>>> fmap (+1) (Pair [1, 2, 3] (Just 0)) Pair [2,3,4] (Just 1)
>>> Pair "Hello, " (Left 'x') <> Pair "World" (Right 'y') Pair "Hello, World" (Right 'y')
Product x <> Product y == Product (x * y)
>>> Product 3 <> Product 4 <> mempty
Product {getProduct = 12}
>>> mconcat [ Product n | n <- [2 .. 10]]
Product {getProduct = 3628800}
>>> getProduct (Product 3 <> Product 4 <> mempty) 12
>>> getProduct (Product 3 <> Product 4 <> mempty) 12
>>> getProduct (Product 3 <> Product 4 <> mempty) 12
>>> product [] 1
>>> product [42] 42
>>> product [1..10] 3628800
>>> product [4.1, 2.0, 1.7] 13.939999999999998
>>> product [1..] * Hangs forever *