3 version - Perl extension for Version Objects
8 $version = version->new("12.2.1"); # must be quoted for Perl < 5.8.1
9 print $version; # v12.2.1
10 print $version->numify; # 12.002001
11 if ( $version gt "12.2" ) # true
13 $alphaver = version->new("1.02_03"); # must be quoted!
14 print $alphaver; # 1.02_0300
15 print $alphaver->is_alpha(); # true
17 $ver = qv("1.2.0"); # v1.2.0
19 $perlver = version->new(5.005_03); # must not be quoted!
20 print $perlver; # 5.005030
24 Overloaded version objects for all modern versions of Perl. This module
25 implements all of the features of version objects which will be part
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:
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.
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.:
46 use version; our $VERSION = qv("1.2.3");
48 on a single line as above.
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.
57 If you are using Module::Build or ExtUtils::MakeMaker, so that you can
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:
63 my $builder = Module::Build->new(
73 and it should Just Work(TM). Module::Build will [hopefully soon]
74 include full support for version objects; there are no current plans
75 to patch ExtUtils::MakeMaker to support version objects.
79 =head2 Using modules that use version.pm
81 As much as possible, the version.pm module remains compatible with all
82 current code. However, if your module is using a module that has defined
83 C<$VERSION> using the version class, there are a couple of things to be
84 aware of. For purposes of discussion, we will assume that we have the
85 following module installed:
88 use version; $VERSION = qv('1.2.2');
89 ...module code here...
94 =item Numeric versions always work
100 will always work correctly. The C<use> will perform an automatic
101 C<$VERSION> comparison using the floating point number given as the first
102 term after the module name (e.g. above 1.002.003). In this case, the
103 installed module is too old for the requested line, so you would see an
106 Example version 1.002003 (v1.2.3) required--this is only version 1.002002 (v1.2.2)...
108 =item Extended version work sometimes
110 With Perl >= 5.6.2, you can also use a line like this:
114 and it will again work (i.e. give the error message as above), even with
115 releases of Perl which do not normally support v-strings (see L<What about
116 v-strings> below). This has to do with that fact that C<use> only checks
117 to see if the second term I<looks like a number> and passes that to the
118 replacement L<UNIVERSAL::VERSION>. This is not true in Perl 5.005_04,
119 however, so you are B<strongly encouraged> to always use a numeric version
120 in your code, even for those versions of Perl which support the extended
125 =head2 What IS a version
127 For the purposes of this module, a version "number" is a sequence of
128 positive integer values separated by one or more decimal points and
129 optionally a single underscore. This corresponds to what Perl itself
130 uses for a version, as well as extending the "version as number" that
131 is discussed in the various editions of the Camel book.
133 There are actually two distinct kinds of version objects:
137 =item * Numeric Versions
139 Any initial parameter which "looks like a number", see L<Numeric
140 Versions>. This also covers versions with a single decimal point and
141 a single embedded underscore, see L<Numeric Alpha Versions>, even though
142 these must be quoted to preserve the underscore formatting.
144 =item * Extended Versions
146 Any initial parameter which contains more than one decimal point
147 and an optional embedded underscore, see L<Extended Versions>. This
148 is what is commonly used in most open source software as the "external"
149 version (the one used as part of the tag or tarfile name). The use
150 of the exported L<qv()> function also produces this kind of version
155 Both of these methods will produce similar version objects, in that
156 the default stringification will yield the version L<Normal Form> only
159 $v = version->new(1.002); # 1.002, but compares like 1.2.0
160 $v = version->new(1.002003); # 1.002003
161 $v2 = version->new( "1.2.3"); # v1.2.3
163 In specific, version numbers initialized as L<Numeric Versions> will
164 stringify in Numeric form. Version numbers initialized as L<Extended Versions>
165 will be stringified as L<Normal Form>.
167 =head2 Numeric Versions
169 These correspond to historical versions of Perl itself prior to 5.6.0,
170 as well as all other modules which follow the Camel rules for the
171 $VERSION scalar. A numeric version is initialized with what looks like
172 a floating point number. Leading zeros B<are> significant and trailing
173 zeros are implied so that a minimum of three places is maintained
174 between subversions. What this means is that any subversion (digits
175 to the right of the decimal place) that contains less than three digits
176 will have trailing zeros added to make up the difference, but only for
177 purposes of comparison with other version objects. For example:
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
187 All of the preceding examples are true whether or not the input value is
188 quoted. The important feature is that the input value contains only a
189 single decimal. See also L<Alpha Versions> for how to handle
191 IMPORTANT NOTE: As shown above, if your numeric version contains more
192 than 3 significant digits after the decimal place, it will be split on
193 each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need
194 to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation.
