use strict;

for (0..20,) {
   $a = dec2bin($_+1);
   $b = dec2bin($_);
   print "$a = ", $_ + 1, "\n",
         "$b = ", $_, "\n",
         "--------\n", 
         dec2bin(($_+1) & $_), " = ", 
         (($_+1) & $_), "\n\n";

}

# Perl Cookbook recipe 2.4.
sub dec2bin {
   my $s = unpack("B32", pack("N",shift));
   #$s =~ s/^0+(?=\d)//;
   $s = substr($s,-8,8);
   return $s;
}
[download]

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

Actually Anonymonk has a valid point as this is a buffer overflow type bug. 4294967296 is a 33 bit integer, which is of course one bit more than 32. Perhaps you should meditate on this:

print "2**32 is: ", 2**32, "\n";
print <<TEXT;
This is what we should have:
100000000000000000000000000000000 = 4294967296
011111111111111111111111111111111 = 4294967295
----------------------------------------------
000000000000000000000000000000000 = 0

But we get a buffer overflow like so, resulting in erroneous output:
TEXT

for (4294967295) {
    $a = dec2bin($_+1);
    $b = dec2bin($_);
    print "$a = ", $_ + 1, "\n",
    "$b = ", $_, "\n",
    "--------\n", 
    dec2bin(($_+1) & $_), " = ", 
    (($_+1) & $_), "\n\n";
    
}

sub dec2bin {
   return unpack("B*", pack("N",shift));
}
[download]

I have no call for it personally but Math::BigInt might be useful.

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

#!/usr/local/bin/perl

use strict;

use Devel::Peek;

my $a = 4294967296;
my $b = 4294967295;
my $c = $a & $b;

print '$a:';Dump($a);
print '$b:';Dump($b);
print '$c:';Dump($c);

$a:SV = PVNV(0x1abe608) at 0x1ab30a0
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,IOK,NOK,pIOK,pNOK,IsUV)
  UV = 4294967295
  NV = 4294967296
  PV = 0
$b:SV = IV(0x1ab2420) at 0x1ab3058
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,IOK,pIOK,IsUV)
  UV = 4294967295
$c:SV = IV(0x1ab2428) at 0x1ab3088
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,IOK,pIOK,IsUV)
  UV = 4294967295

Whether this is expected behaviour or not is maybe upto Larry or p5p.

perl -MMath::BigInt -le '
 $i=new Math::BigInt "4294967296";
 $j=new Math::BigInt "4294967295";
 print $i->as_hex();
 print $j->as_hex();
 print $i->band($j)->as_hex()'
[download]

0x100000000
0xffffffff
0x0
[download]