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1=head1 NAME
2
6369c739 3version::Internals - Perl extension for Version Objects
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4
5=head1 DESCRIPTION
6
7Overloaded version objects for all modern versions of Perl. This documents
8the internal data representation and underlying code for version.pm. See
fe6e8b3e 9F<version.pod> for daily usage. This document is only useful for users
6369c739 10interested in the gory details.
692a467c 11
6369c739 12=head1 WHAT IS A VERSION?
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13
14For the purposes of this module, a version "number" is a sequence of
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15positive integer values separated by one or more decimal points and
16optionally a single underscore. This corresponds to what Perl itself
17uses for a version, as well as extending the "version as number" that
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18is discussed in the various editions of the Camel book.
19
20There are actually two distinct kinds of version objects:
21
22=over 4
23
345e2394 24=item Decimal Versions
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25
26Any version which "looks like a number", see L<Decimal Versions>. This
27also includes versions with a single decimal point and a single embedded
6369c739 28underscore, see L<Alpha Versions>, even though these must be quoted
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29to preserve the underscore formatting.
30
345e2394 31=item Dotted-Decimal Versions
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32
33Also referred to as "Dotted-Integer", these contains more than one decimal
34point and may have an optional embedded underscore, see L<Dotted-Decimal
35Versions>. This is what is commonly used in most open source software as
36the "external" version (the one used as part of the tag or tarfile name).
37A leading 'v' character is now required and will warn if it missing.
38
39=back
40
41Both of these methods will produce similar version objects, in that
6369c739 42the default stringification will yield the version L<Normal Form> only
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43if 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 $v2 = version->new("v1.2.3"); # v1.2.3
48
49In specific, version numbers initialized as L<Decimal Versions> will
50stringify as they were originally created (i.e. the same string that was
51passed to C<new()>. Version numbers initialized as L<Dotted-Decimal Versions>
52will be stringified as L<Normal Form>.
53
54=head2 Decimal Versions
55
56These correspond to historical versions of Perl itself prior to 5.6.0,
57as well as all other modules which follow the Camel rules for the
58$VERSION scalar. A Decimal version is initialized with what looks like
59a floating point number. Leading zeros B<are> significant and trailing
60zeros are implied so that a minimum of three places is maintained
61between subversions. What this means is that any subversion (digits
62to the right of the decimal place) that contains less than three digits
63will have trailing zeros added to make up the difference, but only for
64purposes of comparison with other version objects. For example:
65
6369c739 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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74All of the preceding examples are true whether or not the input value is
75quoted. The important feature is that the input value contains only a
76single decimal. See also L<Alpha Versions>.
692a467c 77
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78IMPORTANT NOTE: As shown above, if your Decimal version contains more
79than 3 significant digits after the decimal place, it will be split on
80each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need
81to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation.
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82Any trailing zeros are ignored for mathematical comparison purposes.
83
84=head2 Dotted-Decimal Versions
85
86These are the newest form of versions, and correspond to Perl's own
87version style beginning with 5.6.0. Starting with Perl 5.10.0,
88and most likely Perl 6, this is likely to be the preferred form. This
6369c739 89method normally requires that the input parameter be quoted, although
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90Perl's after 5.8.1 can use v-strings as a special form of quoting, but
91this is highly discouraged.
92
93Unlike L<Decimal Versions>, Dotted-Decimal Versions have more than
94a 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
103In general, Dotted-Decimal Versions permit the greatest amount of freedom
104to specify a version, whereas Decimal Versions enforce a certain
dc08a87b 105uniformity.
692a467c 106
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107Just like L</Decimal Versions>, Dotted-Decimal Versions can be used as
108L</Alpha Versions>.
692a467c 109
6369c739 110=head2 Alpha Versions
692a467c 111
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112For module authors using CPAN, the convention has been to note unstable
113releases with an underscore in the version string. (See L<CPAN>.) version.pm
114follows this convention and alpha releases will test as being newer than the
115more recent stable release, and less than the next stable release. Only the
116last element may be separated by an underscore:
692a467c 117
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118 # Declaring
119 use version 0.77; our $VERSION = version->declare("v1.2_3");
692a467c 120
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121 # Parsing
122 $v1 = version->parse("v1.2_3");
123 $v1 = version->parse("1.002_003");
124
125Note that you B<must> quote the version when writing an alpha Decimal version.
