/usr/share/perl5/Math/PlanePath/CubicBase.pm is in libmath-planepath-perl 113-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# This file is part of Math-PlanePath.
#
# Math-PlanePath 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.
#
# Math-PlanePath 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 Math-PlanePath. If not, see <http://www.gnu.org/licenses/>.
# math-image --path=CubicBase --all --output=numbers --size=60x20
# math-image --path=CubicBase --values=Multiples,multiples=27 --output=numbers --size=60x20
# math-image --path=CubicBase --expression='i<128?i:0' --output=numbers --size=132x20
#
package Math::PlanePath::CubicBase;
use 5.004;
use strict;
#use List::Util 'max';
*max = \&Math::PlanePath::_max;
use vars '$VERSION', '@ISA';
$VERSION = 113;
use Math::PlanePath;
@ISA = ('Math::PlanePath');
use Math::PlanePath::Base::Generic
'is_infinite',
'round_nearest';
use Math::PlanePath::Base::Digits
'parameter_info_array',
'digit_split_lowtohigh',
'digit_join_lowtohigh';
# uncomment this to run the ### lines
#use Smart::Comments;
use constant n_start => 0;
*xy_is_visited = \&Math::PlanePath::Base::Generic::xy_is_even;
# use constant parameter_info_array =>
# [ Math::PlanePath::Base::Digits::parameter_info_radix2(),
#
# # Experimental ...
# # { name => 'skewed',
# # type => 'boolean',
# # default => 0,
# # },
# ];
use constant absdx_minimum => 2;
use constant dir_maximum_dxdy => (-1, -3); # supremum
#------------------------------------------------------------------------------
sub new {
my $self = shift->SUPER::new(@_);
my $radix = $self->{'radix'};
if (! defined $radix || $radix <= 2) { $radix = 2; }
$self->{'radix'} = $radix;
return $self;
}
sub n_to_xy {
my ($self, $n) = @_;
### CubicBase n_to_xy(): "$n"
if ($n < 0) { return; }
if (is_infinite($n)) { return ($n,$n); }
# is this sort of midpoint worthwhile? not documented yet
{
my $int = int($n);
### $int
### $n
if ($n != $int) {
my ($x1,$y1) = $self->n_to_xy($int);
my ($x2,$y2) = $self->n_to_xy($int+1);
my $frac = $n - $int; # inherit possible BigFloat
my $dx = $x2-$x1;
my $dy = $y2-$y1;
return ($frac*$dx + $x1, $frac*$dy + $y1);
}
$n = $int; # BigFloat int() gives BigInt, use that
}
my $x = 0;
my $y = 0;
my $radix = $self->{'radix'};
if (my @digits = digit_split_lowtohigh($n,$radix)) {
my $len = ($n * 0) + 1; # inherit bignum 1
my $ext = 1;
for (;;) {
{ # 0 degrees
$x += (2*(shift @digits)) * $len; # low to high
}
@digits || last;
if ($ext ^= 1) {
$len *= $radix;
}
{ # +120 degrees
my $dlen = (shift @digits) * $len; # low to high
$x -= $dlen;
$y += $dlen;
}
@digits || last;
if ($ext ^= 1) {
$len *= $radix;
}
{ # +240 degrees
my $dlen = (shift @digits) * $len; # low to high
$x -= $dlen;
$y -= $dlen;
}
@digits || last;
if ($ext ^= 1) {
$len *= $radix;
}
}
if ($self->{'skewed'}) {
$x = ($x + $y) / 2;
}
}
### result: "$x,$y"
return ($x,$y);
}
sub xy_to_n {
my ($self, $x, $y) = @_;
### CubicBase xy_to_n(): "$x, $y"
$x = round_nearest ($x);
$y = round_nearest ($y);
if (is_infinite($x)) { return ($x); }
if (is_infinite($y)) { return ($y); }
if ($self->{'skewed'}) {
$x = 2*$x - $y;
} else {
if (($x + $y) % 2) {
