5 ways to do the same thing

0_map.hs

products = concatMap (\x -> map (*x) [1..10]) [1..10]

1_list_comp.hs

products = [ x * y | x <- [1..10], y <- [1..10] ]

2_monad.hs

products = [1..10] >>= \x -> [1..10] >>= \y -> return $ x * y

3_do_monad.hs

products = do
  x <- [1..10]
  y <- [1..10]
  return $ x * y

4_applicative.hs

import Control.Applicative
products = (*) <$> [1..10] <*> [1..10]

This is how you would do it in ruby, for reference. It is conceptually equivalent to the first example.

products = (1..10).map {|x| (1..10).map {|y| x*y}}.flatten

List comprehensions always seemed kind of awkward to me, but I think they kind of win here for clarity, length, and not requiring an import.

Applicative rocks, obviously, and if your program is already using the applicative style, I would go with it.