--- /dev/null
+
+package Class::MOP;
+
+use strict;
+use warnings;
+
+use 5.008;
+
+use MRO::Compat;
+
+use Carp 'confess';
+use Scalar::Util 'weaken', 'reftype', 'blessed';
+use Try::Tiny;
+
+use Class::MOP::Class;
+use Class::MOP::Attribute;
+use Class::MOP::Method;
+
+BEGIN {
+ *IS_RUNNING_ON_5_10 = ($] < 5.009_005)
+ ? sub () { 0 }
+ : sub () { 1 };
+
+ # this is either part of core or set up appropriately by MRO::Compat
+ *check_package_cache_flag = \&mro::get_pkg_gen;
+}
+
+our $VERSION = '0.95';
+our $XS_VERSION = $VERSION;
+$VERSION = eval $VERSION;
+our $AUTHORITY = 'cpan:STEVAN';
+
+require XSLoader;
+XSLoader::load( __PACKAGE__, $XS_VERSION );
+
+
+{
+ # Metaclasses are singletons, so we cache them here.
+ # there is no need to worry about destruction though
+ # because they should die only when the program dies.
+ # After all, do package definitions even get reaped?
+ # Anonymous classes manage their own destruction.
+ my %METAS;
+
+ sub get_all_metaclasses { %METAS }
+ sub get_all_metaclass_instances { values %METAS }
+ sub get_all_metaclass_names { keys %METAS }
+ sub get_metaclass_by_name { $METAS{$_[0]} }
+ sub store_metaclass_by_name { $METAS{$_[0]} = $_[1] }
+ sub weaken_metaclass { weaken($METAS{$_[0]}) }
+ sub does_metaclass_exist { exists $METAS{$_[0]} && defined $METAS{$_[0]} }
+ sub remove_metaclass_by_name { delete $METAS{$_[0]}; return }
+
+ # This handles instances as well as class names
+ sub class_of {
+ return unless defined $_[0];
+ my $class = blessed($_[0]) || $_[0];
+ return $METAS{$class};
+ }
+
+ # NOTE:
+ # We only cache metaclasses, meaning instances of
+ # Class::MOP::Class. We do not cache instance of
+ # Class::MOP::Package or Class::MOP::Module. Mostly
+ # because I don't yet see a good reason to do so.
+}
+
+sub _class_to_pmfile {
+ my $class = shift;
+
+ my $file = $class . '.pm';
+ $file =~ s{::}{/}g;
+
+ return $file;
+}
+
+sub load_first_existing_class {
+ my @classes = @_
+ or return;
+
+ foreach my $class (@classes) {
+ unless ( _is_valid_class_name($class) ) {
+ my $display = defined($class) ? $class : 'undef';
+ confess "Invalid class name ($display)";
+ }
+ }
+
+ my $found;
+ my %exceptions;
+
+ for my $class (@classes) {
+ my $file = _class_to_pmfile($class);
+
+ return $class if is_class_loaded($class);;
+
+ return $class if try {
+ local $SIG{__DIE__};
+ require $file;
+ return 1;
+ }
+ catch {
+ unless (/^Can't locate \Q$file\E in \@INC/) {
+ confess "Couldn't load class ($class) because: $_";
+ }
+
+ return;
+ };
+ }
+
+ if ( @classes > 1 ) {
+ confess "Can't locate any of @classes in \@INC (\@INC contains: @INC).";
+ } else {
+ confess "Can't locate " . _class_to_pmfile($classes[0]) . " in \@INC (\@INC contains: @INC).";
+ }
+}
+
+sub load_class {
+ load_first_existing_class($_[0]);
+
+ # This is done to avoid breaking code which checked the return value. Said
+ # code is dumb. The return value was _always_ true, since it dies on
+ # failure!
+ return 1;
+}
+
+sub _is_valid_class_name {
+ my $class = shift;
+
+ return 0 if ref($class);
+ return 0 unless defined($class);
+ return 0 unless length($class);
+
+ return 1 if $class =~ /^\w+(?:::\w+)*$/;
+
+ return 0;
+}
+
+## ----------------------------------------------------------------------------
+## Setting up our environment ...
