### comment on

 Need Help??

Hello Perl Monks,

I'm working on a tsv, one of its columns is a csv list of keywords (28 unique values). I'd like to compute the Jaccard Index (Intersection / Union) of this list of keywords. To do so efficiently I'd like to use a bit array to represent the list of keywords.

I tried to read few articles on Perlmonks and stackoverflow, but so far I feel I'm missing something completely obvious.

Here is what I wrote:

```use common::sense;

my \$a = '';
my \$b = '';

\$a += 1 << 0;
\$a += 1 << 1;

\$b += 1 << 1;
\$b += 1 << 2;

my \$i = \$a & \$b;
my \$u = \$a | \$b;

my \$i_cnt = unpack '%32b*', \$i;
my \$u_cnt = unpack '%32b*', \$u;

printf "a is %#032b  %d\n", \$a, \$a;
printf "b is %#032b  %d\n", \$b, \$b;
printf "intersection is %#032b  %d\n", \$i, \$i;
printf "union is %#032b  %d\n", \$u, \$u;
say "set bit count in intersection: \$i_cnt";
say "set bit count in union: \$u_cnt";

Actual result:

```a is 0b000000000000000000000000000011  3
b is 0b000000000000000000000000000110  6
intersection is 0b000000000000000000000000000010  2
union is 0b000000000000000000000000000111  7
set bit count in intersection: 3
set bit count in union: 5

Expected result:

```a is 0b000000000000000000000000000011  3
b is 0b000000000000000000000000000110  6
intersection is 0b000000000000000000000000000010  2
union is 0b000000000000000000000000000111  7
set bit count in intersection: 1
set bit count in union: 3

In reply to bit array comparison by Amendil

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