File Coverage

blib/lib/Math/PlanePath/FlowsnakeCentres.pm

Criterion	Covered	Total	%
statement	240	274	87.5
branch	78	96	81.2
condition	25	26	96.1
subroutine	27	32	84.3
pod	9	9	100.0
total	379	437	86.7

# Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 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=FlowsnakeCentres --lines --scale=10
#
# http://80386.nl/projects/flowsnake/
#


package Math::PlanePath::FlowsnakeCentres;
use 5.004;
use strict;
use POSIX 'ceil';
use List::Util 'min'; # 'max'
*max = \&Math::PlanePath::_max;

use vars '$VERSION', '@ISA';
$VERSION = 129;
use Math::PlanePath;
@ISA = ('Math::PlanePath');
*_divrem_mutate = \&Math::PlanePath::_divrem_mutate;

use Math::PlanePath::Base::Generic
  'is_infinite',
  'round_nearest',
  'xy_is_even';
use Math::PlanePath::Base::Digits
  'digit_split_lowtohigh',
  'round_up_pow';

use Math::PlanePath::SacksSpiral;
*_rect_to_radius_range = \&Math::PlanePath::SacksSpiral::_rect_to_radius_range;

# uncomment this to run the ### lines
#use Devel::Comments;


use constant n_start => 0;

use constant parameter_info_array => [ { name      => 'arms',
                                         share_key => 'arms_3',
                                         display   => 'Arms',
                                         type      => 'integer',
                                         minimum   => 1,
                                         maximum   => 3,
                                         default   => 1,
                                         width     => 1,
                                         description => 'Arms',
                                       } ];

{
  my @x_negative_at_n = (undef, 3, 1, 1);
  sub x_negative_at_n {
    my ($self) = @_;
    return $x_negative_at_n[$self->{'arms'}];
  }
}
{
  my @y_negative_at_n = (undef, 8597, 7, 2);
  sub y_negative_at_n {
    my ($self) = @_;
    return $y_negative_at_n[$self->{'arms'}];
  }
}

use constant dx_minimum => -2;
use constant dx_maximum => 2;
use constant dy_minimum => -1;
use constant dy_maximum => 1;
*_UNDOCUMENTED__dxdy_list = \&Math::PlanePath::_UNDOCUMENTED__dxdy_list_six;
{
  my @_UNDOCUMENTED__dxdy_list_at_n = (undef, 10, 6, 8);
  sub _UNDOCUMENTED__dxdy_list_at_n {
    my ($self) = @_;
    return $_UNDOCUMENTED__dxdy_list_at_n[$self->{'arms'}];
  }
}
use constant absdx_minimum => 1;
use constant dsumxy_minimum => -2; # diagonals
use constant dsumxy_maximum => 2;
use constant ddiffxy_minimum => -2;
use constant ddiffxy_maximum => 2;
use constant dir_maximum_dxdy => (1,-1); # South-East



#------------------------------------------------------------------------------
#         *
#        / \
#       /   \
#      *-----*
#
# (b/2)^2 + h^2 = s
# (1/2)^2 + h^2 = 1
# h^2 = 1 - 1/4
# h = sqrt(3)/2 = 0.866
#

sub new {
  my $self = shift->SUPER::new(@_);
  $self->{'arms'} = max(1, min(3, $self->{'arms'} || 1));
  return $self;
}


