(VAR f x xs )
(STRATEGY INNERMOST)
(RULES 
        app(half, 0) -> 0
        app(half, app(s, 0)) -> 0
        app(half, app(s, app(s, x))) -> app(s, app(half, x))
        app(bits, 0) -> 0
        app(bits, app(s, x)) -> app(s, app(bits, app(half, app(s, x))))
        app(app(map, f), nil) -> nil
        app(app(map, f), app(app(cons, x), xs)) -> app(app(cons, app(f, x)), app(app(map, f), xs))
        app(app(filter, f), nil) -> nil
        app(app(filter, f), app(app(cons, x), xs)) -> app(app(app(app(filter2, app(f, x)), f), x), xs)
        app(app(app(app(filter2, true), f), x), xs) -> app(app(cons, x), app(app(filter, f), xs))
        app(app(app(app(filter2, false), f), x), xs) -> app(app(filter, f), xs)
        
)