gistfile1.txt

irb(main):001:0> a = ["q", "u"]
=> ["q", "u"]
irb(main):002:0> b = ["x", "y"]
=> ["x", "y"]
irb(main):009:0> first_pass = a.map do |i|
irb(main):010:1*       b.map do |j|
irb(main):011:2*         i+j
irb(main):012:2>       end
irb(main):013:1>     end
=> [["qx", "qy"], ["ux", "uy"]]
irb(main):014:0>
irb(main):015:0*     second_pass = a.map do |i|
irb(main):016:1*       b.map do |j|
irb(main):017:2*         j+i
irb(main):018:2>       end
irb(main):019:1>     end
=> [["xq", "yq"], ["xu", "yu"]]
irb(main):020:0>
irb(main):021:0*     result = first_pass + second_pass
=> [["qx", "qy"], ["ux", "uy"], ["xq", "yq"], ["xu", "yu"]]
irb(main):023:0> result.flatten
=> ["qx", "qy", "ux", "uy", "xq", "yq", "xu", "yu"]