* average_salary report + salary_records {
                                           -> list:filter ((p_salary record) {
                                                                               ...
                                                                             }) + 
                                           -> list:map ((p_salary record) {
                                                                            ...
                                                                          }, (p_salary -&w record) {
                                                                                                     ...
                                                                                                   }) + 
                                           -> list:reduce ((p_average_salary -&w report, p_salary record) {
                                                                                                            ...
                                                                                                          });
                                         }
                                         /
                                         {
                                           free (&*);
                                         }
