strongly> discouraged in all circumstances. Also, bare |
285 | v-strings are not completely supported in any version of Perl prior to |
286 | 5.8.1. |
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287 | |
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288 | If you insist on using bare v-strings with Perl > 5.6.0, be aware of the |
289 | following limitations: |
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290 | |
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291 | 1) For Perl releases 5.6.0 through 5.8.0, the v-string code merely guesses, |
292 | based on some characteristics of v-strings. You B<must> use a three part |
293 | version, e.g. 1.2.3 or v1.2.3 in order for this heuristic to be successful. |
294 | |
295 | 2) For Perl releases 5.8.1 and later, v-strings have changed in the Perl |
296 | core to be magical, which means that the version.pm code can automatically |
297 | determine whether the v-string encoding was used. |
298 | |
299 | 3) In all cases, a version created using v-strings will have a stringified |
300 | form that has a leading 'v' character, for the simple reason that sometimes |
301 | it is impossible to tell whether one was present initially. |
302 | |
303 | =head2 Version Object Internals |
304 | |
305 | version.pm provides an overloaded version object that is designed to both |
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306 | encapsulate the author's intended $VERSION assignment as well as make it |
307 | completely natural to use those objects as if they were numbers (e.g. for |
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308 | comparisons). To do this, a version object contains both the original |
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309 | representation as typed by the author, as well as a parsed representation |
310 | to ease comparisons. Version objects employ L<overload> methods to |
311 | simplify code that needs to compare, print, etc the objects. |
312 | |
313 | The internal structure of version objects is a blessed hash with several |
314 | components: |
315 | |
316 | bless( { |
317 | 'original' => 'v1.2.3_4', |
318 | 'alpha' => 1, |
319 | 'qv' => 1, |
320 | 'version' => [ |
321 | 1, |
322 | 2, |
323 | 3, |
324 | 4 |
325 | ] |
326 | }, 'version' ); |
327 | |
328 | =over 4 |
329 | |
330 | =item original |
331 | |
332 | A faithful representation of the value used to initialize this version |
333 | object. The only time this will not be precisely the same characters |
334 | that exist in the source file is if a short dotted-decimal version like |
335 | v1.2 was used (in which case it will contain 'v1.2'). This form is |
336 | B<STRONGLY> discouraged, in that it will confuse you and your users. |
337 | |
338 | =item qv |
339 | |
340 | A boolean that denotes whether this is a decimal or dotted-decimal version. |
341 | See L<is_qv>. |
342 | |
343 | =item alpha |
344 | |
345 | A boolean that denotes whether this is an alpha version. NOTE: that the |
346 | underscore can can only appear in the last position. See L<is_alpha>. |
347 | |
348 | =item version |
349 | |
350 | An array of non-negative integers that is used for comparison purposes with |
351 | other version objects. |
352 | |
353 | =back |
354 | |
355 | =head2 Replacement UNIVERSAL::VERSION |
356 | |
357 | In addition to the version objects, this modules also replaces the core |
358 | UNIVERSAL::VERSION function with one that uses version objects for its |
359 | comparisons. The return from this operator is always the stringified form |
360 | as a simple scalar (i.e. not an object), but the warning message generated |
361 | includes either the stringified form or the normal form, depending on how |
362 | it was called. |
363 | |
364 | For example: |
365 | |
366 | package Foo; |
367 | $VERSION = 1.2; |
368 | |
369 | package Bar; |
370 | $VERSION = "v1.3.5"; # works with all Perl's (since it is quoted) |
371 | |
372 | package main; |
373 | use version; |
374 | |
375 | print $Foo::VERSION; # prints 1.2 |
376 | |
377 | print $Bar::VERSION; # prints 1.003005 |
378 | |
379 | eval "use foo 10"; |
380 | print $@; # prints "foo version 10 required..." |
381 | eval "use foo 1.3.5; # work in Perl 5.6.1 or better |
382 | print $@; # prints "foo version 1.3.5 required..." |
383 | |
384 | eval "use bar 1.3.6"; |
385 | print $@; # prints "bar version 1.3.6 required..." |
386 | eval "use bar 1.004"; # note Decimal version |
387 | print $@; # prints "bar version 1.004 required..." |
388 | |
389 | |
390 | IMPORTANT NOTE: This may mean that code which searches for a specific |
391 | string (to determine whether a given module is available) may need to be |
392 | changed. It is always better to use the built-in comparison implicit in |
