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1 | =head1 NAME |
2 | |
3 | version - Perl extension for Version Objects |
4 | |
5 | =head1 SYNOPSIS |
6 | |
7 | use version; |
8 | $version = version->new("12.2.1"); # must be quoted for Perl < 5.8.1 |
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9 | print $version; # v12.2.1 |
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10 | print $version->numify; # 12.002001 |
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11 | if ( $version gt "12.2" ) # true |
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12 | |
13 | $alphaver = version->new("1.02_03"); # must be quoted! |
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14 | print $alphaver; # 1.02_0300 |
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15 | print $alphaver->is_alpha(); # true |
16 | |
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17 | $ver = qv("1.2.0"); # v1.2.0 |
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18 | |
19 | $perlver = version->new(5.005_03); # must not be quoted! |
20 | print $perlver; # 5.005030 |
21 | |
22 | =head1 DESCRIPTION |
23 | |
24 | Overloaded version objects for all versions of Perl. This module |
25 | implements all of the features of version objects which will be part |
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26 | of Perl 5.10.0. |
27 | |
28 | =head2 BEST PRACTICES |
29 | |
30 | If you intend for your module to be used by different releases of Perl, |
31 | and/or for your $VERSION scalar to mean what you think it means, there |
32 | are a few simple rules to follow: |
33 | |
34 | =over 4 |
35 | |
36 | =item * Be consistent |
37 | |
38 | Whichever of the two types of version objects that you choose to employ, |
39 | you should stick to either L<Numeric Versions> or L<Extended Versions> |
40 | and not mix them together. While this is I<possible>, it is very |
41 | confusing to the average user. |
42 | |
43 | If you intend to use L<Extended Versions>, you are strongly encouraged |
44 | to use the L<qv()> operator with a quoted term, e.g.: |
45 | |
46 | use version; our $VERSION = qv("1.2.3"); |
47 | |
48 | on a single line as above. |
49 | |
50 | At the very least, decide on which of the several ways to initialize |
51 | your version objects you prefer and stick with it. It is also best to |
52 | be explicit about what value you intend to assign your version object |
53 | and to not rely on hidden behavior of the parser. |
54 | |
55 | =item * Be careful |
56 | |
57 | If you are using Module::Build or ExtUtils::MakeMaker, so that you can |
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58 | release your module to CPAN, you have to recognize that neither of those |
59 | programs completely handles version objects natively (yet). If you use |
60 | version objects with Module::Build, you should add an explicit dependency |
61 | to the release of version.pm in your Build.PL: |
62 | |
63 | my $builder = Module::Build->new( |
64 | ... |
65 | requires => { |
66 | ... , |
67 | 'version' => 0.50, |
68 | ..., |
69 | }, |
70 | ... |
71 | ); |
72 | |
73 | and it should Just Work(TM). Module::Build will [hopefully soon] |
74 | include full support for version objects; there are no current plans |
75 | to patch ExtUtils::MakeMaker to support version objects. |
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76 | |
77 | =head2 What IS a version |
78 | |
79 | For the purposes of this module, a version "number" is a sequence of |
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80 | positive integer values separated by one or more decimal points and |
81 | optionally a single underscore. This corresponds to what Perl itself |
82 | uses for a version, as well as extending the "version as number" that |
83 | is discussed in the various editions of the Camel book. |
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84 | |
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85 | There are actually two distinct kinds of version objects: |
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86 | |
87 | =over 4 |
88 | |
89 | =item * Numeric Versions |
90 | |
91 | Any initial parameter which "looks like a number", see L<Numeric |
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92 | Versions>. This also covers versions with a single decimal point and |
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93 | a single embedded underscore, see L<Numeric Alpha Versions>, even though |
94 | these must be quoted to preserve the underscore formatting. |
95 | |
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96 | =item * Extended Versions |
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97 | |
98 | Any initial parameter which contains more than one decimal point |
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99 | and an optional embedded underscore, see L<Extended Versions>. This |
100 | is what is commonly used in most open source software as the "external" |
101 | version (the one used as part of the tag or tarfile name). The use |
102 | of the exported L<qv()> function also produces this kind of version |