+## ----------------------------------------------------------------------------
+## Class::MOP needs to have a few things in the global perl environment so
+## that it can operate effectively. Those things are done here.
+## ----------------------------------------------------------------------------
+
+# ... nothing yet actually ;)
+
+## ----------------------------------------------------------------------------
+## Bootstrapping
+## ----------------------------------------------------------------------------
+## The code below here is to bootstrap our MOP with itself. This is also
+## sometimes called "tying the knot". By doing this, we make it much easier
+## to extend the MOP through subclassing and such since now you can use the
+## MOP itself to extend itself.
+##
+## Yes, I know, thats weird and insane, but it's a good thing, trust me :)
+## ----------------------------------------------------------------------------
+
+# We need to add in the meta-attributes here so that
+# any subclass of Class::MOP::* will be able to
+# inherit them using _construct_instance
+
+## --------------------------------------------------------
+## Class::MOP::Package
+
+Class::MOP::Package->meta->add_attribute(
+ Class::MOP::Attribute->new('package' => (
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
+ # we just alias the original method
+ # rather than re-produce it here
+ 'name' => \&Class::MOP::Package::name
+ },
+ ))
+);
+
+Class::MOP::Package->meta->add_attribute(
+ Class::MOP::Attribute->new('namespace' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'namespace' => \&Class::MOP::Package::namespace
+ },
+ init_arg => undef,
+ default => sub { \undef }
+ ))
+);
+
+Class::MOP::Package->meta->add_attribute(
+ Class::MOP::Attribute->new('_methods' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ '_full_method_map' => \&Class::MOP::Package::_full_method_map
+ },
+ default => sub { {} }
+ ))
+);
+
+Class::MOP::Package->meta->add_attribute(
+ Class::MOP::Attribute->new('method_metaclass' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'method_metaclass' => \&Class::MOP::Package::method_metaclass
+ },
+ default => 'Class::MOP::Method',
+ ))
+);
+
+Class::MOP::Package->meta->add_attribute(
+ Class::MOP::Attribute->new('wrapped_method_metaclass' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'wrapped_method_metaclass' => \&Class::MOP::Package::wrapped_method_metaclass
+ },
+ default => 'Class::MOP::Method::Wrapped',
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Module
+
+# NOTE:
+# yeah this is kind of stretching things a bit,
+# but truthfully the version should be an attribute
+# of the Module, the weirdness comes from having to
+# stick to Perl 5 convention and store it in the
+# $VERSION package variable. Basically if you just
+# squint at it, it will look how you want it to look.
+# Either as a package variable, or as a attribute of
+# the metaclass, isn't abstraction great :)
+
+Class::MOP::Module->meta->add_attribute(
+ Class::MOP::Attribute->new('version' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'version' => \&Class::MOP::Module::version
+ },
+ init_arg => undef,
+ default => sub { \undef }
+ ))
+);
+
+# NOTE:
+# By following the same conventions as version here,
+# we are opening up the possibility that people can
+# use the $AUTHORITY in non-Class::MOP modules as
+# well.
