/usr/share/perl5/Math/PlanePath/AlternatePaperMidpoint.pm is in libmath-planepath-perl 123-1.
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=AlternatePaperMidpoint,arms=8 --all --output=numbers_dash
# math-image --path=AlternatePaperMidpoint --lines --scale=20
package Math::PlanePath::AlternatePaperMidpoint;
use 5.004;
use strict;
use List::Util 'min'; # 'max'
*max = \&Math::PlanePath::_max;
use vars '$VERSION', '@ISA';
$VERSION = 123;
use Math::PlanePath;
use Math::PlanePath::Base::NSEW;
@ISA = ('Math::PlanePath::Base::NSEW',
'Math::PlanePath');
use Math::PlanePath::Base::Generic
'is_infinite',
'round_nearest';
use Math::PlanePath::Base::Digits
'round_down_pow',
'digit_split_lowtohigh',
'digit_join_lowtohigh';
*_divrem_mutate = \&Math::PlanePath::_divrem_mutate;
use Math::PlanePath::AlternatePaper;
# uncomment this to run the ### lines
#use Smart::Comments;
use constant parameter_info_array => [ { name => 'arms',
share_key => 'arms_8',
display => 'Arms',
type => 'integer',
minimum => 1,
maximum => 8,
default => 1,
width => 1,
description => 'Arms',
} ];
use constant n_start => 0;
sub x_negative {
my ($self) = @_;
return ($self->{'arms'} >= 3);
}
sub y_negative {
my ($self) = @_;
return ($self->{'arms'} >= 5);
}
{
my @x_negative_at_n = (undef,
undef,undef,11,3,
3,3,3,3);
sub x_negative_at_n {
my ($self) = @_;
return $x_negative_at_n[$self->{'arms'}];
}
}
{
my @y_negative_at_n = (undef,
undef,undef,undef,undef,
24,11,12,7);
sub y_negative_at_n {
my ($self) = @_;
return $y_negative_at_n[$self->{'arms'}];
}
}
sub sumxy_minimum {
my ($self) = @_;
return ($self->arms_count <= 3
? 0 # 1,2,3 arms above X=-Y diagonal
: undef);
}
sub diffxy_minimum {
my ($self) = @_;
return ($self->arms_count == 1
? 0 # 1 arms right of X=Y diagonal
: undef);
}
#------------------------------------------------------------------------------
sub new {
my $self = shift->SUPER::new(@_);
$self->{'arms'} = max(1, min(8, $self->{'arms'} || 1));
return $self;
}
# +-----------+ states
# |\ -------/|
# | \ \ 4 / |
# |^ \ \ / |
# || \ v / /||
# || \ / / ||
# ||8 / * /12||
# || / / \ ||
# ||/ / ^ \ ||
# | / \ \ v|
# | / 0 \ \ |
# |/ ------ \|
# +-----------+
#
# + state=0 digits
# /|\
# / | \
# / | \
# /\ 1|3 /\
# / \ | / \
# / 0 \|/ 2 \
# +------+------+
my @next_state = (0, 12, 0, 8, # 0 forward
4, 8, 4, 12, # 4 forward NW
4, 8, 0, 8, # 8 reverse
0, 12, 4, 12, # 12 reverse NE
);
my @digit_to_x = (0,0,1,1,
1,1,0,0,
0,0,0,0,
1,1,1,1,
);
my @digit_to_y = (0,0,0,0,
1,1,1,1,
0,0,1,1,
1,1,0,0,
);
sub n_to_xy {
my ($self, $n) = @_;
### AlternatePaperMidpoint n_to_xy(): $n
if ($n < 0) { return; }
if (is_infinite($n)) { return ($n, $n); }
{
my $int = int($n);
if ($n != $int) {
my ($x1,$y1) = $self->n_to_xy($int);
my ($x2,$y2) = $self->n_to_xy($int+$self->{'arms'});
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 $zero = ($n * 0); # inherit bignum 0
my $arm = _divrem_mutate ($n, $self->{'arms'});