103 | object. |
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104 | |
105 | =back |
106 | |
107 | Both of these methods will produce similar version objects, in that |
108 | the default stringification will yield the version L<Normal Form> only |
109 | if required: |
110 | |
111 | $v = version->new(1.002); # 1.002, but compares like 1.2.0 |
112 | $v = version->new(1.002003); # 1.002003 |
113 | $v2 = version->new( "1.2.3"); # v1.2.3 |
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114 | |
115 | In specific, version numbers initialized as L<Numeric Versions> will |
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116 | stringify in Numeric form. Version numbers initialized as L<Extended Versions> |
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117 | will be stringified as L<Normal Form>. |
118 | |
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119 | =head2 Numeric Versions |
120 | |
121 | These correspond to historical versions of Perl itself prior to 5.6.0, |
122 | as well as all other modules which follow the Camel rules for the |
123 | $VERSION scalar. A numeric version is initialized with what looks like |
124 | a floating point number. Leading zeros B<are> significant and trailing |
125 | zeros are implied so that a minimum of three places is maintained |
126 | between subversions. What this means is that any subversion (digits |
127 | to the right of the decimal place) that contains less than three digits |
128 | will have trailing zeros added to make up the difference, but only for |
129 | purposes of comparison with other version objects. For example: |
130 | |
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131 | # Prints Equivalent to |
132 | $v = version->new( 1.2); # 1.200 v1.200.0 |
133 | $v = version->new( 1.02); # 1.020 v1.20.0 |
134 | $v = version->new( 1.002); # 1.002 v1.2.0 |
135 | $v = version->new( 1.0023); # 1.002300 v1.2.300 |
136 | $v = version->new( 1.00203); # 1.002030 v1.2.30 |
137 | $v = version->new( 1.002003); # 1.002003 v1.2.3 |
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138 | |
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139 | All of the preceding examples are true whether or not the input value is |
140 | quoted. The important feature is that the input value contains only a |
141 | single decimal. See also L<Alpha Versions> for how to handle |
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142 | |
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143 | IMPORTANT NOTE: As shown above, if your numeric version contains more |
144 | than 3 significant digits after the decimal place, it will be split on |
145 | each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need |
146 | to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation. |
147 | Any trailing zeros are ignored for mathematical comparison purposes. |
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148 | |
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149 | =head2 Extended Versions |
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150 | |
151 | These are the newest form of versions, and correspond to Perl's own |
152 | version style beginning with 5.6.0. Starting with Perl 5.10.0, |
153 | and most likely Perl 6, this is likely to be the preferred form. This |
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154 | method normally requires that the input parameter be quoted, although |
155 | Perl's after 5.8.1 can use v-strings as a special form of quoting, but |
156 | this is highly discouraged. |
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157 | |
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158 | Unlike L<Numeric Versions>, Extended Versions have more than |
159 | a single decimal point, e.g.: |
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160 | |
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161 | # Prints |
162 | $v = version->new( "v1.200"); # v1.200.0 |
163 | $v = version->new("v1.20.0"); # v1.20.0 |
164 | $v = qv("v1.2.3); # v1.2.3 |
165 | $v = qv("1.2.3"); # v1.2.3 |
166 | $v = qv("1.20"); # v1.20.0 |
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167 | |
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168 | In general, Extended Versions permit the greatest amount of freedom |
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169 | to specify a version, whereas Numeric Versions enforce a certain |
170 | uniformity. See also L<New Operator> for an additional method of |
171 | initializing version objects. |
172 | |
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173 | Just like L<Numeric Versions>, Extended Versions can be used as |
174 | L<Alpha Versions>. |
175 | |
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176 | =head2 Numeric Alpha Versions |
177 | |
178 | The one time that a numeric version must be quoted is when a alpha form is |
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179 | used with an otherwise numeric version (i.e. a single decimal point). This |