+
+Class::MOP::Module->meta->add_attribute(
+ Class::MOP::Attribute->new('authority' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'authority' => \&Class::MOP::Module::authority
+ },
+ init_arg => undef,
+ default => sub { \undef }
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Class
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('attributes' => (
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
+ # we just alias the original method
+ # rather than re-produce it here
+ '_attribute_map' => \&Class::MOP::Class::_attribute_map
+ },
+ default => sub { {} }
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('superclasses' => (
+ accessor => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'superclasses' => \&Class::MOP::Class::superclasses
+ },
+ init_arg => undef,
+ default => sub { \undef }
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('attribute_metaclass' => (
+ reader => {
+ # NOTE:
+ # we just alias the original method
+ # rather than re-produce it here
+ 'attribute_metaclass' => \&Class::MOP::Class::attribute_metaclass
+ },
+ default => 'Class::MOP::Attribute',
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('instance_metaclass' => (
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
+ # we just alias the original method
+ # rather than re-produce it here
+ 'instance_metaclass' => \&Class::MOP::Class::instance_metaclass
+ },
+ default => 'Class::MOP::Instance',
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('immutable_trait' => (
+ reader => {
+ 'immutable_trait' => \&Class::MOP::Class::immutable_trait
+ },
+ default => "Class::MOP::Class::Immutable::Trait",
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('constructor_name' => (
+ reader => {
+ 'constructor_name' => \&Class::MOP::Class::constructor_name,
+ },
+ default => "new",
+ ))
+);
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('constructor_class' => (
+ reader => {
+ 'constructor_class' => \&Class::MOP::Class::constructor_class,
+ },
+ default => "Class::MOP::Method::Constructor",
+ ))
+);
+
+
+Class::MOP::Class->meta->add_attribute(
+ Class::MOP::Attribute->new('destructor_class' => (
+ reader => {
+ 'destructor_class' => \&Class::MOP::Class::destructor_class,
+ },
+ ))
+);
+
+# NOTE:
+# we don't actually need to tie the knot with
+# Class::MOP::Class here, it is actually handled
+# within Class::MOP::Class itself in the
+# _construct_class_instance method.
+
+## --------------------------------------------------------
+## Class::MOP::Attribute
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('name' => (
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
+ # we just alias the original method
+ # rather than re-produce it here
+ 'name' => \&Class::MOP::Attribute::name
+ }
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_class' => (
+ reader => {
+ # NOTE: we need to do this in order
+ # for the instance meta-object to
+ # not fall into meta-circular death
+ #
+ # we just alias the original method
+ # rather than re-produce it here
+ 'associated_class' => \&Class::MOP::Attribute::associated_class
+ }
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('accessor' => (
+ reader => { 'accessor' => \&Class::MOP::Attribute::accessor },
+ predicate => { 'has_accessor' => \&Class::MOP::Attribute::has_accessor },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('reader' => (
+ reader => { 'reader' => \&Class::MOP::Attribute::reader },
+ predicate => { 'has_reader' => \&Class::MOP::Attribute::has_reader },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('initializer' => (
+ reader => { 'initializer' => \&Class::MOP::Attribute::initializer },
+ predicate => { 'has_initializer' => \&Class::MOP::Attribute::has_initializer },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('definition_context' => (
+ reader => { 'definition_context' => \&Class::MOP::Attribute::definition_context },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('writer' => (
+ reader => { 'writer' => \&Class::MOP::Attribute::writer },
+ predicate => { 'has_writer' => \&Class::MOP::Attribute::has_writer },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('predicate' => (
+ reader => { 'predicate' => \&Class::MOP::Attribute::predicate },
+ predicate => { 'has_predicate' => \&Class::MOP::Attribute::has_predicate },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('clearer' => (
+ reader => { 'clearer' => \&Class::MOP::Attribute::clearer },
+ predicate => { 'has_clearer' => \&Class::MOP::Attribute::has_clearer },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('builder' => (
+ reader => { 'builder' => \&Class::MOP::Attribute::builder },
+ predicate => { 'has_builder' => \&Class::MOP::Attribute::has_builder },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('init_arg' => (
+ reader => { 'init_arg' => \&Class::MOP::Attribute::init_arg },
+ predicate => { 'has_init_arg' => \&Class::MOP::Attribute::has_init_arg },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('default' => (
+ # default has a custom 'reader' method ...