# nothing on odd squares, only A2 even squares
return undef;
}
}
# $x = ($x-$y)/2; # into i,j coordinates
foreach my $overflow ($x+$y, $x-$y) {
if (is_infinite($overflow)) { return $overflow; }
}
my $radix = $self->{'radix'};
my $zero = ($x * 0 * $y); # inherit bignum 0
my @n; # digits low to high
if ($x || $y) {
my $ext = 1;
for (;;) {
### at: "x=$x y=$y"
{
my $digit = (($x+$y)/2) % $radix;
push @n, $digit;
$x -= 2*$digit;
### 0deg digit: $digit
### subtract to: "x=$x y=$y"
}
last unless $x || $y;
if ($ext ^= 1) {
### assert: ($x % $radix) == 0
### assert: ($y % $radix) == 0
$x = int($x/$radix);
$y = int($y/$radix);
### divide out to: "x=$x y=$y"
}
{
my $digit = (($y-$x)/2) % $radix;
push @n, $digit;
$x += $digit;
$y -= $digit;
### 120deg digit: $digit
### subtract to: "x=$x y=$y"
}
last unless $x || $y;
if ($ext ^= 1) {
### assert: ($x % $radix) == 0
### assert: ($y % $radix) == 0
$x = int($x/$radix);
$y = int($y/$radix);
### divide out to: "x=$x y=$y"
}
{
my $digit = (-$y) % $radix;
push @n, $digit;
$x += $digit;
$y += $digit;
### 240deg digit: $digit
### subtract to: "x=$x y=$y"
}
last unless $x || $y;
if ($ext ^= 1) {
### assert: ($x % $radix) == 0
### assert: ($y % $radix) == 0
$x = int($x/$radix);
$y = int($y/$radix);
### divide out to: "x=$x y=$y"
}
}
}
return digit_join_lowtohigh (\@n, $radix, $zero);
}
# ENHANCE-ME: Can probably do better by measuring extents in 3 directions
# for a hexagonal boundary.
#
# not exact
sub rect_to_n_range {
my ($self, $x1,$y1, $x2,$y2) = @_;
### CubicBase rect_to_n_range(): "$x1,$y1 $x2,$y2"
$x1 = round_nearest ($x1);
$y1 = round_nearest ($y1);
$x2 = round_nearest ($x2);
$y2 = round_nearest ($y2);
my $radix = $self->{'radix'} ;
my $xm = max(abs($x1),abs($x2)) * $radix*$radix*$radix;
my $ym = max(abs($y1),abs($y2)) * $radix*$radix*$radix;
return (0,
$xm*$xm+$ym*$ym);
}
1;
__END__
# xy_to_n() high to low
#
# use Math::PlanePath::Base::Digits
# 'round_down_pow';
#
# my ($len, $level) = round_down_pow(abs($x)+abs($y), $radix);
# $len *= $radix;
# $level++;
# $len *= $radix;
# ### $level
# ### $len
#
# for (;;) {
# ### at: "x=$x y=$y"
#
# {
# my $k = -$y;
# my $digit = ($k >= 0
# ? int($k/$len)
# : -int(-$k/$len));
# $n = $n*$radix + $digit;
# $x += $digit*$len;
# $y += $digit*$len;
#
# ### 240deg digit: $digit
# ### add to: "x=$x y=$y"
# }
#
# $len = int($len/$radix);
# ### $len
#
# {
# my $k = $y;
# my $digit = int($k/$len) % $radix;
# $n = $n*$radix + $digit;
# $x += $digit*$len;
# $y -= $digit*$len;
#
# ### 120deg digit: $digit
# ### subtract to: "x=$x y=$y"
# }
#
# {
# my $digit = ($x >= 0
# ? int($x/(2*$len))
# : -int(-$x/(2*$len)));
# $n = $n*$radix + $digit;
# $x -= 2*$digit;
#
# ### 0deg digit: $digit
# ### subtract to: "x=$x y=$y"
# }
#
# last unless $level-- > 0;
#
# }
=for stopwords eg Ryde Math-PlanePath Radix ie radix
=head1 NAME
Math::PlanePath::CubicBase -- replications in three directions
=head1 SYNOPSIS
use Math::PlanePath::CubicBase;
my $path = Math::PlanePath::CubicBase->new (radix => 4);
my ($x, $y) = $path->n_to_xy (123);
=head1 DESCRIPTION
This is a pattern of replications in three directions 0, 120 and 240 degrees.
