#!/usr/bin/perl

# author: bliako
# date: 16/11/2018
# https://perlmonks.org/?node_id=1225889

# for given width, it counts from 0 to 2**W
# and prints the count in binary.
# It misses logic to discard some nibbles

use strict;
use warnings;

my $W = 4; # width in nibbles

my $count = 0;
my $stop = 2**$W;
# format an integer as binary
my $format = "%0.${W}b";
while( $count < $stop ){
        my $x = sprintf($format, $count);
        # x now contains a binary number of the count
        # between 0 and the stop 2^width_in_nibbles
        # now make each digit a nibble, e.g 0 -> 0000
        $x =~ s/0/a/g;
        $x =~ s/1/b/g;
        $x =~ s/a/0000 /g;
        $x =~ s/b/1111 /g;
        print "x=$x ($count)\n";
        $count++;
}

##</code><code>##

0       0000 0000 0000 0000
1       0000 0000 0000 1111
2       0000 0000 1111 0000
3       0000 0000 1111 1111
4       0000 1111 0000 0000
5       0000 1111 0000 1111
6       0000 1111 1111 0000
7       0000 1111 1111 1111
8       1111 0000 0000 0000
9       1111 0000 0000 1111
10      1111 0000 1111 0000
11      1111 0000 1111 1111
12      1111 1111 0000 0000
13      1111 1111 0000 1111
14      1111 1111 1111 0000
15      1111 1111 1111 1111