### $arm
### $n
my @digits = digit_split_lowtohigh($n,4);
my $state = my $dirstate = 0;
my @x;
my @y;
foreach my $i (reverse 1 .. scalar(@digits)) {
my $digit = $digits[$i-1]; # high to low, all digits
$state += $digit;
if ($digit != 3) {
$dirstate = $state;
}
$x[$i] = $digit_to_x[$state]; # high to low, leaving one lowest
$y[$i] = $digit_to_y[$state];
$state = $next_state[$state];
}
$x[0] = $digit_to_x[$state]; # state=4,12 increment
$y[0] = $digit_to_y[$state + 3]; # state=4,8 increment
my $x = digit_join_lowtohigh(\@x,2,$zero);
my $y = digit_join_lowtohigh(\@y,2,$zero);
### final: "x=$x,y=$y state=$state"
if ($arm & 1) {
($x,$y) = ($y+1,$x+1); # transpose and offset
}
if ($arm & 2) {
($x,$y) = (-$y,$x+1); # rotate +90 and offset
}
if ($arm & 4) {
$x = -1 - $x; # rotate 180 and offset
$y = 1 - $y;
}
# ### rotated return: "$x,$y"
return ($x,$y);
}
# | |
# 64-65-66 71-72-73-74 95
# | |
# 63 98-97-96
# | |
# 20-21 62 99
# | | |
# 19 22 61-60-59
# | | |
# 16-17-18 23 56-57-58
# | | |
# 15 26-25-24 55 50-49-48-47
# | | | | |
# 4--5 14 27-28-29 54 51 36-37 46
# | | | | | | | | |
# 3 6 13-12-11 30 53-52 35 38 45-44-43
# | | | | | | |
# 0--1--2 7--8--9-10 31-32-33-34 39-40-41-42
#
# 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
# 43-35 42-50-58 57-49-41
# | | | |
# 91-99 51 27 34-26-18 17-25-33
# | | | | |
# 83-75-67-59 19-11--3 10 9 32-40
# | | | |
# 84-76-68-60 20-12--4 2 1 24 48 96-88
# | | | | | |
# 92 52 28 5 6 0--8-16 56-64-72-80
# | | | |
# 44-36 13 14 7-15-23 63-71-79-87
# | | | | |
# 37-29-21 22-30-38 31 55 95
# | | | |
# 45-53-61 62-54-46 39-47
# | |
# 69 70
sub xy_to_n {
my ($self, $x, $y) = @_;
### AlternatePaperMidpoint xy_to_n(): "$x, $y"
$x = round_nearest($x);
$y = round_nearest($y);
if (is_infinite($x)) {
return $x; # infinity
}
if (is_infinite($y)) {
return $y; # infinity
}
# arm in various octants, rotate/transpose to first
my $arm;
if ($y >= ($x>=0?0:2)) { # Y>=0 when X positive, Y>=2 when X negative
$arm = 0;
} else {
# lower arms 4,5,6,7 ...
$arm = 4;
$x = -1 - $x; # rotate 180, offset
$y = 1 - $y;
}
if ($x < ($y>0?1:0)) {
### second quad arms 2,3 ...
($x,$y) = ($y-1,-$x); # rotate -90, offset
$arm += 2;
}
if ($y > $x-($x%2)) {
### above diagonal, arm 1 ...
($x,$y) = ($y-1,$x-1); # offset and transpose
$arm++;
}
### assert: $x >= 0
### assert: $y >= 0
### assert: $y <= $x - ($x%2)
if ($arm >= $self->{'arms'}) {
return undef;
}
my ($len, $level) = round_down_pow ($x, 2);
if (is_infinite($level)) {
return ($level);
}
# + state=0 digits
# /|\
# / | \
# / | \
# /\ 1|3 /\
# / \ | / \
# / 0 \|/ 2 \
# +------+------+
# + state=0 digits
# /|\
# / | \
# / | \
# /\ 2|0 /\
# / \ | / \
# / 3 \|/ 1 \
# +------+------+
my $n = ($x * 0 * $y); # inherit bignum 0
my $rev = 0;
$len *= 2;
while ($level-- >= 0) {
### at: "xy=$x,$y rev=$rev len=$len n=".sprintf('%#x',$n)
### assert: $x >= 0
### assert: $y >= 0
### assert: $y <= $x - ($x%2)
### assert: $x+$y+($x%2) < 2*$len
my $digit;