+ predicate => { 'has_default' => \&Class::MOP::Attribute::has_default },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_methods' => (
+ reader => { 'associated_methods' => \&Class::MOP::Attribute::associated_methods },
+ default => sub { [] }
+ ))
+);
+
+Class::MOP::Attribute->meta->add_attribute(
+ Class::MOP::Attribute->new('insertion_order' => (
+ reader => { 'insertion_order' => \&Class::MOP::Attribute::insertion_order },
+ writer => { '_set_insertion_order' => \&Class::MOP::Attribute::_set_insertion_order },
+ predicate => { 'has_insertion_order' => \&Class::MOP::Attribute::has_insertion_order },
+ ))
+);
+
+Class::MOP::Attribute->meta->add_method('clone' => sub {
+ my $self = shift;
+ $self->meta->clone_object($self, @_);
+});
+
+## --------------------------------------------------------
+## Class::MOP::Method
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('body' => (
+ reader => { 'body' => \&Class::MOP::Method::body },
+ ))
+);
+
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_metaclass' => (
+ reader => { 'associated_metaclass' => \&Class::MOP::Method::associated_metaclass },
+ ))
+);
+
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('package_name' => (
+ reader => { 'package_name' => \&Class::MOP::Method::package_name },
+ ))
+);
+
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('name' => (
+ reader => { 'name' => \&Class::MOP::Method::name },
+ ))
+);
+
+Class::MOP::Method->meta->add_attribute(
+ Class::MOP::Attribute->new('original_method' => (
+ reader => { 'original_method' => \&Class::MOP::Method::original_method },
+ writer => { '_set_original_method' => \&Class::MOP::Method::_set_original_method },
+ ))
+);
+
+Class::MOP::Method->meta->add_method('clone' => sub {
+ my $self = shift;
+ my $clone = $self->meta->clone_object($self, @_);
+ $clone->_set_original_method($self);
+ return $clone;
+});
+
+## --------------------------------------------------------
+## Class::MOP::Method::Wrapped
+
+# NOTE:
+# the way this item is initialized, this
+# really does not follow the standard
+# practices of attributes, but we put
+# it here for completeness
+Class::MOP::Method::Wrapped->meta->add_attribute(
+ Class::MOP::Attribute->new('modifier_table')
+);
+
+## --------------------------------------------------------
+## Class::MOP::Method::Generated
+
+Class::MOP::Method::Generated->meta->add_attribute(
+ Class::MOP::Attribute->new('is_inline' => (
+ reader => { 'is_inline' => \&Class::MOP::Method::Generated::is_inline },
+ default => 0,
+ ))
+);
+
+Class::MOP::Method::Generated->meta->add_attribute(
+ Class::MOP::Attribute->new('definition_context' => (
+ reader => { 'definition_context' => \&Class::MOP::Method::Generated::definition_context },
+ ))
+);
+
+
+## --------------------------------------------------------
+## Class::MOP::Method::Inlined
+
+Class::MOP::Method::Inlined->meta->add_attribute(
+ Class::MOP::Attribute->new('_expected_method_class' => (
+ reader => { '_expected_method_class' => \&Class::MOP::Method::Inlined::_expected_method_class },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Method::Accessor
+
+Class::MOP::Method::Accessor->meta->add_attribute(
+ Class::MOP::Attribute->new('attribute' => (
+ reader => {
+ 'associated_attribute' => \&Class::MOP::Method::Accessor::associated_attribute
+ },
+ ))
+);
+
+Class::MOP::Method::Accessor->meta->add_attribute(
+ Class::MOP::Attribute->new('accessor_type' => (
+ reader => { 'accessor_type' => \&Class::MOP::Method::Accessor::accessor_type },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Method::Constructor
+
+Class::MOP::Method::Constructor->meta->add_attribute(
+ Class::MOP::Attribute->new('options' => (
+ reader => {
+ 'options' => \&Class::MOP::Method::Constructor::options
+ },
+ default => sub { +{} }
+ ))
+);
+
+Class::MOP::Method::Constructor->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_metaclass' => (
+ init_arg => "metaclass", # FIXME alias and rename
+ reader => {
+ 'associated_metaclass' => \&Class::MOP::Method::Constructor::associated_metaclass
+ },
+ ))
+);
+
+## --------------------------------------------------------
+## Class::MOP::Instance
+
+# NOTE:
+# these don't yet do much of anything, but are just
+# included for completeness
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('associated_metaclass',
+ reader => { associated_metaclass => \&Class::MOP::Instance::associated_metaclass },
+ ),
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('_class_name',
+ init_arg => undef,
+ reader => { _class_name => \&Class::MOP::Instance::_class_name },
+ #lazy => 1, # not yet supported by Class::MOP but out our version does it anyway
+ #default => sub { $_[0]->associated_metaclass->name },
+ ),
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('attributes',
+ reader => { attributes => \&Class::MOP::Instance::get_all_attributes },
+ ),
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('slots',
+ reader => { slots => \&Class::MOP::Instance::slots },
+ ),
+);
+
+Class::MOP::Instance->meta->add_attribute(
+ Class::MOP::Attribute->new('slot_hash',
+ reader => { slot_hash => \&Class::MOP::Instance::slot_hash },
+ ),
+);
+
+require Class::MOP::Deprecated unless our $no_deprecated;
+
+# we need the meta instance of the meta instance to be created now, in order
+# for the constructor to be able to use it
+Class::MOP::Instance->meta->get_meta_instance;
+
+# pretend the add_method never happenned. it hasn't yet affected anything
+undef Class::MOP::Instance->meta->{_package_cache_flag};
+
+## --------------------------------------------------------
+## Now close all the Class::MOP::* classes
+
+# NOTE: we don't need to inline the the accessors this only lengthens
+# the compile time of the MOP, and gives us no actual benefits.
