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1=head1 NAME
2
3version - 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
43eaf59d 9 print $version; # v12.2.1
cb5772bb 10 print $version->numify; # 12.002001
43eaf59d 11 if ( $version gt "12.2" ) # true
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12
13 $alphaver = version->new("1.02_03"); # must be quoted!
43eaf59d 14 print $alphaver; # 1.02_0300
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15 print $alphaver->is_alpha(); # true
16
43eaf59d 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
317f7c8a 24Overloaded version objects for all modern versions of Perl. This module
cb5772bb 25implements all of the features of version objects which will be part
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26of Perl 5.10.0.
27
28=head2 BEST PRACTICES
29
30If you intend for your module to be used by different releases of Perl,
31and/or for your $VERSION scalar to mean what you think it means, there
32are a few simple rules to follow:
33
34=over 4
35
36=item * Be consistent
37
38Whichever of the two types of version objects that you choose to employ,
39you should stick to either L<Numeric Versions> or L<Extended Versions>
40and not mix them together. While this is I<possible>, it is very
41confusing to the average user.
42
43If you intend to use L<Extended Versions>, you are strongly encouraged
44to use the L<qv()> operator with a quoted term, e.g.:
45
46 use version; our $VERSION = qv("1.2.3");
47
48on a single line as above.
49
50At the very least, decide on which of the several ways to initialize
51your version objects you prefer and stick with it. It is also best to
52be explicit about what value you intend to assign your version object
53and to not rely on hidden behavior of the parser.
54
55=item * Be careful
56
57If you are using Module::Build or ExtUtils::MakeMaker, so that you can
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58release your module to CPAN, you have to recognize that neither of those
59programs completely handles version objects natively (yet). If you use
60version objects with Module::Build, you should add an explicit dependency
61to the release of version.pm in your Build.PL:
62
63 my $builder = Module::Build->new(
64 ...
65 requires => {
66 ... ,
67 'version' => 0.50,
68 ...,
69 },
70 ...
71 );
72
73and it should Just Work(TM). Module::Build will [hopefully soon]
74include full support for version objects; there are no current plans
75to patch ExtUtils::MakeMaker to support version objects.
cb5772bb 76
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77=back
78
79=head2 Using modules that use version.pm
80
81As much as possible, the version.pm module remains compatible with all
82current code. However, if your module is using a module that has defined
83C<$VERSION> using the version class, there are a couple of things to be
84aware of. For purposes of discussion, we will assume that we have the
85following module installed:
86
87 package Example;
88 use version; $VERSION = qv('1.2.2');
89 ...module code here...
90 1;
91
92=over 4
93
94=item Numeric versions always work
95
96Code of the form:
97
98 use Example 1.002003;
99
100will always work correctly. The C<use> will perform an automatic
101C<$VERSION> comparison using the floating point number given as the first
102term after the module name (e.g. above 1.002.003). In this case, the
103installed module is too old for the requested line, so you would see an
104error like:
105
106 Example version 1.002003 (v1.2.3) required--this is only version 1.002002 (v1.2.2)...
107
108=item Extended version work sometimes
109
110With Perl >= 5.6.2, you can also use a line like this:
111
112 use Example 1.2.3;
113
114and it will again work (i.e. give the error message as above), even with
115releases of Perl which do not normally support v-strings (see L<What about
116v-strings> below). This has to do with that fact that C<use> only checks
117to see if the second term I<looks like a number> and passes that to the
118replacement L<UNIVERSAL::VERSION>. This is not true in Perl 5.005_04,
119however, so you are B<strongly encouraged> to always use a numeric version
120in your code, even for those versions of Perl which support the extended
121version.
