(VAR f u x xs y z )
(RULES 
        app(app(:,app(app(:,app(app(:,app(app(:,C),x)),y)),z)),u) -> app(app(:,app(app(:,x),z)),app(app(:,app(app(:,app(app(:,x),y)),z)),u))
        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)
        
)