Why does calling zip on an array with a block always return nil

Question

So I was trying to take two arrays a and b return a third array such that the n^th element of the third array is the sum of the n^th elements of arrays a and b. I was looking at the #zip method which interleaves arrays such that if a = [1, 2, 3] and b = [4, 5, 6] a.zip(b) = [[1, 4], [2, 5], [3, 6]]. ruby-doc.org says If a block is given, it is invoked for each output array... While messing around with it, I found something interesting though. If you call zip with a block, it always seems to return nil. Am I doing something wrong here?

c = a.zip(b) { |x| x.reduce(:+) }

returns nil

c = a.zip(b).map { |x| x.reduce(:+) }

returns the desired result

Answer 1

No

For better or for worse, that's just how it works. It either returns the result or yields it to the block; it doesn't do both.

By the way, in your example a.zip(b) is actually [[1, 4], [2, 5], [3, 6]].