122
123=back
124
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125=head2 What IS a version
126
127For the purposes of this module, a version "number" is a sequence of
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128positive integer values separated by one or more decimal points and
129optionally a single underscore. This corresponds to what Perl itself
130uses for a version, as well as extending the "version as number" that
131is discussed in the various editions of the Camel book.
cb5772bb 132
43eaf59d 133There are actually two distinct kinds of version objects:
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134
135=over 4
136
137=item * Numeric Versions
138
139Any initial parameter which "looks like a number", see L<Numeric
43eaf59d 140Versions>. This also covers versions with a single decimal point and
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141a single embedded underscore, see L<Numeric Alpha Versions>, even though
142these must be quoted to preserve the underscore formatting.
143
7de739db 144=item * Extended Versions
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145
146Any initial parameter which contains more than one decimal point
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147and an optional embedded underscore, see L<Extended Versions>. This
148is what is commonly used in most open source software as the "external"
149version (the one used as part of the tag or tarfile name). The use
150of the exported L<qv()> function also produces this kind of version
151object.
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152
153=back
154
155Both of these methods will produce similar version objects, in that
156the default stringification will yield the version L<Normal Form> only
157if required:
158
159 $v = version->new(1.002); # 1.002, but compares like 1.2.0
160 $v = version->new(1.002003); # 1.002003
f34c6aaf 161 $v2 = version->new("1.2.3"); # v1.2.3
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162
163In specific, version numbers initialized as L<Numeric Versions> will
7de739db 164stringify in Numeric form. Version numbers initialized as L<Extended Versions>
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165will be stringified as L<Normal Form>.
166
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167=head2 Numeric Versions
168
169These correspond to historical versions of Perl itself prior to 5.6.0,
170as well as all other modules which follow the Camel rules for the
171$VERSION scalar. A numeric version is initialized with what looks like
172a floating point number. Leading zeros B<are> significant and trailing
173zeros are implied so that a minimum of three places is maintained
174between subversions. What this means is that any subversion (digits
175to the right of the decimal place) that contains less than three digits
176will have trailing zeros added to make up the difference, but only for
177purposes of comparison with other version objects. For example:
178
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179 # Prints Equivalent to
180 $v = version->new( 1.2); # 1.200 v1.200.0
181 $v = version->new( 1.02); # 1.020 v1.20.0
182 $v = version->new( 1.002); # 1.002 v1.2.0
183 $v = version->new( 1.0023); # 1.002300 v1.2.300
184 $v = version->new( 1.00203); # 1.002030 v1.2.30
185 $v = version->new( 1.002003); # 1.002003 v1.2.3
cb5772bb 186
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187All of the preceding examples are true whether or not the input value is
188quoted. The important feature is that the input value contains only a
189single decimal. See also L<Alpha Versions> for how to handle
cb5772bb 190
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191IMPORTANT NOTE: As shown above, if your numeric version contains more
192than 3 significant digits after the decimal place, it will be split on
193each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need
194to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation.
195Any trailing zeros are ignored for mathematical comparison purposes.
cb5772bb 196
7de739db 197=head2 Extended Versions
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198
199These are the newest form of versions, and correspond to Perl's own
200version style beginning with 5.6.0. Starting with Perl 5.10.0,
201and most likely Perl 6, this is likely to be the preferred form. This
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202method normally requires that the input parameter be quoted, although
203Perl's after 5.8.1 can use v-strings as a special form of quoting, but
204this is highly discouraged.
cb5772bb 205
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206Unlike L<Numeric Versions>, Extended Versions have more than
207a single decimal point, e.g.:
cb5772bb 208
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209 # Prints
210 $v = version->new( "v1.200"); # v1.200.0
211 $v = version->new("v1.20.0"); # v1.20.0
f34c6aaf 212 $v = qv("v1.2.3"); # v1.2.3
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213 $v = qv("1.2.3"); # v1.2.3
214 $v = qv("1.20"); # v1.20.0
cb5772bb 215
7de739db 216In general, Extended Versions permit the greatest amount of freedom
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217to specify a version, whereas Numeric Versions enforce a certain
218uniformity. See also L<New Operator> for an additional method of
219initializing version objects.
220
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221Just like L<Numeric Versions>, Extended Versions can be used as
222L<Alpha Versions>.
