# Copyright 2011, 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 .
# math-image --path=PyramidReplicate --lines --scale=10
# math-image --path=PyramidReplicate --all --output=numbers_dash --size=80x50
package Math::PlanePath::PyramidReplicate;
use 5.004;
use strict;
use vars '$VERSION', '@ISA';
$VERSION = 100;
use Math::PlanePath;
@ISA = ('Math::PlanePath');
use Math::PlanePath::Base::Generic
'is_infinite',
'round_nearest';
use Math::PlanePath::Base::Digits
'round_down_pow';
# uncomment this to run the ### lines
#use Devel::Comments;
use constant n_start => 0;
# 4 3 2
# 5 0 1
# 6 7 8
#
my @digit_to_x = (0,1,0,-1, -2,-3,-2,-1, 0,-1, 0, 1, 2,1,2,3);
my @digit_to_y = (0,0,1, 0, 1, 1, 0, 1, -1,-1,-2,-1, 1,1,0,1);
sub n_to_xy {
my ($self, $n) = @_;
### PyramidReplicate n_to_xy(): $n
if ($n < 0) { return; }
if (is_infinite($n)) { return ($n,$n); }
{
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 = my $y = ($n * 0); # inherit bignum 0
my $len = ($x + 1); # inherit bignum 1
my $bx = 1;
my $by = 1;
while ($n) {
my $digit = $n % 16;
$n = int($n/16);
### at: "$x,$y"
### $digit
$x += $digit_to_x[$digit] * $bx;
$y += $digit_to_y[$digit] * $by;
$bx *= 6;
$by *= 4;
}
### final: "$x,$y"
return ($x,$y);
}
# mod digit
# 5 3 4 4 3 2 (x mod 3) + 3*(y mod 3)
# 2 0 1 5 0 1
# 8 6 7 6 7 8
#
my @mod_to_digit = (0,1,5, 3,2,4, 7,8,6);
sub xy_to_n {
my ($self, $x, $y) = @_;
### PyramidReplicate xy_to_n(): "$x, $y"
return undef;
$x = round_nearest ($x);
$y = round_nearest ($y);
my ($len,$level_limit);
{
my $xa = abs($x);
my $ya = abs($y);
($len,$level_limit) = round_down_pow (2*($xa > $ya ? $xa : $ya) || 1, 3);
### $level_limit
### $len
}
$level_limit += 2;
if (is_infinite($level_limit)) {
return $level_limit;
}
my $n = ($x * 0 * $y); # inherit bignum 0
my $power = ($n + 1); # inherit bignum 1
while ($x || $y) {
if ($level_limit-- < 0) {
### oops, level limit reached ...
return undef;
}
my $m = ($x % 3) + 3*($y % 3);
my $digit = $mod_to_digit[$m];
### at: "$x,$y m=$m digit=$digit"
$x -= $digit_to_x[$digit];
$y -= $digit_to_y[$digit];
### subtract: "$digit_to_x[$digit],$digit_to_y[$digit] to $x,$y"
### assert: $x % 3 == 0
### assert: $y % 3 == 0
$x /= 3;
$y /= 3;
$n += $digit * $power;
$power *= 9;
}
return $n;
}
# level N Xmax
# 1 9^1-1 1
# 2 9^2-1 1+3
# 3 9^3-1 1+3+9
# X <= 3^0+3^1+...+3^(level-1)
# X <= 1 + 3^0+3^1+...+3^(level-1)
# X <= (3^level - 1)/2
# 2*X+1 <= 3^level
# level >= log3(2*X+1)
#
# X < 1 + 3^0+3^1+...+3^(level-1)
# X < 1 + (3^level - 1)/2
# (3^level - 1)/2 > X-1
# 3^level - 1 > 2*X-2
# 3^level > 2*X-1
#
# not exact
sub rect_to_n_range {
my ($self, $x1,$y1, $x2,$y2) = @_;
### PyramidReplicate rect_to_n_range(): "$x1,$y1 $x2,$y2"
my $max = abs(round_nearest($x1));
foreach ($y1, $x2, $y2) {
my $m = abs(round_nearest($_));
if ($m > $max) { $max = $m }
}
my ($len,$level) = round_down_pow (2*($max||1)-1, 3);
return (0, 9*$len*$len - 1); # 9^level-1
}
1;
__END__
=for stopwords eg Ryde Math-PlanePath aabbccdd
=head1 NAME
Math::PlanePath::PyramidReplicate -- replicating squares
=head1 SYNOPSIS
use Math::PlanePath::PyramidReplicate;
my $path = Math::PlanePath::PyramidReplicate->new;
my ($x, $y) = $path->n_to_xy (123);
=head1 DESCRIPTION
This is a self-similar replicating pyramid shape made from 4 points each,
4
3
2
1
<- Y=0
-1
-2
-3
-4
^
-4 -3 -2 -1 X=0 1 2 3 4
The base shape is the initial N=0 to N=8 section,
+---+
| 2 |
+---+---+---+
| 3 | 0 | 1 |
+---+---+---+
It then repeats inverted to make a similar shape but upside-down,
+---+---+---+---+---+---+---+
| 5 4 7 | 2 |13 12 15 |
+---+ +---+ +---+ +---+
| 6 | 3 0 1 |14 |
+---+---+---+---+---+
| 9 8 11 |
+---+ +---+
|10 |
+---+
=head2 Level Ranges
A given replication extends to ...
Nlevel = 4^level - 1
- ... <= X <= ...
- ... <= Y <= ...
=head2 Complex Base
This pattern corresponds to expressing a complex integer X+i*Y in base b=...
X+Yi = a[n]*b^n + ... + a[2]*b^2 + a[1]*b + a[0]
using complex digits a[i] encoded in N in integer base 4 ...
a[i] digit N digit
---------- -------
0 0
1 1
i 2
-1 3
=head1 FUNCTIONS
See L for the behaviour common to all path
classes.
=over 4
=item C<$path = Math::PlanePath::PyramidReplicate-Enew ()>
Create and return a new path object.
=item C<($x,$y) = $path-En_to_xy ($n)>
Return the X,Y coordinates of point number C<$n> on the path. Points begin
at 0 and if C<$n E 0> then the return is an empty list.
=back
=head1 SEE ALSO
L,
L,
L,
L,
L,
L
=head1 HOME PAGE
http://user42.tuxfamily.org/math-planepath/index.html
=head1 LICENSE
Copyright 2011, 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 .
=cut