perl function vec

The vec function in Perl is used to manipulate a bit vector. It returns or sets the value of a specified bit in the bit vector.

Here's an example:

# Creating a bit vector
my $bit_vector = pack('B*', '00000000');

# Setting the 4th bit
vec($bit_vector, 4, 1) = 1;

# Setting the 7th bit
vec($bit_vector, 7, 1) = 1;

# Getting the value of the 4th bit
my $fourth_bit = vec($bit_vector, 4, 1);

# Getting the value of the 7th bit
my $seventh_bit = vec($bit_vector, 7, 1);

print "Fourth bit: $fourth_bit\n";
print "Seventh bit: $seventh_bit\n";

Output:

Fourth bit: 1
Seventh bit: 1

In this example, we first create a bit vector using the pack function. The pack function is used to pack the bit string into a byte string. The B* format is used to specify that the string should be interpreted as a bit string.

We then set the 4th and 7th bits in the bit vector using the vec function. The first argument to the vec function is the bit vector itself, the second argument is the index of the bit we want to get or set, and the third argument is the new value of the bit if we're setting it.

Finally, we get the value of the 4th and 7th bits using the vec function and print them out.