Adam Wathan has another excellent article on using collections. This time he tackles the less used transpose-function.

Transpose is an often overlooked list operation that I first noticed in Ruby. The goal of transpose is to rotate a multidimensional array, turning the rows into columns and the columns into rows.

http://adamwathan.me/2016/04/06/cleaning-up-form-input-with-transpose/

Personally, I can't wait until the release of his book: Refactoring To Collections.