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393 | C<use> or C<require>, rather than manually poking at C<< class->VERSION >> |
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394 | and then doing a comparison yourself. |
395 | |
396 | The replacement UNIVERSAL::VERSION, when used as a function, like this: |
397 | |
398 | print $module->VERSION; |
399 | |
400 | will also exclusively return the stringified form. See L<Stringification> |
401 | for more details. |
402 | |
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403 | =head1 USAGE DETAILS |
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404 | |
405 | =head2 Using modules that use version.pm |
406 | |
407 | As much as possible, the version.pm module remains compatible with all |
408 | current code. However, if your module is using a module that has defined |
409 | C<$VERSION> using the version class, there are a couple of things to be |
410 | aware of. For purposes of discussion, we will assume that we have the |
411 | following module installed: |
412 | |
413 | package Example; |
414 | use version; $VERSION = qv('1.2.2'); |
415 | ...module code here... |
416 | 1; |
417 | |
418 | =over 4 |
419 | |
420 | =item Decimal versions always work |
421 | |
422 | Code of the form: |
423 | |
424 | use Example 1.002003; |
425 | |
426 | will always work correctly. The C<use> will perform an automatic |
427 | C<$VERSION> comparison using the floating point number given as the first |
428 | term after the module name (e.g. above 1.002.003). In this case, the |
429 | installed module is too old for the requested line, so you would see an |
430 | error like: |
431 | |
432 | Example version 1.002003 (v1.2.3) required--this is only version 1.002002 (v1.2.2)... |
433 | |
434 | =item Dotted-Decimal version work sometimes |
435 | |
436 | With Perl >= 5.6.2, you can also use a line like this: |
437 | |
438 | use Example 1.2.3; |
439 | |
440 | and it will again work (i.e. give the error message as above), even with |
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441 | releases of Perl which do not normally support v-strings (see L<version/What about v-strings> below). This has to do with that fact that C<use> only checks |
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442 | to see if the second term I<looks like a number> and passes that to the |
443 | replacement L<UNIVERSAL::VERSION>. This is not true in Perl 5.005_04, |
444 | however, so you are B<strongly encouraged> to always use a Decimal version |
445 | in your code, even for those versions of Perl which support the Dotted-Decimal |
446 | version. |
447 | |
448 | =back |
449 | |
450 | =head2 Object Methods |
451 | |
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452 | =over 4 |
453 | |
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454 | =item new() |
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455 | |
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456 | Like many OO interfaces, the new() method is used to initialize version |
457 | objects. If two arguments are passed to C<new()>, the B<second> one will be |
458 | used as if it were prefixed with "v". This is to support historical use of the |
459 | C<qw> operator with the CVS variable $Revision, which is automatically |
460 | incremented by CVS every time the file is committed to the repository. |
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461 | |
462 | In order to facilitate this feature, the following |
463 | code can be employed: |
464 | |
465 | $VERSION = version->new(qw$Revision: 2.7 $); |
466 | |
467 | and the version object will be created as if the following code |
468 | were used: |
469 | |
470 | $VERSION = version->new("v2.7"); |
471 | |
472 | In other words, the version will be automatically parsed out of the |
473 | string, and it will be quoted to preserve the meaning CVS normally |
474 | carries for versions. The CVS $Revision$ increments differently from |
475 | Decimal versions (i.e. 1.10 follows 1.9), so it must be handled as if |
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476 | it were a Dotted-Decimal Version. |
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477 | |
478 | A new version object can be created as a copy of an existing version |
479 | object, either as a class method: |
480 | |
481 | $v1 = version->new(12.3); |
482 | $v2 = version->new($v1); |
483 | |
484 | or as an object method: |
485 | |
486 | $v1 = version->new(12.3); |
487 | $v2 = $v1->new(12.3); |
488 | |
489 | and in each case, $v1 and $v2 will be identical. NOTE: if you create |
490 | a new object using an existing object like this: |
491 | |
492 | $v2 = $v1->new(); |
493 | |
