forcing a haskell object to WHNF from C

Hi all, This might seem like a strange thing to do, but ... Presume I have a HaskellObj in some C code. I know that it is a thunk. I want to force it to _WHNF_ . Should/can I use rts_eval()? Any pointers on what this does (start new threads, cause garbage collection ...) would be appreciated. I can (and have) gone over the code but a more high level description would be helpful. Or perhaps there is another/better way. In essence I want a C version of seq (perhaps I can call to Haskell to perform a seq on it, but I think this might be overkill). A lightweight solution would be nice. Cheers, Bernie.