if ($x < $len) {
### diagonal: $x+$y+($x%2), $len
if ($x+$y+($x%2) < $len) {
### part 0 ...
$digit = 0;
} else {
### part 1 ...
($x,$y) = ($y,$len-1-$x); # shift, rotate -90
$rev ^= 3;
$digit = 2; # becoming digit=1 with reverse
}
} else {
$x -= $len;
### 2,3 ycmp: $y, $x-($x%2)
if ($y <= $x-($x%2)) {
### part 2 ...
$digit = 2;
} else {
### part 3 ...
($x,$y) = ($len-1-$y,$x); # shift, rotate +90
$rev ^= 3;
$digit = 0; # becoming digit=3 with reverse
}
}
### $digit
$digit ^= $rev; # $digit = 3-$digit if reverse
### reversed digit: $digit
$n *= 4;
$n += $digit;
$len /= 2;
}
### final: "xy=$x,$y rev=$rev"
### assert: $x == 0
### assert: $y == 0
return $n*$self->{'arms'} + $arm;
}
# not exact
sub rect_to_n_range {
my ($self, $x1,$y1, $x2,$y2) = @_;
### AlternatePaperMidpoint rect_to_n_range(): "$x1,$y1 $x2,$y2 arms=$self->{'arms'}"
$x1 = round_nearest($x1);
$x2 = round_nearest($x2);
$y1 = round_nearest($y1);
$y2 = round_nearest($y2);
($x1,$x2) = ($x2,$x1) if $x1 > $x2;
($y1,$y2) = ($y2,$y1) if $y1 > $y2;
my $arms = $self->{'arms'};
if (($arms == 1 && $y1 > $x2) # x2,y1 bottom right corner
|| ($arms <= 2 && $x2 < 0)
|| ($arms <= 4 && $y2 < 0)) {
### outside ...
return (1,0);
}
my ($len) = round_down_pow (max ($x2,
($arms >= 2 ? $y2-1 : ()),
($arms >= 4 ? -1-$x1 : ()),
($arms >= 6 ? -$y1 : ())),
2);
return (0, 2*$arms*$len*$len-1);
}
#------------------------------------------------------------------------------
# levels
use Math::PlanePath::DragonMidpoint;
*level_to_n_range = \&Math::PlanePath::DragonMidpoint::level_to_n_range;
*n_to_level = \&Math::PlanePath::DragonMidpoint::n_to_level;
#------------------------------------------------------------------------------
1;
__END__
=for stopwords Math-PlanePath eg Ryde OEIS
=head1 NAME
Math::PlanePath::AlternatePaperMidpoint -- alternate paper folding midpoints
=head1 SYNOPSIS
use Math::PlanePath::AlternatePaperMidpoint;
my $path = Math::PlanePath::AlternatePaperMidpoint->new;
my ($x, $y) = $path->n_to_xy (123);
=head1 DESCRIPTION
This is the midpoints of each alternate paper folding curve
(L<Math::PlanePath::AlternatePaper>).
8 | 64-65-...
| |
7 | 63
| |
6 | 20-21 62
| | | |
5 | 19 22 61-60-59
| | | |
4 | 16-17-18 23 56-57-58
| | | |
3 | 15 26-25-24 55 50-49-48-47
| | | | | |
2 | 4--5 14 27-28-29 54 51 36-37 46
| | | | | | | | | |
1 | 3 6 13-12-11 30 53-52 35 38 45-44-43
| | | | | | | |
Y=0 | 0--1--2 7--8--9-10 31-32-33-34 39-40-41-42
+----------------------------------------------
X=0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
The C<AlternatePaper> curve begins as follows and the midpoints are numbered
from 0,
|
9
|
--8--
| |
7 |
| |
--2-- --6--
| | |
1 3 5
| | |
*--0-- --4--
These midpoints are on fractions X=0.5,Y=0, X=1,Y=0.5, etc. For this
C<AlternatePaperMidpoint> they're turned 45 degrees and mirrored so the
0,1,2 upward diagonal becomes horizontal along the X axis, and the 2,3,4
downward diagonal becomes a vertical at X=2, extending to X=2,Y=2 at N=4.
