1Math::PlanePath::QuinteUtsCeerntCroenst(r3i)buted Perl DMoactuhm:e:nPtlaatnieoPnath::QuintetCentres(3)
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NAME

6       Math::PlanePath::QuintetCentres -- self-similar "plus" shape centres
7

SYNOPSIS

9        use Math::PlanePath::QuintetCentres;
10        my $path = Math::PlanePath::QuintetCentres->new;
11        my ($x, $y) = $path->n_to_xy (123);
12

DESCRIPTION

14       This a self-similar curve tracing out a "+" shape like the
15       "QuintetCurve" but taking the centre of each square visited by that
16       curve.
17
18                                                92                        12
19                                              /  |
20                   124-...                  93  91--90      88            11
21                     |                        \       \   /   \
22               122-123 120     102              94  82  89  86--87        10
23                  \   /  |    /  |            /   /  |       |
24                   121 119 103 101-100      95  81  83--84--85             9
25                          \   \       \       \   \
26               114-115-116 118 104  32  99--98  96  80  78                 8
27                 |       |/   /   /  |       |/      |/   \
28           112-113 110 117 105  31  33--34  97  36  79  76--77             7
29              \   /   \       \   \       \   /   \      |
30               111     109-108 106  30  42  35  38--37  75                 6
31                             |/   /   /  |       |    /
32                           107  29  43  41--40--39  74                     5
33                                  \   \              |
34                        24--25--26  28  44  46  72--73  70      68         4
35                         |       |/      |/   \   \   /   \   /   \
36                    22--23  20  27  18  45  48--47  71  56  69  66--67     3
37                      \   /   \   /   \      |        /   \      |
38                        21   6  19  16--17  49  54--55  58--57  65         2
39                          /   \      |       |    \      |    /
40                     4-- 5   8-- 7  15      50--51  53  59  64             1
41                      \      |    /              |/      |    \
42                 0-- 1   3   9  14              52      60--61  63     <- Y=0
43                     |/      |    \                          |/
44                     2      10--11  13                      62            -1
45                                 |/
46                                12                                        -2
47
48                 ^
49            -1  X=0  1   2   3   4   5   6   7   8   9  10  11  12  13
50
51       The base figure is the initial the initial N=0 to N=4.  It fills a "+"
52       shape as
53
54                  .....
55                  .   .
56                  . 4 .
57                  .  \.
58              ........\....
59              .   .   .\  .
60              . 0---1 . 3 .
61              .   . | ./  .
62              ......|./....
63                  . |/.
64                  . 2 .
65                  .   .
66                  .....
67
68   Arms
69       The optional "arms" parameter can give up to four copies of the curve,
70       each advancing successively.  For example "arms=>4" is as follows.
71       Notice the N=4*k points are the plain curve, and N=4*k+1, N=4*k+2 and
72       N=4*k+3 are rotated copies of it.
73
74                                69                     ...              7
75                              /  |                        \
76               121     113  73  65--61      53             120          6
77              /   \   /   \   \       \   /   \           /
78           ...     117 105-109  77  29  57  45--49     116              5
79                         |    /   /  |       |            \
80                       101  81  25  33--37--41  96-100-104 112          4
81                         |    \   \              |       |/
82                    50  97--93  85  21  13  88--92  80 108  72          3
83                  /  |       |/      |/   \   \   /   \   /   \
84                54  46--42  89  10  17   5-- 9  84  24  76  64--68      2
85                  \      |    /  |       |        /   \      |
86                    58  38  14   6-- 2   1  16--20  32--28  60          1
87                  /      |    \               \      |    /
88                62  30--34  22--18   3   0-- 4  12  36  56          <- Y=0
89                 |    \   /          |       |/      |    \
90            70--66  78  26  86  11-- 7  19   8  91  40--44  52         -1
91              \   /   \   /   \   \   /  |    /  |       |/
92                74 110  82  94--90  15  23  87  95--99  48             -2
93                  /  |       |            \   \      |
94               114 106-102--98  43--39--35  27  83 103                 -3
95                  \              |       |/   /      |
96                   118      51--47  59  31  79 111-107 119     ...     -4
97                  /           \   /   \       \   \   /   \   /
98               122              55      63--67  75 115     123         -5
99                  \                          |/
100                   ...                      71                         -6
101
102                                         ^
103            -7  -6  -5  -4  -3  -2  -1  X=0  1   2   3   4   5   6
104
105       The pattern an ever expanding "+" shape with first cell N=0 at the
106       origin.  The further parts are effectively as follows,
107
108                       +---+
109                       |   |
110               +---+---    +---+
111               |   |           |
112           +---+   +---+   +---+
113           |         2 | 1 |   |
114           +---+   +---+---+   +---+
115               |   | 3 | 0         |
116               +---+   +---+   +---+
117               |           |   |
118               +---+   +---+---+
119                   |   |
120                   +---+
121
122       At higher replication levels the sides become wiggly and spiralling,
123       but they're symmetric and mesh to fill the plane.
124

