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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 0.77; our $VERSION = version->declare("v1.2.3"); # formal
	 use version 0.77; our $VERSION = qv("v1.2.3"); 	      # shorthand
	 use version 0.77; our $VERSION = qv("v1.2_3"); 	      # alpha

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

	 our $VERSION = "1.0203";				      # recommended
	 use version 0.77; our $VERSION = version->parse("1.0203");   # formal
	 use version 0.77; 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
	 seperated 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.

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 0.77; 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 youself 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 v5.12.1				    2010-04-26				     version(3pm)
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