(VAR f x xs y )
(RULES 
        app(app(\, x), x) -> e
        app(app(\, e), x) -> x
        app(app(\, x), app(app(., x), y)) -> y
        app(app(\, app(app(/, x), y)), x) -> y
        app(app(/, x), x) -> e
        app(app(/, x), e) -> x
        app(app(/, app(app(., y), x)), x) -> y
        app(app(/, x), app(app(\, y), x)) -> y
        app(app(., e), x) -> x
        app(app(., x), e) -> x
        app(app(., x), app(app(\, x), y)) -> y
        app(app(., app(app(/, y), x)), x) -> y
        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)
        
)