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180 | is commonly used for CPAN releases, where CPAN or CPANPLUS will ignore alpha |
181 | versions for automatic updating purposes. Since some developers have used |
182 | only two significant decimal places for their non-alpha releases, the |
183 | version object will automatically take that into account if the initializer |
184 | is quoted. For example Module::Example was released to CPAN with the |
185 | following sequence of $VERSION's: |
186 | |
187 | # $VERSION Stringified |
188 | 0.01 0.010 |
189 | 0.02 0.020 |
190 | 0.02_01 0.02_0100 |
191 | 0.02_02 0.02_0200 |
192 | 0.03 0.030 |
193 | etc. |
194 | |
195 | As you can see, the version object created from the values in the first |
196 | column may contain a trailing 0, but will otherwise be both mathematically |
197 | equivalent and sorts alpha-numerically as would be expected. |
198 | |
199 | =head2 Object Methods |
200 | |
201 | Overloading has been used with version objects to provide a natural |
202 | interface for their use. All mathematical operations are forbidden, |
203 | since they don't make any sense for base version objects. |
204 | |
205 | =over 4 |
206 | |
207 | =item * New Operator |
208 | |
209 | Like all OO interfaces, the new() operator is used to initialize |
210 | version objects. One way to increment versions when programming is to |
211 | use the CVS variable $Revision, which is automatically incremented by |
212 | CVS every time the file is committed to the repository. |
213 | |
214 | In order to facilitate this feature, the following |
215 | code can be employed: |
216 | |
217 | $VERSION = version->new(qw$Revision: 2.7 $); |
218 | |
219 | and the version object will be created as if the following code |
220 | were used: |
221 | |
222 | $VERSION = version->new("v2.7"); |
223 | |
224 | In other words, the version will be automatically parsed out of the |
225 | string, and it will be quoted to preserve the meaning CVS normally |
226 | carries for versions. The CVS $Revision$ increments differently from |
227 | numeric versions (i.e. 1.10 follows 1.9), so it must be handled as if |
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228 | it were a L<Extended Version>. |
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229 | |
230 | A new version object can be created as a copy of an existing version |
231 | object, either as a class method: |
232 | |
233 | $v1 = version->new(12.3); |
234 | $v2 = version->new($v1); |
235 | |
236 | or as an object method: |
237 | |
238 | $v1 = version->new(12.3); |
239 | $v2 = $v1->new(); |
240 | |
241 | and in each case, $v1 and $v2 will be identical. |
242 | |
243 | =back |
244 | |
245 | =over 4 |
246 | |
247 | =item * qv() |
248 | |
249 | An alternate way to create a new version object is through the exported |
250 | qv() sub. This is not strictly like other q? operators (like qq, qw), |
251 | in that the only delimiters supported are parentheses (or spaces). It is |
252 | the best way to initialize a short version without triggering the floating |
253 | point interpretation. For example: |
254 | |
255 | $v1 = qv(1.2); # 1.2.0 |
256 | $v2 = qv("1.2"); # also 1.2.0 |
257 | |
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258 | As you can see, either a bare number or a quoted string can usually |
259 | be used interchangably, except in the case of a trailing zero, which |
260 | must be quoted to be converted properly. For this reason, it is strongly |
261 | recommended that all initializers to qv() be quoted strings instead of |
262 | bare numbers. |
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263 | |
264 | =back |
265 | |
266 | For the subsequent examples, the following three objects will be used: |
267 | |
268 | $ver = version->new("1.2.3.4"); # see "Quoting" below |
269 | $alpha = version->new("1.2.3_4"); # see "Alpha versions" below |
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270 | $nver = version->new(1.002); # see "Numeric Versions" above |
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271 | |
272 | =over 4 |
273 | |
274 | =item * Normal Form |
275 | |
276 | For any version object which is initialized with multiple decimal |
277 | places (either quoted or if possible v-string), or initialized using |
278 | the L<qv()> operator, the stringified representation is returned in |
279 | a normalized or reduced form (no extraneous zeros), and with a leading 'v': |
280 | |
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281 | print $ver->normal; # prints as v1.2.3.4 |
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282 | print $ver->stringify; # ditto |
283 | print $ver; # ditto |
284 | print $nver->normal; # prints as v1.2.0 |
285 | print $nver->stringify; # prints as 1.002, see "Stringification" |
286 | |
287 | In order to preserve the meaning of the processed version, the |
288 | normalized representation will always contain at least three sub terms. |
289 | In other words, the following is guaranteed to always be true: |
290 | |
291 | my $newver = version->new($ver->stringify); |
292 | if ($newver eq $ver ) # always true |
