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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");               # shorthand
         use version; our $VERSION = qv("v1.2_3");               # alpha

         # 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:

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

       • Always use a leading-v

       • 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.

       • 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.

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

       Some examples:

         $variable   version->parse($variable)
         ---------   -------------------------1.23 ------------------------1.23
         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;     # 1.2

   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.

       perl.



perl v5.16.2                                     2012-10-11                                     version(3pm)