+
+$_->meta->make_immutable(
+ inline_constructor => 0,
+ constructor_name => "_new",
+ inline_accessors => 0,
+) for qw/
+ Class::MOP::Package
+ Class::MOP::Module
+ Class::MOP::Class
+
+ Class::MOP::Attribute
+ Class::MOP::Method
+ Class::MOP::Instance
+
+ Class::MOP::Object
+
+ Class::MOP::Method::Generated
+ Class::MOP::Method::Inlined
+
+ Class::MOP::Method::Accessor
+ Class::MOP::Method::Constructor
+ Class::MOP::Method::Wrapped
+/;
+
+1;
+
+__END__
+
+=pod
+
+=head1 NAME
+
+Class::MOP - A Meta Object Protocol for Perl 5
+
+=head1 DESCRIPTION
+
+This module is a fully functioning meta object protocol for the
+Perl 5 object system. It makes no attempt to change the behavior or
+characteristics of the Perl 5 object system, only to create a
+protocol for its manipulation and introspection.
+
+That said, it does attempt to create the tools for building a rich set
+of extensions to the Perl 5 object system. Every attempt has been made
+to abide by the spirit of the Perl 5 object system that we all know
+and love.
+
+This documentation is sparse on conceptual details. We suggest looking
+at the items listed in the L<SEE ALSO> section for more
+information. In particular the book "The Art of the Meta Object
+Protocol" was very influential in the development of this system.
+
+=head2 What is a Meta Object Protocol?
+
+A meta object protocol is an API to an object system.
+
+To be more specific, it abstracts the components of an object system
+(classes, object, methods, object attributes, etc.). These
+abstractions can then be used to inspect and manipulate the object
+system which they describe.
+
+It can be said that there are two MOPs for any object system; the
+implicit MOP and the explicit MOP. The implicit MOP handles things
+like method dispatch or inheritance, which happen automatically as
+part of how the object system works. The explicit MOP typically
+handles the introspection/reflection features of the object system.
+
+All object systems have implicit MOPs. Without one, they would not
+work. Explicit MOPs are much less common, and depending on the
+language can vary from restrictive (Reflection in Java or C#) to wide
+open (CLOS is a perfect example).
+
+=head2 Yet Another Class Builder! Why?
+
+This is B<not> a class builder so much as a I<class builder
+B<builder>>. The intent is that an end user will not use this module
+directly, but instead this module is used by module authors to build
+extensions and features onto the Perl 5 object system.
+
+This system is used by L<Moose>, which supplies a powerful class
+builder system built entirely on top of C<Class::MOP>.
+
+=head2 Who is this module for?
+
+This module is for anyone who has ever created or wanted to create a
+module for the Class:: namespace. The tools which this module provides
+make doing complex Perl 5 wizardry simpler, by removing such barriers
+as the need to hack symbol tables, or understand the fine details of
+method dispatch.
+
+=head2 What changes do I have to make to use this module?
+
+This module was designed to be as unintrusive as possible. Many of its
+features are accessible without B<any> change to your existing
+code. It is meant to be a compliment to your existing code and not an
+intrusion on your code base. Unlike many other B<Class::> modules,
+this module B<does not> require you subclass it, or even that you
+C<use> it in within your module's package.