494 | the new object B<will not> be a clone of the existing object. In the |
495 | example case, $v2 will be an empty object of the same type as $v1. |
496 | |
497 | =back |
498 | |
499 | =over 4 |
500 | |
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501 | =item qv() |
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502 | |
503 | An alternate way to create a new version object is through the exported |
504 | qv() sub. This is not strictly like other q? operators (like qq, qw), |
505 | in that the only delimiters supported are parentheses (or spaces). It is |
506 | the best way to initialize a short version without triggering the floating |
507 | point interpretation. For example: |
508 | |
509 | $v1 = qv(1.2); # v1.2.0 |
510 | $v2 = qv("1.2"); # also v1.2.0 |
511 | |
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512 | As you can see, either a bare number or a quoted string can usually |
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513 | be used interchangably, except in the case of a trailing zero, which |
514 | must be quoted to be converted properly. For this reason, it is strongly |
515 | recommended that all initializers to qv() be quoted strings instead of |
516 | bare numbers. |
517 | |
518 | To prevent the C<qv()> function from being exported to the caller's namespace, |
519 | either use version with a null parameter: |
520 | |
521 | use version (); |
522 | |
523 | or just require version, like this: |
524 | |
525 | require version; |
526 | |
527 | Both methods will prevent the import() method from firing and exporting the |
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528 | C<qv()> sub. |
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529 | |
530 | =back |
531 | |
532 | For the subsequent examples, the following three objects will be used: |
533 | |
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534 | $ver = version->new("1.2.3.4"); # see "Quoting Rules" |
535 | $alpha = version->new("1.2.3_4"); # see "Alpha Versions" |
536 | $nver = version->new(1.002); # see "Decimal Versions" |
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537 | |
538 | =over 4 |
539 | |
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540 | =item Normal Form |
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541 | |
542 | For any version object which is initialized with multiple decimal |
543 | places (either quoted or if possible v-string), or initialized using |
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544 | the L<qv>() operator, the stringified representation is returned in |
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545 | a normalized or reduced form (no extraneous zeros), and with a leading 'v': |
546 | |
547 | print $ver->normal; # prints as v1.2.3.4 |
548 | print $ver->stringify; # ditto |
549 | print $ver; # ditto |
550 | print $nver->normal; # prints as v1.2.0 |
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551 | print $nver->stringify; # prints as 1.002, see "Stringification" |
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552 | |
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553 | In order to preserve the meaning of the processed version, the |
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554 | normalized representation will always contain at least three sub terms. |
555 | In other words, the following is guaranteed to always be true: |
556 | |
557 | my $newver = version->new($ver->stringify); |
558 | if ($newver eq $ver ) # always true |
559 | {...} |
560 | |
561 | =back |
562 | |
563 | =over 4 |
564 | |
345e2394 |
565 | =item Numification |
692a467c |
566 | |
567 | Although all mathematical operations on version objects are forbidden |
6369c739 |
568 | by default, it is possible to retrieve a number which corresponds |
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569 | to the version object through the use of the $obj->numify |
570 | method. For formatting purposes, when displaying a number which |
571 | corresponds a version object, all sub versions are assumed to have |
572 | three decimal places. So for example: |
573 | |
574 | print $ver->numify; # prints 1.002003004 |
575 | print $nver->numify; # prints 1.002 |
576 | |
577 | Unlike the stringification operator, there is never any need to append |
578 | trailing zeros to preserve the correct version value. |
579 | |
580 | =back |
581 | |
582 | =over 4 |
583 | |
345e2394 |
584 | =item Stringification |
692a467c |
585 | |
586 | The default stringification for version objects returns exactly the same |
587 | string as was used to create it, whether you used C<new()> or C<qv()>, |
588 | with one exception. The sole exception is if the object was created using |
