(VAR g h x xs )
(RULES 
        ap(ap(f, x), x) -> ap(ap(x, ap(f, x)), ap(ap(cons, x), nil))
        ap(ap(ap(foldr, g), h), nil) -> h
        ap(ap(ap(foldr, g), h), ap(ap(cons, x), xs)) -> ap(ap(g, x), ap(ap(ap(foldr, g), h), xs))
        
)