+
+The only features which requires additions to your code are the
+attribute handling and instance construction features, and these are
+both completely optional features. The only reason for this is because
+Perl 5's object system does not actually have these features built
+in. More information about this feature can be found below.
+
+=head2 About Performance
+
+It is a common misconception that explicit MOPs are a performance hit.
+This is not a universal truth, it is a side-effect of some specific
+implementations. For instance, using Java reflection is slow because
+the JVM cannot take advantage of any compiler optimizations, and the
+JVM has to deal with much more runtime type information as well.
+
+Reflection in C# is marginally better as it was designed into the
+language and runtime (the CLR). In contrast, CLOS (the Common Lisp
+Object System) was built to support an explicit MOP, and so
+performance is tuned for it.
+
+This library in particular does its absolute best to avoid putting
+B<any> drain at all upon your code's performance. In fact, by itself
+it does nothing to affect your existing code. So you only pay for what
+you actually use.
+
+=head2 About Metaclass compatibility
+
+This module makes sure that all metaclasses created are both upwards
+and downwards compatible. The topic of metaclass compatibility is
+highly esoteric and is something only encountered when doing deep and
+involved metaclass hacking. There are two basic kinds of metaclass
+incompatibility; upwards and downwards.
+
+Upwards metaclass compatibility means that the metaclass of a
+given class is either the same as (or a subclass of) all of the
+class's ancestors.
+
+Downward metaclass compatibility means that the metaclasses of a
+given class's ancestors are all either the same as (or a subclass
+of) that metaclass.
+
+Here is a diagram showing a set of two classes (C<A> and C<B>) and
+two metaclasses (C<Meta::A> and C<Meta::B>) which have correct
+metaclass compatibility both upwards and downwards.
+
+ +---------+ +---------+
+ | Meta::A |<----| Meta::B | <....... (instance of )
+ +---------+ +---------+ <------- (inherits from)
+ ^ ^
+ : :
+ +---------+ +---------+
+ | A |<----| B |
+ +---------+ +---------+
+
+As I said this is a highly esoteric topic and one you will only run
+into if you do a lot of subclassing of L<Class::MOP::Class>. If you
+are interested in why this is an issue see the paper I<Uniform and
+safe metaclass composition> linked to in the L<SEE ALSO> section of
+this document.
+
+=head2 Using custom metaclasses
+
+Always use the L<metaclass> pragma when using a custom metaclass, this
+will ensure the proper initialization order and not accidentally
+create an incorrect type of metaclass for you. This is a very rare
+problem, and one which can only occur if you are doing deep metaclass
+programming. So in other words, don't worry about it.
+
+Note that if you're using L<Moose> we encourage you to I<not> use
+L<metaclass> pragma, and instead use L<Moose::Util::MetaRole> to apply
+roles to a class's metaclasses. This topic is covered at length in
+various L<Moose::Cookbook> recipes.
+
+=head1 PROTOCOLS
+
+The meta-object protocol is divided into 4 main sub-protocols:
+
+=head2 The Class protocol
+
+This provides a means of manipulating and introspecting a Perl 5
+class. It handles symbol table hacking for you, and provides a rich
+set of methods that go beyond simple package introspection.
+
+See L<Class::MOP::Class> for more details.
+
+=head2 The Attribute protocol
+
+This provides a consistent representation for an attribute of a Perl 5
+class. Since there are so many ways to create and handle attributes in
+Perl 5 OO, the Attribute protocol provide as much of a unified
+approach as possible. Of course, you are always free to extend this
+protocol by subclassing the appropriate classes.
+
+See L<Class::MOP::Attribute> for more details.
+
+=head2 The Method protocol
+
+This provides a means of manipulating and introspecting methods in the
+Perl 5 object system. As with attributes, there are many ways to
+approach this topic, so we try to keep it pretty basic, while still
+making it possible to extend the system in many ways.
+
+See L<Class::MOP::Method> for more details.
+
+=head2 The Instance protocol
+
+This provides a layer of abstraction for creating object instances.
