plucky (3) Math::PlanePath::LTiling.3pm.gz

Provided by: libmath-planepath-perl_129-1_all bug

NAME

       Math::PlanePath::LTiling -- 2x2 self-similar of four pattern parts

SYNOPSIS

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

DESCRIPTION

       This is a self-similar tiling by "L" shapes.  A base "L" is replicated four times with end parts turned
       +90 and -90 degrees to make a larger L,

                                               +-----+-----+
                                               |12   |   15|
                                               |  +--+--+  |
                                               |  |14   |  |
                                               +--+  +--+--+
                                               |  |  |11   |
                                               |  +--+  +--+
                                               |13   |  |  |
                          +-----+              +-----+--+  +--+--+-----+
                          | 3   |              | 3   |  |10   |  |    5|
                          |  +--+        -->   |  +--+  +--+--+  +--+  |
                          |  |  |              |  |  | 8   |   9 |  |  |
           +--+           +--+  +--+--+        +--+  +--+--+--+--+  +--+
           |  |     -->   |  | 2   |  |        |  | 2   |  |  |   6 |  |
           |  +--+        |  +--+--+  |        |  +--+--+  |  +--+--+  |
           | 0   |        | 0   |   1 |        | 0   |   1 | 7   |   4 |
           +-----+        +-----+-----+        +-----+-----+-----+-----+

       The parts are numbered to the left then middle then upper.  This relative numbering is maintained when
       rotated at the next replication level, as for example N=4 to N=7.

       The result is to visit 1 of every 3 points in the first quadrant with a subtle layout of points and
       spaces making diagonal lines and little 2x2 blocks.

           15  |  48          51  61          60 140         143 163
           14  |      50                  62         142                 168
           13  |          56          59                 139         162
           12  |  49          58              63 141             160
           11  |  55              44          47 131         138
           10  |          57          46                 136         137
            9  |      54                  43         130                 134
            8  |  52          53  45             128         129 135
            7  |  12          15  35          42              37  21
            6  |      14                  40          41                  22
            5  |          11          34                  38          25
            4  |  13              32          33  39          36
            3  |   3          10               5  31              26
            2  |           8           9                  27          24
            1  |       2                   6          30                  18
           Y=0 |   0           1   7           4  28          29  19
               +------------------------------------------------------------
                 X=0   1   2   3   4   5   6   7   8   9  10  11  12  13  14

       On the X=Y leading diagonal N=0,2,8,10,32,etc is the integers made from only digits 0 and 2 in base 4.
       Or equivalently integers which have zero bits at all even numbered positions, binary c0d0e0f0.

   Left or Upper
       Option "L_fill => "left"" or "L_fill => "upper"" numbers the tiles instead at their left end or upper end
       respectively.

           L_fill => 'left'           8  |      52              45  43
                                      7  |          15                      42
           +-----+                    6  |  12              35          40
           |     |                    5  |      14                  34  33
           |  +--+                    4  |      13  11          32
           | 3|  |                    3  |                  10   9   5
           +--+  +--+--+              2  |   3           8           6      31
           |  |    2| 1|              1  |           2   1               4
           |  +--+--+  |             Y=0 |       0               7
           |    0|     |                 +------------------------------------
           +-----+-----+                   X=0   1   2   3   4   5   6   7   8

           L_fill => 'upper'          8  |          53                  42
                                      7  |      12              35  40
           +-----+                    6  |          14  15      34          41
           |    3|                    5  |  13          11  32              39
           |  +--+                    4  |              10          33
           |  | 2|                    3  |       3   8
           +--+  +--+--+              2  |       2           9           5
           | 0|     |  |              1  |   0               7   6          28
           |  +--+--+  |             Y=0 |           1               4
           |     | 1   |                 +------------------------------------
           +-----+-----+                   X=0   1   2   3   4   5   6   7   8

       The effect is to disrupt the pattern a bit though the overall structure of the replications is unchanged.

       "left" is as viewed looking towards the L from above.  It may have been better to call it "right", but
       won't change that now.

   Ends
       Option "L_fill => "ends"" numbers the two endpoints within each "L", first the left then upper.  This is
       the inverse of the default middle shown above, ie. it visits all the points which the middle option
       doesn't, and so 2 of every 3 points in the first quadrant.

