sub pairwise_tally {
    my ($self, $votelist)=@_;

#  $self is an object (ala Perl 5) that stores all basic pairwise
#  election data
#
#  @self->{'tally'} is a two-dimensional array (also ala Perl 5) that
#  stores the pairwise tally results.  
#
#  $self->{'tally'}[$candx][$candy] is the number of votes that $candx
#  received over $candy. 
#
#  $votelist is a string that is essentially a raw text file that
#  contains all of the ballots.  

    for(split(/\n/,$votelist)) { 

	#  $loservec-a boolean vector with a flag set for all "losers"
	#  reset with every new ballot.  All are losers until they are
	#  listed on a ballot.
	my($loservec)=$self->{'candvec'};

	# Parse ballot.  Skip if no ballot is returned.
        (!(my($ballot)=new ballot_obj($self, $_))) && next;
	
	# @{$ballot->{'rankings'}} is an array of integers
        # representing the candidates this voter (or voters) voted
        # for, in order of preference.
			  
        # In addition, $ballot->{'quantity'} is the number of identical
        # ballots we are considering at this time.

	my(@votelist)=@{$ballot->{'rankings'}};
	    
	foreach $tier (@votelist) {	  # For each preference listed...
            # Remove the chosen candidate(s) from the loser vector.
	    foreach $peer (@{$tier}) { 
		vec($loservec, $peer, 1) = 0; 
	    }

	    # For all candidates...
	    for ($i = 0; $i<= $#{$self->{'candidate'}}; $i++) {

		# If said candidate hasn't been listed yet...
		if(vec($loservec,$i,1)) {

		    # ...they've been beat by the chosen candidate.
                    # Increment their "votes for the other guy"
                    # counter by the appropriate number of ballots
		    foreach $peer (@{$tier}) { 
			if(defined($self->{'tally'}[$peer][$i])) {
			    $self->{'tally'}[$peer][$i]
				+=$ballot->{'quantity'};
			} else {  
			    $self->{'tally'}[$peer][$i]
				=$ballot->{'quantity'};
			}
		    }
		}
	    }
	}
	$self->{'total_vote'}+=$ballot->{'quantity'};
    }
}