Provided by: libmath-planepath-perl_113-1_all bug

NAME

       Math::PlanePath::CellularRule -- cellular automaton points of binary rule

SYNOPSIS

        use Math::PlanePath::CellularRule;
        my $path = Math::PlanePath::CellularRule->new (rule => 30);
        my ($x, $y) = $path->n_to_xy (123);

DESCRIPTION

       This is the patterns of Stephen Wolfram's bit-rule based cellular automatons

           <http://mathworld.wolfram.com/ElementaryCellularAutomaton.html>

       Points are numbered left to right in rows so for example

           rule => 30

           51 52    53 54 55 56    57 58       59          60 61 62       9
              44 45       46          47 48 49                50          8
                 32 33    34 35 36 37       38 39 40 41 42 43             7
                    27 28       29             30       31                6
                       18 19    20 21 22 23    24 25 26                   5
                          14 15       16          17                      4
                              8  9    10 11 12 13                         3
                                 5  6        7                            2
                                    2  3  4                               1
                                       1                              <- Y=0

           -9 -8 -7 -6 -5 -4 -3 -2 -1 X=0 1  2  3  4  5  6  7  8  9

       The automaton starts from a single point N=1 at the origin and grows into the rows above.
       The "rule" parameter controls how the 3 cells below and diagonally below produce a new
       cell,

                    +-----+
                    | new |              next row, Y+1
                    +-----+
                   ^   ^   ^
                 /     |     \
                /      |      \
           +-----+  +-----+  +-----+
           |  A  |  |  B  |  |  C  |     row Y
           +-----+  +-----+  +-----+

       There's 8 possible combinations of ABC being each 0 or 1.  Each such combination can
       become 0 or 1 in the "new" cell.  Those 0 or 1 for "new" is encoded as 8 bits to make a
       rule number 0 to 255,

           ABC cells below     new cell bit from rule

                  1,1,1   ->   bit7
                  1,1,0   ->   bit6
                  1,0,1   ->   bit5
                  ...
                  0,0,1   ->   bit1
                  0,0,0   ->   bit0

       When cells 0,0,0 become 1, ie. "rule" bit0 is 1 (an odd number), the "off" cells either
       side of the initial N=1 become all "on" infinitely to the sides.  Or if rule bit7 for
       1,1,1 is a 0 (ie. rule < 128) then they turn on and off alternately in odd and even rows.
       In both cases only the pyramid portion part -Y<=X<=Y is considered for the N points but
       the infinite cells to the sides are included in the calculation.

       The full set of patterns can be seen at the Math World page above, or can be printed with
       the examples/cellular-rules.pl program in the Math-PlanePath sources.  The patterns range
       from simple to complex.  For some the N=1 cell doesn't grow at all such as rule 0 or rule
       8.  Some grow to mere straight lines such as rule 2 or rule 5.  Others make columns or
       patterns with "quadratic" style stepping of 1 or 2 rows, or self-similar replications such
       as the Sierpinski triangle of rule 18 and 60.  Some rules have complicated non-repeating
       patterns when there's feedback across from one half to the other, such as rule 30.

       For some rules there's specific PlanePath code which this class dispatches to, such as
       "CellularRule54", "CellularRule57", "CellularRule190" or "SierpinskiTriangle" (with
       "n_start=1").

       For rules without specific code the current implementation is not particularly efficient
       as it builds and holds onto the bit pattern for all rows through to the highest N or X,Y
       used.  There's no doubt better ways to iterate an automaton, but this module offers the
       patterns in PlanePath style.

   N Start
       The default is to number points starting N=1 as shown above.  An optional "n_start" can
       give a different start, in the same pattern.  For example to start at 0,

           n_start => 0, rule => 62

           18 19    20 21    22    23 24 25          5
              13 14    15 16          17             4
                  7  8     9 10 11 12                3
                     4  5        6                   2
                        1  2  3                      1
                           0                     <- Y=0

           -5 -4 -3 -2 -1 X=0 1  2  3  4  5

FUNCTIONS

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

       "$path = Math::PlanePath::CellularRule->new (rule => 123)"
       "$path = Math::PlanePath::CellularRule->new (rule => 123, n_start => $n)"
           Create and return a new path object.  "rule" should be an integer 0 to 255.  A "rule"
           should be given always.  There is a default, but it's secret and likely to change.

           If there's specific PlanePath code implementing the pattern then the returned object
           is from that class and generally is not "isa('Math::PlanePath::CellularRule')".

       "$n = $path->xy_to_n ($x,$y)"
           Return the point number for coordinates "$x,$y".  $x and $y are each rounded to the
           nearest integer, which has the effect of treating each cell as a square of side 1.  If
           "$x,$y" is outside the pyramid or on a skipped cell the return is "undef".

SEE ALSO

       Math::PlanePath, Math::PlanePath::CellularRule54, Math::PlanePath::CellularRule57,
       Math::PlanePath::CellularRule190, Math::PlanePath::SierpinskiTriangle,
       Math::PlanePath::PyramidRows

       Cellular::Automata::Wolfram

       <http://mathworld.wolfram.com/ElementaryCellularAutomaton.html>

       <http://oeis.org/wiki/Index_to_OEIS:_Section_Ce#cell>

HOME PAGE

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

LICENSE

       Copyright 2011, 2012, 2013 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/>.