# # next_state length 84
# my @next_state = (0, 35,49,14, 0,70, 7,  0,21, 7,21,42,28, 7,  # 0,7
#                   14,49,63,28,14, 0,21, 14,35,21,35,56,42,21,  # 14,21
#                   28,63,77,42,28,14,35, 28,49,35,49,70,56,35,  # 28,35
#                   42,77, 7,56,42,28,49, 42,63,49,63, 0,70,49,  # 42,49
#                   56, 7,21,70,56,42,63, 56,77,63,77,14, 0,63,  # 56,63
#                   70,21,35, 0,70,56,77, 70, 7,77, 7,28,14,77);  # 70,77
# my @digit_to_i = (0,  1, 0,-1,-1, 0, 1,  0, 1, 2, 3, 3, 2, 1,  # 0,7
#                   0,  0,-1,-1,-2,-2,-1,  0, 0, 1, 1, 0, 0,-1,  # 14,21
#                   0, -1,-1, 0,-1,-2,-2,  0,-1,-1,-2,-3,-2,-2,  # 28,35
#                   0, -1, 0, 1, 1, 0,-1,  0,-1,-2,-3,-3,-2,-1,  # 42,49
#                   0,  0, 1, 1, 2, 2, 1,  0, 0,-1,-1, 0, 0, 1,  # 56,63
#                   0,  1, 1, 0, 1, 2, 2,  0, 1, 1, 2, 3, 2,2);  # 70,77
# my @digit_to_j = (0,  0, 1, 1, 2, 2, 1,  0, 0,-1,-1, 0, 0, 1,  # 0,7
#                   0,  1, 1, 0, 1, 2, 2,  0, 1, 1, 2, 3, 2, 2,  # 14,21
#                   0,  1, 0,-1,-1, 0, 1,  0, 1, 2, 3, 3, 2, 1,  # 28,35
#                   0,  0,-1,-1,-2,-2,-1,  0, 0, 1, 1, 0, 0,-1,  # 42,49
#                   0, -1,-1, 0,-1,-2,-2,  0,-1,-1,-2,-3,-2,-2,  # 56,63
#                   0, -1, 0, 1, 1, 0,-1,  0,-1,-2,-3,-3,-2,-1);  # 70,77
# my @state_to_di = ( 1, 1, 0, 0,-1,-1,  -1,-1, 0, 0, 1,1);
# my @state_to_dj = ( 0, 0, 1, 1, 1, 1,   0, 0,-1,-1,-1,-1);
#
#
# sub n_to_xy {
#   my ($self, $n) = @_;
#   ### Flowsnake n_to_xy(): $n
#
#   if ($n < 0) { return; }
#   if (is_infinite($n)) { return ($n,$n); }
#
#   my $int = int($n);
#   $n -= $int;  # fraction part
#   ### $int
#   ### frac: $n
#
#   my $state;
#   {
#     my $arm = _divrem_mutate ($int, $self->{'arms'});
#     $state = 28 * $arm;  # initial rotation
#
#     # adjust so that for arms=2 point N=1 has $int==1
#     # or for arms=3 then points N=1 and N=2 have $int==1
#     if ($arm) { $int += 1; }
#   }
#   ### initial state: $state
#
#   my $i = my $j = $int*0;  # bignum zero
#
#   foreach my $digit (reverse digit_split_lowtohigh($int,7)) { # high to low
#     ### at: "state=$state digit=$digit  i=$i,j=$j  di=".$digit_to_i[$state+$digit]." dj=".$digit_to_j[$state+$digit]
#
#     # i,j * (2+w), being 2*(i,j)+rot60(i,j)
#     # then add low digit position
#     #
#     $state += $digit;
#     ($i, $j) = (2*$i - $j + $digit_to_i[$state],
#                 3*$j + $i + $digit_to_j[$state]);
#     $state = $next_state[$state];
#   }
#   ### integer: "i=$i, j=$j"
#
#   # fraction in final $state direction
#   if ($n) {
#     ### apply: "frac=$n  state=$state"
#     $state /= 7;
#     $i = $n * $state_to_di[$state] + $i;
#     $j = $n * $state_to_dj[$state] + $j;
#   }
#
#   ### ret: "$i, $j  x=".(2*$i+$j)." y=$j"
#   return (2*$i+$j,
#           $j);
#
# }

#       4-->5
#       ^    ^
#     /       \
#    3--- 2    6--
#          \
#           v
#       0-->1
#

my @digit_reverse = (0,1,1,0,0,0,1);   # 1,2,6

sub n_to_xy {
  my ($self, $n) = @_;
  ### FlowsnakeCentres n_to_xy(): $n

  if ($n < 0) { return; }
  if (is_infinite($n)) { return ($n,$n); }

  # ENHANCE-ME: work $frac into initial $x,$y somehow
  # my $frac;
  # {
  #   my $int = int($n);
  #   $frac = $n - $int;  # inherit possible BigFloat/BigRat
  #   $n = $int;  # BigInt instead of BigFloat
  # }
  {
    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+$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
  }

