Problem with function indexing

Hi,

I hate to resort to posting here but I got no responses
in the other groups.  I am following up on an earlier
response on promotion of float4 to float8 in the WHERE
clause.

To get around this, Tom Lockhart suggested that I make a 
function index on float8, but this is what happens:

final99=> create index mx on psc using btree (float8(glat) float8_ops);
ERROR:  internal error: untrusted function not supported.

["psc" is my table and "glat" is a float4].

Any ideas how to do this?  I have successfully made an index
on an externally linked function . . . 

Thanks,

--Martin

===========================================================================

Martin Weinberg                      Phone: (413) 545-3821
Dept. of Physics and Astronomy       FAX:   (413) 545-2117/0648
530 Graduate Research Tower
University of Massachusetts
Amherst, MA  01003-4525