— Function: int gsl_multiset_next (gsl_multiset * c)

This function advances the multiset c to the next multiset element in lexicographic order and returns GSL_SUCCESS. If no further multisets elements are available it returns GSL_FAILURE and leaves c unmodified. Starting with the first multiset and repeatedly applying this function will iterate through all possible multisets of a given order.

— Function: int gsl_multiset_prev (gsl_multiset * c)

This function steps backwards from the multiset c to the previous multiset element in lexicographic order, returning GSL_SUCCESS. If no previous multiset is available it returns GSL_FAILURE and leaves c unmodified.