(VAR f x xs y )
(RULES 
        app(D,t) -> 1
        app(D,constant) -> 0
        app(D,app(app(+,x),y)) -> app(app(+,app(D,x)),app(D,y))
        app(D,app(app(*,x),y)) -> app(app(+,app(app(*,y),app(D,x))),app(app(*,x),app(D,y)))
        app(D,app(app(-,x),y)) -> app(app(-,app(D,x)),app(D,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)
        
)