195 Any trailing zeros are ignored for mathematical comparison purposes.
197 =head2 Extended Versions
199 These are the newest form of versions, and correspond to Perl's own
200 version style beginning with 5.6.0. Starting with Perl 5.10.0,
201 and most likely Perl 6, this is likely to be the preferred form. This
202 method normally requires that the input parameter be quoted, although
203 Perl's after 5.8.1 can use v-strings as a special form of quoting, but
204 this is highly discouraged.
206 Unlike L<Numeric Versions>, Extended Versions have more than
207 a single decimal point, e.g.:
210 $v = version->new( "v1.200"); # v1.200.0
211 $v = version->new("v1.20.0"); # v1.20.0
212 $v = qv("v1.2.3); # v1.2.3
213 $v = qv("1.2.3"); # v1.2.3
214 $v = qv("1.20"); # v1.20.0
216 In general, Extended Versions permit the greatest amount of freedom
217 to specify a version, whereas Numeric Versions enforce a certain
218 uniformity. See also L<New Operator> for an additional method of
219 initializing version objects.
221 Just like L<Numeric Versions>, Extended Versions can be used as
224 =head2 Numeric Alpha Versions
226 The one time that a numeric version must be quoted is when a alpha form is
227 used with an otherwise numeric version (i.e. a single decimal point). This
228 is commonly used for CPAN releases, where CPAN or CPANPLUS will ignore alpha
229 versions for automatic updating purposes. Since some developers have used
230 only two significant decimal places for their non-alpha releases, the
231 version object will automatically take that into account if the initializer
232 is quoted. For example Module::Example was released to CPAN with the
233 following sequence of $VERSION's:
235 # $VERSION Stringified
243 As you can see, the version object created from the values in the first
244 column may contain a trailing 0, but will otherwise be both mathematically
245 equivalent and sorts alpha-numerically as would be expected.
247 =head2 Object Methods
249 Overloading has been used with version objects to provide a natural
250 interface for their use. All mathematical operations are forbidden,
251 since they don't make any sense for base version objects.
257 Like all OO interfaces, the new() operator is used to initialize
258 version objects. One way to increment versions when programming is to
259 use the CVS variable $Revision, which is automatically incremented by
260 CVS every time the file is committed to the repository.
262 In order to facilitate this feature, the following
263 code can be employed:
265 $VERSION = version->new(qw$Revision: 2.7 $);
267 and the version object will be created as if the following code
270 $VERSION = version->new("v2.7");
272 In other words, the version will be automatically parsed out of the
273 string, and it will be quoted to preserve the meaning CVS normally
274 carries for versions. The CVS $Revision$ increments differently from
275 numeric versions (i.e. 1.10 follows 1.9), so it must be handled as if
276 it were a L<Extended Version>.
278 A new version object can be created as a copy of an existing version
279 object, either as a class method:
281 $v1 = version->new(12.3);
282 $v2 = version->new($v1);
284 or as an object method:
286 $v1 = version->new(12.3);
289 and in each case, $v1 and $v2 will be identical.
297 An alternate way to create a new version object is through the exported
298 qv() sub. This is not strictly like other q? operators (like qq, qw),
299 in that the only delimiters supported are parentheses (or spaces). It is
300 the best way to initialize a short version without triggering the floating
301 point interpretation. For example:
303 $v1 = qv(1.2); # 1.2.0
304 $v2 = qv("1.2"); # also 1.2.0
306 As you can see, either a bare number or a quoted string can usually
307 be used interchangably, except in the case of a trailing zero, which
308 must be quoted to be converted properly. For this reason, it is strongly
309 recommended that all initializers to qv() be quoted strings instead of
312 To prevent the C<qv()> function from being exported to the caller's namespace,
313 either use version with a null parameter:
317 or just require version, like this:
321 Both methods will prevent the import() method from firing and exporting the
322 C<qv()> sub. This is true of subclasses of version as well, see
323 L<SUBCLASSING> for details.
327 For the subsequent examples, the following three objects will be used:
329 $ver = version->new("1.2.3.4"); # see "Quoting" below
330 $alpha = version->new("1.2.3_4"); # see "Alpha versions" below
331 $nver = version->new(1.002); # see "Numeric Versions" above
337 For any version object which is initialized with multiple decimal
338 places (either quoted or if possible v-string), or initialized using
339 the L<qv()> operator, the stringified representation is returned in
340 a normalized or reduced form (no extraneous zeros), and with a leading 'v':
342 print $ver->normal; # prints as v1.2.3.4
343 print $ver->stringify; # ditto
345 print $nver->normal; # prints as v1.2.0
346 print $nver->stringify; # prints as 1.002, see "Stringification"
348 In order to preserve the meaning of the processed version, the
349 normalized representation will always contain at least three sub terms.
