haskell - Non exhaustive pattern in function in GHCi -

I want to create a function that displays the last element in the list. This is my code:

< Pre> ghci & gt; My last :: [A] - & gt; A GSC & gt; My last [] = error ghci & gt; My real [x] = x ghci & gt; My list (x: xs) = myLast xs

and I get the following error:

  *** Exception: The non-complete pattern My latest in the function  

I understand that when you recall a case you get this error, but I think I have included all the possibilities . Any ideas?

If you use two in each line, then each definition A new function will be named myLast , to hide all the previous definitions, then whatever you are ending with is

GHCI> Is equal to: let alone my last (x: x) = my last x

> You probably want to create a hyscale file, MyLast.hs , where

  module is MyLast, where is myLast :: [a] ] - & gt; A myLast [] = error with myLast [x] = x myLast (x: xs) = myLast xs  

then you will get that file with ghci MyLast.hs Can load in GHCi. Code>.

The keyword let is required only if you are already in GHCI (or, in some modes like IO , or any other function ) And want to create an local definition but then you should only use twice , e.g., <. MyLast [] = Error; MyLast [x] = x; MyLast (x: xs) = myLast xs

or

  twice Lost :: [int] - & gt; [EIT] Let me lie = Give my [] = error my list [x] = x my list (x: x) = in my list x \ xs -> 2 * The last xs  
, which I want,  
  likes to write twice as Lust = (2 *). MyLast where myLast [] = Error myLast [x] = x myLast (x: xs) = myLast xs