(VAR X Y Z )
(RULES 
        and(true, X) -> X
        and(false, Y) -> false
        if(true, X, Y) -> X
        if(false, X, Y) -> Y
        add(0, X) -> X
        add(s(X), Y) -> s(add(X, Y))
        first(0, X) -> nil
        first(s(X), cons(Y, Z)) -> cons(Y, first(X, Z))
        from(X) -> cons(X, from(s(X)))
        
)