350 In other words, the following is guaranteed to always be true:
352 my $newver = version->new($ver->stringify);
353 if ($newver eq $ver ) # always true
362 Although all mathematical operations on version objects are forbidden
363 by default, it is possible to retrieve a number which corresponds
364 to the version object through the use of the $obj->numify
365 method. For formatting purposes, when displaying a number which
366 corresponds a version object, all sub versions are assumed to have
367 three decimal places. So for example:
369 print $ver->numify; # prints 1.002003004
370 print $nver->numify; # prints 1.002
372 Unlike the stringification operator, there is never any need to append
373 trailing zeros to preserve the correct version value.
379 =item * Stringification
381 In order to mirror as much as possible the existing behavior of ordinary
382 $VERSION scalars, the stringification operation will display differently,
383 depending on whether the version was initialized as a L<Numeric Version>
384 or L<Extended Version>.
386 What this means in practice is that if the normal CPAN and Camel rules are
387 followed ($VERSION is a floating point number with no more than 3 decimal
388 points), the stringified output will be exactly the same as the numified
389 output. There will be no visible difference, although the internal
390 representation will be different, and the L<Comparison operators> will
391 function using the internal coding.
393 If a version object is initialized using a L<Extended Version> form, then
394 the stringified form will be the L<Normal Form>. The $obj->normal
395 operation can always be used to produce the L<Normal Form>, even if the
396 version was originally a L<Numeric Version>.
398 print $ver->stringify; # prints v1.2.3.4
399 print $nver->stringify; # prints 1.002
405 =item * Comparison operators
407 Both C<cmp> and C<E<lt>=E<gt>> operators perform the same comparison between
408 terms (upgrading to a version object automatically). Perl automatically
409 generates all of the other comparison operators based on those two.
410 In addition to the obvious equalities listed below, appending a single
411 trailing 0 term does not change the value of a version for comparison
412 purposes. In other words "v1.2" and "1.2.0" will compare as identical.
414 For example, the following relations hold:
416 As Number As String Truth Value
417 ------------- ---------------- -----------
418 $ver > 1.0 $ver gt "1.0" true
419 $ver < 2.5 $ver lt true
420 $ver != 1.3 $ver ne "1.3" true
421 $ver == 1.2 $ver eq "1.2" false
422 $ver == 1.2.3.4 $ver eq "1.2.3.4" see discussion below
424 It is probably best to chose either the numeric notation or the string
425 notation and stick with it, to reduce confusion. Perl6 version objects
426 B<may> only support numeric comparisons. See also L<Quoting>.
428 WARNING: Comparing version with unequal numbers of decimal points (whether
429 explicitly or implicitly initialized), may yield unexpected results at
430 first glance. For example, the following inequalities hold:
432 version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
433 version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
435 For this reason, it is best to use either exclusively L<Numeric Versions> or
436 L<Extended Versions> with multiple decimal points.
442 =item * Logical Operators
444 If you need to test whether a version object
445 has been initialized, you can simply test it directly:
447 $vobj = version->new($something);
448 if ( $vobj ) # true only if $something was non-blank
450 You can also test whether a version object is an L<Alpha version>, for
451 example to prevent the use of some feature not present in the main
454 $vobj = version->new("1.2_3"); # MUST QUOTE
456 if ( $vobj->is_alpha ) # True
462 Because of the nature of the Perl parsing and tokenizing routines,
463 certain initialization values B<must> be quoted in order to correctly
464 parse as the intended version, especially when using the L<qv()> operator.
465 In all cases, a floating point number passed to version->new() will be
466 identically converted whether or not the value itself is quoted. This is
467 not true for L<qv()>, however, when trailing zeros would be stripped on
468 an unquoted input, which would result in a very different version object.
470 In addition, in order to be compatible with earlier Perl version styles,
471 any use of versions of the form 5.006001 will be translated as v5.6.1.
472 In other words, a version with a single decimal point will be parsed as
473 implicitly having three digits between subversions, but only for internal
476 The complicating factor is that in bare numbers (i.e. unquoted), the
477 underscore is a legal numeric character and is automatically stripped
478 by the Perl tokenizer before the version code is called. However, if
479 a number containing one or more decimals and an underscore is quoted, i.e.
480 not bare, that is considered a L<Alpha Version> and the underscore is
483 If you use a mathematic formula that resolves to a floating point number,
484 you are dependent on Perl's conversion routines to yield the version you
485 expect. You are pretty safe by dividing by a power of 10, for example,
486 but other operations are not likely to be what you intend. For example:
488 $VERSION = version->new((qw$Revision: 1.4)[1]/10);
489 print $VERSION; # yields 0.14
490 $V2 = version->new(100/9); # Integer overflow in decimal number
491 print $V2; # yields something like 11.111.111.100
493 Perl 5.8.1 and beyond will be able to automatically quote v-strings but
494 that is not possible in earlier versions of Perl. In other words:
496 $version = version->new("v2.5.4"); # legal in all versions of Perl
497 $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1
499 =head2 What about v-strings?
