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lib/Algorithm/Evolutionary/Op/Base.pm  view on Meta::CPAN

Base class for operators applied to Individuals and Populations and
all the rest.  An operator is any object with the "apply" method,
which does things to individuals or populations. It is intendedly
quite general so that any genetic or population operator can fit in. 

=head1 METHODS

=cut

package Algorithm::Evolutionary::Op::Base;

use lib qw( ../.. ../../.. );

use Memoize;
memoize('arity'); #To speed up this frequent computation

use B::Deparse; #For serializing code
use Algorithm::Evolutionary::Utils qw(parse_xml);

use Carp;
our ($VERSION) = ( '$Revision: 3.3 $ ' =~ / (\d+\.\d+)/ ) ;
our %parameters;

=head2 AUTOLOAD

Automatically define accesors for instance variables. You should
probably not worry about this unless you are going to subclass.

=cut

sub AUTOLOAD {
  my $self = shift;
  our $AUTOLOAD;
  my ($method) = ($AUTOLOAD =~ /::(\w+)/);
  my $instanceVar = "_".lcfirst($method);
  if (defined ($self->{$instanceVar})) {
    if ( @_ ) {
	  $self->{$instanceVar} = shift;
    } else {
	  return $self->{$instanceVar};
    }
  }    

}

=head2 new( [$priority] [,$options_hash] )

Takes a hash with specific parameters for each subclass, creates the 
object, and leaves subclass-specific assignments to subclasses

=cut

sub new {
  my $class = shift;
  carp "Should be called from subclasses" if ( $class eq  __PACKAGE__ );
  my $rate = shift || 1;
  my $hash = shift; #No carp here, some operators do not need specific stuff
  my $self = { rate => $rate,
	       _arity => eval( "\$"."$class"."::ARITY" )}; # Create a reference
  bless $self, $class; # And bless it
  $self->set( $hash ) if $hash ;
  return $self;
}

=head2 create( [@operator_parameters] )

Creates an operator via its default parameters. Probably obsolete

=cut

sub create {
  my $class = shift;
  my $self;
  for my $p ( keys %parameters ) {
    $self->{"_$p"} = shift || $parameters{$p}; # Default
  }
  bless $self, $class;
  return $self;
}

=head2 fromXML()

Takes a definition in the shape <op></op> and turns it into an object, 
if it knows how to do it. The definition must have been processed using XML::Simple.

It parses the common part of the operator, and leaves specific parameters for the
subclass via the "set" method.

=cut

sub fromXML {
  my $class = shift;
  my $xml = shift || croak "XML fragment missing ";
  my $fragment; # Inner part of the XML
  if ( ref $xml eq ''  ) { #We are receiving a string, parse it
    $xml = parse_xml( $xml );
    croak "Incorrect XML fragment" if !$xml->{'op'}; #
    $fragment = $xml->{'op'};
  } else {
    $fragment = $xml;
  }
  my $rate = shift;
  if ( !defined $rate && $fragment->{'-rate'} ) {
    $rate = $fragment->{'-rate'};
  }
  my $self = { rate => $rate }; # Create a reference

  if ( $class eq  __PACKAGE__ ) { #Deduct class from the XML
    $class = $fragment->{'-name'} || shift || croak "Class name missing";
  }
  
  $class = "Algorithm::Evolutionary::Op::$class" if $class !~ /Algorithm::Evolutionary/;
  bless $self, $class; # And bless it
  
  my (%params, %code_fragments, %ops);
  
  for ( @{ (ref $fragment->{'param'} eq 'ARRAY')?
	     $fragment->{'param'}:
	       [ $fragment->{'param'}] } ) {
    if  ( defined $_->{'-value'} ) {
      $params{$_->{'-name'}} = $_->{'-value'};
    } elsif ( $_->{'param'} ) {
      my %params_hash;
      for my $p ( @{ (ref $_->{'param'} eq 'ARRAY')?
		       $_->{'param'}:
			 [ $_->{'param'}] } ) {
	$params_hash{ $p->{'-name'}} = $p->{'-value'};
      }
      $params{$_->{'-name'}} = \%params_hash;
    }
  }
  
  if ($fragment->{'code'} ) {
    $code_fragments{$fragment->{'code'}->{'-type'}} = $fragment->{'code'}->{'src'};
  }    
       
  for ( @{$fragment->{'op'}} ) { 
    $ops{$_->{'-name'}} = [$_->{'-rate'}, $_];
  }

  #If the class is not loaded, we load it. The 
  eval "require $class" || croak "Can't find $class Module";

  #Let the class configure itself
  $self->set( \%params, \%code_fragments, \%ops );
  return $self;
}


=head2 asXML( [$id] )

Prints as XML, following the EvoSpec 0.2 XML specification. Should be
called from derived classes, not by itself. Provides a default
implementation of XML serialization, with a void tag that includes the
name of the operator and the rate (all operators have a default
rate). For instance, a C<foo> operator would be serialized as C< E<lt>op
name='foo' rate='1' E<gt> >.

If there is not anything special, this takes also care of the instance
variables different from C<rate>: they are inserted as C<param> within
the XML file. In this case, C<param>s are void tags; if you want
anything more fancy, you will have to override this method. An
optional ID can be used.

=cut

sub asXML {
  my $self = shift;
  my ($opName) = ( ( ref $self) =~ /::(\w+)$/ );
  my $name = shift; #instance variable it corresponds to
  my $str =  "<op name='$opName' ";
  $str .= "id ='$name' " if $name;
  if ( $self->{rate} ) { # "Rated" ops, such as genetic ops