Very cool. This is much nicer than when I asked much the same question a few years back (and I can think of all sorts of interesting things I can learn from the interface in that module). But what about indirection chasing? Surely we want isWHNF to return True if we have an indirection to a WHNF. Possibly one wants something a bit like this (untested, and rather depends on GHC's indirection semantics):
removingIndirections :: (forall c . c -> IO b) -> a -> IO b removingIndirections k a = do closureData <- getClosureData a if isConstr (tipe closureData) then removingIndirections (ptrs closureData ! 0) else k a
simpleIsWHNF :: a -> IO Boolean simpleIsWHNF = fmap (isConstr . tipe) . getClosureData
isWHNF = removingIndirections simpleIsWHNF
Very true, isWHNF needs to follow indirections indeed. To decide whether to recurse, you probably intended to test for Indirections and not for Constructors:
removingIndirections :: (forall c . c -> IO b) -> a -> IO b removingIndirections k a = do closureData <- getClosureData a if isIndirection (tipe closureData) then removingIndirections (ptrs closureData ! 0) else k a
Thanks, pepe