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Diffstat (limited to 'gnu/usr.bin/perl/lib/version/Internals.pod')
| -rw-r--r-- | gnu/usr.bin/perl/lib/version/Internals.pod | 402 |
1 files changed, 246 insertions, 156 deletions
diff --git a/gnu/usr.bin/perl/lib/version/Internals.pod b/gnu/usr.bin/perl/lib/version/Internals.pod index 5ff365e2762..a4f0543fe16 100644 --- a/gnu/usr.bin/perl/lib/version/Internals.pod +++ b/gnu/usr.bin/perl/lib/version/Internals.pod @@ -1,34 +1,34 @@ =head1 NAME -version::Internal - Perl extension for Version Objects +version::Internals - Perl extension for Version Objects =head1 DESCRIPTION Overloaded version objects for all modern versions of Perl. This documents the internal data representation and underlying code for version.pm. See L<version.pod> for daily usage. This document is only useful for users -writing a subclass of version.pm or interested in the gory details. +interested in the gory details. -=head1 What IS a version +=head1 WHAT IS A VERSION? For the purposes of this module, a version "number" is a sequence of -positive integer values separated by one or more 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 +positive integer values separated by one or more 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 kinds of version objects: =over 4 -=item * Decimal Versions +=item Decimal Versions Any version which "looks like a number", see L<Decimal Versions>. This also includes versions with a single decimal point and a single embedded -underscore, see L<Decimal Alpha Versions>, even though these must be quoted +underscore, see L<Alpha Versions>, even though these must be quoted to preserve the underscore formatting. -=item * Dotted-Decimal Versions +=item Dotted-Decimal Versions Also referred to as "Dotted-Integer", these contains more than one decimal point and may have an optional embedded underscore, see L<Dotted-Decimal @@ -39,7 +39,7 @@ A leading 'v' character is now required and will warn if it missing. =back Both of these methods will produce similar version objects, in that -the default stringification will yield the version L<Normal Form> only +the default stringification will yield the version L<Normal Form> only if required: $v = version->new(1.002); # 1.002, but compares like 1.2.0 @@ -63,7 +63,7 @@ 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: - # Prints Equivalent to + # Prints Equivalent to $v = version->new( 1.2); # 1.2 v1.200.0 $v = version->new( 1.02); # 1.02 v1.20.0 $v = version->new( 1.002); # 1.002 v1.2.0 @@ -71,14 +71,14 @@ purposes of comparison with other version objects. For example: $v = version->new( 1.00203); # 1.00203 v1.2.30 $v = version->new( 1.002003); # 1.002003 v1.2.3 -All of the preceding examples are true whether or not the input value is -quoted. The important feature is that the input value contains only a -single decimal. See also L<Alpha Versions> for how to handle +All of the preceding examples are true whether or not the input value is +quoted. The important feature is that the input value contains only a +single decimal. See also L<Alpha Versions>. -IMPORTANT NOTE: As shown above, if your Decimal version contains more -than 3 significant digits after the decimal place, it will be split on -each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need -to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation. +IMPORTANT NOTE: As shown above, if your Decimal version contains more +than 3 significant digits after the decimal place, it will be split on +each multiple of 3, so 1.0003 is equivalent to v1.0.300, due to the need +to remain compatible with Perl's own 5.005_03 == 5.5.30 interpretation. Any trailing zeros are ignored for mathematical comparison purposes. =head2 Dotted-Decimal Versions @@ -86,7 +86,7 @@ Any trailing zeros are ignored for mathematical comparison purposes. 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 normally requires that the input parameter be quoted, although +method normally requires that the input parameter be quoted, although Perl's after 5.8.1 can use v-strings as a special form of quoting, but this is highly discouraged. @@ -102,42 +102,210 @@ a single decimal point, e.g.: In general, Dotted-Decimal Versions permit the greatest amount of freedom to specify a version, whereas Decimal Versions enforce a certain -uniformity. See also L<New Operator> for an additional method of -initializing version objects. +uniformity. -Just like L<Decimal Versions>, Dotted-Decimal Versions can be used as +Just like L<Decimal Versions>, Dotted-Decimal Versions can be used as L<Alpha Versions>. -=head2 Decimal Alpha Versions +=head2 Alpha Versions -The one time that a Decimal version must be quoted is when a alpha form is -used with an otherwise Decimal version (i.e. a single decimal point). 