Richard Wesley wrote:

> On Jan 5, 2007, at 09:36, Martijn Tonies wrote:
>
> Just about every UDF that ships with FB seems to assume that NULL ==
> 0. Round, Sign, Sin, you name it. So for our calculations, we have
> to wrap each one in a
>
> (CASE WHEN arg is NULL THEN CAST(NULL AS result_type) ELSE func(arg)
> END)
>
> which I am sure wreaks havoc on any indexing we may have defined.
>
> (Gotta love those typed NULLs too...)
>

What Firebird version do you use? Because in 2.0 this is fixed AFAIK.
See the release notes.
Perhaps it is interesting for you to see
http://udf.adhoc-data.de/index_eng.html which is compliant with the Fb
2.0 NULL handling.

hth,

m. th.