Re: [Haskell-cafe] Trouble with function with two clauses

On Wed, 9 Jan 2008, Fernando Rodriguez wrote:

I have the following type and function:

data ConsCell a = Nil | Cons a (ConsCell a) deriving Show head' Nil = Nothing head' (Cons a _) = Just a

Works fine, however, what's wrong with the following function?

head'' | Nil = Nothing | Cons a _ = Just a

Maybe you want head''' x = case x of Nil -> Nothing Cons a _ -> Just a