(VAR F X Y Z )
(RULES 
        eval(fun(F, X, Y), Z) -> 
        dom(s(X), s(Y), s(Z)) -> s(dom(X, Y, Z))
        dom(o, s(Y), s(Z)) -> s(dom(o, Y, Z))
        dom(X, Y, o) -> X
        dom(o, o, Z) -> o
        
)