>>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".

Private memvar is usually fixed during query.

But yes, these things are known to work now, even with native functions, still there are people that do not know to use PADR in index and SQL commands.