223
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224=head2 Numeric Alpha Versions
225
226The one time that a numeric version must be quoted is when a alpha form is
43eaf59d 227used with an otherwise numeric version (i.e. a single decimal point). This
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228is commonly used for CPAN releases, where CPAN or CPANPLUS will ignore alpha
229versions for automatic updating purposes. Since some developers have used
230only two significant decimal places for their non-alpha releases, the
231version object will automatically take that into account if the initializer
232is quoted. For example Module::Example was released to CPAN with the
233following sequence of $VERSION's:
234
235 # $VERSION Stringified
236 0.01 0.010
237 0.02 0.020
238 0.02_01 0.02_0100
239 0.02_02 0.02_0200
240 0.03 0.030
241 etc.
242
243As you can see, the version object created from the values in the first
244column may contain a trailing 0, but will otherwise be both mathematically
245equivalent and sorts alpha-numerically as would be expected.
246
247=head2 Object Methods
248
249Overloading has been used with version objects to provide a natural
250interface for their use. All mathematical operations are forbidden,
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251since they don't make any sense for base version objects. Consequently,
252there is no overloaded numification available. If you want to use a
253version object in a numeric context for some reason, see the L<numify>
254object method.
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255
256=over 4
257
258=item * New Operator
259
260Like all OO interfaces, the new() operator is used to initialize
261version objects. One way to increment versions when programming is to
262use the CVS variable $Revision, which is automatically incremented by
263CVS every time the file is committed to the repository.
264
265In order to facilitate this feature, the following
266code can be employed:
267
268 $VERSION = version->new(qw$Revision: 2.7 $);
269
270and the version object will be created as if the following code
271were used:
272
273 $VERSION = version->new("v2.7");
274
275In other words, the version will be automatically parsed out of the
276string, and it will be quoted to preserve the meaning CVS normally
277carries for versions. The CVS $Revision$ increments differently from
278numeric versions (i.e. 1.10 follows 1.9), so it must be handled as if
7de739db 279it were a L<Extended Version>.
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280
281A new version object can be created as a copy of an existing version
282object, either as a class method:
283
284 $v1 = version->new(12.3);
285 $v2 = version->new($v1);
286
287or as an object method:
288
289 $v1 = version->new(12.3);
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290 $v2 = $v1->new(12.3);
291
292and in each case, $v1 and $v2 will be identical. NOTE: if you create
293a new object using an existing object like this:
294
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295 $v2 = $v1->new();
296
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297the new object B<will not> be a clone of the existing object. In the
298example case, $v2 will be an empty object of the same type as $v1.
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299
300=back
301
302=over 4
303
304=item * qv()
305
306An alternate way to create a new version object is through the exported
307qv() sub. This is not strictly like other q? operators (like qq, qw),
308in that the only delimiters supported are parentheses (or spaces). It is
309the best way to initialize a short version without triggering the floating
310point interpretation. For example:
311
312 $v1 = qv(1.2); # 1.2.0
313 $v2 = qv("1.2"); # also 1.2.0
314
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315As you can see, either a bare number or a quoted string can usually
316be used interchangably, except in the case of a trailing zero, which
317must be quoted to be converted properly. For this reason, it is strongly
318recommended that all initializers to qv() be quoted strings instead of
319bare numbers.
cb5772bb 320
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321To prevent the C<qv()> function from being exported to the caller's namespace,
322either use version with a null parameter:
323
324 use version ();
325
326or just require version, like this:
327
328 require version;
329
330Both methods will prevent the import() method from firing and exporting the
331C<qv()> sub. This is true of subclasses of version as well, see
332L<SUBCLASSING> for details.
