Product x <> Product y == Product (x * y)
>>> Product 3 <> Product 4 <> mempty Product {getProduct = 12}
>>> mconcat [ Product n | n <- [2 .. 10]] Product {getProduct = 3628800}
>>> product [] 1
>>> product [42] 42
>>> product [1..10] 3628800
>>> product [4.1, 2.0, 1.7] 13.939999999999998
>>> product [1..] * Hangs forever *
>>> product [] 1 >>> product [42] 42 >>> product [1..10] 3628800 >>> product [4.1, 2.0, 1.7] 13.939999999999998 >>> product [1..] * Hangs forever *