#!/usr/bin/perl

@one = ( 2, 5);
@two = ( -4, -3);
@three = (2, -6);
@result = ();

$r = &dProduct(\@one,\@two,\@three);

print "\n Dot Product = $r \n";

# ------------------------------------------------
#  Returns dot product of three vectors.
#  Takes three pointers to arrays as input
#  Returns a scalar.

 sub dProduct {  
      my ($x,$y, $z) = @_;
      my $sum;
      my $ct1 = $#{$x} + 1;   # items in $x
      my $ct2 = $#{$y} + 1;   # items in $y
      my $ct3 = $#{$z} + 1;   # items in $z
      return undef if ($ct1 != $ct2) ;

      for ($i=0;$i<$ct1;$i++) {
      $sum += $$x[$i] * $$y[$i] * $$z[$i];
      }
      return $sum;
 }