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_FAILURE and 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_FAILURE and leaves c unmodified.