The type of (.)
Means that "last' [1,2,3]" should be a function, which it isn't
Or equivalently,
(.) :: (b -> c)
-> (a -> b) -> a -> c
You can instead try,
main = (print .
last') [1,2,3]
main = print . last'
$ [1,2,3]
On 12 May 2015 at 18:06, Roelof Wobben
<r.wobben@home.nl>
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 a0’ with actual type ‘a1 -> 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 enthusiastOn May 12, 2015, at 11:40 AM, Kim-Ee Yeoh <ky3@atamo.com> wrote:
On Tue, May 12, 2015 at 1:42 PM, Roelof Wobben <r.wobben@home.nl> 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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