126The stringified form of Decimal versions will always be the same string that
127was used to initialize the version object.
692a467c 128
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129=head2 Regular Expressions for Version Parsing
130
131A formalized definition of the legal forms for version strings is
db9cb848 132included in the C<version::regex> class. Primitives are included for
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133common elements, although they are scoped to the file so they are useful
134for reference purposes only. There are two publicly accessible scalars
135that can be used in other code (not exported):
136
137=over 4
138
139=item C<$version::LAX>
140
141This regexp covers all of the legal forms allowed under the current
142version string parser. This is not to say that all of these forms
143are recommended, and some of them can only be used when quoted.
144
145For dotted decimals:
146
147 v1.2
148 1.2345.6
149 v1.23_4
150
151The leading 'v' is optional if two or more decimals appear. If only
152a single decimal is included, then the leading 'v' is required to
153trigger the dotted-decimal parsing. A leading zero is permitted,
154though not recommended except when quoted, because of the risk that
155Perl will treat the number as octal. A trailing underscore plus one
156or more digits denotes an alpha or development release (and must be
157quoted to be parsed properly).
158
159For decimal versions:
160
161 1
162 1.2345
163 1.2345_01
164
165an integer portion, an optional decimal point, and optionally one or
166more digits to the right of the decimal are all required. A trailing
167underscore is permitted and a leading zero is permitted. Just like
168the lax dotted-decimal version, quoting the values is required for
169alpha/development forms to be parsed correctly.
170
171=item C<$version::STRICT>
172
173This regexp covers a much more limited set of formats and constitutes
174the best practices for initializing version objects. Whether you choose
175to employ decimal or dotted-decimal for is a personal preference however.
176
177=over 4
178
179=item v1.234.5
180
181For dotted-decimal versions, a leading 'v' is required, with three or
182more sub-versions of no more than three digits. A leading 0 (zero)
183before the first sub-version (in the above example, '1') is also
184prohibited.
185
186=item 2.3456
187
188For decimal versions, an integer portion (no leading 0), a decimal point,
189and one or more digits to the right of the decimal are all required.
190
191=back
192
193=back
194
195Both of the provided scalars are already compiled as regular expressions
196and do not contain either anchors or implicit groupings, so they can be
197included in your own regular expressions freely. For example, consider
198the following code:
199
200 ($pkg, $ver) =~ /
201 ^[ \t]*
202 use [ \t]+($PKGNAME)
203 (?:[ \t]+($version::STRICT))?
204 [ \t]*;
205 /x;
206
207This would match a line of the form:
208
209 use Foo::Bar::Baz v1.2.3; # legal only in Perl 5.8.1+
210
211where C<$PKGNAME> is another regular expression that defines the legal
212forms for package names.
213
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214=head1 IMPLEMENTATION DETAILS
215
216=head2 Equivalence between Decimal and Dotted-Decimal Versions
217
218When Perl 5.6.0 was released, the decision was made to provide a
219transformation between the old-style decimal versions and new-style
220dotted-decimal versions:
221
222 5.6.0 == 5.006000
223 5.005_04 == 5.5.40
224
225The floating point number is taken and split first on the single decimal
226place, then each group of three digits to the right of the decimal makes up
227the next digit, and so on until the number of significant digits is exhausted,
228B<plus> enough trailing zeros to reach the next multiple of three.
229
230This was the method that version.pm adopted as well. Some examples may be
231helpful:
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
245Because of the nature of the Perl parsing and tokenizing routines,
246certain initialization values B<must> be quoted in order to correctly
fe6e8b3e 247parse as the intended version, especially when using the C<declare> or
c5009e80 248L</qv()> methods. While you do not have to quote decimal numbers when
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249creating version objects, it is always safe to quote B<all> initial values
250when using version.pm methods, as this will ensure that what you type is
251what is used.
252
253Additionally, if you quote your initializer, then the quoted value that goes
8524aa6e 254B<in> will be exactly what comes B<out> when your $VERSION is printed
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255(stringified). If you do not quote your value, Perl's normal numeric handling
256comes into play and you may not get back what you were expecting.
