David's Blague

In our final segment of Part V, we tie together all the code into a single, cohesive whole, and run it. In the interest of getting it done more quickly, and in a literate programming style, I've noted some of the nice features of Perl 6 in the comments.

A simple Copy/Paste should get this code going for you in Pugs:

use v6-alpha;  # By Christmas, we should be able to say "use v6;"
class Rule {   # See Deus Ex Automatis Part V(a)
   has Int  $.number    is ro;
   has Int  $.neighbors is ro;
   has Bool %.lookup    is rw;
   submethod BUILD (:$.number, :$.neighbors) {
       for ( 0 .. (2 ** $.neighbors -1) ) -> $key {
           my $format = "\%0" ~ $.neighbors ~ "b";
           %.lookup{sprintf($format,$key)} = ?($.number +& (1 ~ 0 x $key) );
       }
   }
}

class Grid {
   has Int  $.diameter is rw;
   has Bool @.state    is rw;

   submethod BUILD (:$.diameter) {
       @.state = 1,;
       @.state.push( 0 xx ($.diameter-1) );
   }
}

class Automaton does Rule does Grid { # "does" gives us a mix-in pattern
   has Rule $.rule is rw; # the "Rule" is a reference to our own class
   has Grid $.grid is rw; # as is Grid

   submethod BUILD (:$diameter, :$rule) { # new() takes two arguments
       $.grid = Grid.new(:$diameter);
       $.rule = Rule.new(:number($rule), :neighbors(2));
   }

   method next { # The "guts" where we apply the rule to the grid
                 # Also, incidentally, our first method !!
       my @old = $.grid.state();
       for ( 0 .. $.grid.diameter-1 ) -> $i {
           $.grid.state[$i] = ~+$.rule.lookup{ @old[$i] ~ @old[$i-1] };
       }
       return Bool::True; # Lets us easily use this in a loop
   }
}

##
# The script!  This will print beautiful cellular automata on your screen.
my Automaton $ca .= new(:diameter(10), :rule(6));
say $ca.grid.state while $ca.next();

Whew!

I may come back later and edit this post to add a bit more commentary. In the meantime, note that this code (in a somewhat complicated, and somewhat slow manner) implements the class of cellular automata we've been discussing through this entire series.

I'm going to move on in the next segment to talking about why it's important.

Labels: cellular automata, deusexautomatis, etech