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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' occurence.

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

    use strict;
    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 occurence after $x = ",
    $recurrence->{param}[0]->( $x ), "\n"; # 235
    print "previous occurence before $x = ",
    $recurrence->{param}[2]->( $x ), "\n"; # 234
    }
    {
    my $x = 234;
    print "next occurence after $x = ",
    $recurrence->{param}[0]->( $x ), "\n"; # 235
    print "previous occurence 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@pucrs.br>

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.