For: [your code hear]

[Manfred Nowak]

Goal: show some skill of D for implementing mathematics. 

A definition:

Let T1, T2, T3 be sets. A problem P of type ( T1, T2, T3) is 
interpretable as a function from the domain
   cartesian product of T1 and powerset of T2
to the codomain
   T3.

Objective: Present code, that is usefull for all P, i.e. for all 
variations of ( T1, T2, T3) and all algoritm to compute the map from 
the domain to the codomain.

-manfred