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: +For module authors using CPAN, the convention has been to note unstable +releases with an underscore in the version string. (See L<CPAN>.) version.pm +follows this convention and alpha releases will test as being newer than the +more recent stable release, and less than the next stable release. Only the +last element may be separated by an underscore: - # $VERSION Stringified - 0.01 0.01 - 0.02 0.02 - 0.02_01 0.02_01 - 0.02_02 0.02_02 - 0.03 0.03 - etc. + # Declaring + use version 0.77; our $VERSION = version->declare("v1.2_3"); -The stringified form of Decimal versions will always be the same string -that was used to initialize the version object. + # Parsing + $v1 = version->parse("v1.2_3"); + $v1 = version->parse("1.002_003"); -=head1 High level design +Note that you B<must> quote the version when writing an alpha Decimal version. +The stringified form of Decimal versions will always be the same string that +was used to initialize the version object. -=head2 version objects +=head2 Regular Expressions for Version Parsing -version.pm provides an overloaded version object that is designed to both +A formalized definition of the legal forms for version strings is +included in the main F<version.pm> file. Primitives are included for +common elements, although they are scoped to the file so they are useful +for reference purposes only. There are two publicly accessible scalars +that can be used in other code (not exported): + +=over 4 + +=item C<$version::LAX> + +This regexp covers all of the legal forms allowed under the current +version string parser. This is not to say that all of these forms +are recommended, and some of them can only be used when quoted. + +For dotted decimals: + + v1.2 + 1.2345.6 + v1.23_4 + +The leading 'v' is optional if two or more decimals appear. If only +a single decimal is included, then the leading 'v' is required to +trigger the dotted-decimal parsing. A leading zero is permitted, +though not recommended except when quoted, because of the risk that +Perl will treat the number as octal. A trailing underscore plus one +or more digits denotes an alpha or development release (and must be +quoted to be parsed properly). + +For decimal versions: + + 1 + 1.2345 + 1.2345_01 + +an integer portion, an optional decimal point, and optionally one or +more digits to the right of the decimal are all required. A trailing +underscore is permitted and a leading zero is permitted. Just like +the lax dotted-decimal version, quoting the values is required for +alpha/development forms to be parsed correctly. + +=item C<$version::STRICT> + +This regexp covers a much more limited set of formats and constitutes +the best practices for initializing version objects. Whether you choose +to employ decimal or dotted-decimal for is a personal preference however. + +=over 4 + +=item v1.234.5 + +For dotted-decimal versions, a leading 'v' is required, with three or +more sub-versions of no more than three digits. A leading 0 (zero) +before the first sub-version (in the above example, '1') is also +prohibited. + +=item 2.3456 + +For decimal versions, an integer portion (no leading 0), a decimal point, +and one or more digits to the right of the decimal are all required. + +=back + +=back + +Both of the provided scalars are already compiled as regular expressions +and do not contain either anchors or implicit groupings, so they can be +included in your own regular expressions freely. For example, consider +the following code: + + ($pkg, $ver) =~ / + ^[ \t]* + use [ \t]+($PKGNAME) + (?:[ \t]+($version::STRICT))? + [ \t]*; + /x; + +This would match a line of the form: + + use Foo::Bar::Baz v1.2.3; # legal only in Perl 5.8.1+ + +where C<$PKGNAME> is another regular expression that defines the legal +forms for package names. + +=head1 IMPLEMENTATION DETAILS + +=head2 Equivalence between Decimal and Dotted-Decimal Versions + +When Perl 5.6.0 was released, the decision was made to provide a +transformation between the old-style decimal versions and new-style +dotted-decimal versions: + + 5.6.0 == 5.006000 + 5.005_04 == 5.5.40 + +The floating point number is taken and split first on the single