The Stat_Module class

class Stat_Module {
public:
   virtual bool is_valid();
   virtual Error create_stream(Variable *, Stream_type, int);                
   virtual Error destroy_stream(Variable *);
   virtual Error compute(Variable *, Analysis);
   virtual Error destroy_computation(Variable *, Analysis);                
   virtual Error in(Variable *, void *);
   virtual Error reset(Variable *, Analysis, void *);
   virtual void *result(Variable *, Analysis, void *, Error *);
};    // end Stat_Module