  # arm as initial rotation
  my $rot = _divrem_mutate ($n, $self->{'arms'});

  my @digits = digit_split_lowtohigh($n,7);
  ### @digits

  my $x = 0;
  my $y = 0;
  {
    # if (! @n || $digits[0] == 0) {
    #   $x = 2*$frac;
    # } elsif ($digits[0] == 1) {
    #   $x = $frac;
    #   $y = -$frac;
    # } elsif ($digits[0] == 2) {
    #   $x = -2*$frac;
    # } elsif ($digits[0] == 3) {
    #   $x = $frac;
    #   $y = -$frac;
    # } elsif ($digits[0] == 4) {
    #   $x = 2*$frac;
    # } elsif ($digits[0] == 5) {
    #   $x = $frac;
    #   $y = -$frac;
    # } elsif ($digits[0] == 6) {
    #   $x = -$frac;
    #   $y = -$frac;
    # }

    my $rev = 0;
    foreach my $digit (reverse @digits) {   # high to low
      ### $digit
      if ($rev) {
        ### reverse: "$digit to ".(6 - $digit)
        $digit = 6 - $digit;  # mutate the array
      }
      $rev ^= $digit_reverse[$digit];
      ### now rev: $rev
    }
    ### reversed n: @n
  }

  my ($ox,$oy,$sx,$sy);
  if ($rot == 0) {
    $ox = 0;
    $oy = 0;
    $sx = 2;
    $sy = 0;
  } elsif ($rot == 1) {
    $ox = -1;  # at +120
    $oy = 1;
    $sx = -1;  # rot to +120
    $sy = 1;
  } else {
    $ox = -2;   # at 180
    $oy = 0;
    $sx = -1;  # rot to +240
    $sy = -1;
  }

  while (@digits) {
    my $digit = shift @digits;  # low to high
    ### digit: "$digit  $x,$y  side $sx,$sy  origin $ox,$oy"

    if ($digit == 0) {
      $x += (3*$sy - $sx)/2;    # at -120
      $y += ($sx + $sy)/-2;

    } elsif ($digit == 1) {
      ($x,$y) = ((3*$y-$x)/2,   # rotate -120
                 ($x+$y)/-2);
      $x += ($sx + 3*$sy)/2;    # at -60
      $y += ($sy - $sx)/2;

    } elsif ($digit == 2) {
      # centre

    } elsif ($digit == 3) {
      ($x,$y) = (($x+3*$y)/-2,  # rotate +120
                 ($x-$y)/2);
      $x -= $sx;                # at -180
      $y -= $sy;

    } elsif ($digit == 4) {
      $x += ($sx + 3*$sy)/-2;   # at +120
      $y += ($sx - $sy)/2;

    } elsif ($digit == 5) {
      $x += ($sx - 3*$sy)/2;    # at +60
      $y += ($sx + $sy)/2;

    } elsif ($digit == 6) {
      ($x,$y) = (($x+3*$y)/-2,  # rotate +120
                 ($x-$y)/2);
      $x += $sx;                # at X axis
      $y += $sy;
    }

    $ox += $sx;
    $oy += $sy;

    # 2*(sx,sy) + rot+60(sx,sy)
    ($sx,$sy) = ((5*$sx - 3*$sy) / 2,
                 ($sx + 5*$sy) / 2);
  }


  ### digits to: "$x,$y"
  ### origin sum: "$ox,$oy"
  ### origin rotated: (($ox-3*$oy)/2).','.(($ox+$oy)/2)
  $x += ($ox-3*$oy)/2;     # rotate +60
  $y += ($ox+$oy)/2;

  ### final: "$x,$y"
  return ($x,$y);
}

# all even points when arms==3
sub xy_is_visited {
  my ($self, $x, $y) = @_;
  if ($self->{'arms'} == 3) {
    return xy_is_even($self,$x,$y);
  } else {
    return defined($self->xy_to_n($x,$y));
  }
}

#       4-->5
#       ^    ^      forw
#     /       \
#    3--- 2    6---
#          \
#           v
#       0-->1
#
#       5   3
#            \       rev
#     /  \ /  v
#  --6    4    2
#             /
#           v
#       0-->1
#

my @modulus_to_digit
  = (0,3,1,2,4,6,5,    0,42,14,28, 0,56, 0,      # 0   right forw 0
     0,5,1,4,6,2,3,    0,42,14,70,14,14,28,    # 14  +120 rev   1
     6,3,5,4,2,0,1,   28,56,70, 0,28,42,28,    # 28  left rev   2
     4,5,3,2,6,0,1,   42,42,70,56,14,42,28,   # 42  +60 forw   3
     2,1,3,4,0,6,5,   56,56,14,42,70,56, 0,    # 56  -60 rev    6
     6,1,5,2,0,4,3,   28,56,70,14,70,70, 0,    # 70      forw
    );
sub xy_to_n {
  my ($self, $x, $y) = @_;
  ### FlowsnakeCentres xy_to_n(): "$x, $y"

