From: Mathieu Bouchard <matju@...>
Date: 2001-03-16T02:14:51+09:00
Subject: [ruby-talk:12690] Re: Sum of Squares

On Tue, 13 Mar 2001, rashworth wrote:
> Thank you for your note. The new coding worked just fine.
> Do you have some code for the Sum of the Cross-Products?
> Sumxy = (x1 * y1) + (x2 * y2) + ....

That is called a dot product, not a "sum of cross-products". Unfortunately
you can't run two iterators at once easily, but you can still write:

class Array
	def dot(other)
		# other.type == Array
		# other.length == self.length
		sum = 0
		length.times {|i| sum += self[i]*other[i] }
		sum
	end
end

(not tested)

matju