This enumeration provides the special values for use as the index when retrieving choice values through the functions IG_ISIS_choice_get_long, IG_ISIS_choice_get_rational. They are not valid for IG_ISIS_choice_get_ascii.
Values:
| IG_ISIS_CHOICE_LOW | Value indicating to retrieve the lowest value in a range, or the first value in a list. |
| IG_ISIS_CHOICE_HIGH | Value indicating to retrieve the highest value in a range, or the last value in a list. |
| IG_ISIS_CHOICE_STEP | Value indicating to retrieve the step value in a range. |