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authorNorbert Preining <preining@logic.at>2010-05-12 16:51:27 +0000
committerNorbert Preining <preining@logic.at>2010-05-12 16:51:27 +0000
commitb645030efc22e13c2498a1522083634ab91b2de1 (patch)
treec75c7a71998200d419af56eb755dac2f5115b585 /Master/tlpkg/tlperl.old/lib/UNIVERSAL.pm
parent44ccd4efc5352f9eb1099ba357708e7b5ff03b83 (diff)
move tlperl to tlperl.old
git-svn-id: svn://tug.org/texlive/trunk@18209 c570f23f-e606-0410-a88d-b1316a301751
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+package UNIVERSAL;
+
+our $VERSION = '1.01';
+
+# UNIVERSAL should not contain any extra subs/methods beyond those
+# that it exists to define. The use of Exporter below is a historical
+# accident that can't be fixed without breaking code. Note that we
+# *don't* set @ISA here, don't want all classes/objects inheriting from
+# Exporter. It's bad enough that all classes have a import() method
+# whenever UNIVERSAL.pm is loaded.
+require Exporter;
+*import = \&Exporter::import;
+@EXPORT_OK = qw(isa can VERSION);
+
+1;
+__END__
+
+=head1 NAME
+
+UNIVERSAL - base class for ALL classes (blessed references)
+
+=head1 SYNOPSIS
+
+ $is_io = $fd->isa("IO::Handle");
+ $is_io = Class->isa("IO::Handle");
+
+ $sub = $obj->can("print");
+ $sub = Class->can("print");
+
+ use UNIVERSAL qw( isa can VERSION );
+ $yes = isa $ref, "HASH" ;
+ $sub = can $ref, "fandango" ;
+ $ver = VERSION $obj ;
+
+=head1 DESCRIPTION
+
+C<UNIVERSAL> is the base class which all bless references will inherit from,
+see L<perlobj>.
+
+C<UNIVERSAL> provides the following methods and functions:
+
+=over 4
+
+=item C<< $obj->isa( TYPE ) >>
+
+=item C<< CLASS->isa( TYPE ) >>
+
+=item C<isa( VAL, TYPE )>
+
+Where
+
+=over 4
+
+=item C<TYPE>
+
+is a package name
+
+=item C<$obj>
+
+is a blessed reference or a string containing a package name
+
+=item C<CLASS>
+
+is a package name
+
+=item C<VAL>
+
+is any of the above or an unblessed reference
+
+=back
+
+When used as an instance or class method (C<< $obj->isa( TYPE ) >>),
+C<isa> returns I<true> if $obj is blessed into package C<TYPE> or
+inherits from package C<TYPE>.
+
+When used as a class method (C<< CLASS->isa( TYPE ) >>: sometimes
+referred to as a static method), C<isa> returns I<true> if C<CLASS>
+inherits from (or is itself) the name of the package C<TYPE> or
+inherits from package C<TYPE>.
+
+When used as a function, like
+
+ use UNIVERSAL qw( isa ) ;
+ $yes = isa $h, "HASH";
+ $yes = isa "Foo", "Bar";
+
+or
+
+ require UNIVERSAL ;
+ $yes = UNIVERSAL::isa $a, "ARRAY";
+
+C<isa> returns I<true> in the same cases as above and also if C<VAL> is an
+unblessed reference to a perl variable of type C<TYPE>, such as "HASH",
+"ARRAY", or "Regexp".
+
+=item C<< $obj->can( METHOD ) >>
+
+=item C<< CLASS->can( METHOD ) >>
+
+=item C<can( VAL, METHOD )>
+
+C<can> checks if the object or class has a method called C<METHOD>. If it does
+then a reference to the sub is returned. If it does not then I<undef> is
+returned. This includes methods inherited or imported by C<$obj>, C<CLASS>, or
+C<VAL>.
+
+C<can> cannot know whether an object will be able to provide a method
+through AUTOLOAD, so a return value of I<undef> does not necessarily mean
+the object will not be able to handle the method call. To get around
+this some module authors use a forward declaration (see L<perlsub>)
+for methods they will handle via AUTOLOAD. For such 'dummy' subs, C<can>
+will still return a code reference, which, when called, will fall through
+to the AUTOLOAD. If no suitable AUTOLOAD is provided, calling the coderef
+will cause an error.
+
+C<can> can be called as a class (static) method, an object method, or a
+function.
+
+When used as a function, if C<VAL> is a blessed reference or package name which
+has a method called C<METHOD>, C<can> returns a reference to the subroutine.
+If C<VAL> is not a blessed reference, or if it does not have a method
+C<METHOD>, I<undef> is returned.
+
+=item C<VERSION ( [ REQUIRE ] )>
+
+C<VERSION> will return the value of the variable C<$VERSION> in the
+package the object is blessed into. If C<REQUIRE> is given then
+it will do a comparison and die if the package version is not
+greater than or equal to C<REQUIRE>.
+
+C<VERSION> can be called as either a class (static) method, an object
+method or a function.
+
+
+=back
+
+=head1 EXPORTS
+
+None by default.
+
+You may request the import of all three functions (C<isa>, C<can>, and
+C<VERSION>), however it isn't usually necessary to do so. Perl magically
+makes these functions act as methods on all objects. The one exception is
+C<isa>, which is useful as a function when operating on non-blessed
+references.
+
+=cut