Re: [Haskell-beginners] why is this type wrong

The type of (.) (.) :: (b -> c) -> (a -> b) -> a -> c Means that "last' [1,2,3]" should be a function, which it isn't You can instead try, main = (print . last') [1,2,3] Or equivalently, main = print . last' $ [1,2,3] On 12 May 2015 at 18:06, Roelof Wobben wrote:

Thanks all.

I have now this :

-- | The main entry point. last' :: [a] -> Maybe a last' [] = Nothing last' [x] = Just x last' (_:xs) = last' xs

main = print . last' [1,2,3]

but I see this message about main :

* GHC threw an exception : Couldn't match expected type ‘GHC.Types.IO http://GHC.Types.IO a0’ with actual type ‘a1 -> GHC.Types.IO http://GHC.Types.IO ()’ I work wih the fpcomplete and they demand a main in the code . Roelof *

Nicolas SCHOEMAEKER schreef op 12-5-2015 om 11:45:

Hi

In your definition, you seem to have forgotten the case when your list is empty. [x] won't bind on [].

Regards, Nicolas SCHOEMAEKER

(*This email was composed from a mobile phone, please** excuse** any resulting mistakes*)

Web, Cloud Computing & WebRTC developer Haskell Programmer Artificial Intelligence & Robotics enthusiast On May 12, 2015, at 11:40 AM, Kim-Ee Yeoh wrote:

...

On Tue, May 12, 2015 at 1:42 PM, Roelof Wobben wrote:

-- | The main entry point.

...

last' :: [a] -> a last' [x] = x last' (x:xs) = last xs

Notice that the last line does no recursion: it invokes the Prelude's definition of last.

-- Kim-Ee

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