+Since the other layers use this protocol, it is relatively easy to
+change the type of your instances from the default hash reference to
+some other type of reference. Several examples are provided in the
+F<examples/> directory included in this distribution.
+
+See L<Class::MOP::Instance> for more details.
+
+=head1 FUNCTIONS
+
+Note that this module does not export any constants or functions.
+
+=head2 Constants
+
+=over 4
+
+=item I<Class::MOP::IS_RUNNING_ON_5_10>
+
+We set this constant depending on what version perl we are on, this
+allows us to take advantage of new 5.10 features and stay backwards
+compatible.
+
+=back
+
+=head2 Utility functions
+
+Note that these are all called as B<functions, not methods>.
+
+=over 4
+
+=item B<Class::MOP::load_class($class_name)>
+
+This will load the specified C<$class_name>, if it is not already
+loaded (as reported by C<is_class_loaded>). This function can be used
+in place of tricks like C<eval "use $module"> or using C<require>
+unconditionally.
+
+If the module cannot be loaded, an exception is thrown.
+
+For historical reasons, this function explicitly returns a true value.
+
+=item B<Class::MOP::is_class_loaded($class_name)>
+
+Returns a boolean indicating whether or not C<$class_name> has been
+loaded.
+
+This does a basic check of the symbol table to try and determine as
+best it can if the C<$class_name> is loaded, it is probably correct
+about 99% of the time, but it can be fooled into reporting false
+positives. In particular, loading any of the core L<IO> modules will
+cause most of the rest of the core L<IO> modules to falsely report
+having been loaded, due to the way the base L<IO> module works.
+
+=item B<Class::MOP::get_code_info($code)>
+
+This function returns two values, the name of the package the C<$code>
+is from and the name of the C<$code> itself. This is used by several
+elements of the MOP to determine where a given C<$code> reference is
+from.
+
+=item B<Class::MOP::class_of($instance_or_class_name)>
+
+This will return the metaclass of the given instance or class name. If the
+class lacks a metaclass, no metaclass will be initialized, and C<undef> will be
+returned.
+
+=item B<Class::MOP::check_package_cache_flag($pkg)>
+
+B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!>
+
+This will return an integer that is managed by L<Class::MOP::Class> to
+determine if a module's symbol table has been altered.
+
+In Perl 5.10 or greater, this flag is package specific. However in
+versions prior to 5.10, this will use the C<PL_sub_generation>
+variable which is not package specific.
+
+=item B<Class::MOP::load_first_existing_class(@class_names)>
+
+B<NOTE: DO NOT USE THIS FUNCTION, IT IS FOR INTERNAL USE ONLY!>
+
+Given a list of class names, this function will attempt to load each
+one in turn.
+
+If it finds a class it can load, it will return that class' name. If
+none of the classes can be loaded, it will throw an exception.
+
+=back
+
+=head2 Metaclass cache functions
+
+Class::MOP holds a cache of metaclasses. The following are functions
+(B<not methods>) which can be used to access that cache. It is not
+recommended that you mess with these. Bad things could happen, but if
+you are brave and willing to risk it: go for it!
+
+=over 4
+
+=item B<Class::MOP::get_all_metaclasses>
+
+This will return a hash of all the metaclass instances that have
+been cached by L<Class::MOP::Class>, keyed by the package name.
+
+=item B<Class::MOP::get_all_metaclass_instances>
+
+This will return a list of all the metaclass instances that have
+been cached by L<Class::MOP::Class>.
+
+=item B<Class::MOP::get_all_metaclass_names>
+
+This will return a list of all the metaclass names that have
+been cached by L<Class::MOP::Class>.
+
+=item B<Class::MOP::get_metaclass_by_name($name)>
+
+This will return a cached L<Class::MOP::Class> instance, or nothing
+if no metaclass exists with that C<$name>.
+
+=item B<Class::MOP::store_metaclass_by_name($name, $meta)>
+
+This will store a metaclass in the cache at the supplied C<$key>.
+
+=item B<Class::MOP::weaken_metaclass($name)>
+
+In rare cases (e.g. anonymous metaclasses) it is desirable to
+store a weakened reference in the metaclass cache. This
+function will weaken the reference to the metaclass stored
+in C<$name>.
