Using pipe name as a variable in the template in Angular2

Question

I am struggling with using a standard angular2 pipe in a non-standard way and I was wondering if there are any ways around it.

Assume I have a variable which its value equals the definition of a standard pipe, for example, the common "date:'medium'" pipe.

let a = "date:\':medium\'";

Now, somewhere in my html, I would like to be able to use this "a" variable the following way:

<p>{{myRecord.date | a}}</p>

And I want this "a" to have the same effect of the date pipe it contains. Is there any way to achieve this?