``````package Math::Spiral;

use strict;
use warnings;

# perl -MPod::Markdown -e 'Pod::Markdown->new->filter(@ARGV)' lib/Math/Spiral.pm  > README.md

Math::Spiral - Perl extension to return an endless stream of X, Y offset coordinates which represent a spiral shape

#!/usr/bin/perl -w

use Math::Spiral;

my \$s = new Math::Spiral();
my(\$xo,\$yo)=\$s->Next();

# perl -MMath::Spiral -e '\$s=new Math::Spiral(); foreach(0..9) { (\$xo,\$yo)=\$s->Next(); \$chart[2+\$xo][2+\$yo]=\$_; } foreach \$y (0..4){foreach \$x(0..4){if(defined(\$chart[\$x][\$y])){print \$chart[\$x][\$y]} else {print " ";} } print "\n"}'

This module outputs an infinte sequence of coordinate offsets, which you can use to plot things in a spiral shape.
The numbers return "clockwise"; negate one if you want to go anti-clockwise instead.

It is useful for charting things where you need to concentrate something around the center of the chart.

#!/usr/bin/perl -w

use Math::Spiral;

my \$s = new Math::Spiral();

foreach(0..9) {
(\$xo,\$yo)=\$s->Next();	# Returns a sequnce like (0,0) (1,0) (1,1) (0,1) (-1,1) (-1,0) (-1,-1) (0,-1) (1,-1) (2,-1) ... etc
\$chart[2+\$xo][2+\$yo]=\$_;
}

foreach \$y (0..4) {
foreach \$x(0..4) {
if(defined(\$chart[\$x][\$y])) {
print \$chart[\$x][\$y]
} else {
print " ";
}
}
print "\n"
}

6789
501
432

None by default.

Usage is

my \$s = new Math::Spiral();

Returns the next x and y offsets (note that these start at 0,0 and will go negative to circle around this origin)

Usage is

my(\$xo,\$yo)=\$s->Next();
# Returns a sequnce like (0,0) (1,0) (1,1) (0,1) (-1,1) (-1,0) (-1,-1) (0,-1) (1,-1) (2,-1) ... etc (i.e. the x,y coordinates for a spiral)

=cut

require Exporter;

our @ISA = qw(Exporter);
our(\$VERSION)='1.01';
our(\$UntarError) = '';

our %EXPORT_TAGS = ( 'all' => [ qw( ) ] );

our @EXPORT_OK = ( @{ \$EXPORT_TAGS{'all'} } );

our @EXPORT = qw( );

sub new {
my \$class = shift;
my \$this={};
foreach(qw(x xmin y ydir ymin)){ \$this->{\$_}=0; }
foreach(qw(xdir xmax ymax)){ \$this->{\$_}=1; }
# my(\$x,\$xdir,\$xmax,\$xmin) = (0,1,1,0);
# my(\$y,\$ydir,\$ymax,\$ymin) = (0,0,1,0);
bless \$this,\$class;
return \$this;
} # new

sub Next {
my \$this = shift;

my @ret=(\$this->{x},\$this->{y});

\$this->{x}+=\$this->{xdir};
\$this->{y}+=\$this->{ydir};

if(     (\$this->{x}>=\$this->{xmax})&&(\$this->{xdir})) {
\$this->{xmin}=-\$this->{xmax}; \$this->{xdir}=0; \$this->{ydir}=1;
} elsif((\$this->{x}<=\$this->{xmin})&&(\$this->{xdir})) {
\$this->{xmax}=-\$this->{xmin}+1; \$this->{xdir}=0; \$this->{ydir}=-1;
} elsif((\$this->{y}>=\$this->{ymax})&&(\$this->{ydir})) {
\$this->{ymin}=-\$this->{ymax}; \$this->{xdir}=-1; \$this->{ydir}=0;
} elsif((\$this->{y}<=\$this->{ymin})&&(\$this->{ydir})) {
\$this->{ymax}=-\$this->{ymin}+1; \$this->{xdir}=1; \$this->{ydir}=0;
}

return @ret;
} # Next

# testing # perl -MMath::Spiral -e '\$s=new Math::Spiral(); foreach(0..25) { (\$xo,\$yo)=\$s->Next(); \$chart[3+\$xo][3+\$yo]=\$_; } foreach \$y (0..6){foreach \$x(0..6){if(defined(\$chart[\$x][\$y])){print chr(97+\$chart[\$x][\$y])} else {print " ";} } print "\n"}'

1;

__END__

This module was written by Chris Drake F<cdrake@cpan.org>