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version - Perl extension for Version Objects |
version - Perl extension for Version Objects
use version;
$version = version->new("12.2.1"); # must be quoted for Perl < 5.8.1
print $version; # 12.2.1
print $version->numify; # 12.002001
if ( $version gt "12.2" ) # true
$alphaver = version->new("1.02_03"); # must be quoted!
print $alphaver; # 1.02_030
print $alphaver->is_alpha(); # true
$ver = qv(1.2); # 1.2.0
$ver = qv("1.2"); # 1.2.0
$perlver = version->new(5.005_03); # must not be quoted! print $perlver; # 5.005030
Overloaded version objects for all versions of Perl. This module implements all of the features of version objects which will be part of Perl 5.10.0 except automatic version object creation.
For the purposes of this module, a version ``number'' is a sequence of positive integral values separated by decimal points and optionally a single underscore. This corresponds to what Perl itself uses for a version, as well as extending the ``version as number'' that is discussed in the various editions of the Camel book.
There are actually two distinct ways to initialize versions:
Both of these methods will produce similar version objects, in that the default stringification will yield the version Normal Form only if required:
$v = version->new(1.002); # 1.002, but compares like 1.2.0 $v = version->new(1.002003); # 1.002003 $v2 = version->new( "1.2.3"); # v1.2.3 $v3 = version->new( 1.2.3); # v1.2.3 for Perl >= 5.8.1
In specific, version numbers initialized as Numeric Versions will stringify in Numeric form. Version numbers initialized as Quoted Versions will be stringified as Normal Form.
Please see Quoting for more details on how Perl will parse various input values.
Any value passed to the new() operator will be parsed only so far as it
contains a numeric, decimal, or underscore character. So, for example:
$v1 = version->new("99 and 94/100 percent pure"); # $v1 == 99.0
$v2 = version->new("something"); # $v2 == "" and $v2->numify == 0
However, see New Operator for one case where non-numeric text is acceptable when initializing version objects.
Beginning with Perl 5.6.0, an alternate method to code arbitrary strings of bytes was introduced, called v-strings. They were intended to be an easy way to enter, for example, Unicode strings (which contain two bytes per character). Some programs have used them to encode printer control characters (e.g. CRLF). They were also intended to be used for $VERSION. Their use has been problematic from the start and they will be phased out beginning in Perl 5.10.0.
There are two ways to enter v-strings: a bare number with two or more decimal places, or a bare number with one or more decimal places and a leading 'v' character (also bare). For example:
$vs1 = 1.2.3; # encoded as \1\2\3 $vs2 = v1.2; # encoded as \1\2
The first of those two syntaxes is destined to be the default way to create a version object in 5.10.0, whereas the second will issue a mandatory deprecation warning beginning at the same time. In both cases, a v-string encoded version will always be stringified in the version Normal Form.
Consequently, the use of v-strings to initialize version objects with this module is only possible with Perl 5.8.1 or better (which contain special code to enable it). Their use is strongly discouraged in all circumstances (especially the leading 'v' style), since the meaning will change depending on which Perl you are running. It is better to use Quoted Versions to ensure the proper interpretation.
These correspond to historical versions of Perl itself prior to 5.6.0, as well as all other modules which follow the Camel rules for the $VERSION scalar. A numeric version is initialized with what looks like a floating point number. Leading zeros are significant and trailing zeros are implied so that a minimum of three places is maintained between subversions. What this means is that any subversion (digits to the right of the decimal place) that contains less than three digits will have trailing zeros added to make up the difference, but only for purposes of comparison with other version objects. For example:
$v = version->new( 1.2); # prints 1.2, compares as 1.200.0 $v = version->new( 1.02); # prints 1.02, compares as 1.20.0 $v = version->new( 1.002); # prints 1.002, compares as 1.2.0 $v = version->new( 1.0023); # 1.2.300 $v = version->new( 1.00203); # 1.2.30 $v = version->new( 1.002_03); # 1.2.30 See "Quoting" $v = version->new( 1.002003); # 1.2.3
All of the preceding examples except the second to last are true whether or not the input value is quoted. The important feature is that the input value contains only a single decimal.
IMPORTANT NOTE: If your numeric version contains more than 3 significant digits after the decimal place, it will be split on each multiple of 3, so 1.0003 becomes 1.0.300, due to the need to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation.
These are the newest form of versions, and correspond to Perl's own version style beginning with 5.6.0. Starting with Perl 5.10.0, and most likely Perl 6, this is likely to be the preferred form. This method requires that the input parameter be quoted, although Perl's after 5.9.0 can use bare numbers with multiple decimal places as a special form of quoting.