293 | {...} |
294 | |
295 | =back |
296 | |
297 | =over 4 |
298 | |
299 | =item * Numification |
300 | |
301 | Although all mathematical operations on version objects are forbidden |
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302 | by default, it is possible to retrieve a number which corresponds |
303 | to the version object through the use of the $obj->numify |
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304 | method. For formatting purposes, when displaying a number which |
305 | corresponds a version object, all sub versions are assumed to have |
306 | three decimal places. So for example: |
307 | |
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308 | print $ver->numify; # prints 1.002003004 |
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309 | print $nver->numify; # prints 1.002 |
310 | |
311 | Unlike the stringification operator, there is never any need to append |
312 | trailing zeros to preserve the correct version value. |
313 | |
314 | =back |
315 | |
316 | =over 4 |
317 | |
318 | =item * Stringification |
319 | |
320 | In order to mirror as much as possible the existing behavior of ordinary |
321 | $VERSION scalars, the stringification operation will display differently, |
322 | depending on whether the version was initialized as a L<Numeric Version> |
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323 | or L<Extended Version>. |
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324 | |
325 | What this means in practice is that if the normal CPAN and Camel rules are |
326 | followed ($VERSION is a floating point number with no more than 3 decimal |
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327 | points), the stringified output will be exactly the same as the numified |
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328 | output. There will be no visible difference, although the internal |
329 | representation will be different, and the L<Comparison operators> will |
330 | function using the internal coding. |
331 | |
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332 | If a version object is initialized using a L<Extended Version> form, then |
333 | the stringified form will be the L<Normal Form>. The $obj->normal |
334 | operation can always be used to produce the L<Normal Form>, even if the |
335 | version was originally a L<Numeric Version>. |
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336 | |
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337 | print $ver->stringify; # prints v1.2.3.4 |
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338 | print $nver->stringify; # prints 1.002 |
339 | |
340 | =back |
341 | |
342 | =over 4 |
343 | |
344 | =item * Comparison operators |
345 | |
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346 | Both C<cmp> and C<E<lt>=E<gt>> operators perform the same comparison between |
347 | terms (upgrading to a version object automatically). Perl automatically |
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348 | generates all of the other comparison operators based on those two. |
349 | In addition to the obvious equalities listed below, appending a single |
350 | trailing 0 term does not change the value of a version for comparison |
351 | purposes. In other words "v1.2" and "1.2.0" will compare as identical. |
352 | |
353 | For example, the following relations hold: |
354 | |
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355 | As Number As String Truth Value |
356 | ------------- ---------------- ----------- |
357 | $ver > 1.0 $ver gt "1.0" true |
358 | $ver < 2.5 $ver lt true |
359 | $ver != 1.3 $ver ne "1.3" true |
360 | $ver == 1.2 $ver eq "1.2" false |
361 | $ver == 1.2.3.4 $ver eq "1.2.3.4" see discussion below |
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362 | |
363 | It is probably best to chose either the numeric notation or the string |
364 | notation and stick with it, to reduce confusion. Perl6 version objects |
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365 | B<may> only support numeric comparisons. See also L<Quoting>. |
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366 | |
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367 | WARNING: Comparing version with unequal numbers of decimal points (whether |
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368 | explicitly or implicitly initialized), may yield unexpected results at |
369 | first glance. For example, the following inequalities hold: |
370 | |
371 | version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0 |
372 | version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0 |
373 | |
374 | For this reason, it is best to use either exclusively L<Numeric Versions> or |
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375 | L<Extended Versions> with multiple decimal points. |
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376 | |
377 | =back |
378 | |
379 | =over 4 |
380 | |
381 | =item * Logical Operators |
382 | |
383 | If you need to test whether a version object |
384 | has been initialized, you can simply test it directly: |
