08.Answer

We get back the original list! Why is that? As we mentioned earlier, one way of thinking about what foldRight "does" is it replaces the Nil constructor of the list with the z argument, and it replaces the Cons constructor with the given function, f. If we just supply Nil for z and Cons for f, then we get back the input list.

foldRight(Cons(1, Cons(2, Cons(3, Nil))), Nil:List[Int])(Cons(_,_))
Cons(1, foldRight(Cons(2, Cons(3, Nil)), Nil:List[Int])(Cons(_,_)))
Cons(1, Cons(2, foldRight(Cons(3, Nil), Nil:List[Int])(Cons(_,_))))
Cons(1, Cons(2, Cons(3, foldRight(Nil, Nil:List[Int])(Cons(_,_)))))
Cons(1, Cons(2, Cons(3, Nil)))