From: snacktime <snacktime@...>
Date: 2006-08-13T03:40:15+09:00
Subject: Re: perl tr and ruby String#tr

my $even_bits = "\0";
my $odd_bits = "\200";
foreach (0 .. 7) {
    $even_bits .= $odd_bits;
    $odd_bits = $even_bits;
    $odd_bits  =~ tr/\0\200/\200\0/;
}
print unpack("c*","$odd_bits");

Output:
-12800-1280-128-12800-128-1280-12800-1280-128-1280-12800-128-12800-1280-128-12800-128-1280-12800-128-12800-1280-128-1280-12800-1280-128-12800-
128-1280-12800-1280-128-1280-12800-128-12800-1280-128-1280-12800-1280-128-12800-128-1280-12800-128-12800-1280-128-12800-128-1280-12800-1280-12
8-1280-12800-128-12800-1280-128-12800-128-1280-12800-128-12800-1280-128-1280-12800-1280-128-12800-128-1280-12800-128-12800-1280-128-12800-128-
1280-12800-1280-128-1280-12800-128-12800-1280-128-1280-12800-1280-128-12800-128-1280-12800-1280-128-1280-12800-128-12800-1280-128-12800-128-12
80-12800-128-12800-1280-128-1280-12800-1280-128-12800-128-1280-12800-128

even_bits = "\0"
odd_bits = "\200"
8.times do
  even_bits << odd_bits
  odd_bits = even_bits
  odd_bits.tr!("\0\200","\200\0")
end

print odd_bits.unpack('c*')

Output:
0-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-
1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-12
80-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280
-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1
280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-1280-128