On May 12, 2015 1:32 AM, "Roelof Wobben"
Hello,
To practice recursion I try to make some functions of Data list myself on
the recursive way.
First I will try last.
So I did this :
-- | Main entry point to the application. module Main where
-- | The main entry point. last' :: [a] -> a last' [] = [] last' (x:xs) = last xs
but now I see this error message :
src/Main.hs@6:12-6:14 Couldn't match expected type a with actual type [t0] a is a rigid type variable bound by the type signature for last' :: [a] ->
a at /home/app/isolation-runner-work/projects/112712/session.207/src/src/Main.hs:5:10 Relevant bindings include last' :: [a] -> a (bound at /home/app/isolation-runner-work/projects/112712/session.207/src/src/Main.hs:6:1) …
I my oponion I have said that the input is a array and the output a
string, Except for saying list instead of array, I'd agree with that. But when you write last' [] = [], the output is [], which does not have the expected type of strong. So the actual type is a list. You need to return a string.