589 | C<qv()> and the initializer did not have two decimal places or a leading |
590 | 'v' (both optional), then the stringified form will have a leading 'v' |
591 | prepended, in order to support round-trip processing. |
592 | |
593 | For example: |
594 | |
595 | Initialized as Stringifies to |
596 | ============== ============== |
597 | version->new("1.2") 1.2 |
598 | version->new("v1.2") v1.2 |
599 | qv("1.2.3") 1.2.3 |
600 | qv("v1.3.5") v1.3.5 |
6369c739 |
601 | qv("1.2") v1.2 ### exceptional case |
692a467c |
602 | |
603 | See also L<UNIVERSAL::VERSION>, as this also returns the stringified form |
604 | when used as a class method. |
605 | |
606 | IMPORTANT NOTE: There is one exceptional cases shown in the above table |
607 | where the "initializer" is not stringwise equivalent to the stringified |
64da3008 |
608 | representation. If you use the C<qv>() operator on a version without a |
692a467c |
609 | leading 'v' B<and> with only a single decimal place, the stringified output |
64da3008 |
610 | will have a leading 'v', to preserve the sense. See the L<qv>() operator |
692a467c |
611 | for more details. |
612 | |
613 | IMPORTANT NOTE 2: Attempting to bypass the normal stringification rules by |
64da3008 |
614 | manually applying L<numify>() and L<normal>() will sometimes yield |
692a467c |
615 | surprising results: |
616 | |
617 | print version->new(version->new("v1.0")->numify)->normal; # v1.0.0 |
618 | |
64da3008 |
619 | The reason for this is that the L<numify>() operator will turn "v1.0" |
692a467c |
620 | into the equivalent string "1.000000". Forcing the outer version object |
64da3008 |
621 | to L<normal>() form will display the mathematically equivalent "v1.0.0". |
692a467c |
622 | |
64da3008 |
623 | As the example in L<new>() shows, you can always create a copy of an |
692a467c |
624 | existing version object with the same value by the very compact: |
625 | |
626 | $v2 = $v1->new($v1); |
627 | |
628 | and be assured that both C<$v1> and C<$v2> will be completely equivalent, |
629 | down to the same internal representation as well as stringification. |
630 | |
631 | =back |
632 | |
633 | =over 4 |
634 | |
345e2394 |
635 | =item Comparison operators |
692a467c |
636 | |
637 | Both C<cmp> and C<E<lt>=E<gt>> operators perform the same comparison between |
638 | terms (upgrading to a version object automatically). Perl automatically |
639 | generates all of the other comparison operators based on those two. |
640 | In addition to the obvious equalities listed below, appending a single |
641 | trailing 0 term does not change the value of a version for comparison |
642 | purposes. In other words "v1.2" and "1.2.0" will compare as identical. |
643 | |
644 | For example, the following relations hold: |
645 | |
646 | As Number As String Truth Value |
647 | ------------- ---------------- ----------- |
648 | $ver > 1.0 $ver gt "1.0" true |
649 | $ver < 2.5 $ver lt true |
650 | $ver != 1.3 $ver ne "1.3" true |
651 | $ver == 1.2 $ver eq "1.2" false |
652 | $ver == 1.2.3.4 $ver eq "1.2.3.4" see discussion below |
653 | |
654 | It is probably best to chose either the Decimal notation or the string |
655 | notation and stick with it, to reduce confusion. Perl6 version objects |
6369c739 |
656 | B<may> only support Decimal comparisons. See also L<Quoting Rules>. |
692a467c |
657 | |
658 | WARNING: Comparing version with unequal numbers of decimal points (whether |
659 | explicitly or implicitly initialized), may yield unexpected results at |
660 | first glance. For example, the following inequalities hold: |
661 | |
662 | version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0 |
663 | version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0 |
664 | |
665 | For this reason, it is best to use either exclusively L<Decimal Versions> or |
666 | L<Dotted-Decimal Versions> with multiple decimal points. |
667 | |
668 | =back |
669 | |
670 | =over 4 |
671 | |
345e2394 |
672 | =item Logical Operators |
692a467c |
673 | |
674 | If you need to test whether a version object |
675 | has been initialized, you can simply test it directly: |
676 | |
677 | $vobj = version->new($something); |
678 | if ( $vobj ) # true only if $something was non-blank |
679 | |
dc08a87b |
680 | You can also test whether a version object is an alpha version, for |
692a467c |
681 | example to prevent the use of some feature not present in the main |
682 | release: |
683 | |
684 | $vobj = version->new("1.2_3"); # MUST QUOTE |
685 | ...later... |
686 | if ( $vobj->is_alpha ) # True |
687 | |
688 | =back |
689 | |
692a467c |
690 | =head1 AUTHOR |
691 | |
692 | John Peacock E<lt>jpeacock@cpan.orgE<gt> |
693 | |
694 | =head1 SEE ALSO |
695 | |
696 | L<perl>. |
697 | |
698 | =cut |