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  #Do not run this module directly

=head1 DESCRIPTION

This provides a standard BioPerl range interface that should be
implemented by any object that wants to be treated as a range. This
serves purely as an abstract base class for implementers and can not
be instantiated.

Ranges are modeled as having (start, end, length, strand). They use
Bio-coordinates - all points E<gt>= start and E<lt>= end are within the
range. End is always greater-than or equal-to start, and length is
greater than or equal to 1. The behaviour of a range is undefined if
ranges with negative numbers or zero are used.

So, in summary:

  length = end - start + 1
  end >= start
  strand = (-1 | 0 | +1)

=head1 FEEDBACK

=head2 Mailing Lists

User feedback is an integral part of the evolution of this and other
Bioperl modules. Send your comments and suggestions preferably to one
of the Bioperl mailing lists.  Your participation is much appreciated.

  bioperl-l@bioperl.org                  - General discussion
  http://bioperl.org/wiki/Mailing_lists  - About the mailing lists

=head2 Support 

Please direct usage questions or support issues to the mailing list:

I<bioperl-l@bioperl.org>

rather than to the module maintainer directly. Many experienced and 
reponsive experts will be able look at the problem and quickly 
address it. Please include a thorough description of the problem 
with code and data examples if at all possible.

=head2 Reporting Bugs

Report bugs to the Bioperl bug tracking system to help us keep track
the bugs and their resolution.  Bug reports can be submitted via the
web:

  https://github.com/bioperl/bioperl-live/issues

=head1 AUTHOR - Heikki Lehvaslaiho

Email:  heikki-at-bioperl-dot-org

=head1 CONTRIBUTORS

Juha Muilu (muilu@ebi.ac.uk)
Sendu Bala (bix@sendu.me.uk)
Malcolm Cook (mec@stowers-institute.org)
Stephen Montgomery (sm8 at sanger.ac.uk)

=head1 APPENDIX

The rest of the documentation details each of the object
methods. Internal methods are usually preceded with a _

=cut

package Bio::RangeI;

use strict;
use Carp;
use integer;
use vars qw(%STRAND_OPTIONS);

use base qw(Bio::Root::RootI);

BEGIN {
# STRAND_OPTIONS contains the legal values for the strand-testing options
    %STRAND_OPTIONS = map { $_, '_' . $_ }
    (
     'strong', # ranges must have the same strand
     'weak',   # ranges must have the same strand or no strand
     'ignore', # ignore strand information
     );
}

# utility methods
#

# returns true if strands are equal and non-zero
sub _strong {
    my ($r1, $r2) = @_;
    my ($s1, $s2) = ($r1->strand(), $r2->strand());

    return 1 if $s1 != 0 && $s1 == $s2;
}

# returns true if strands are equal or either is zero
sub _weak {
    my ($r1, $r2) = @_;
    my ($s1, $s2) = ($r1->strand(), $r2->strand());
    return 1 if $s1 == 0 || $s2 == 0 || $s1 == $s2;
}

# returns true for any strandedness
sub _ignore {
    return 1;
}

# works out what test to use for the strictness and returns true/false
# e.g. $r1->_testStrand($r2, 'strong')
sub _testStrand() {
    my ($r1, $r2, $comp) = @_;
    return 1 unless $comp;
    my $func = $STRAND_OPTIONS{$comp};
    return $r1->$func($r2);
}