  $x = round_nearest($x);
  $y = round_nearest($y);
  if (($x ^ $y) & 1) {
    ### odd x,y ...
    return undef;
  }

  my $level_limit = log($x*$x + 3*$y*$y + 1) * 0.835 * 2;
  if (is_infinite($level_limit)) { return $level_limit; }

  my @digits;
  my $arm;
  my $state;
  for (;;) {
    if ($level_limit-- < 0) {
      ### oops, level limit ...
      return undef;
    }
    if ($x == 0 && $y == 0) {
      ### found first arm 0,0 ...
      $arm = 0;
      $state = 0;
      last;
    }
    if ($x == -2 && $y == 0) {
      ### found second arm -2,0 ...
      $arm = 1;
      $state = 42;
      last;
    }
    if ($x == -1 && $y == -1) {
      ### found third arm -1,-1 ...
      $arm = 2;
      $state = 70;
      last;
    }

    # if ((($x == -1 || $x == 1) && $y == -1)
    #     || ($x == 0 && $y == -2)) {
    #   ### below island ...
    #   return undef;
    # }

    my $m = ($x + 2*$y) % 7;
    ### at: "$x,$y   digits=".join(',',@digits)
    ### mod remainder: $m

    # 0,0 is m=0
    if ($m == 2) {  # 2,0  = 2
      $x -= 2;
    } elsif ($m == 3) {  # 1,1 = 1+2 = 3
      $x -= 1;
      $y -= 1;
    } elsif ($m == 1) {  # -1,1 = -1+2 = 1
      $x += 1;
      $y -= 1;
    } elsif ($m == 4) {  # 0,2 = 0+2*2 = 4
      $y -= 2;
    } elsif ($m == 6) {  # 2,2 = 2+2*2 = 6
      $x -= 2;
      $y -= 2;
    } elsif ($m == 5) {  # 3,1 = 3+2*1 = 5
      $x -= 3;
      $y -= 1;
    }
    push @digits, $m;

    ### digit: "$m  to $x,$y"
    ### shrink to: ((3*$y + 5*$x) / 14).','.((5*$y - $x) / 14)
    ### assert: (3*$y + 5*$x) % 14 == 0
    ### assert: (5*$y - $x) % 14 == 0

    # shrink
    ($x,$y) = ((3*$y + 5*$x) / 14,
               (5*$y - $x) / 14);
  }

  ### @digits
  my $arms = $self->{'arms'};
  if ($arm >= $arms) {
    return undef;
  }

  my $n = 0;
  foreach my $m (reverse @digits) {  # high to low
    ### $m
    ### digit: $modulus_to_digit[$state + $m]
    ### state: $state
    ### next state: $modulus_to_digit[$state+7 + $m]

    $n = 7*$n + $modulus_to_digit[$state + $m];
    $state = $modulus_to_digit[$state+7 + $m];
  }
  ### final n along arm: $n

  return $n*$arms + $arm;
}

# exact
sub rect_to_n_range {
  my ($self, $x1,$y1, $x2,$y2) = @_;
  ### FlowsnakeCentres rect_to_n_range(): "$x1,$y1  $x2,$y2"

  my ($r_lo, $r_hi) = _rect_to_radius_range ($x1,$y1*sqrt(3), $x2,$y2*sqrt(3));
  $r_hi *= 2;
  my $level_plus_1 = ceil( log(max(1,$r_hi/4)) / log(sqrt(7)) ) + 2;
  # return (0, 7**$level_plus_1);


  my $level_limit = $level_plus_1;
  ### $level_limit
  if (is_infinite($level_limit)) { return ($level_limit,$level_limit); }