Unlike Numeric Versions, Quoted Versions may have more than a single decimal point, e.g. ``5.6.1'' (for all versions of Perl). If a Quoted Version has only one decimal place (and no embedded underscore), it is interpreted exactly like a Numeric Version.
So, for example:
$v = version->new( "1.002"); # 1.2
$v = version->new( "1.2.3"); # 1.2.3
$v = version->new("1.0003"); # 1.0.300
In addition to conventional versions, Quoted Versions can be used to create Alpha Versions.
In general, Quoted Versions permit the greatest amount of freedom to specify a version, whereas Numeric Versions enforce a certain uniformity. See also New Operator for an additional method of initializing version objects.
The one time that a numeric version must be quoted is when a alpha form is used with an otherwise numeric version (i.e. a single decimal place). This is commonly used for CPAN releases, where CPAN or CPANPLUS will ignore alpha versions for automatic updating purposes. Since some developers have used only two significant decimal places for their non-alpha releases, the version object will automatically take that into account if the initializer is quoted. For example Module::Example was released to CPAN with the following sequence of $VERSION's:
# $VERSION Stringified 0.01 0.010 0.02 0.020 0.02_01 0.02_0100 0.02_02 0.02_0200 0.03 0.030 etc.
As you can see, the version object created from the values in the first column may contain a trailing 0, but will otherwise be both mathematically equivalent and sorts alpha-numerically as would be expected.
Overloading has been used with version objects to provide a natural interface for their use. All mathematical operations are forbidden, since they don't make any sense for base version objects.
new() operator is used to initialize
version objects. One way to increment versions when programming is to
use the CVS variable $Revision, which is automatically incremented by
CVS every time the file is committed to the repository.
In order to facilitate this feature, the following code can be employed:
$VERSION = version->new(qw$Revision: 2.7 $);
and the version object will be created as if the following code were used:
$VERSION = version->new("v2.7");
In other words, the version will be automatically parsed out of the string, and it will be quoted to preserve the meaning CVS normally carries for versions. The CVS $Revision$ increments differently from numeric versions (i.e. 1.10 follows 1.9), so it must be handled as if it were a Quoted Version.
A new version object can be created as a copy of an existing version object, either as a class method:
$v1 = version->new(12.3); $v2 = version->new($v1);
or as an object method:
$v1 = version->new(12.3); $v2 = $v1->new();
and in each case, $v1 and $v2 will be identical.
qv()qv() sub. This is not strictly like other q? operators (like qq, qw),
in that the only delimiters supported are parentheses (or spaces). It is
the best way to initialize a short version without triggering the floating
point interpretation. For example:
$v1 = qv(1.2); # 1.2.0
$v2 = qv("1.2"); # also 1.2.0
As you can see, either a bare number or a quoted string can be used, and either will yield the same version number.
For the subsequent examples, the following three objects will be used:
$ver = version->new("1.2.3.4"); # see "Quoting" below
$alpha = version->new("1.2.3_4"); # see "Alpha versions" below
$nver = version->new(1.002); # see "Numeric Versions" above
print $ver->normal; # prints as v1.2.3 print $ver->stringify; # ditto print $ver; # ditto print $nver->normal; # prints as v1.2.0 print $nver->stringify; # prints as 1.002, see "Stringification"
In order to preserve the meaning of the processed version, the normalized representation will always contain at least three sub terms. In other words, the following is guaranteed to always be true:
my $newver = version->new($ver->stringify);
if ($newver eq $ver ) # always true
{...}
print $ver->numify; # prints 1.002003 print $nver->numify; # prints 1.002
Unlike the stringification operator, there is never any need to append trailing zeros to preserve the correct version value.
What this means in practice is that if the normal CPAN and Camel rules are followed ($VERSION is a floating point number with no more than 3 decimal places), the stringified output will be exactly the same as the numified output. There will be no visible difference, although the internal representation will be different, and the Comparison operators will function using the internal coding.
If a version object is initialized using a Quoted Version form, or if the number of significant decimal places exceed three, then the stringified form will be the Normal Form. The $obj->normal operation can always be used to produce the Normal Form, even if the version was originally a Numeric Version.
print $ver->stringify; # prints v1.2.3 print $nver->stringify; # prints 1.002
For example, the following relations hold:
As Number As String Truth Value --------- ------------ ----------- $ver > 1.0 $ver gt "1.0" true $ver < 2.5 $ver lt true $ver != 1.3 $ver ne "1.3" true $ver == 1.2 $ver eq "1.2" false $ver == 1.2.3 $ver eq "1.2.3" see discussion below
It is probably best to chose either the numeric notation or the string notation and stick with it, to reduce confusion. Perl6 version objects may only support numeric comparisons. See also Quoting.
