On 17 December 2010 18:04, michael rice <nowgate@yahoo.com> wrote:

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f :: [Int] -> IO [Int]
f lst = do return lst

main = do let lst = f [1,2,3,4,5]
fmap (+1) lst

The problem is that you are applying fmap to a type IO a.

fmap (+1) (return [1,2,3])

But to achieve the behaviour you expect, you need another fmap:

fmap (fmap (+1)) (return [1,2,3])