  $x1 = round_nearest ($x1);
  $y1 = round_nearest ($y1);
  $x2 = round_nearest ($x2);
  $y2 = round_nearest ($y2);
  ($x1,$x2) = ($x2,$x1) if $x1 > $x2;
  ($y1,$y2) = ($y2,$y1) if $y1 > $y2;
  ### sorted range: "$x1,$y1  $x2,$y2"

  my $rect_dist = sub {
    my ($x,$y) = @_;
    my $xd = ($x < $x1 ? $x1 - $x
              : $x > $x2 ? $x - $x2
              : 0);
    my $yd = ($y < $y1 ? $y1 - $y
              : $y > $y2 ? $y - $y2
              : 0);
    return ($xd*$xd + 3*$yd*$yd);
  };

  my $arms = $self->{'arms'};
  ### $arms
  my $n_lo;
  {
    my @hypot = (6);
    my $top = 0;
    for (;;) {
    ARM_LO: foreach my $arm (0 .. $arms-1) {
        my $i = 0;
        my @digits;
        if ($top > 0) {
          @digits = ((0)x($top-1), 1);
        } else {
          @digits = (0);
        }

        for (;;) {
          my $n = 0;
          foreach my $digit (reverse @digits) { # high to low
            $n = 7*$n + $digit;
          }
          $n = $n*$arms + $arm;
          ### lo consider: "i=$i  digits=".join(',',reverse @digits)."  is n=$n"

          my ($nx,$ny) = $self->n_to_xy($n);
          my $nh = &$rect_dist ($nx,$ny);
          if ($i == 0 && $nh == 0) {
            ### lo found inside: $n
            if (! defined $n_lo || $n < $n_lo) {
              $n_lo = $n;
            }
            next ARM_LO;
          }

          if ($i == 0 || $nh > $hypot[$i]) {
            ### too far away: "nxy=$nx,$ny   nh=$nh vs ".$hypot[$i]

            while (++$digits[$i] > 6) {
              $digits[$i] = 0;
              if (++$i <= $top) {
                ### backtrack up ...
              } else {
                ### not found within this top and arm, next arm ...
                next ARM_LO;
              }
            }
          } else {
            ### lo descend ...
            ### assert: $i > 0
            $i--;
            $digits[$i] = 0;
          }
        }
      }

      # if an $n_lo was found on any arm within this $top then done
      if (defined $n_lo) {
        last;
      }

      ### lo extend top ...
      if (++$top > $level_limit) {
        ### nothing below level limit ...
        return (1,0);
      }
      $hypot[$top] = 7 * $hypot[$top-1];
    }
  }

  my $n_hi = 0;
 ARM_HI: foreach my $arm (reverse 0 .. $arms-1) {
    my @digits = ((6) x $level_limit);
    my $i = $#digits;
    for (;;) {
      my $n = 0;
      foreach my $digit (reverse @digits) { # high to low
        $n = 7*$n + $digit;
      }
      $n = $n*$arms + $arm;
      ### hi consider: "arm=$arm  i=$i  digits=".join(',',reverse @digits)."  is n=$n"

      my ($nx,$ny) = $self->n_to_xy($n);
      my $nh = &$rect_dist ($nx,$ny);
      if ($i == 0 && $nh == 0) {
        ### hi found inside: $n
        if ($n > $n_hi) {
          $n_hi = $n;
          next ARM_HI;
        }
      }

      if ($i == 0 || $nh > (6 * 7**$i)) {
        ### too far away: "$nx,$ny   nh=$nh vs ".(6 * 7**$i)

        while (--$digits[$i] < 0) {
          $digits[$i] = 6;
          if (++$i < $level_limit) {
            ### hi backtrack up ...
          } else {
            ### hi nothing within level limit for this arm ...
            next ARM_HI;
          }
        }

      } else {
        ### hi descend
        ### assert: $i > 0
        $i--;
        $digits[$i] = 6;
      }
    }
  }

  if ($n_hi == 0) {
    ### oops, lo found but hi not found
    $n_hi = $n_lo;
  }

  return ($n_lo, $n_hi);
}

#------------------------------------------------------------------------------
# levels

#           arms=1       arms=2
# level 1  0..6  = 7    0..13 = 14
# level 2  0..48 = 49   0..97 = 98
#            7^k-1        2*7^k-1

# level 7^k points
# or arms*7^k
# counting from 0
sub level_to_n_range {
  my ($self, $level) = @_;
  return (0, 7**$level * $self->{'arms'} - 1);
}
sub n_to_level {
  my ($self, $n) = @_;
  if ($n < 0) { return undef; }
  if (is_infinite($n)) { return $n; }
  $n = round_nearest($n);
  _divrem_mutate ($n, $self->{'arms'});
  my ($pow, $exp) = round_up_pow ($n+1, 7);
  return $exp;
}

#------------------------------------------------------------------------------
1;
__END__