333
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334=back
335
336For the subsequent examples, the following three objects will be used:
337
338 $ver = version->new("1.2.3.4"); # see "Quoting" below
339 $alpha = version->new("1.2.3_4"); # see "Alpha versions" below
43eaf59d 340 $nver = version->new(1.002); # see "Numeric Versions" above
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341
342=over 4
343
344=item * Normal Form
345
346For any version object which is initialized with multiple decimal
347places (either quoted or if possible v-string), or initialized using
348the L<qv()> operator, the stringified representation is returned in
349a normalized or reduced form (no extraneous zeros), and with a leading 'v':
350
43eaf59d 351 print $ver->normal; # prints as v1.2.3.4
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352 print $ver->stringify; # ditto
353 print $ver; # ditto
354 print $nver->normal; # prints as v1.2.0
355 print $nver->stringify; # prints as 1.002, see "Stringification"
356
357In order to preserve the meaning of the processed version, the
358normalized representation will always contain at least three sub terms.
359In other words, the following is guaranteed to always be true:
360
361 my $newver = version->new($ver->stringify);
362 if ($newver eq $ver ) # always true
363 {...}
364
365=back
366
367=over 4
368
369=item * Numification
370
371Although all mathematical operations on version objects are forbidden
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372by default, it is possible to retrieve a number which corresponds
373to the version object through the use of the $obj->numify
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374method. For formatting purposes, when displaying a number which
375corresponds a version object, all sub versions are assumed to have
376three decimal places. So for example:
377
43eaf59d 378 print $ver->numify; # prints 1.002003004
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379 print $nver->numify; # prints 1.002
380
381Unlike the stringification operator, there is never any need to append
382trailing zeros to preserve the correct version value.
383
384=back
385
386=over 4
387
388=item * Stringification
389
390In order to mirror as much as possible the existing behavior of ordinary
391$VERSION scalars, the stringification operation will display differently,
392depending on whether the version was initialized as a L<Numeric Version>
7de739db 393or L<Extended Version>.
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394
395What this means in practice is that if the normal CPAN and Camel rules are
396followed ($VERSION is a floating point number with no more than 3 decimal
43eaf59d 397points), the stringified output will be exactly the same as the numified
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398output. There will be no visible difference, although the internal
399representation will be different, and the L<Comparison operators> will
400function using the internal coding.
401
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402If a version object is initialized using a L<Extended Version> form, then
403the stringified form will be the L<Normal Form>. The $obj->normal
404operation can always be used to produce the L<Normal Form>, even if the
405version was originally a L<Numeric Version>.
cb5772bb 406
43eaf59d 407 print $ver->stringify; # prints v1.2.3.4
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408 print $nver->stringify; # prints 1.002
409
410=back
411
412=over 4
413
414=item * Comparison operators
415
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416Both C<cmp> and C<E<lt>=E<gt>> operators perform the same comparison between
417terms (upgrading to a version object automatically). Perl automatically
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418generates all of the other comparison operators based on those two.
419In addition to the obvious equalities listed below, appending a single
420trailing 0 term does not change the value of a version for comparison
421purposes. In other words "v1.2" and "1.2.0" will compare as identical.
422
423For example, the following relations hold:
424
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425 As Number As String Truth Value
426 ------------- ---------------- -----------
427 $ver > 1.0 $ver gt "1.0" true
428 $ver < 2.5 $ver lt true
429 $ver != 1.3 $ver ne "1.3" true
430 $ver == 1.2 $ver eq "1.2" false
431 $ver == 1.2.3.4 $ver eq "1.2.3.4" see discussion below
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432
433It is probably best to chose either the numeric notation or the string
434notation and stick with it, to reduce confusion. Perl6 version objects
43eaf59d 435B<may> only support numeric comparisons. See also L<Quoting>.
cb5772bb 436
43eaf59d 437WARNING: Comparing version with unequal numbers of decimal points (whether
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438explicitly or implicitly initialized), may yield unexpected results at
439first glance. For example, the following inequalities hold:
440
441 version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
442 version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
443
444For this reason, it is best to use either exclusively L<Numeric Versions> or
43eaf59d 445L<Extended Versions> with multiple decimal points.