=cut
# these numbers generated with
# math-image --path=CubicBase --expression='i<64?i:0' --output=numbers --size=132x20
=pod
18 19 26 27 5
16 17 24 25 4
22 23 30 31 3
20 21 28 29 2
50 51 58 59 2 3 10 11 1
48 49 56 57 0 1 8 9 <- Y=0
54 55 62 63 6 7 14 15 -1
52 53 60 61 4 5 12 13 -2
34 35 42 43 -3
32 33 40 41 -4
38 39 46 47 -5
36 37 44 45 -6
^
-11-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 X=0 1 2 3 4 5 6
The points are on a triangular grid by using every second integer X,Y, as
per L<Math::PlanePath/Triangular Lattice>. All points on that triangular
grid are visited.
The initial N=0,N=1 is replicated at +120 degrees. Then that trapezoid at
+240 degrees
+-----------+ +-----------+
\ 2 3 \ \ 2 3 \
+-----------+ \ \
\ 0 1 \ \ 0 1 \
+-----------+ --------- -----------+
\ 6 7 \
replicate +120deg \ \ rep +240deg
\ 4 5 \
+----------+
Then that bow-tie N=0to7 is replicated at 0 degrees again. Each replication
is 1/3 of the circle around, 0, 120, 240 degrees repeating. The relative
layout within a replication is unchanged.
-----------------------
\ 18 19 26 27 \
\ \
\ 16 17 24 25 \
---------- ----------
\ 22 23 30 31 \
\ \
\ 20 21 28 29 \
--------- ------------ +----------- -----------
\ 50 51 58 59 \ 2 3 \ 10 11 \
\ +-----------+ \
\ 48 49 56 57 \ 0 1 \ 8 9 \
---------- --------- +----------- ---------+
\ 54 55 62 63 \ 6 7 \ 14 15 \
\ \ \ \
\ 52 53 60 61 \ 4 5 \ 12 13 \
-------------- +----------+------------
\ 34 35 42 43 \
\ \
\ 32 33 40 41 \
---------+ -----------
\ 38 39 46 47 \
\ \
\ 36 37 44 45 \
-----------------------
The radial distance doubles on every second replication, so N=1 and N=2 are
at 1 unit from the origin, then N=4 and N=8 at 2 units, then N=16 and N=32
at 4 units. N=64 is not shown but is then at 8 units away (X=8,Y=0).
This is similar to the C<ImaginaryBase>, but where that path repeats in 4
directions based on i=squareroot(-1), here it's 3 directions based on
w=cuberoot(1) = -1/2+i*sqrt(3)/2.
=head2 Radix
The C<radix> parameter controls the "r" used to break N into X,Y. For
example radix 4 gives 4x4 blocks, with r-1 replications of the preceding
level at each stage.
=cut
# math-image --path=CubicBase,radix=4 --expression='i<64?i:0' --output=numbers --size=150x30
=pod
3 radix => 4 12 13 14 15
2 8 9 10 11
1 4 5 6 7
Y=0 -> 0 1 2 3
-1 28 29 30 31
-2 24 25 26 27
-3 20 21 22 23
-4 16 17 18 19
-5 44 45 46 47
... 40 41 42 43
36 37 38 39
32 33 34 35
60 61 62 63
56 57 58 59
52 53 54 55
48 49 50 51
^
-15-14-13-12-11-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 X=0 1 2 3 4 5 6
Notice the parts always replicate away from the origin, so the block N=16 to
N=31 is near the origin at X=-4, then N=32,48,64 are further away.
In this layout the replications still mesh together perfectly and all points
on the triangular grid are visited.
=head1 FUNCTIONS
See L<Math::PlanePath/FUNCTIONS> for behaviour common to all path classes.
=over 4
=item C<$path = Math::PlanePath::CubicBase-E<gt>new ()>
=item C<$path = Math::PlanePath::CubicBase-E<gt>new (radix =E<gt> $r)>
Create and return a new path object.
=item C<($x,$y) = $path-E<gt>n_to_xy ($n)>
Return the X,Y coordinates of point number C<$n> on the path. Points begin
at 0 and if C<$n E<lt> 0> then the return is an empty list.
=back
=head1 SEE ALSO
L<Math::PlanePath>,
L<Math::PlanePath::ImaginaryBase>,
L<Math::PlanePath::ImaginaryHalf>
=head1 HOME PAGE
L<http://user42.tuxfamily.org/math-planepath/index.html>
=head1 LICENSE
Copyright 2012, 2013 Kevin Ryde
This file is part of Math-PlanePath.
Math-PlanePath 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.
Math-PlanePath 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
Math-PlanePath. If not, see <http://www.gnu.org/licenses/>.
=cut
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