File Coverage

blib/lib/Graph/Maker/GosperIsland.pm

Criterion	Covered	Total	%
statement	6	8	75.0
branch			n/a
condition			n/a
subroutine	3	3	100.0
pod			n/a
total	9	11	81.8

# Copyright 2017 Kevin Ryde
#
# This file is part of Graph-Maker-Other.
#
# This file is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 3, or (at your option) any later
# version.
#
# This file is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License along
# with Graph-Maker-Other.  See the file COPYING.  If not, see
# .

package Graph::Maker::GosperIsland;
use 5.004;
use strict;
use Graph::Maker;

use vars '$VERSION','@ISA';
$VERSION = 8;
@ISA = ('Graph::Maker');


sub _default_graph_maker {
  require Graph;
  return Graph->new(@_);
}
sub _make_graph {
  my ($params) = @_;
  my $graph_maker = delete($params->{'graph_maker'}) || \&_default_graph_maker;
  return $graph_maker->(%$params);
}

sub _mul {
  my ($x,$y) = @_;
  return ((5*$x - 3*$y)/2, ($x+5*$y)/2);
}
sub _add {
  my ($v, $ax,$ay) = @_;
  my ($x,$y) = split /,/, $v;
  $x += $ax;
  $y += $ay;
  return "$x,$y";
}
sub _rotate_plus60 {
  my ($x, $y) = @_;
  return (($x-3*$y)/2,  # rotate +60
          ($x+$y)/2);
}

my @level_0 = ('2,0', '1,1', '-1,1', '-2,0', '-1,-1', '1,-1');

sub init {
  my ($self, %params) = @_;

  my $level = delete($params{'level'}) || 0;

  my $graph = _make_graph(\%params);
  $graph->set_graph_attribute (name => "Gosper Island $level");
  $graph->set_graph_attribute (vertex_name_type_xy => 1);
  $graph->set_graph_attribute (vertex_name_type_xy_triangular => 1);
  my $multiedged = $graph->is_countedged || $graph->is_multiedged;

  $graph->add_cycle(@level_0);
  if ($graph->is_directed) { $graph->add_cycle(reverse @level_0); }

  my $cx = 3;
  my $cy = 1;
  foreach my $i (1 .. $level) {
    foreach my $edge ($graph->edges) {
      foreach (1 .. 6) {
        my ($u,$v) = @$edge;
        $u = _add($u, $cx,$cy);
        $v = _add($v, $cx,$cy);
        if (! $multiedged || ! $graph->has_edge($u,$v)) { # no duplicates
          $graph->add_edge($u,$v);
        }
        ($cx,$cy) = _rotate_plus60($cx,$cy);
      }
    }
    ($cx,$cy) = _mul($cx,$cy);
  }
  return $graph;
}

Graph::Maker->add_factory_type('Gosper_island' => __PACKAGE__);
1;

__END__