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version(3pm)           Perl Programmers Reference Guide           version(3pm)




NAME

       version - Perl extension for Version Objects


SYNOPSIS

         # Parsing version strings (decimal or dotted-decimal)

         use version 0.77; # get latest bug-fixes and API
         $ver = version->parse($string)

         # Declaring a dotted-decimal $VERSION (keep on one line!)

         use version; our $VERSION = version->declare("v1.2.3"); # formal
         use version; our $VERSION = qv("v1.2.3");               # deprecated
         use version; our $VERSION = qv("v1.2_3");               # deprecated

         # Declaring an old-style decimal $VERSION (use quotes!)

         our $VERSION = "1.0203";                                # recommended
         use version; our $VERSION = version->parse("1.0203");   # formal
         use version; our $VERSION = version->parse("1.02_03");  # alpha

         # Comparing mixed version styles (decimals, dotted-decimals, objects)

         if ( version->parse($v1) == version->parse($v2) ) {
           # do stuff
         }

         # Sorting mixed version styles

         @ordered = sort { version->parse($a) <=> version->parse($b) } @list;


DESCRIPTION

       Version objects were added to Perl in 5.10.  This module implements
       version objects for older version of Perl and provides the version
       object API for all versions of Perl.  All previous releases before 0.74
       are deprecated and should not be used due to incompatible API changes.
       Version 0.77 introduces the new 'parse' and 'declare' methods to
       standardize usage.  You are strongly urged to set 0.77 as a minimum in
       your code, e.g.

         use version 0.77; # even for Perl v.5.10.0


TYPES OF VERSION OBJECTS

       There are two different types of version objects, corresponding to the
       two different styles of versions in use:

       Decimal Versions
         The classic floating-point number $VERSION.  The advantage to this
         style is that you don't need to do anything special, just type a
         number into your source file.  Quoting is recommended, as it ensures
         that trailing zeroes ("1.50") are preserved in any warnings or other
         output.

       Dotted Decimal Versions
         The more modern form of version assignment, with 3 (or potentially
         more) integers separated by decimal points (e.g. v1.2.3).  This is
         the form that Perl itself has used since 5.6.0 was released.  The
         leading 'v' is now strongly recommended for clarity, and will throw a
         warning in a future release if omitted.  A leading 'v' character is
         required to pass the "is_strict()" test.


DECLARING VERSIONS

       If you have a module that uses a decimal $VERSION (floating point), and
       you do not intend to ever change that, this module is not for you.
       There is nothing that version.pm gains you over a simple $VERSION
       assignment:

         our $VERSION = "1.02";

       Since Perl v5.10.0 includes the version.pm comparison logic anyways,
       you don't need to do anything at all.

   How to convert a module from decimal to dotted-decimal
       If you have used a decimal $VERSION in the past and wish to switch to a
       dotted-decimal $VERSION, then you need to make a one-time conversion to
       the new format.

       Important Note: you must ensure that your new $VERSION is numerically
       greater than your current decimal $VERSION; this is not always obvious.
       First, convert your old decimal version (e.g. 1.02) to a normalized
       dotted-decimal form:

         $ perl -Mversion -e 'print version->parse("1.02")->normal'
         v1.20.0

       Then increment any of the dotted-decimal components (v1.20.1 or
       v1.21.0).

   How to "declare()" a dotted-decimal version
         use version; our $VERSION = version->declare("v1.2.3");

       The "declare()" method always creates dotted-decimal version objects.
       When used in a module, you must put it on the same line as "use
       version" to ensure that $VERSION is read correctly by PAUSE and
       installer tools.  You should also add 'version' to the
       'configure_requires' section of your module metadata file.  See
       instructions in ExtUtils::MakeMaker or Module::Build for details.

       Important Note: Even if you pass in what looks like a decimal number
       ("1.2"), a dotted-decimal will be created ("v1.200.0"). To avoid
       confusion or unintentional errors on older Perls, follow these
       guidelines:

       o Always use a dotted-decimal with (at least) three components

       o Always use a leading-v

       o Always quote the version

       If you really insist on using version.pm with an ordinary decimal
       version, use "parse()" instead of declare.  See the "PARSING AND
       COMPARING VERSIONS" for details.

       See also version::Internals for more on version number conversion,
       quoting, calculated version numbers and declaring developer or "alpha"
       version numbers.


PARSING AND COMPARING VERSIONS

       If you need to compare version numbers, but can't be sure whether they
       are expressed as numbers, strings, v-strings or version objects,  then
       you should use version.pm to parse them all into objects for
       comparison.