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446
447=back
448
449=over 4
450
451=item * Logical Operators
452
453If you need to test whether a version object
454has been initialized, you can simply test it directly:
455
456 $vobj = version->new($something);
457 if ( $vobj ) # true only if $something was non-blank
458
459You can also test whether a version object is an L<Alpha version>, for
460example to prevent the use of some feature not present in the main
461release:
462
463 $vobj = version->new("1.2_3"); # MUST QUOTE
464 ...later...
465 if ( $vobj->is_alpha ) # True
466
467=back
468
469=head2 Quoting
470
471Because of the nature of the Perl parsing and tokenizing routines,
472certain initialization values B<must> be quoted in order to correctly
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473parse as the intended version, especially when using the L<qv()> operator.
474In all cases, a floating point number passed to version->new() will be
475identically converted whether or not the value itself is quoted. This is
476not true for L<qv()>, however, when trailing zeros would be stripped on
477an unquoted input, which would result in a very different version object.
478
479In addition, in order to be compatible with earlier Perl version styles,
480any use of versions of the form 5.006001 will be translated as v5.6.1.
481In other words, a version with a single decimal point will be parsed as
482implicitly having three digits between subversions, but only for internal
483comparison purposes.
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484
485The complicating factor is that in bare numbers (i.e. unquoted), the
486underscore is a legal numeric character and is automatically stripped
487by the Perl tokenizer before the version code is called. However, if
488a number containing one or more decimals and an underscore is quoted, i.e.
489not bare, that is considered a L<Alpha Version> and the underscore is
490significant.
491
492If you use a mathematic formula that resolves to a floating point number,
493you are dependent on Perl's conversion routines to yield the version you
494expect. You are pretty safe by dividing by a power of 10, for example,
495but other operations are not likely to be what you intend. For example:
496
497 $VERSION = version->new((qw$Revision: 1.4)[1]/10);
498 print $VERSION; # yields 0.14
499 $V2 = version->new(100/9); # Integer overflow in decimal number
500 print $V2; # yields something like 11.111.111.100
501
502Perl 5.8.1 and beyond will be able to automatically quote v-strings but
503that is not possible in earlier versions of Perl. In other words:
504
505 $version = version->new("v2.5.4"); # legal in all versions of Perl
506 $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1
507
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508=head2 What about v-strings?
509
510Beginning with Perl 5.6.0, an alternate method to code arbitrary strings
511of bytes was introduced, called v-strings. They were intended to be an
512easy way to enter, for example, Unicode strings (which contain two bytes
513per character). Some programs have used them to encode printer control
514characters (e.g. CRLF). They were also intended to be used for $VERSION,
515but their use as such has been problematic from the start.
516
517There are two ways to enter v-strings: a bare number with two or more
518decimal points, or a bare number with one or more decimal points and a
519leading 'v' character (also bare). For example:
520
521 $vs1 = 1.2.3; # encoded as \1\2\3
522 $vs2 = v1.2; # encoded as \1\2
523
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524However, the use of bare v-strings to initialize version objects is
525B<strongly> discouraged in all circumstances (especially the leading
526'v' style), since the meaning will change depending on which Perl you
527are running. It is better to directly use L<"Extended Versions"> to
528ensure the proper interpretation.
529
530If you insist on using bare v-strings with Perl > 5.6.0, be aware of the
531following limitations:
43eaf59d 532
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5331) For Perl releases 5.6.0 through 5.8.0, the v-string code merely guesses,
534based on some characteristics of v-strings. You B<must> use a three part
535version, e.g. 1.2.3 or v1.2.3 in order for this heuristic to be successful.
536
5372) For Perl releases 5.8.1 and later, v-strings have changed in the Perl
538core to be magical, which means that the version.pm code can automatically
539determine whether the v-string encoding was used.
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540
541=head2 Types of Versions Objects
542
543There are two types of Version Objects:
544
545=over 4
546
547=item * Ordinary versions
548
549These are the versions that normal modules will use. Can contain as
550many subversions as required. In particular, those using RCS/CVS can
551use the following:
552
553 $VERSION = version->new(qw$Revision: 2.7 $);
554
555and the current RCS Revision for that file will be inserted
556automatically. If the file has been moved to a branch, the Revision
557will have three or more elements; otherwise, it will have only two.
