Re: Confusion about code sample in perlfaq4

[thundergnat]

The wording does seem to imply that it would return a list of bit values, but that isn't what it is doing. Rather, that routine returns a list of bit positions that are set (have a 1 in them).

If you just want the list of bits, it is probably simplest to split an unpacked string.

my @bits = split //, unpack "b*", $vec;

To furthur demonstrate:

use integer;
my $vec = 42;
my @ints;
my $bits = unpack "b*", $vec;
my @bits = split //, unpack "b*", $vec;
push @ints, 0 if $bits =~ s/^(\d)// && $1;
push @ints, pos $bits while($bits =~ /1/g);

print "\n";
print join ', ', @ints;
print " <-- bit positions set\n";
print join ', ', @bits;
print " <-- bits \n";

2, 4, 5, 9, 12, 13 <-- bit positions set
0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0 <-- bits