385 | |
386 | $vobj = version->new($something); |
387 | if ( $vobj ) # true only if $something was non-blank |
388 | |
389 | You can also test whether a version object is an L<Alpha version>, for |
390 | example to prevent the use of some feature not present in the main |
391 | release: |
392 | |
393 | $vobj = version->new("1.2_3"); # MUST QUOTE |
394 | ...later... |
395 | if ( $vobj->is_alpha ) # True |
396 | |
397 | =back |
398 | |
399 | =head2 Quoting |
400 | |
401 | Because of the nature of the Perl parsing and tokenizing routines, |
402 | certain initialization values B<must> be quoted in order to correctly |
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403 | parse as the intended version, especially when using the L<qv()> operator. |
404 | In all cases, a floating point number passed to version->new() will be |
405 | identically converted whether or not the value itself is quoted. This is |
406 | not true for L<qv()>, however, when trailing zeros would be stripped on |
407 | an unquoted input, which would result in a very different version object. |
408 | |
409 | In addition, in order to be compatible with earlier Perl version styles, |
410 | any use of versions of the form 5.006001 will be translated as v5.6.1. |
411 | In other words, a version with a single decimal point will be parsed as |
412 | implicitly having three digits between subversions, but only for internal |
413 | comparison purposes. |
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414 | |
415 | The complicating factor is that in bare numbers (i.e. unquoted), the |
416 | underscore is a legal numeric character and is automatically stripped |
417 | by the Perl tokenizer before the version code is called. However, if |
418 | a number containing one or more decimals and an underscore is quoted, i.e. |
419 | not bare, that is considered a L<Alpha Version> and the underscore is |
420 | significant. |
421 | |
422 | If you use a mathematic formula that resolves to a floating point number, |
423 | you are dependent on Perl's conversion routines to yield the version you |
424 | expect. You are pretty safe by dividing by a power of 10, for example, |
425 | but other operations are not likely to be what you intend. For example: |
426 | |
427 | $VERSION = version->new((qw$Revision: 1.4)[1]/10); |
428 | print $VERSION; # yields 0.14 |
429 | $V2 = version->new(100/9); # Integer overflow in decimal number |
430 | print $V2; # yields something like 11.111.111.100 |
431 | |
432 | Perl 5.8.1 and beyond will be able to automatically quote v-strings but |
433 | that is not possible in earlier versions of Perl. In other words: |
434 | |
435 | $version = version->new("v2.5.4"); # legal in all versions of Perl |
436 | $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1 |
437 | |
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438 | =head2 What about v-strings? |
439 | |
440 | Beginning with Perl 5.6.0, an alternate method to code arbitrary strings |
441 | of bytes was introduced, called v-strings. They were intended to be an |
442 | easy way to enter, for example, Unicode strings (which contain two bytes |
443 | per character). Some programs have used them to encode printer control |
444 | characters (e.g. CRLF). They were also intended to be used for $VERSION, |
445 | but their use as such has been problematic from the start. |
446 | |
447 | There are two ways to enter v-strings: a bare number with two or more |
448 | decimal points, or a bare number with one or more decimal points and a |
449 | leading 'v' character (also bare). For example: |
450 | |
451 | $vs1 = 1.2.3; # encoded as \1\2\3 |
452 | $vs2 = v1.2; # encoded as \1\2 |
453 | |
454 | However, the use of v-strings to initialize version objects with this |
455 | module is only possible with Perl 5.8.1 or better (which contain special |
456 | code to enable it). Their use is B<strongly> discouraged in all |
457 | circumstances (especially the leading 'v' style), since the meaning will |
458 | change depending on which Perl you are running. It is better to directly |
459 | use L<"Extended Versions"> to ensure the proper interpretation. |
460 | |
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461 | |
462 | =head2 Types of Versions Objects |
463 | |
464 | There are two types of Version Objects: |
465 | |
466 | =over 4 |
467 | |
468 | =item * Ordinary versions |
469 | |
470 | These are the versions that normal modules will use. Can contain as |
471 | many subversions as required. In particular, those using RCS/CVS can |
472 | use the following: |
473 | |
474 | $VERSION = version->new(qw$Revision: 2.7 $); |
475 | |
476 | and the current RCS Revision for that file will be inserted |
477 | automatically. If the file has been moved to a branch, the Revision |
478 | will have three or more elements; otherwise, it will have only two. |
479 | This allows you to automatically increment your module version by |
480 | using the Revision number from the primary file in a distribution, see |
481 | L<ExtUtils::MakeMaker/"VERSION_FROM">. |
