module Enumerable
def cartesian(other)
res = []
each { |x| other.each { |y| res << [x, y] } }
return res
end
end
p [1,2,3].cartesian(['a',5,6])
# => [[1, "a"], [1, 5], [1, 6],
# => [2, "a"], [2, 5], [2, 6],
# => [3, "a"], [3, 5], [3, 6]]