decimal +place, then each group of three digits to the right of the decimal makes up +the next digit, and so on until the number of significant digits is exhausted, +B<plus> enough trailing zeros to reach the next multiple of three. + +This was the method that version.pm adopted as well. Some examples may be +helpful: + + equivalent + decimal zero-padded dotted-decimal + ------- ----------- -------------- + 1.2 1.200 v1.200.0 + 1.02 1.020 v1.20.0 + 1.002 1.002 v1.2.0 + 1.0023 1.002300 v1.2.300 + 1.00203 1.002030 v1.2.30 + 1.002003 1.002003 v1.2.3 + +=head2 Quoting Rules + +Because of the nature of the Perl parsing and tokenizing routines, +certain initialization values B<must> be quoted in order to correctly +parse as the intended version, especially when using the L<declare> or +L<qv> methods. While you do not have to quote decimal numbers when +creating version objects, it is always safe to quote B<all> initial values +when using version.pm methods, as this will ensure that what you type is +what is used. + +Additionally, if you quote your initializer, then the quoted value that goes +B<in> will be be exactly what comes B<out> when your $VERSION is printed +(stringified). If you do not quote your value, Perl's normal numeric handling +comes into play and you may not get back what you were expecting. + +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 are 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 + +=head2 What about v-strings? + +There are two ways to enter v-strings: a bare number with two or more +decimal points, or a bare number with one or more decimal points 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 + +However, the use of bare v-strings to initialize version objects is +B<strongly> discouraged in all circumstances. Also, bare +v-strings are not completely supported in any version of Perl prior to +5.8.1. + +If you insist on using bare v-strings with Perl > 5.6.0, be aware of the +following limitations: + +1) For Perl releases 5.6.0 through 5.8.0, the v-string code merely guesses, +based on some characteristics of v-strings. You B<must> use a three part +version, e.g. 1.2.3 or v1.2.3 in order for this heuristic to be successful. + +2) For Perl releases 5.8.1 and later, v-strings have changed in the Perl +core to be magical, which means that the version.pm code can automatically +determine whether the v-string encoding was used. + +3) In all cases, a version created using v-strings will have a stringified +form that has a leading 'v' character, for the simple reason that sometimes +it is impossible to tell whether one was present initially. + +=head2 Version Object Internals + +version.pm provides an overloaded version object that is designed to both encapsulate the author's intended $VERSION assignment as well as make it completely natural to use those objects as if they were numbers (e.g. for -comparisons). To do this, a version object contains both the original +comparisons). To do this, a version object contains both the original representation as typed by the author, as well as a parsed representation to ease comparisons. Version objects employ L<overload> methods to simplify code that needs to compare, print, etc the objects. @@ -222,7 +390,7 @@ For example: 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. It is always better to use the built-in comparison implicit in -C<use> or C<require>, rather than manually poking at C<class->VERSION> +C<use> or C<require>, rather than manually poking at C<< class->VERSION >> and then doing a comparison yourself. The replacement UNIVERSAL::VERSION, when used as a function, like this: @@ -232,7 +400,7 @@ The replacement UNIVERSAL::VERSION, when used as a function, like this: will also exclusively return the stringified form. See L<Stringification> for more details. -=head1 Usage question +=head1 USAGE DETAILS =head2 Using modules that use version.pm @@ -270,8 +438,7 @@ With Perl >= 5.6.2, you can also use a line like this: use Example 1.2.3; and it will again work (i.e. give the error message as above), even with -releases of Perl which do not normally support v-strings (see L<What about -v-strings> below). This has to do with that fact that C<use> only checks +releases of Perl which do not normally support v-strings (see L<version/What about v-strings> below). This has to do with that fact that C<use> only checks to see if the second term I<looks like a number> and passes that to the replacement L<UNIVERSAL::VERSION>. This is not true in Perl 