package attributes;
-$VERSION = 0.01;
+our $VERSION = 0.06;
-#@EXPORT_OK = qw(get reftype);
-#@EXPORT = ();
+@EXPORT_OK = qw(get reftype);
+@EXPORT = ();
+%EXPORT_TAGS = (ALL => [@EXPORT, @EXPORT_OK]);
use strict;
#
# The extra trips through newATTRSUB in the interpreter wipe out any savings
# from avoiding the BEGIN block. Just do the bootstrap now.
-BEGIN { bootstrap }
+BEGIN { bootstrap attributes }
sub import {
- @_ > 2 && ref $_[2] or
- croak 'Usage: use '.__PACKAGE__.' $home_stash, $ref, @attrlist';
+ @_ > 2 && ref $_[2] or do {
+ require Exporter;
+ goto &Exporter::import;
+ };
my (undef,$home_stash,$svref,@attrs) = @_;
my $svtype = uc reftype($svref);
my $s = ((@pkgattrs == 1) ? '' : 's');
carp "$svtype package attribute$s " .
"may clash with future reserved word$s: " .
- join(' , ' , @pkgattrs);
+ join(' : ' , @pkgattrs);
}
}
}
croak "Invalid $svtype attribute" .
(( @badattrs == 1 ) ? '' : 's') .
": " .
- join(' , ', @badattrs);
+ join(' : ', @badattrs);
}
}
;
}
-#sub export {
-# require Exporter;
-# goto &Exporter::import;
-#}
-#
-#sub require_version { goto &UNIVERSAL::VERSION }
+sub require_version { goto &UNIVERSAL::VERSION }
1;
__END__
=head1 SYNOPSIS
sub foo : method ;
- my ($x,@y,%z) : Bent ;
+ my ($x,@y,%z) : Bent = 1;
my $s = sub : method { ... };
use attributes (); # optional, to get subroutine declarations
my @attrlist = attributes::get(\&foo);
+ use attributes 'get'; # import the attributes::get subroutine
+ my @attrlist = get \&foo;
+
=head1 DESCRIPTION
Subroutine declarations and definitions may optionally have attribute lists
associated with them. (Variable C<my> declarations also may, but see the
warning below.) Perl handles these declarations by passing some information
about the call site and the thing being declared along with the attribute
-list to this module. In particular, first example above is equivalent to
+list to this module. In particular, the first example above is equivalent to
the following:
use attributes __PACKAGE__, \&foo, 'method';
The second example in the synopsis does something equivalent to this:
- use attributes __PACKAGE__, \$x, 'Bent';
- use attributes __PACKAGE__, \@y, 'Bent';
- use attributes __PACKAGE__, \%z, 'Bent';
+ use attributes ();
+ my ($x,@y,%z);
+ attributes::->import(__PACKAGE__, \$x, 'Bent');
+ attributes::->import(__PACKAGE__, \@y, 'Bent');
+ attributes::->import(__PACKAGE__, \%z, 'Bent');
+ ($x,@y,%z) = 1;
-Yes, that's three invocations.
+Yes, that's a lot of expansion.
-B<WARNING>: attribute declarations for variables are an I<experimental>
-feature. The semantics of such declarations could change or be removed
-in future versions. They are present for purposes of experimentation
+B<WARNING>: attribute declarations for variables are still evolving.
+The semantics and interfaces of such declarations could change in
+future versions. They are present for purposes of experimentation
with what the semantics ought to be. Do not rely on the current
implementation of this feature.
package-specific attributes are allowed by an extension mechanism.
(See L<"Package-specific Attribute Handling"> below.)
-The setting of attributes happens at compile time. An attempt to set
-an unrecognized attribute is a fatal error. (The error is trappable, but
-it still stops the compilation within that C<eval>.) Setting an attribute
-with a name that's all lowercase letters that's not a built-in attribute
-(such as "foo")
-will result in a warning with B<-w> or C<use warnings 'reserved'>.
+The setting of subroutine attributes happens at compile time.
+Variable attributes in C<our> declarations are also applied at compile time.
+However, C<my> variables get their attributes applied at run-time.