257
258If you use a mathematic formula that resolves to a floating point number,
259you are dependent on Perl's conversion routines to yield the version you
260expect. You are pretty safe by dividing by a power of 10, for example,
261but 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
268Perl 5.8.1 and beyond are able to automatically quote v-strings but
269that 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
276There are two ways to enter v-strings: a bare number with two or more
277decimal points, or a bare number with one or more decimal points and a
278leading '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
283However, the use of bare v-strings to initialize version objects is
284B<strongly> discouraged in all circumstances. Also, bare
285v-strings are not completely supported in any version of Perl prior to
2865.8.1.
692a467c 287
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288If you insist on using bare v-strings with Perl > 5.6.0, be aware of the
289following limitations:
692a467c 290
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2911) For Perl releases 5.6.0 through 5.8.0, the v-string code merely guesses,
292based on some characteristics of v-strings. You B<must> use a three part
293version, e.g. 1.2.3 or v1.2.3 in order for this heuristic to be successful.
294
2952) For Perl releases 5.8.1 and later, v-strings have changed in the Perl
296core to be magical, which means that the version.pm code can automatically
297determine whether the v-string encoding was used.
298
2993) In all cases, a version created using v-strings will have a stringified
300form that has a leading 'v' character, for the simple reason that sometimes
301it is impossible to tell whether one was present initially.
302
303=head2 Version Object Internals
304
305version.pm provides an overloaded version object that is designed to both
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306encapsulate the author's intended $VERSION assignment as well as make it
307completely natural to use those objects as if they were numbers (e.g. for
6369c739 308comparisons). To do this, a version object contains both the original
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309representation as typed by the author, as well as a parsed representation
310to ease comparisons. Version objects employ L<overload> methods to
311simplify code that needs to compare, print, etc the objects.
312
313The internal structure of version objects is a blessed hash with several
314components:
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
332A faithful representation of the value used to initialize this version
333object. The only time this will not be precisely the same characters
334that exist in the source file is if a short dotted-decimal version like
335v1.2 was used (in which case it will contain 'v1.2'). This form is
336B<STRONGLY> discouraged, in that it will confuse you and your users.
337
338=item qv
339
340A boolean that denotes whether this is a decimal or dotted-decimal version.
fe6e8b3e 341See L<version/is_qv()>.
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342
343=item alpha
344
345A boolean that denotes whether this is an alpha version. NOTE: that the
8524aa6e 346underscore can only appear in the last position. See L<version/is_alpha()>.
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347
348=item version
349
350An array of non-negative integers that is used for comparison purposes with
351other version objects.
352
353=back
354
355=head2 Replacement UNIVERSAL::VERSION
356
357In addition to the version objects, this modules also replaces the core
358UNIVERSAL::VERSION function with one that uses version objects for its
359comparisons. The return from this operator is always the stringified form
360as a simple scalar (i.e. not an object), but the warning message generated
361includes either the stringified form or the normal form, depending on how
362it was called.
363
364For 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
390IMPORTANT NOTE: This may mean that code which searches for a specific
391string (to determine whether a given module is available) may need to be
392changed. It is always better to use the built-in comparison implicit in
d5213412 393C<use> or C<require>, rather than manually poking at C<< class->VERSION >>
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394and then doing a comparison yourself.
395
396The replacement UNIVERSAL::VERSION, when used as a function, like this:
397
398 print $module->VERSION;
399
fe6e8b3e 400will also exclusively return the stringified form. See L</Stringification>
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401for more details.
402
6369c739 403=head1 USAGE DETAILS
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404
405=head2 Using modules that use version.pm
406
407As much as possible, the version.pm module remains compatible with all
408current code. However, if your module is using a module that has defined
409C<$VERSION> using the version class, there are a couple of things to be
410aware of. For purposes of discussion, we will assume that we have the
411following module installed:
412
413 package Example;
414 use version; $VERSION = qv('1.2.2');
415 ...module code here...
416 1;
417
418=over 4
419
420=item Decimal versions always work
421
422Code of the form:
423
424 use Example 1.002003;
425
426will always work correctly. The C<use> will perform an automatic
427C<$VERSION> comparison using the floating point number given as the first
428term after the module name (e.g. above 1.002.003). In this case, the
429installed module is too old for the requested line, so you would see an
430error 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
436With Perl >= 5.6.2, you can also use a line like this:
437
438 use Example 1.2.3;
439
440and it will again work (i.e. give the error message as above), even with
fe6e8b3e 441releases of Perl which do not normally support v-strings (see L<What about v-strings?> above). This has to do with that fact that C<use> only checks
692a467c 442to see if the second term I<looks like a number> and passes that to the
5bbbd807 443replacement L<UNIVERSAL::VERSION|UNIVERSAL/VERSION>. This is not true in Perl 5.005_04,
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444however, so you are B<strongly encouraged> to always use a Decimal version
445in your code, even for those versions of Perl which support the Dotted-Decimal
446version.