5.005_04, however, so you are B<strongly encouraged> to always use a Decimal version @@ -282,21 +449,15 @@ version. =head2 Object Methods -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. Consequently, -there is no overloaded numification available. If you want to use a -version object in a Decimal context for some reason, see the L<numify> -object method. - =over 4 -=item * New Operator +=item new() -Like all OO interfaces, the 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. +Like many OO interfaces, the new() method is used to initialize version +objects. If two arguments are passed to C<new()>, the B<second> one will be +used as if it were prefixed with "v". This is to support historical use of the +C<qw> operator with 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: @@ -312,7 +473,7 @@ 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 Decimal versions (i.e. 1.10 follows 1.9), so it must be handled as if -it were a L<Dotted-Decimal Version>. +it were a Dotted-Decimal Version. A new version object can be created as a copy of an existing version object, either as a class method: @@ -337,7 +498,7 @@ example case, $v2 will be an empty object of the same type as $v1. =over 4 -=item * qv() +=item qv() An alternate way to create a new version object is through the exported qv() sub. This is not strictly like other q? operators (like qq, qw), @@ -348,7 +509,7 @@ point interpretation. For example: $v1 = qv(1.2); # v1.2.0 $v2 = qv("1.2"); # also v1.2.0 -As you can see, either a bare number or a quoted string can usually +As you can see, either a bare number or a quoted string can usually be used interchangably, except in the case of a trailing zero, which must be quoted to be converted properly. For this reason, it is strongly recommended that all initializers to qv() be quoted strings instead of @@ -364,33 +525,32 @@ or just require version, like this: require version; Both methods will prevent the import() method from firing and exporting the -C<qv()> sub. This is true of subclasses of version as well, see -L<SUBCLASSING> for details. +C<qv()> sub. =back 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 "Decimal Versions" above + $ver = version->new("1.2.3.4"); # see "Quoting Rules" + $alpha = version->new("1.2.3_4"); # see "Alpha Versions" + $nver = version->new(1.002); # see "Decimal Versions" =over 4 -=item * Normal Form +=item Normal Form For any version object which is initialized with multiple decimal places (either quoted or if possible v-string), or initialized using -the L<qv()> operator, the stringified representation is returned in +the L<qv>() operator, the stringified representation is returned in a normalized or reduced form (no extraneous zeros), and with a leading 'v': print $ver->normal; # prints as v1.2.3.4 print $ver->stringify; # ditto print $ver; # ditto print $nver->normal; # prints as v1.2.0 - print $nver->stringify; # prints as 1.002, see "Stringification" + print $nver->stringify; # prints as 1.002, see "Stringification" -In order to preserve the meaning of the processed version, the +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: @@ -402,10 +562,10 @@ In other words, the following is guaranteed to always be true: =over 4 -=item * Numification +=item Numification Although all mathematical operations on version objects are forbidden -by default, it is possible to retrieve a number which corresponds +by default, it is possible to retrieve a number which corresponds to the version object through the use of the $obj->numify method. For formatting purposes, when displaying a number which corresponds a version object, all sub versions are assumed to have @@ -421,7 +581,7 @@ trailing zeros to preserve the correct version value. =over 4 -=item * Stringification +=item Stringification The default stringification for version objects returns exactly the same string as was used to create it, whether you used C<new()> or C<qv()>, @@ -438,29 +598,29 @@ For example: version->new("v1.2") v1.2 qv("1.2.3") 1.2.3 qv("v1.3.5") v1.3.5 - qv("1.2") v1.2 ### exceptional case + qv("1.2") v1.2 ### exceptional case See also L<UNIVERSAL::VERSION>, as this also returns the stringified form when used as a class method. IMPORTANT NOTE: There is one exceptional cases shown in the above table where the "initializer" is not stringwise equivalent to the stringified -representation. If you use the C<qv()> operator on a version without a +representation. If you use the C<qv>() operator on a version without a