I am sure that there is something I don't grasp about Associations. Here is my problem. I have an association. Call it A. It has a number of Keys, let's say 3 for the sake of argument and call them K1,K2 and K3. I also have 2 functions F1[] and F2[V,N] which takes an Association of type A as argument and a number N. In the call to F1[] I create that Association of type A in a variable V by calling a function initializeA[] which returns an Association of type A. I find that after I have created V, I can modify the values associated with keys K1,K2 and K3. Now, while in F1[] I call F2[V,N] and here lies the problem. Having passed V to F2 I find it impossible to set the values of V associated with the keys K1, K2 and K3. F2[V,N] returns V via Return[V]. The idea was to have F2 do some calculations and modify V. But I can't modify V while in F2. What I had to do was make my calculations in F2 and return the result and V with the following statement: { R,V} = F2[V,N]; while I am in F1[]. Only after having returned from F2[V,N] can I (while still in the call to F1[]) go ahead and modify some values in V, as in: AppendTo[V[[K1]],R]; I had hoped to place the line above inside F2[V,N].

This also leads to another question. Supposed I have created an initialized Association as above with V = initializeA[]. if I do, F2[V,#] & /@ {1,2,3,4,5} while hoping that F2[V,1] would modify V and that F2[V,2] would now have the modified value of V and then F2[V,3] would work with the value of V that was modified by the 2 previous calls to F. That did not work and I had to write a For[] loop so that I first call F2[V,1] and then modify V. Once that is done, in my next iteration of the loop I call F2[V,2] where V is the modified version (due to the call F2[V,1]). This 2nd call to F2 modifies V further and on the next iteration I call F2[V,3] and so on. That works. But I am nagged with the idea that I am missing something and that there is a ready made way to do this in Mathematica.

Any answers/suggestions?