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#!/usr/bin/perl -w
# Copyright 2019 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/>.
use 5.010;
use strict;
use warnings;
use POSIX;
use List::Util 'min', 'max';
use Math::BaseCnv;
use Math::PlanePath::Base::Digits
'digit_split_lowtohigh',
'digit_join_lowtohigh';
use Math::PlanePath::ComplexPlus;
use lib 'xt';
use MyOEIS;
# uncomment this to run the ### lines
# use Smart::Comments;
{
# picture of ComplexPlus Gray one bit different, cf TA
require Image::Base::GD;
my $width = 900;
my $height = 600;
my $scale = 20;
my $ox = int($width * .7);
my $oy = int($height * .7);
my $transform = sub {
my ($x,$y) = @_;
$x *= $scale;
$y *= $scale;
$x += $ox;
$y += $oy;
return ($x,$height-1-$y);
};
my @dir4_to_dx = (1,0,-1,0);
my @dir4_to_dy = (0,1,0,-1);
require Math::PlanePath::ComplexPlus;
my $path = Math::PlanePath::ComplexPlus->new;
my $image = Image::Base::GD->new (-height => $height,
-width => $width);
$image->rectangle(0,0, $width-1,$height-1, 'black');
$image->ellipse($transform->(-.2,-.2),
$transform->(.2,.2),
'red', 1);
foreach my $n (0 .. 2**8-1) {
my ($x,$y) = $path->n_to_xy($n);
my $n_gray = Gray($n);
foreach my $dir4 (0 .. 3) {
my $dx = $dir4_to_dx[$dir4];
my $dy = $dir4_to_dy[$dir4];
my $x2 = $x + $dx;
my $y2 = $y + $dy;
my $n_dir = $path->xy_to_n($x2,$y2) // next;
my $n_dir_gray = Gray($n_dir);
### neighbour: sprintf "%d to %d Gray %b to %b", $n, $n_dir, $n_gray, $n_dir_gray
if (CountOneBits($n_gray ^ $n_dir_gray) == 1) {
$image->line($transform->($x,$y),
$transform->($x2,$y2),
'white');
}
}
}
my $filename = '/tmp/gray.png';
$image->save($filename);
require IPC::Run;
IPC::Run::start(['xzgv',$filename],'&');
exit 0;
}
{
# Gray codes
my $path = Math::PlanePath::ComplexPlus->new;
# {
# my $n = $path->xy_to_n(0,-1);
# print "$n\n";
# $n = $path->xy_to_n(0,1);
# print "$n\n";
# }
foreach my $y (reverse -5 .. 5) {
foreach my $x (-5 .. 5) {
my $n = $path->xy_to_n($x,$y);
if (defined $n) {
$n = sprintf '%b', Gray($n);
} else {
$n = '';
}
printf " %8s", $n;
}
print "\n";
}
exit 0;
}
sub Gray {
my ($n) = @_;
require Math::PlanePath::GrayCode;
my $digits = [ digit_split_lowtohigh($n,2) ];
Math::PlanePath::GrayCode::_digits_to_gray_reflected($digits,2);
return digit_join_lowtohigh($digits,2);
}
CHECK {
Gray(0) == 0 or die;
}
sub CountOneBits {
my ($n) = @_;
my $count = 0;
for ( ; $n; $n>>=1) {
$count += ($n & 1);
}
return $count;
}
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