Oracle 8.0 - Can't use function index

I am building an application that accesses to a customer provided Oracle. I was assuming function-based indices in Oracle 8.0+, but I am wrong. It is only avail since 8i.

For now, I can only think of introducing another field that stored the result of my function, and then I create an index on it. I prefer not to because:
(1) it introduces another field (in fact, I have a few function-based
indices)
(2) my C/C++ code that access it will have to be modified
(3) because of the above, it will be a waste if I move to another customer
who uses Oracle 8i+

I just want to see ideas from different people: how do you work around this?

Thanks

• Will