examples/ca_wolfram.pl

   1 use v6;
   2
   3 ##
   4 #  Script to output Wolfram-esque cellular automata
   5 #
   6 #  usage: 'perl ca_wolfram.pl', followed by:
   7 #   -r rule_number (Specify in decimal, integer from 0 to 255)
   8 #   -s steps (Specify number of steps to display)
   9 #   -w width
  10 #   -i initial_state
  11 #   -t true_char
  12 #   -f false_char
  13 ##
  14
  15 use Getopt::Std;
  16 my %opts = getopts( 'rswitf' );
  17
  18 ##
  19 # options, with some reasonable defaults
  20 my $rule_number = %opts<r> || 110;
  21 my $steps       = %opts<s> || 30;
  22 my $width       = %opts<w> || 30;
  23 my $initial     = %opts<i> || 'right';
  24 my $true_char   = %opts<t> || 'x';
  25 my $false_char  = %opts<f> || '.';
  26
  27 ##
  28 # Single cell in the left, right, or middle for initial state
  29 my $left  = $steps;
  30 my $right = $width + $steps - 1;
  31 $width += ( $steps * 2 );
  32 my $middle = int( $width / 2 );
  33
  34
  35 ##
  36 # Initialize and fill up the array with 0
  37 my Bool @line = 0 xx ($width-1);
  38
  39 ##
  40 # Set an initial state on the left, right, or middle
  41 given $initial {
  42     when 'left'   { @line[$left] = 1 }
  43     when 'right'  { @line[$right] = 1 }
  44     when 'middle' { @line[$middle] = 1 }
  45 }
  46
  47 ##
  48 # Unpack the Wolfram rule number into a hash
  49
  50 my Bool %rule_hash;
  51 for ( 0 .. 7 ) -> $key {
  52     %rule_hash{$key} = ?($rule_number +& (1 ~ 0 x $key) );
  53 }
  54
  55 ##
  56 # Print the rule hash, using shiny, new sprintf
  57 say "Rule $rule_number:";
  58 for %rule_hash.keys -> $key {
  59     say sprintf("%03b",$key) ~ " becomes " ~ +%rule_hash{$key};
  60 }
  61
  62 ##
  63 # Render the output on the screen.
  64 my $beginprint = $steps;
  65 my $endprint   = @line.elems() - $steps;
  66
  67 while ( $steps-- ) {
  68     my $newline = (+<<@line[ $beginprint .. $endprint ]).join("") ;
  69     $newline ~~ s:g/1/$true_char/;
  70     $newline ~~ s:g/0/$false_char/;
  71     say $newline;
  72
  73     my @old_line = @line;
  74
  75     for ( 0 .. $width - 3 ) -> $index {
  76         my $index_key = :2((+<<@old_line[ $index .. $index + 2 ]).join(""));
  77         @line[ $index + 1 ] = %rule_hash{$index_key};
  78     }
  79
  80 }