-- a simple list data type containing ints
data List () where {
    Cons : Int -> List () -> List ()
    Nil  : List ()
};

main = sumlength (Cons 1 (Cons 2 (Cons 3 (Cons 4 (Cons 5 Nil))))); 

-- take the length of a list
length : List () -> Int ;
length x = case x of {
    Cons _ xs => 1 + length xs ;
    Nil => 0 ;
};
-- sum a list
sum : List () -> Int ;
sum x = case x of {
    Cons a xs => a + sum xs ;
    Nil => 0 ;
};

-- sum + length of a list
sumlength: List () -> Int ;
sumlength x = sum x + length x ;