Is it possible to iterate three arrays at the same time?

Question

We can iterate two arrays at the same time using Array's zip method like:

@budget.zip(@actual).each do |budget, actual|
  ...
end

Is it possible to iterate three arrays? Can we use the transpose method to do the same?

Answer 1

>> [1,2,3].zip(["a","b","c"], [:a,:b,:c]) { |x, y, z| p [x, y, z] }
[1, "a", :a]
[2, "b", :b]
[3, "c", :c]

transpose also works but, unlike zip, it creates a new array right away:

>> [[1,2,3], ["a","b","c"], [:a,:b,:c]].transpose.each { |x, y, z| p [x, y, z] }
[1, "a", :a]
[2, "b", :b]
[3, "c", :c]

Notes:

• You don't need each with zip, it takes a block.

• Functional expressions are also possible. For example, using map: sums = xs.zip(ys, zs).map { |x, y, z| x + y + z }.

• For an arbitrary number of arrays you can do xss[0].zip(*xss[1..-1]) or simply xss.transpose.