501 Beginning with Perl 5.6.0, an alternate method to code arbitrary strings
502 of bytes was introduced, called v-strings. They were intended to be an
503 easy way to enter, for example, Unicode strings (which contain two bytes
504 per character). Some programs have used them to encode printer control
505 characters (e.g. CRLF). They were also intended to be used for $VERSION,
506 but their use as such has been problematic from the start.
508 There are two ways to enter v-strings: a bare number with two or more
509 decimal points, or a bare number with one or more decimal points and a
510 leading 'v' character (also bare). For example:
512 $vs1 = 1.2.3; # encoded as \1\2\3
513 $vs2 = v1.2; # encoded as \1\2
515 However, the use of v-strings to initialize version objects with this
516 module is only possible with Perl 5.8.1 or better (which contain special
517 code to enable it). Their use is B<strongly> discouraged in all
518 circumstances (especially the leading 'v' style), since the meaning will
519 change depending on which Perl you are running. It is better to directly
520 use L<"Extended Versions"> to ensure the proper interpretation.
523 =head2 Types of Versions Objects
525 There are two types of Version Objects:
529 =item * Ordinary versions
531 These are the versions that normal modules will use. Can contain as
532 many subversions as required. In particular, those using RCS/CVS can
535 $VERSION = version->new(qw$Revision: 2.7 $);
537 and the current RCS Revision for that file will be inserted
538 automatically. If the file has been moved to a branch, the Revision
539 will have three or more elements; otherwise, it will have only two.
540 This allows you to automatically increment your module version by
541 using the Revision number from the primary file in a distribution, see
542 L<ExtUtils::MakeMaker/"VERSION_FROM">.
544 =item * Alpha Versions
546 For module authors using CPAN, the convention has been to note
547 unstable releases with an underscore in the version string, see
548 L<CPAN>. Alpha releases will test as being newer than the more recent
549 stable release, and less than the next stable release. For example:
551 $alphaver = version->new("12.03_01"); # must be quoted
553 obeys the relationship
555 12.03 < $alphaver < 12.04
557 Alpha versions with a single decimal point will be treated exactly as if
558 they were L<Numeric Versions>, for parsing purposes. The stringification for
559 alpha versions with a single decimal point may seem surprising, since any
560 trailing zeros will visible. For example, the above $alphaver will print as
564 which is mathematically equivalent and ASCII sorts exactly the same as
565 without the trailing zeros.
567 Alpha versions with more than a single decimal point will be treated
568 exactly as if they were L<Extended Versions>, and will display without any
569 trailing (or leading) zeros, in the L<Version Normal> form. For example,
571 $newver = version->new("12.3.1_1");
572 print $newver; # v12.3.1_1
574 =head2 Replacement UNIVERSAL::VERSION
576 In addition to the version objects, this modules also replaces the core
577 UNIVERSAL::VERSION function with one that uses version objects for its
578 comparisons. The return from this operator is always the numified form,
579 and the warning message generated includes both the numified and normal
588 $VERSION = "1.3.5"; # works with all Perl's (since it is quoted)
593 print $Foo::VERSION; # prints 1.2
595 print $Bar::VERSION; # prints 1.003005
597 eval "use CGI 10"; # some far future release
598 print $@; # prints "CGI version 10 (10.0.0) required..."
600 IMPORTANT NOTE: This may mean that code which searches for a specific
601 string (to determine whether a given module is available) may need to be
604 The replacement UNIVERSAL::VERSION, when used as a function, like this:
606 print $module->VERSION;
608 will also exclusively return the numified form. Technically, the
609 $module->VERSION function returns a string (PV) that can be converted to a
610 number following the normal Perl rules, when used in a numeric context.
614 This module is specifically designed and tested to be easily subclassed.
615 In practice, you only need to override the methods you want to change, but
616 you have to take some care when overriding new() (since that is where all
617 of the parsing takes place). For example, this is a perfect acceptable
625 # perform any special input handling here
626 $obj = $self->SUPER::new($n);
627 # and/or add additional hash elements here
631 See also L<version::AlphaBeta> on CPAN for an alternate representation of
634 B<NOTE:> Although the L<qv> operator is not a true class method, but rather a
635 function exported into the caller's namespace, a subclass of version will
636 inherit an import() function which will perform the correct magic on behalf
641 qv - Extended Version initialization operator
645 John Peacock E<lt>jpeacock@cpan.orgE<gt>