 xs of [] -> error "Empty list has no head."
                         (x:_) -> x

describeList :: [a] -> String
describ
headCase :: [a] -> a
headCase xs = case xs of [] -> error "Empty list has no head."
                         (x:_) -> x
headCase xs = case xs of [] -> error "Empty list has no head."
                         (x:_) -> x