# arguments – How can I set a certain predicate for the result of a function to true?

I have an object called `f` (basically a vector of functions) and a predicate called `MemberQR`(actually its with subscript R).

`MemberQR(f):=True` I.e. I set the predicate to true.

Now I want to apply a Transformation on `f`, and the result still should have the predicate set to `True`.

So for `fooFunction(f_?MemberQR):= 2 f;` the result should also yield true when tested for MemberQR.

Of course, I do not know what exactly the components of `f` are, they might be different each time.

I have tried the use of `%` but was not sucessful. `fooFunction` is not supposed to produce output, it just transforms `f`.