gistfile1.rb

irb(main):027:0> array2 = []; array = []
=> []
irb(main):028:0> 3.imes {|x| array << x}
irb(main):028:0> array = []
=> []
irb(main):029:0> 3.times {|x| array << x}
=> 3
irb(main):030:0> (1..3).each { |x| array.combination(x) { |y| array2 << y } }
=> 1..3
irb(main):031:0> array2
=> [[0], [1], [2], [0, 1], [0, 2], [1, 2], [0, 1, 2]]