Prove the following theorem about the search provided in the
following file that you should import.
You will also need to import the following files from Deduce’s library.
import Nat
import List
import Pair
import Option
import Set
theorem search_correct: all y: Nat. all xs: List<Nat>.
define front = first(search(xs, y));
define back = second(search(xs, y));
(back = [] or head(back) = just(y)) and
not (y ∈ set_of(front)) and
front ++ back = xs
proof
?
end