# bf stands for best fit; eventually I'll need several that
# will mimick this format closely.

my $bf_1 = sub {
              # Arguments are: Add|Equate; [x value; y value].
              my $sum_x;
              my $sum_y;
              my $sum_x2;
              my $sum_xy;
              my $n;

              $sum_x  = 0 unless $sum_x;
              $sum_y  = 0 unless $sum_y;
              $sum_x2 = 0 unless $sum_x2;
              $sum_xy = 0 unless $sum_xy;
              $n      = 0 unless $n;

              if($ARGV[0] eq 'Add') {
                my @args = @_;
                $sum_x  += $args[1];
                $sum_y  += $args[2];
                $sum_x2 += $args[1]*$args[2];
                $sum_xy += $args[1] ** 2;
                $n++;
              } elsif ($ARGV[0] eq 'Equate') {
                my $a;
                my $b;
                $a = "(($sum_y - $n*$b)/$sum_x)";
                $b = "($sum_xy-$sum_x2*$a)/$sum_x";
                eval $b;
                eval $a;
                ($a,$b);
              } else { print "Called with unkown argument\n" }
};