+
+=item B<Class::MOP::does_metaclass_exist($name)>
+
+This will return true of there exists a metaclass stored in the
+C<$name> key, and return false otherwise.
+
+=item B<Class::MOP::remove_metaclass_by_name($name)>
+
+This will remove the metaclass stored in the C<$name> key.
+
+=back
+
+=head1 SEE ALSO
+
+=head2 Books
+
+There are very few books out on Meta Object Protocols and Metaclasses
+because it is such an esoteric topic. The following books are really
+the only ones I have found. If you know of any more, B<I<please>>
+email me and let me know, I would love to hear about them.
+
+=over 4
+
+=item I<The Art of the Meta Object Protocol>
+
+=item I<Advances in Object-Oriented Metalevel Architecture and Reflection>
+
+=item I<Putting MetaClasses to Work>
+
+=item I<Smalltalk: The Language>
+
+=back
+
+=head2 Papers
+
+=over 4
+
+=item "Uniform and safe metaclass composition"
+
+An excellent paper by the people who brought us the original Traits paper.
+This paper is on how Traits can be used to do safe metaclass composition,
+and offers an excellent introduction section which delves into the topic of
+metaclass compatibility.
+
+L<http://www.iam.unibe.ch/~scg/Archive/Papers/Duca05ySafeMetaclassTrait.pdf>
+
+=item "Safe Metaclass Programming"
+
+This paper seems to precede the above paper, and propose a mix-in based
+approach as opposed to the Traits based approach. Both papers have similar
+information on the metaclass compatibility problem space.
+
+L<http://citeseer.ist.psu.edu/37617.html>
+
+=back
+
+=head2 Prior Art
+
+=over 4
+
+=item The Perl 6 MetaModel work in the Pugs project
+
+=over 4
+
+=item L<http://svn.openfoundry.org/pugs/misc/Perl-MetaModel/>
+
+=item L<http://svn.openfoundry.org/pugs/perl5/Perl6-ObjectSpace>
+
+=back
+
+=back
+
+=head2 Articles
+
+=over 4
+
+=item CPAN Module Review of Class::MOP
+
+L<http://www.oreillynet.com/onlamp/blog/2006/06/cpan_module_review_classmop.html>
+
+=back
+
+=head1 SIMILAR MODULES
+
+As I have said above, this module is a class-builder-builder, so it is
+not the same thing as modules like L<Class::Accessor> and
+L<Class::MethodMaker>. That being said there are very few modules on CPAN
+with similar goals to this module. The one I have found which is most
+like this module is L<Class::Meta>, although it's philosophy and the MOP it
+creates are very different from this modules.
+
+=head1 BUGS
+
+All complex software has bugs lurking in it, and this module is no
+exception.
+
+Please report any bugs to C<bug-class-mop@rt.cpan.org>, or through the
+web interface at L<http://rt.cpan.org>.
+
+You can also discuss feature requests or possible bugs on the Moose
+mailing list (moose@perl.org) or on IRC at
+L<irc://irc.perl.org/#moose>.
+
+=head1 ACKNOWLEDGEMENTS
+
+=over 4
+
+=item Rob Kinyon
+
+Thanks to Rob for actually getting the development of this module kick-started.
+
+=back
+
+=head1 AUTHORS
+
+Stevan Little E<lt>stevan@iinteractive.comE<gt>
+
+B<with contributions from:>
+
+Brandon (blblack) Black
+
+Florian (rafl) Ragwitz
+
+Guillermo (groditi) Roditi
+
+Dave (autarch) Rolsky
+
+Matt (mst) Trout
+
+Rob (robkinyon) Kinyon
+
+Yuval (nothingmuch) Kogman
+
+Scott (konobi) McWhirter
+
+Dylan Hardison
+
+=head1 COPYRIGHT AND LICENSE
+
+Copyright 2006-2009 by Infinity Interactive, Inc.
+
+L<http://www.iinteractive.com>
+
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself.
+
+=cut
projects / catagits/Gitalist.git / blobdiff