On 23 November 2005 18:29, Sigbjorn Finne wrote:
The appended snippet might help..
--sigbjorn
-- whnf.hs import Foreign.StablePtr import System.IO.Unsafe
isWHNF :: a -> Bool isWHNF a = unsafePerformIO $ do stl <- newStablePtr a rc <- isWhnf stl freeStablePtr stl return (rc /= 0)
foreign import ccall safe "isWhnf" isWhnf :: StablePtr a -> IO Int
/* whnf.c */ #include "Rts.h" int isWhnf(StgStablePtr st) { StgClosure* c = (StgClosure*)(stable_ptr_table[(StgWord)st].addr); return !(closure_THUNK(c)); }
using deRefStablePtr() would be slightly better. Also, you should consider whether you want indirections to be counted as WHNF or not. Also, I think you can make that foreign import "unsafe" (safe will be slow). For more speed you could implement it directly as a primitive. Cheers, Simon