+This means that you have to I<reach> the run-time component of the C<my>
+before those attributes will get applied. For example:
+
+ my $x : Bent = 42 if 0;
+
+will neither assign 42 to $x I<nor> will it apply the C<Bent> attribute
+to the variable.
+
+An attempt to set an unrecognized attribute is a fatal error. (The
+error is trappable, but it still stops the compilation within that
+C<eval>.) Setting an attribute with a name that's all lowercase
+letters that's not a built-in attribute (such as "foo") will result in
+a warning with B<-w> or C<use warnings 'reserved'>.
=head2 Built-in Attributes
=item locked
+B<5.005 threads only! The use of the "locked" attribute currently
+only makes sense if you are using the deprecated "Perl 5.005 threads"
+implementation of threads.>
+
Setting this attribute is only meaningful when the subroutine or
method is to be called by multiple threads. When set on a method
subroutine (i.e., one marked with the B<method> attribute below),
as described there. It also means that a subroutine so marked
will not trigger the "Ambiguous call resolved as CORE::%s" warning.
+=item lvalue
+
+Indicates that the referenced subroutine is a valid lvalue and can
+be assigned to. The subroutine must return a modifiable value such
+as a scalar variable, as described in L<perlsub>.
+
=back
-There are no built-in attributes for anything other than subroutines.
+For global variables there is C<unique> attribute: see L<perlfunc/our>.
=head2 Available Subroutines
to raise a fatal exception. If it can find an appropriate package name
for a class method lookup, it will include the results from a
C<FETCH_I<type>_ATTRIBUTES> call in its return list, as described in
-L"Package-specific Attribute Handling"> below.
+L<"Package-specific Attribute Handling"> below.
Otherwise, only L<built-in attributes|"Built-in Attributes"> will be returned.
=item reftype
variable. It returns the built-in type of the referenced variable,
ignoring any package into which it might have been blessed.
This can be useful for determining the I<type> value which forms part of
-the method names described in L"Package-specific Attribute Handling"> below.
+the method names described in L<"Package-specific Attribute Handling"> below.
=back
-Note that these routines are I<not> exported. This is primarily because
-the C<use> mechanism which would normally import them is already in use
-by Perl itself to implement the C<sub : attributes> syntax.
+Note that these routines are I<not> exported by default.
=head2 Package-specific Attribute Handling
This method is called with two fixed arguments, followed by the list of
attributes from the relevant declaration. The two fixed arguments are
the relevant package name and a reference to the declared subroutine or
-variable. The expected return value as a list of attributes which were
+variable. The expected return value is a list of attributes which were
not recognized by this handler. Note that this allows for a derived class
to delegate a call to its base class, and then only examine the attributes
which the base class didn't already handle for it.
=head2 Syntax of Attribute Lists
An attribute list is a sequence of attribute specifications, separated by
-whitespace, commas, or both. Each attribute specification is a simple
+whitespace or a colon (with optional whitespace).
+Each attribute specification is a simple
name, optionally followed by a parenthesised parameter list.
If such a parameter list is present, it is scanned past as for the rules
for the C<q()> operator. (See L<perlop/"Quote and Quote-like Operators">.)
Some examples of syntactically valid attribute lists:
- switch(10,foo(7,3)) , , expensive
- Ugly('\(") , Bad
+ switch(10,foo(7,3)) : expensive
+ Ugly('\(") :Bad
_5x5
locked method
Ugly('(') # ()-string not balanced
5x5 # "5x5" not a valid identifier
Y2::north # "Y2::north" not a simple identifier
- foo + bar # "+" neither a comma nor whitespace
+ foo + bar # "+" neither a colon nor whitespace
+
+=head1 EXPORTS
+
+=head2 Default exports
+
+None.
+
+=head2 Available exports
+
+The routines C<get> and C<reftype> are exportable.
+
+=head2 Export tags defined
+
+The C<:ALL> tag will get all of the above exports.
=head1 EXAMPLES
Effect:
- use attributes Canine => \$spot, "Watchful";
+ use attributes ();
+ attributes::->import(Canine => \$spot, "Watchful");
=item 2.
Effect:
- use attributes Felis => \$cat, "Nervous";
+ use attributes ();
+ attributes::->import(Felis => \$cat, "Nervous");
=item 3.
https://perl5.git.perl.org / perl5.git / blobdiff