help needed for adding isWHNF primop to 5.00.2

[Julian Seward (Intl Vendor)]

| > I would like to add a primitive to GHC 5.00.2 of the form:
| >
| >    isWHNF :: a -> Bool

One might be inclined to ask what for?  Such a primitive is
probably difficult to implement, given the variety of GHC's
closures, and is potentially dangerous -- you could conceivably
break referential transparency (?)  I can also imagine it
could interact badly with the complexities of GHC's=20
simplifer.

What would you hope to gain from such a thing?  Perhaps
you have some wider purpose which could be achieved some=20
other way?

J