1Math::PlanePath::QuadriUcsIesrlaCnodnst(r3i)buted Perl DMoactuhm:e:nPtlaatnieoPnath::QuadricIslands(3)
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NAME

6       Math::PlanePath::QuadricIslands -- quadric curve rings
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SYNOPSIS

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

14       This path is concentric islands made from four sides each an eight
15       segment zig-zag (per the "QuadicCurve" path).
16
17                   27--26                     3
18                    |   |
19               29--28  25  22--21             2
20                |       |   |   |
21               30--31  24--23  20--19         1
22                    | 4--3          |
23           34--33--32    | 16--17--18     <- Y=0
24            |         1--2  |
25           35--36   7---8  15--14            -1
26                    |   |       |
27                5---6   9  12--13            -2
28                        |   |
29                       10--11                -3
30
31                        ^
32           -3  -2  -1  X=0  1   2   3   4
33
34       The initial figure is the square N=1,2,3,4 then for the next level each
35       straight side expands to 4x longer and a zigzag like N=5 through N=13
36       and the further sides to N=36.  The individual sides are levels of the
37       "QuadricCurve" path.
38
39                                       *---*
40                                       |   |
41             *---*     becomes     *---*   *   *---*
42                                           |   |
43                                           *---*
44                * <------ *
45                |         ^
46                |         |
47                |         |
48                v         |
49                * ------> *
50
51       The name "QuadricIslands" here is a slight mistake.  Mandelbrot
52       ("Fractal Geometry of Nature" 1982 page 50) calls any islands initiated
53       from a square "quadric", not just this eight segment expansion.  This
54       curve also appears (unnamed) in Mandelbrot's "How Long is the Coast of
55       Britain", 1967.
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57   Level Ranges
58       Counting the innermost square as level 0, each ring is
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60           length = 4 * 8^level     many points
61           Nlevel = 1 + length[0] + ... + length[level-1]
62                  = (4*8^level + 3)/7
63           Xstart = - 4^level / 2
64           Ystart = - 4^level / 2
65
66       For example the lower partial ring shown above is level 2 starting
67       N=(4*8^2+3)/7=37 at X=-(4^2)/2=-8,Y=-8.
68
69       The innermost square N=1,2,3,4 is on 0.5 coordinates, for example N=1
70       at X=-0.5,Y=-0.5.  This is centred on the origin and consistent with
71       the (4^level)/2.  Points from N=5 onwards are integer X,Y.
72
73              4-------3    Y=+1/2
74              |       |
75              |   o   |
76                      |
77              1-------2    Y=-1/2
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79           X=-1/2   X=+1/2
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FUNCTIONS

82       See "FUNCTIONS" in Math::PlanePath for behaviour common to all path
83       classes.
84
85       "$path = Math::PlanePath::QuadricIslands->new ()"
86           Create and return a new path object.
87
88   Level Methods
89       "($n_lo, $n_hi) = $path->level_to_n_range($level)"
90           Return per "Level Ranges" above,
91
92               ( ( 4 * 8**$level + 3) / 7,
93                 (32 * 8**$level - 4) / 7 )
94

SEE ALSO

96       Math::PlanePath, Math::PlanePath::QuadricCurve,
97       Math::PlanePath::KochSnowflakes, Math::PlanePath::GosperIslands
98

HOME PAGE

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

103       Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018 Kevin Ryde
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105       This file is part of Math-PlanePath.
106
107       Math-PlanePath is free software; you can redistribute it and/or modify
108       it under the terms of the GNU General Public License as published by
109       the Free Software Foundation; either version 3, or (at your option) any
110       later version.
111
112       Math-PlanePath is distributed in the hope that it will be useful, but
113       WITHOUT ANY WARRANTY; without even the implied warranty of
114       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
115       General Public License for more details.
116
117       You should have received a copy of the GNU General Public License along
118       with Math-PlanePath.  If not, see <http://www.gnu.org/licenses/>.
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122perl v5.30.1                      2020-01-30Math::PlanePath::QuadricIslands(3)
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