3 Couldn't match type ‘[a0]’ with ‘[a] -> m [a]’
4 Expected type: (a -> Integer) -> [a] -> m [a]
5 Actual type: [a0] -> [a0]
6 Relevant bindings include foo :: m Int (bound at mc24.hs:8:1)
7 Possible cause: ‘take’ is applied to too many arguments
8 In the expression: take 2
9 In a stmt of a monad comprehension: then group by x using take 2