[23] pry(main)> x = [1,2,3,4,5,6,7]
=> [1, 2, 3, 4, 5, 6, 7]
[24] pry(main)> while(not x.empty?)
[24] pry(main)*   puts "#{x[0]} -- #{_[1]||"(null)"}"
[24] pry(main)*   x.shift
[24] pry(main)* end
1 -- 2
2 -- 3
3 -- 4
4 -- 5
5 -- 6
6 -- 7
7 -- (null)
=> nil