You have a foldM function which takes a " a -> b -> m a " as a first
argument. But you are passing it f1 which has a type (a, b) -> m a.
Unfortunately I'm not sure what you were trying to do. The function
you have just doesn't fit. :(
Maybe you intended to have f1 :: String -> (String, String) -> IO
String, and then go
:t foldM f1 "" x
foldM f1 "" [("a","b"),("c","d")] :: IO String
?
On Mon, Dec 30, 2013 at 6:42 PM, Miro Karpis
Hi, please can you help me with following?
I have a following function: f1 :: (String, String) -> IO (Maybe String)
which I would like to apply to a list of tuples.I have defined the function like this, but that gives me error (below):
f2 :: [(String, String)] -> IO (Maybe String) f2 x = foldM f1 0 x
error: Couldn't match expected type `IO (Maybe String)' with actual type `[b0] -> m0 (String, String)' In the return type of a call of `foldM'
thanks, m.
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