NAME

       Math::PlanePath::FibonacciWordFractal -- turns by Fibonacci word bits

SYNOPSIS

        use Math::PlanePath::FibonacciWordFractal;
        my $path = Math::PlanePath::FibonacciWordFractal->new;
        my ($x, $y) = $path->n_to_xy (123);

DESCRIPTION

       This is an integer version of the Fibonacci word fractal

           Alexis Monnerot-Dumaine, "The Fibonacci Word Fractal", March 2009.
           <https://hal.archives-ouvertes.fr/hal-00367972/>

       It makes turns controlled by the "Fibonacci word" sequence, sometimes called the "golden
       string".

           11  | 27-28-29    33-34-35          53-54-55    59-60-61
               |  |     |     |     |           |     |     |     |
           10  | 26    30-31-32    36          52    56-57-58    62
               |  |                 |           |                 |
            9  | 25-24          38-37          51-50          64-63
               |     |           |                 |           |
            8  |    23          39    43-44-45    49          65
               |     |           |     |     |     |           |
            7  | 21-22          40-41-42    46-47-48          66-67
               |  |                                               |
            6  | 20    16-15-14                      74-73-72    68
               |  |     |     |                       |     |     |
            5  | 19-18-17    13                      75    71-70-69
               |              |                       |
            4  |          11-12                      76-77
               |           |                             |
            3  |          10                            78
               |           |                             |
            2  |           9--8                      80-79
               |              |                       |
            1  |  1--2--3     7                      81    85-86-87
               |  |     |     |                       |     |     |
           Y=0 |  0     4--5--6                      82-83-84    88-89-...
               +-------------------------------------------------------
                 X=0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17

       A current direction up,down,left,right is maintained, starting in the up direction.  The
       path moves in the current direction and then may turn or go straight according to the
       Fibonacci word,

           Fib word
           --------
              0      turn left if even index, right if odd index
              1      straight ahead

       The Fibonacci word is reckoned as starting from index=1, so for example at N=0 draw a line
       upwards to N=1 and the first Fibonacci word value is 0 and its position index=1 is odd so
       turn to the right.

            N     Fibonacci word
           ---    --------------
            1       0    turn right
            2       1
            3       0    turn right
            4       0    turn left
            5       1
            6       0    turn left
            7       1

       The result is self-similar blocks within the first quadrant X>=0,Y>=0.  New blocks extend
       at N values which are Fibonacci numbers.  For example N=21 a new block begins above, then
       N=34 a new block across, N=55 down, N=89 across again, etc.

       The new blocks are a copy of the shape starting N=0 but rotated and/or transposed
       according to the replication level mod 6,

           level mod 6      new block
           -----------      ---------
                0           transpose
                1                         rotate -90
                2           transpose and rotate -90
                3           transpose
                4                         rotate +90
                5           transpose and rotate +90

FUNCTIONS

       See "FUNCTIONS" in Math::PlanePath for behaviour common to all path classes.

       "$path = Math::PlanePath::FibonacciWordFractal->new ()"
           Create and return a new path object.

       "($x,$y) = $path->n_to_xy ($n)"
           Return the X,Y coordinates of point number $n on the path.  Points begin at 0 and if
           "$n < 0" then the return is an empty list.

           Fractional positions give an X,Y position along a straight line between the integer
           positions.

       "$n = $path->n_start()"
           Return 0, the first N in the path.

OEIS

       Entries in Sloane's Online Encyclopedia of Integer Sequences related to this path include,

           <http://oeis.org/A156596> (etc)

           A332298   X coordinate, starting at n=1
           A332299   Y-1 coordinate, starting at n=1
           A156596   turn sequence, 0=straight,1=right,2=left
           A143668   turn sequence, 0=right,1=straight,2=left
           A171587   abs(dX), so 1=horizontal,0=vertical
           A265318   N at locations by diagonals

           A003849   Fibonacci word with values 0,1
           A005614   Fibonacci word with values 1,0
           A003842   Fibonacci word with values 1,2
           A014675   Fibonacci word with values 2,1

SEE ALSO

       Math::PlanePath, Math::PlanePath::DragonCurve, Math::PlanePath::WythoffArray

       Math::NumSeq::FibonacciWord

HOME PAGE

       <http://user42.tuxfamily.org/math-planepath/index.html>

LICENSE

       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 <http://www.gnu.org/licenses/>.