WARNING: Comparing version with unequal numbers of decimal places (whether explicitly or implicitly initialized), may yield unexpected results at first glance. For example, the following inequalities hold:
version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
For this reason, it is best to use either exclusively Numeric Versions or Quoted Versions with multiple decimal places.
$vobj = version->new($something); if ( $vobj ) # true only if $something was non-blank
You can also test whether a version object is an Alpha version, for example to prevent the use of some feature not present in the main release:
$vobj = version->new("1.2_3"); # MUST QUOTE
...later...
if ( $vobj->is_alpha ) # True
Because of the nature of the Perl parsing and tokenizing routines, certain initialization values must be quoted in order to correctly parse as the intended version, and additionally, some initial values must not be quoted to obtain the intended version.
Except for Alpha versions, any version initialized with something that looks like a number (a single decimal place) will be parsed in the same way whether or not the term is quoted. In order to be compatible with earlier Perl version styles, any use of versions of the form 5.006001 will be translated as 5.6.1. In other words, a version with a single decimal place will be parsed as implicitly having three places between subversions.
The complicating factor is that in bare numbers (i.e. unquoted), the underscore is a legal numeric character and is automatically stripped by the Perl tokenizer before the version code is called. However, if a number containing one or more decimals and an underscore is quoted, i.e. not bare, that is considered a Alpha Version and the underscore is significant.
If you use a mathematic formula that resolves to a floating point number, you are dependent on Perl's conversion routines to yield the version you expect. You are pretty safe by dividing by a power of 10, for example, but other operations are not likely to be what you intend. For example:
$VERSION = version->new((qw$Revision: 1.4)[1]/10); print $VERSION; # yields 0.14 $V2 = version->new(100/9); # Integer overflow in decimal number print $V2; # yields something like 11.111.111.100
Perl 5.8.1 and beyond will be able to automatically quote v-strings but that is not possible in earlier versions of Perl. In other words:
$version = version->new("v2.5.4"); # legal in all versions of Perl
$newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1
There are two types of Version Objects:
$VERSION = version->new(qw$Revision: 2.7 $);
and the current RCS Revision for that file will be inserted automatically. If the file has been moved to a branch, the Revision will have three or more elements; otherwise, it will have only two. This allows you to automatically increment your module version by using the Revision number from the primary file in a distribution, see VERSION_FROM in the ExtUtils::MakeMaker manpage.
$alphaver = version->new("12.03_01"); # must be quoted
obeys the relationship
12.03 < $alphaver < 12.04
Alpha versions with a single decimal place will be treated exactly as if they were Numeric Versions, for parsing purposes. The stringification for alpha versions with a single decimal place may seem surprising, since any trailing zeros will visible. For example, the above $alphaver will print as
12.03_0100
which is mathematically equivalent and ASCII sorts exactly the same as without the trailing zeros.
Alpha versions with more than a single decimal place will be treated exactly as if they were Quoted Versions, and will display without any trailing (or leading) zeros, in the Version Normal form. For example,
$newver = version->new("12.3.1_1");
print $newver; # v12.3.1_1
In addition to the version objects, this modules also replaces the core UNIVERSAL::VERSION function with one that uses version objects for its comparisons. The return from this operator is always the numified form, and the warning message generated includes both the numified and normal forms (for clarity).
For example:
package Foo; $VERSION = 1.2;
package Bar; $VERSION = "1.3.5"; # works with all Perl's (since it is quoted)
package main; use version;
print $Foo::VERSION; # prints 1.2
print $Bar::VERSION; # prints 1.003005
eval "use CGI 10"; # some far future release print $@; # prints "CGI version 10 (10.0.0) required..."
IMPORTANT NOTE: This may mean that code which searches for a specific string (to determine whether a given module is available) may need to be changed.
The replacement UNIVERSAL::VERSION, when used as a function, like this:
print $module->VERSION;
will also exclusively return the numified form. Technically, the $module->VERSION function returns a string (PV) that can be converted to a number following the normal Perl rules, when used in a numeric context.
This module is specifically designed and tested to be easily subclassed.
In practice, you only need to override the methods you want to change, but
you have to take some care when overriding new() (since that is where all
of the parsing takes place). For example, this is a perfect acceptable
derived class:
package myversion;
use base version;
sub new {
my($self,$n)=@_;
my $obj;
# perform any special input handling here
$obj = $self->SUPER::new($n);
# and/or add additional hash elements here
return $obj;
}
See also the version::AlphaBeta manpage on CPAN for an alternate representation of version strings.
qv - quoted version initialization operator
John Peacock <jpeacock@cpan.org>
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version - Perl extension for Version Objects |