558This allows you to automatically increment your module version by
559using the Revision number from the primary file in a distribution, see
560L<ExtUtils::MakeMaker/"VERSION_FROM">.
561
562=item * Alpha Versions
563
564For module authors using CPAN, the convention has been to note
565unstable releases with an underscore in the version string, see
566L<CPAN>. Alpha releases will test as being newer than the more recent
567stable release, and less than the next stable release. For example:
568
569 $alphaver = version->new("12.03_01"); # must be quoted
570
571obeys the relationship
572
573 12.03 < $alphaver < 12.04
574
43eaf59d 575Alpha versions with a single decimal point will be treated exactly as if
cb5772bb 576they were L<Numeric Versions>, for parsing purposes. The stringification for
43eaf59d 577alpha versions with a single decimal point may seem surprising, since any
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578trailing zeros will visible. For example, the above $alphaver will print as
579
580 12.03_0100
581
582which is mathematically equivalent and ASCII sorts exactly the same as
583without the trailing zeros.
584
43eaf59d 585Alpha versions with more than a single decimal point will be treated
7de739db 586exactly as if they were L<Extended Versions>, and will display without any
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587trailing (or leading) zeros, in the L<Version Normal> form. For example,
588
589 $newver = version->new("12.3.1_1");
590 print $newver; # v12.3.1_1
591
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592=back
593
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594=head2 Replacement UNIVERSAL::VERSION
595
596In addition to the version objects, this modules also replaces the core
597UNIVERSAL::VERSION function with one that uses version objects for its
598comparisons. The return from this operator is always the numified form,
599and the warning message generated includes both the numified and normal
600forms (for clarity).
601
602For example:
603
604 package Foo;
605 $VERSION = 1.2;
606
607 package Bar;
608 $VERSION = "1.3.5"; # works with all Perl's (since it is quoted)
609
610 package main;
611 use version;
612
613 print $Foo::VERSION; # prints 1.2
614
615 print $Bar::VERSION; # prints 1.003005
616
617 eval "use CGI 10"; # some far future release
618 print $@; # prints "CGI version 10 (10.0.0) required..."
619
620IMPORTANT NOTE: This may mean that code which searches for a specific
621string (to determine whether a given module is available) may need to be
622changed.
623
624The replacement UNIVERSAL::VERSION, when used as a function, like this:
625
626 print $module->VERSION;
627
628will also exclusively return the numified form. Technically, the
629$module->VERSION function returns a string (PV) that can be converted to a
630number following the normal Perl rules, when used in a numeric context.
631
632=head1 SUBCLASSING
633
634This module is specifically designed and tested to be easily subclassed.
635In practice, you only need to override the methods you want to change, but
636you have to take some care when overriding new() (since that is where all
637of the parsing takes place). For example, this is a perfect acceptable
638derived class:
639
640 package myversion;
641 use base version;
642 sub new {
643 my($self,$n)=@_;
644 my $obj;
645 # perform any special input handling here
646 $obj = $self->SUPER::new($n);
647 # and/or add additional hash elements here
648 return $obj;
649 }
650
651See also L<version::AlphaBeta> on CPAN for an alternate representation of
652version strings.
653
92dcf8ce
JP
654B<NOTE:> Although the L<qv> operator is not a true class method, but rather a
655function exported into the caller's namespace, a subclass of version will
656inherit an import() function which will perform the correct magic on behalf
657of the subclass.
cb5772bb
RGS
658
659=head1 EXPORT
660
7de739db 661qv - Extended Version initialization operator
cb5772bb
RGS
662
663=head1 AUTHOR
664
665John Peacock E<lt>jpeacock@cpan.orgE<gt>
666
667=head1 SEE ALSO
668
669L<perl>.
670
671=cut