FUNCTIONS

126       See "FUNCTIONS" in Math::PlanePath for behaviour common to all path
127       classes.
128
129       "$path = Math::PlanePath::QuintetCentres->new ()"
130       "$path = Math::PlanePath::QuintetCentres->new (arms => $a)"
131           Create and return a new path object.
132
133       "($x,$y) = $path->n_to_xy ($n)"
134           Return the X,Y coordinates of point number $n on the path.  Points
135           begin at 0 and if "$n < 0" then the return is an empty list.
136
137           Fractional positions give an X,Y position along a straight line
138           between the integer positions.
139
140       "$n = $path->n_start()"
141           Return 0, the first N in the path.
142
143       "($n_lo, $n_hi) = $path->rect_to_n_range ($x1,$y1, $x2,$y2)"
144           In the current code the returned range is exact, meaning $n_lo and
145           $n_hi are the smallest and biggest in the rectangle, but don't rely
146           on that yet since finding the exact range is a touch on the slow
147           side.  (The advantage of which though is that it helps avoid very
148           big ranges from a simple over-estimate.)
149
150   Level Methods
151       "($n_lo, $n_hi) = $path->level_to_n_range($level)"
152           Return "(0, 5**$level - 1)", or for multiple arms return "(0, $arms
153           * 5**$level - 1)".
154
155           There are 5^level points in a level, or arms*5^level for multiple
156           arms, numbered starting from 0.
157

FORMULAS

159   X,Y to N
160       The "xy_to_n()" calculation is similar to the "FlowsnakeCentres".  For
161       a given X,Y a modulo 5 remainder is formed
162
163           m = (2*X + Y) mod 5
164
165       This distinguishes the five squares making up the base figure.  For
166       example in the base N=0 to N=4 part the m values are
167
168                 +-----+
169                 | m=3 |           1
170           +-----+-----+-----+
171           | m=0 | m=2 | m=4 |   <- Y=0
172           +-----+-----+-----+
173                 | m=1 |          -1
174                 +-----+
175            X=0     1      2
176
177       From this remainder X,Y can be shifted down to the 0 position.  That
178       position corresponds to a vector multiple of X=2,Y=1 and 90-degree
179       rotated forms of that vector.  That vector can be divided out and X,Y
180       shrunk with
181
182           Xshrunk = (Y + 2*X) / 5
183           Yshrunk = (2*Y - X) / 5
184
185       If X,Y are considered a complex integer X+iY the effect is a remainder
186       modulo 2+i, subtract that to give a multiple of 2+i, then divide by
187       2+i.  The vector X=2,Y=1 or 2+i is because that's the N=5 position
188       after the base shape.
189
190       The remainders can then be mapped to base 5 digits of N going from high
191       to low and making suitable rotations for the sub-part orientation of
192       the curve.  The remainders alone give a traversal in the style of
193       "QuintetReplicate".  Applying suitable rotations produces the connected
194       path of "QuintetCentres".
195

OEIS

197       Entries in Sloane's Online Encyclopedia of Integer Sequences related to
198       this path include
199
200           <http://oeis.org/A106665> (etc)
201
202           A099456   level Y end, being Im((2+i)^k)
203
204           arms=2
205             A139011   level Y end, being Re((2+i)^k)
206

SEE ALSO

208       Math::PlanePath, Math::PlanePath::QuintetCurve,
209       Math::PlanePath::QuintetReplicate, Math::PlanePath::FlowsnakeCentres
210

HOME PAGE

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

215       Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018 Kevin Ryde
216
217       This file is part of Math-PlanePath.
218
219       Math-PlanePath is free software; you can redistribute it and/or modify
220       it under the terms of the GNU General Public License as published by
221       the Free Software Foundation; either version 3, or (at your option) any
222       later version.
223
224       Math-PlanePath is distributed in the hope that it will be useful, but
225       WITHOUT ANY WARRANTY; without even the implied warranty of
226       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
227       General Public License for more details.
228
229       You should have received a copy of the GNU General Public License along
230       with Math-PlanePath.  If not, see <http://www.gnu.org/licenses/>.
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234perl v5.30.1                      2020-01-30Math::PlanePath::QuintetCentres(3)
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