This is an example of a bit vector (a vector of "0"s or "1"s)

## Define a bit vector with positions 4 to 7 set to 1
my $bv1='';
vec($bv1,$_,1)=1 foreach (3..6);
dumpbv($bv1);

sub dumpbv
{
    my $bitv = shift @_;
    my $pos=0;
    foreach (split "",unpack("b*",$bitv)){
      print;
      $pos++;
    }
}
[download]

With bit vectors you can do bit operations. for example, to find the overlapping ("OR") of 2 bit vectors:

sub sumbv
{
    return $_[0] | $_[1];
}
[download]

... and the AND operation:

sub cmpbv
{
    return $_[0] & $_[1];
}
[download]

A full working dummy example with these functions would be:

use strict;
use warnings;

## Define a bit vector with positions 4 to 7 set to 1
my $bv1='';
vec($bv1,$_,1)=1 foreach (3..6);
dumpbv ($bv1); print " bv1\n";

# Define a bit vector with positions 3 to 5 set to 1
my $bv2='';
vec($bv2,$_,1)=1 foreach (2..4);
dumpbv ($bv2); print " bv2\n";

print "--------\n";

my $bv_sum = sumbv($bv1,$bv2);
dumpbv ($bv_sum);print " OR\n";

my $bv_cmp = cmpbv($bv1,$bv2);
dumpbv ($bv_cmp);print " AND\n";

sub sumbv
{
    return $_[0] | $_[1];
}

sub cmpbv
{
    return $_[0] & $_[1];
}

sub dumpbv
{
    my $bitv = shift @_;
    my $pos=0;
    foreach (split "",unpack("b*",$bitv)){
      print;
      $pos++;
    }
}
[download]

Outputs:

00011110 bv1
00111000 bv2
--------
00111110 OR
00011000 AND
[download]

Hope this helps

citromatik

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