#!/usr/bin/perl -w

## for Discrete Probability Distribution
## considering that sum of probability values in both arrays equals to 1
 
my $dist = 0;
my @terms = ('a', 'b','c','d');
my @P = (0, 0.3, 0.4, 0.3);
my @Q = (0.2, 0.2, 0.3, 0.3);
	    
if ( (scalar(@P) != scalar(@terms) ) && (scalar(@Q) != scalar(@terms)) ){
	print " The size should be same \n";
	exit;
}
else{
	for(my $i = 0; $i<= $#P; $i++){
		my $temp = 0 if($P[$i] == 0 || $Q[$i] == 0);
		$temp = $P[$i]*log($P[$i]/$Q[$i]) if($P[$i] != 0 && $Q[$i] != 0); 
		$dist = $dist + $temp;
	}
}
print "The Kullback Distance symmetric for discrete Distribution is :", $dist,"\n";