Dustintendo

i thought i read somewhere that it wont work, but ill ask first before i try it

sch

Indexing is controlled by the brifter, not the FD. FD just moves as instructed.

Steev

This is sort of true. The shifter pulls a certain amount of cable per click and will only achieve proper indexing when matched to a derailleur that has moves the correct amount per unit of cable pull.
To answer the original question, if the derailleur was part of an indexed shifting road group, then it should work OK, assuming it is a reasonable match to the number and size of chain-rings.

Gonzo Bob

Maybe. I bought a used Cannondale CAD3 frameset once and it came with a 105 FD attached. Since it was from the early '90s I thought it would index OK with my 8sp Ultegra brifter but the derailer didn't move far enough. I ended up getting a new Ultegra FD which worked fine.

LarDasse74

It may work. RX100 initially came with indexed rear/non-indexed front shifting (downtube shifters, IIRC). However, I have a Campagnolo FD from the same era and it is not hard to make it work with indexed brifters... unless, as Gonzo Bob says, the shifter does not move the derailleur far enough, it is easy to get indexing to work on a double crankset.