NAME

Set::Infinite::_recurrence - Extends Set::Infinite with recurrence functions

SYNOPSIS

$recurrence = $base_set->_recurrence ( \&next, \&previous );

DESCRIPTION

This is an internal class used by the DateTime::Set module. The API is subject to change.

It provides all functionality provided by Set::Infinite, plus the ability to define recurrences with arbitrary objects, such as dates.

METHODS

• _recurrence ( \&next, \&previous )

  Creates a recurrence set. The set is defined inside a 'base set'.

  $recurrence = $base_set->_recurrence ( \&next, \&previous );

  The recurrence functions take one argument, and return the 'next' or the 'previous' occurrence.

  Example: defines the set of all 'integer numbers':

  use strict;
  
  use Set::Infinite::_recurrence;
  use POSIX qw(floor);
  
  # define the recurrence span
  my $forever = Set::Infinite::_recurrence->new( 
      Set::Infinite::_recurrence::NEG_INFINITY, 
      Set::Infinite::_recurrence::INFINITY
  );
  
  my $recurrence = $forever->_recurrence(
      sub {   # next
              floor( $_[0] + 1 ) 
          },   
      sub {   # previous
              my $tmp = floor( $_[0] ); 
              $tmp < $_[0] ? $tmp : $_[0] - 1
          },   
  );
  
  print "sample recurrence ",
        $recurrence->intersection( -5, 5 ), "\n";
  # sample recurrence -5,-4,-3,-2,-1,0,1,2,3,4,5
  
  {
      my $x = 234.567;
      print "next occurrence after $x = ",
            $recurrence->{param}[0]->( $x ), "\n";  # 235
      print "previous occurrence before $x = ",
            $recurrence->{param}[2]->( $x ), "\n";  # 234
  }
  
  {
      my $x = 234;
      print "next occurrence after $x = ",
            $recurrence->{param}[0]->( $x ), "\n";  # 235
      print "previous occurrence before $x = ",
            $recurrence->{param}[2]->( $x ), "\n";  # 233
  }

• is_forever

  Returns true if the set is a single span, ranging from -Infinity to Infinity.

• _is_recurrence

  Returns true if the set is an unbounded recurrence, ranging from -Infinity to Infinity.

CONSTANTS

• INFINITY

  The Infinity value.

• NEG_INFINITY

  The -Infinity value.

SUPPORT

Support is offered through the datetime@perl.org mailing list.

Please report bugs using rt.cpan.org

AUTHOR

Flavio Soibelmann Glock <fglock@gmail.com>

The recurrence generation algorithm is based on an idea from Dave Rolsky.

COPYRIGHT

Copyright (c) 2003 Flavio Soibelmann Glock. All rights reserved. This program is free software; you can distribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

SEE ALSO

Set::Infinite

DateTime::Set

For details on the Perl DateTime Suite project please see http://datetime.perl.org.