The midpoints are distinct X,Y positions because the alternate paper curve
traverses each edge only once.
The curve is self-similar in 2^level sections due to its unfolding. This
can be seen in the midpoints as for example N=0 to N=16 above is the same
shape as N=16 to N=32, but the latter rotated +90 degrees and numbered in
reverse.
=head2 Arms
The midpoints fill an eighth of the plane and eight copies can mesh together
perfectly when mirrored and rotated by 90, 180 and 270 degrees. The C<arms>
parameter can choose 1 to 8 curve arms successively advancing.
For example C<arms =E<gt> 8> begins as follows. N=0,8,16,24,etc is the
first arm, the same as the plain curve above. N=1,9,17,25 is the second,
N=2,10,18,26 the third, etc.
90-82 81-89 7
arms => 8 | | | |
... 74 73 ... 6
| |
66 65 5
| |
43-35 42-50-58 57-49-41 4
| | | |
91-.. 51 27 34-26-18 17-25-33 3
| | | | |
83-75-67-59 19-11--3 10 9 32-40 2
| | | |
84-76-68-60 20-12--4 2 1 24 48 ..-88 1
| | | | | |
92-.. 52 28 5 6 0--8-16 56-64-72-80 <- Y=0
| | | |
44-36 13 14 7-15-23 63-71-79-87 -1
| | | | |
37-29-21 22-30-38 31 55 ..-95 -2
| | | |
45-53-61 62-54-46 39-47 -3
| |
69 70 -4
| |
... 77 78 ... -5
| | | |
93-85 86-94 -6
^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
-7 -6 -5 -4 -3 -2 -1 X=0 1 2 3 4 5 6
With eight arms like this every X,Y point is visited exactly once, because
the 8-arm C<AlternatePaper> traverses every edge exactly once
(L<Math::PlanePath::AlternatePaper/Arms>).
The arm numbering doesn't correspond to the C<AlternatePaper>, due to the
rotate and reflect of the first arm. It ends up arms 0 and 1 of the
C<AlternatePaper> corresponding to arms 7 and 0 of the midpoints here, those
two being a pair going horizontally corresponding to a pair in the
C<AlternatePaper> going diagonally into a quadrant.
=head1 FUNCTIONS
See L<Math::PlanePath/FUNCTIONS> for behaviour common to all path classes.
=over 4
=item C<$path = Math::PlanePath::AlternatePaperMidpoint-E<gt>new ()>
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.
Fractional positions give an X,Y position along a straight line between the
integer positions.
=item C<$n = $path-E<gt>n_start()>
Return 0, the first N in the path.
=back
=head2 Level Methods
=over
=item C<($n_lo, $n_hi) = $path-E<gt>level_to_n_range($level)>
Return C<(0, 2**$level - 1)>, or for multiple arms return C<(0, $arms *
(2**$level - 1)*$arms)>. This is the same as the C<DragonMidpoint>.
=back
=head1 OEIS
Entries in Sloane's Online Encyclopedia of Integer Sequences related to
this path include
=over
L<http://oeis.org/A016116> (etc)
=back
A016116 X/2 at N=2^k, being X/2=2^floor(k/2)
=head1 SEE ALSO
L<Math::PlanePath>,
L<Math::PlanePath::AlternatePaper>
L<Math::PlanePath::DragonMidpoint>,
L<Math::PlanePath::R5DragonMidpoint>,
L<Math::PlanePath::TerdragonMidpoint>
=head1 HOME PAGE
L<http://user42.tuxfamily.org/math-planepath/index.html>
=head1 LICENSE
Copyright 2012, 2013, 2014, 2015, 2016 Kevin Ryde
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
|