           +-----+
           |    7|
           |  +--+
           | 6| 5|
           +--+  +--+--+
           | 1|    4| 2|
           |  +--+--+  |
           |    0| 3   |
           +-----+-----+

            15  |      97 102         123 120         281 286         327 337
            14  |  96     101 103 122 124     121 280     285 287 326 325
            13  |  99 100     113 118     125 126 283 284     279 321     324
            12  |      98 112     117 119 127         282 278 277     320 323
            11  |     111 115 116      89  94         263 273     276 274 266
            10  | 110 109     114  88      93  95 262 261     272 275     268
             9  | 105     108 106  91  92      87 257     260 258 271 269
             8  |     104 107          90  86  85     256 259         270 265
             7  |      25  30          71  81      84  82  74          43  40
             6  |  24      29  31  70  69      80  83      76  75  42  44
             5  |  27  28      23  65      68  66  79  77      72  50      45
             4  |      26  22  21      64  67          78  73      52  51  47
             3  |       7  17      20  18  10          63  55  53      48  34
             2  |   6   5      16  19      12  11  62  61      54  49      36
             1  |   1       4   2  15  13       8  57      60  58  39  37
            Y=0 |       0   3          14   9          56  59          38  33
                +------------------------------------------------------------
                  X=0   1   2   3   4   5   6   7   8   9  10  11  12  13  14

   All
       Option "L_fill => "all"" numbers all three points of each "L", as middle, left then right.  With this the
       path visits all points of the first quadrant.

                                  7  |  36  38  46  45 105 107 122 126
           +-----+                6  |  37  42  44  47 106 104 120 121
           | 9 11|                5  |  41  43  33  35  98 102 103 100
           |  +--+                4  |  39  40  34  32  96  97 101  99
           |10| 8|                3  |   9  11  26  30  31  28  16  15
           +--+  +--+--+          2  |  10   8  24  25  29  27  19  17
           | 2| 6  7| 4|          1  |   2   6   7   4  23  20  18  13
           |  +--+--+  |         Y=0 |   0   1   5   3  21  22  14  12
           | 0  1| 5  3|             +--------------------------------
           +-----+-----+               X=0   1   2   3   4   5   6   7

       Along the X=Y leading diagonal N=0,6,24,30,96,etc are triples of the values from the single-point case,
       so 3* numbers using digits 0 and 2 in base 4, which is the same as 2* numbers using 0 and 3 in base 4.

   Level Ranges
       For the "middles", "left" or "upper" cases with one N per tile, and taking the initial N=0 tile as level
       0, a replication level is

           Nstart = 0
            to
           Nlevel = 4^level - 1      inclusive

           Xmax = Ymax = 2 * 2^level - 1

       For example level 2 which is the large tiling shown in the introduction is N=0 to N=4^2-1=15 and extends
       to Xmax=Ymax=2*2^2-1=7.

       For the "ends" variation there's two points per tile, or for "all" there's three, in which case the
       Nlevel increases to

           Nlevel_ends = 2 * 4^level - 1
           Nlevel_all  = 3 * 4^level - 1

FUNCTIONS

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

       "$path = Math::PlanePath::LTiling->new ()"
       "$path = Math::PlanePath::LTiling->new (L_fill => $str)"
           Create and return a new path object.  The "L_fill" choices are

               "middle"    the default
               "left"
               "upper"
               "ends"
               "all"

       "($x,$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.

   Level Methods
       "($n_lo, $n_hi) = $path->level_to_n_range($level)"
           Return

               0,   4**$level - 1      middle, left, upper
               0, 2*4**$level - 1      ends
               0, 3*4**$level - 1      all

           There are 4^level L shapes in a level, each containing 1, 2 or 3 points, numbered starting from 0.

OEIS

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

           <http://oeis.org/A062880> (etc)

           L_fill=middle
             A062880    N on X=Y diagonal, base 4 digits 0,2 only
             A048647    permutation N at transpose Y,X
                          base4 digits 1<->3 and 0,2 unchanged
             A112539    X+Y+1 mod 2, parity inverted

           L_fill=left or upper
             A112539    X+Y mod 2, parity

       A112539 is a parity of bits at even positions in N, ie. count 1-bits at even bit positions (least
       significant is bit position 0), then add 1 and take mod 2.  This works because in the pattern sub-blocks
       0 and 2 are unchanged and 1 and 3 are turned so as to be on opposite X,Y odd/even parity, so a flip for
       every even position 1-bit.  L_fill=middle starts on a 0 even parity, and L_fill=left and upper start on 1
       odd parity.  The latter is the form in A112539 and L_fill=middle is the bitwise 0<->1 inverse.

SEE ALSO

       Math::PlanePath, Math::PlanePath::CornerReplicate, Math::PlanePath::SquareReplicate,
       Math::PlanePath::QuintetReplicate, Math::PlanePath::GosperReplicate

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/>.