447
448=back
449
450=head2 Object Methods
451
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452=over 4
453
6369c739 454=item new()
692a467c 455
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456Like many OO interfaces, the new() method is used to initialize version
457objects. If two arguments are passed to C<new()>, the B<second> one will be
458used as if it were prefixed with "v". This is to support historical use of the
459C<qw> operator with the CVS variable $Revision, which is automatically
460incremented by CVS every time the file is committed to the repository.
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461
462In order to facilitate this feature, the following
463code can be employed:
464
465 $VERSION = version->new(qw$Revision: 2.7 $);
466
467and the version object will be created as if the following code
468were used:
469
470 $VERSION = version->new("v2.7");
471
472In other words, the version will be automatically parsed out of the
473string, and it will be quoted to preserve the meaning CVS normally
474carries for versions. The CVS $Revision$ increments differently from
475Decimal versions (i.e. 1.10 follows 1.9), so it must be handled as if
64da3008 476it were a Dotted-Decimal Version.
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477
478A new version object can be created as a copy of an existing version
479object, either as a class method:
480
481 $v1 = version->new(12.3);
482 $v2 = version->new($v1);
483
484or as an object method:
485
486 $v1 = version->new(12.3);
487 $v2 = $v1->new(12.3);
488
489and in each case, $v1 and $v2 will be identical. NOTE: if you create
490a new object using an existing object like this:
491
492 $v2 = $v1->new();
493
494the new object B<will not> be a clone of the existing object. In the
495example case, $v2 will be an empty object of the same type as $v1.
496
497=back
498
499=over 4
500
345e2394 501=item qv()
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502
503An alternate way to create a new version object is through the exported
504qv() sub. This is not strictly like other q? operators (like qq, qw),
505in that the only delimiters supported are parentheses (or spaces). It is
506the best way to initialize a short version without triggering the floating
507point interpretation. For example:
508
509 $v1 = qv(1.2); # v1.2.0
510 $v2 = qv("1.2"); # also v1.2.0
511
6369c739 512As you can see, either a bare number or a quoted string can usually
98dc9551 513be used interchangeably, except in the case of a trailing zero, which
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514must be quoted to be converted properly. For this reason, it is strongly
515recommended that all initializers to qv() be quoted strings instead of
516bare numbers.
517
518To prevent the C<qv()> function from being exported to the caller's namespace,
519either use version with a null parameter:
520
521 use version ();
522
523or just require version, like this:
524
525 require version;
526
527Both methods will prevent the import() method from firing and exporting the
6369c739 528C<qv()> sub.
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529
530=back
531
532For 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
345e2394 540=item Normal Form
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541
542For any version object which is initialized with multiple decimal
543places (either quoted or if possible v-string), or initialized using
fe6e8b3e 544the L<qv()|version/qv()> operator, the stringified representation is returned in
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545a 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
555bd962
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551 print $nver->stringify; # prints as 1.002,
552 # see "Stringification"
692a467c 553
6369c739 554In order to preserve the meaning of the processed version, the
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555normalized representation will always contain at least three sub terms.
556In other words, the following is guaranteed to always be true:
557
558 my $newver = version->new($ver->stringify);
559 if ($newver eq $ver ) # always true
560 {...}
561
562=back
563
564=over 4
565
345e2394 566=item Numification
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567
568Although all mathematical operations on version objects are forbidden
6369c739 569by default, it is possible to retrieve a number which corresponds
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570to the version object through the use of the $obj->numify
571method. For formatting purposes, when displaying a number which
572corresponds a version object, all sub versions are assumed to have
573three decimal places. So for example:
574
575 print $ver->numify; # prints 1.002003004
576 print $nver->numify; # prints 1.002
577
578Unlike the stringification operator, there is never any need to append
579trailing zeros to preserve the correct version value.
