3 ms·$ irb 2.3.1 :001 > [1,[2,3], [4, [5,6]]].flatten => [1, 2, 3, 4, 5, 6] BOOM!by nolite 10y ago$ irb 2.3.1 :001 > [1,[2,3], [4, [5,6]]].flatten => [1, 2, 3, 4, 5, 6] BOOM!