operationForDynamicalVariable

This function is designed with the following goals:

---

Discussion

1) the definition of each variable is made once, with the intention of minimizing mistakes and making it easier to read. The challenge with the goals is then that masks have to be applied generically. 2) Masking an entire component (Apm or A0) to zero should avoid any extra computation. This is important because we still want the QG flow to retain its speed.

The solution I came up with was that each variables must specify the recipe for computing itself as three function handles that tell it how to construct the three components Ap,Am,A0. The function then only applies the function handle when necessary.