get partial aggregation results . concode_field_sep ArrayList<Double> a concode_elem_sep State state concode_elem_sep int n concode_field_sep boolean getAscending concode_elem_sep void init concode_elem_sep void binaryInsert concode_elem_sep Comparator<T> getComparator concode_elem_sep boolean merge concode_elem_sep ArrayList<T> sortedMerge concode_elem_sep ArrayList<Double> terminate concode_elem_sep boolean iterate
State function ( ) { return state . a . size ( ) == 0 ? null : state ; }