482 | |
483 | =item * Alpha Versions |
484 | |
485 | For module authors using CPAN, the convention has been to note |
486 | unstable releases with an underscore in the version string, see |
487 | L<CPAN>. Alpha releases will test as being newer than the more recent |
488 | stable release, and less than the next stable release. For example: |
489 | |
490 | $alphaver = version->new("12.03_01"); # must be quoted |
491 | |
492 | obeys the relationship |
493 | |
494 | 12.03 < $alphaver < 12.04 |
495 | |
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496 | Alpha versions with a single decimal point will be treated exactly as if |
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497 | they were L<Numeric Versions>, for parsing purposes. The stringification for |
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498 | alpha versions with a single decimal point may seem surprising, since any |
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499 | trailing zeros will visible. For example, the above $alphaver will print as |
500 | |
501 | 12.03_0100 |
502 | |
503 | which is mathematically equivalent and ASCII sorts exactly the same as |
504 | without the trailing zeros. |
505 | |
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506 | Alpha versions with more than a single decimal point will be treated |
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507 | exactly as if they were L<Extended Versions>, and will display without any |
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508 | trailing (or leading) zeros, in the L<Version Normal> form. For example, |
509 | |
510 | $newver = version->new("12.3.1_1"); |
511 | print $newver; # v12.3.1_1 |
512 | |
513 | =head2 Replacement UNIVERSAL::VERSION |
514 | |
515 | In addition to the version objects, this modules also replaces the core |
516 | UNIVERSAL::VERSION function with one that uses version objects for its |
517 | comparisons. The return from this operator is always the numified form, |
518 | and the warning message generated includes both the numified and normal |
519 | forms (for clarity). |
520 | |
521 | For example: |
522 | |
523 | package Foo; |
524 | $VERSION = 1.2; |
525 | |
526 | package Bar; |
527 | $VERSION = "1.3.5"; # works with all Perl's (since it is quoted) |
528 | |
529 | package main; |
530 | use version; |
531 | |
532 | print $Foo::VERSION; # prints 1.2 |
533 | |
534 | print $Bar::VERSION; # prints 1.003005 |
535 | |
536 | eval "use CGI 10"; # some far future release |
537 | print $@; # prints "CGI version 10 (10.0.0) required..." |
538 | |
539 | IMPORTANT NOTE: This may mean that code which searches for a specific |
540 | string (to determine whether a given module is available) may need to be |
541 | changed. |
542 | |
543 | The replacement UNIVERSAL::VERSION, when used as a function, like this: |
544 | |
545 | print $module->VERSION; |
546 | |
547 | will also exclusively return the numified form. Technically, the |
548 | $module->VERSION function returns a string (PV) that can be converted to a |
549 | number following the normal Perl rules, when used in a numeric context. |
550 | |
551 | =head1 SUBCLASSING |
552 | |
553 | This module is specifically designed and tested to be easily subclassed. |
554 | In practice, you only need to override the methods you want to change, but |
555 | you have to take some care when overriding new() (since that is where all |
556 | of the parsing takes place). For example, this is a perfect acceptable |
557 | derived class: |
558 | |
559 | package myversion; |
560 | use base version; |
561 | sub new { |
562 | my($self,$n)=@_; |
563 | my $obj; |
564 | # perform any special input handling here |
565 | $obj = $self->SUPER::new($n); |
566 | # and/or add additional hash elements here |
567 | return $obj; |
568 | } |
569 | |
570 | See also L<version::AlphaBeta> on CPAN for an alternate representation of |
571 | version strings. |
572 | |
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573 | B<NOTE:> the L<qv> operator is not a class method and will not be inherited |
574 | in the same way as the other methods. L<qv> will always return an object of |
575 | type L<version> and not an object in the derived class. If you need to |
576 | have L<qv> return an object in your derived class, add something like this: |
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577 | |
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578 | *::qv = sub { return bless version::qv(shift), __PACKAGE__ }; |
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579 | |
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580 | as seen in the test file F<t/02derived.t>. |
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581 | |
582 | =head1 EXPORT |
583 | |
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584 | qv - Extended Version initialization operator |
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585 | |
586 | =head1 AUTHOR |
587 | |
588 | John Peacock E<lt>jpeacock@cpan.orgE<gt> |
589 | |
590 | =head1 SEE ALSO |
591 | |
592 | L<perl>. |
593 | |
594 | =cut |