leading 'v' B<and> with only a single decimal place, the stringified output -will have a leading 'v', to preserve the sense. See the L<qv()> operator +will have a leading 'v', to preserve the sense. See the L<qv>() operator for more details. IMPORTANT NOTE 2: Attempting to bypass the normal stringification rules by -manually applying L<numify()> and L<normal()> will sometimes yield +manually applying L<numify>() and L<normal>() will sometimes yield surprising results: print version->new(version->new("v1.0")->numify)->normal; # v1.0.0 -The reason for this is that the L<numify()> operator will turn "v1.0" +The reason for this is that the L<numify>() operator will turn "v1.0" into the equivalent string "1.000000". Forcing the outer version object -to L<normal()> form will display the mathematically equivalent "v1.0.0". +to L<normal>() form will display the mathematically equivalent "v1.0.0". -As the example in L<new()> shows, you can always create a copy of an +As the example in L<new>() shows, you can always create a copy of an existing version object with the same value by the very compact: $v2 = $v1->new($v1); @@ -472,7 +632,7 @@ down to the same internal representation as well as stringification. =over 4 -=item * Comparison operators +=item Comparison operators Both C<cmp> and C<E<lt>=E<gt>> operators perform the same comparison between terms (upgrading to a version object automatically). Perl automatically @@ -493,7 +653,7 @@ For example, the following relations hold: It is probably best to chose either the Decimal notation or the string notation and stick with it, to reduce confusion. Perl6 version objects -B<may> only support Decimal comparisons. See also L<Quoting>. +B<may> only support Decimal comparisons. See also L<Quoting Rules>. WARNING: Comparing version with unequal numbers of decimal points (whether explicitly or implicitly initialized), may yield unexpected results at @@ -509,7 +669,7 @@ L<Dotted-Decimal Versions> with multiple decimal points. =over 4 -=item * Logical Operators +=item Logical Operators If you need to test whether a version object has been initialized, you can simply test it directly: @@ -517,7 +677,7 @@ has been initialized, you can simply test it directly: $vobj = version->new($something); if ( $vobj ) # true only if $something was non-blank -You can also test whether a version object is an L<Alpha version>, for +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: @@ -527,76 +687,6 @@ release: =back -=head2 Quoting - -Because of the nature of the Perl parsing and tokenizing routines, -certain initialization values B<must> be quoted in order to correctly -parse as the intended version, especially when using the L<qv()> operator. -In all cases, a floating point number passed to version->new() will be -identically converted whether or not the value itself is quoted. This is -not true for L<qv()>, however, when trailing zeros would be stripped on -an unquoted input, which would result in a very different version object. - -In addition, in order to be compatible with earlier Perl version styles, -any use of versions of the form 5.006001 will be translated as v5.6.1. -In other words, a version with a single decimal point will be parsed as -implicitly having three digits between subversions, but only for internal -comparison purposes. - -The complicating factor is that in bare numbers (i.e. unquoted), the -underscore is a legal Decimal 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 L<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 - $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1 - -=head1 SUBCLASSING - -This module is specifically designed and tested to be easily subclassed. -In practice, you only need to override the methods you want to change, but -you have to take some care when overriding new() (since that is where all -of the parsing takes place). For example, this is a perfect acceptable -derived class: - - package myversion; - use base version; - sub new { - my($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 L<version::AlphaBeta> on CPAN for an alternate representation of -version strings. - -B<NOTE:> Although the L<qv> operator is not a true class method, but rather a -function exported into the caller's namespace, a subclass of version will -inherit an import() function which will perform the correct magic on behalf -of the subclass. - -=head1 EXPORT - -qv - Dotted-Decimal Version initialization operator - =head1 AUTHOR John Peacock E<lt>jpeacock@cpan.orgE<gt> |