>The UDF has to return fixed length values. If a programmer does not know that, the results will be strange and they will blame vfp.
>
>VFP can at least try to compute length based on known functions, but how to guess what comes from UDF?

Even if I wrap my UDF in calls to PADR(MyUDF(), 20) or Cast(MyUDF() as C(20)) ?
Such an index is MUCH safer than the possible inclusion of a private memvar IMHO,
and vfp merrily uses those in optimizing queries.

Especially any CAST()-wrapped UDF should be considered "safe enough".

regards

thomas