Calculation statements

A calculation of a parameter that is defined over a large of number of sets such as the following can inadvertently cover a huge number of cases

X(A, B, C, D, E) = 5

If each set had 20 members then the calculation would have to cover 3.2 million cases and would take a lot of memory.  Narrowing attention only to good cases employing conditionals can help this

X(A, B, C, D, E) $ GOODCASE (A, B, C, D, E) = 5

where the user must somehow define the good case item, perhaps as a tuple.