ROUTINE
-------

void ug_iaib (INT_ na,
              INT_ nb,
              INT_1D * ibia,
              INT_1D * iaib,
              INT_1D * liaib)

DESCRIPTION
-----------

Create an inverse list.


INPUT ARGUMENTS
---------------

na                       : Number of "a" items.
nb                       : Number of "b" items.

ibia                     : List of the "b" index at each "a" index.
                           The first "a" index is 1 and the last is "na".
                           The first "b" index is 1 and the last is "nb".
                           If the value of the "ibia" array is 0 at a given "a"
                           index then there is no corresponding "b" index.

OUTPUT ARGUMENTS
----------------

iaib                     : List of the "a" index at each "b" index.
                           The first "a" index is 1 and the last is "na".
                           The first "b" index is 1 and the last is "nb".
                           If the value of the "iaib" array is 0 at a given "b"
                           index then there is no corresponding "a" index.
                           If the "a" index has a value of 0 then there is no
                           corresponding "a" index for the given "b" index.

liaib                    : List of locations in the "iaib" array for the
                           first "a" index corresponding to a given "b" index.