   How to "parse()" a version
       The "parse()" method takes in anything that might be a version and
       returns a corresponding version object, doing any necessary conversion
       along the way.

       o Dotted-decimal: bare v-strings (v1.2.3) and strings with more than
         one decimal point and a leading 'v' ("v1.2.3"); NOTE you can
         technically use a v-string or strings with a leading-v and only one
         decimal point (v1.2 or "v1.2"), but you will confuse both yourself
         and others.

       o Decimal: regular decimal numbers (literal or in a string)

       Some examples:

         $variable   version->parse($variable)
         ---------   -------------------------
         1.23        v1.230.0
         "1.23"      v1.230.0
         v1.23       v1.23.0
         "v1.23"     v1.23.0
         "1.2.3"     v1.2.3
         "v1.2.3"    v1.2.3

       See version::Internals for more on version number conversion.

   How to check for a legal version string
       If you do not want to actually create a full blown version object, but
       would still like to verify that a given string meets the criteria to be
       parsed as a version, there are two helper functions that can be
       employed directly:

       "is_lax()"
           The lax criteria corresponds to what is currently allowed by the
           version parser.  All of the following formats are acceptable for
           dotted-decimal formats strings:

               v1.2
               1.2345.6
               v1.23_4
               1.2345
               1.2345_01

       "is_strict()"
           If you want to limit yourself to a much more narrow definition of
           what a version string constitutes, "is_strict()" is limited to
           version strings like the following list:

               v1.234.5
               2.3456

       See version::Internals for details of the regular expressions that
       define the legal version string forms, as well as how to use those
       regular expressions in your own code if "is_lax()" and "is_strict()"
       are not sufficient for your needs.

   How to compare version objects
       Version objects overload the "cmp" and "<=>" operators.  Perl
       automatically generates all of the other comparison operators based on
       those two so all the normal logical comparisons will work.

         if ( version->parse($v1) == version->parse($v2) ) {
           # do stuff
         }

       If a version object is compared against a non-version object, the non-
       object term will be converted to a version object using "parse()".
       This may give surprising results:

         $v1 = version->parse("v0.95.0");
         $bool = $v1 < 0.96; # FALSE since 0.96 is v0.960.0

       Always comparing to a version object will help avoid surprises:

         $bool = $v1 < version->parse("v0.96.0"); # TRUE

       Note that "alpha" version objects (where the version string contains a
       trailing underscore segment) compare as less than the equivalent
       version without an underscore:

         $bool = version->parse("1.23_45") < version->parse("1.2345"); # TRUE

       See version::Internals for more details on "alpha" versions.


OBJECT METHODS

   is_alpha()
       True if and only if the version object was created with a underscore,
       e.g.

         version->parse('1.002_03')->is_alpha;  # TRUE
         version->declare('1.2.3_4')->is_alpha; # TRUE

   is_qv()
       True only if the version object is a dotted-decimal version, e.g.

         version->parse('v1.2.0')->is_qv;       # TRUE
         version->declare('v1.2')->is_qv;       # TRUE
         qv('1.2')->is_qv;                      # TRUE
         version->parse('1.2')->is_qv;          # FALSE

   normal()
       Returns a string with a standard 'normalized' dotted-decimal form with
       a leading-v and at least 3 components.

        version->declare('v1.2')->normal;  # v1.2.0
        version->parse('1.2')->normal;     # v1.200.0

   numify()
       Returns a value representing the object in a pure decimal form without
       trailing zeroes.

        version->declare('v1.2')->numify;  # 1.002
        version->parse('1.2')->numify;     # 1.200

   stringify()
       Returns a string that is as close to the original representation as
       possible.  If the original representation was a numeric literal, it
       will be returned the way perl would normally represent it in a string.
       This method is used whenever a version object is interpolated into a
       string.

        version->declare('v1.2')->stringify;    # v1.2
        version->parse('1.200')->stringify;     # 1.200
        version->parse(1.02_30)->stringify;     # 1.023


EXPORTED FUNCTIONS

   qv()
       This function is no longer recommended for use, but is maintained for
       compatibility with existing code.  If you do not want to have it
       exported to your namespace, use this form:

         use version 0.77 ();

   is_lax()
       (Not exported by default)

       This function takes a scalar argument and returns a boolean value
       indicating whether the argument meets the "lax" rules for a version
       number.  Leading and trailing spaces are not allowed.

   is_strict()
       (Not exported by default)

       This function takes a scalar argument and returns a boolean value
       indicating whether the argument meets the "strict" rules for a version
       number.  Leading and trailing spaces are not allowed.


AUTHOR

       John Peacock <jpeacock@cpan.org>


SEE ALSO

       version::Internals(3).

       perl(1).



perl v5.24.0                      2016-04-06                      version(3pm)

perl 5.24 - Generated Sat Nov 26 10:08:59 CST 2016
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