This function advances the combination c to the next combination in lexicographic order and returns
GSL_SUCCESS. If no further combinations are available it returns
GSL_FAILUREand leaves c unmodified. Starting with the first combination and repeatedly applying this function will iterate through all possible combinations of a given order.
This function steps backwards from the combination c to the previous combination in lexicographic order, returning
GSL_SUCCESS. If no previous combination is available it returns
GSL_FAILUREand leaves c unmodified.