580
581=back
582
583=over 4
584
345e2394 585=item Stringification
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586
587The default stringification for version objects returns exactly the same
588string as was used to create it, whether you used C<new()> or C<qv()>,
589with one exception. The sole exception is if the object was created using
590C<qv()> and the initializer did not have two decimal places or a leading
591'v' (both optional), then the stringified form will have a leading 'v'
592prepended, in order to support round-trip processing.
593
594For example:
595
596 Initialized as Stringifies to
597 ============== ==============
598 version->new("1.2") 1.2
599 version->new("v1.2") v1.2
600 qv("1.2.3") 1.2.3
601 qv("v1.3.5") v1.3.5
6369c739 602 qv("1.2") v1.2 ### exceptional case
692a467c 603
fe6e8b3e 604See also L<UNIVERSAL::VERSION|UNIVERSAL/VERSION>, as this also returns the stringified form
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605when used as a class method.
606
607IMPORTANT NOTE: There is one exceptional cases shown in the above table
608where the "initializer" is not stringwise equivalent to the stringified
64da3008 609representation. If you use the C<qv>() operator on a version without a
692a467c 610leading 'v' B<and> with only a single decimal place, the stringified output
fe6e8b3e 611will have a leading 'v', to preserve the sense. See the L</qv()> operator
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612for more details.
613
614IMPORTANT NOTE 2: Attempting to bypass the normal stringification rules by
fe6e8b3e 615manually applying L<numify()|version/numify()> and L<normal()|version/normal()> will sometimes yield
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616surprising results:
617
618 print version->new(version->new("v1.0")->numify)->normal; # v1.0.0
619
fe6e8b3e 620The reason for this is that the L<numify()|version/numify()> operator will turn "v1.0"
692a467c 621into the equivalent string "1.000000". Forcing the outer version object
fe6e8b3e 622to L<normal()|version/normal()> form will display the mathematically equivalent "v1.0.0".
692a467c 623
1adc55b9 624As the example in L</new()> shows, you can always create a copy of an
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625existing version object with the same value by the very compact:
626
627 $v2 = $v1->new($v1);
628
629and be assured that both C<$v1> and C<$v2> will be completely equivalent,
630down to the same internal representation as well as stringification.
631
632=back
633
634=over 4
635
345e2394 636=item Comparison operators
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637
638Both C<cmp> and C<E<lt>=E<gt>> operators perform the same comparison between
639terms (upgrading to a version object automatically). Perl automatically
640generates all of the other comparison operators based on those two.
641In addition to the obvious equalities listed below, appending a single
642trailing 0 term does not change the value of a version for comparison
643purposes. In other words "v1.2" and "1.2.0" will compare as identical.
644
645For example, the following relations hold:
646
647 As Number As String Truth Value
648 ------------- ---------------- -----------
649 $ver > 1.0 $ver gt "1.0" true
650 $ver < 2.5 $ver lt true
651 $ver != 1.3 $ver ne "1.3" true
652 $ver == 1.2 $ver eq "1.2" false
653 $ver == 1.2.3.4 $ver eq "1.2.3.4" see discussion below
654
655It is probably best to chose either the Decimal notation or the string
656notation and stick with it, to reduce confusion. Perl6 version objects
6369c739 657B<may> only support Decimal comparisons. See also L<Quoting Rules>.
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658
659WARNING: Comparing version with unequal numbers of decimal points (whether
660explicitly or implicitly initialized), may yield unexpected results at
661first glance. For example, the following inequalities hold:
662
663 version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
664 version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
665
666For this reason, it is best to use either exclusively L<Decimal Versions> or
667L<Dotted-Decimal Versions> with multiple decimal points.
668
669=back
670
671=over 4
672
345e2394 673=item Logical Operators
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674
675If you need to test whether a version object
676has been initialized, you can simply test it directly:
677
678 $vobj = version->new($something);
679 if ( $vobj ) # true only if $something was non-blank
680
dc08a87b 681You can also test whether a version object is an alpha version, for
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682example to prevent the use of some feature not present in the main
683release:
684
685 $vobj = version->new("1.2_3"); # MUST QUOTE
686 ...later...
687 if ( $vobj->is_alpha ) # True
688
689=back
690
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691=head1 AUTHOR
692
693John Peacock E<lt>jpeacock@cpan.orgE<gt>
694
695=head1 SEE ALSO
696
697L<perl>.
698
699=cut