[PPL-devel] Re: [Xsb-development] x still a variable after a successful call to c2p_list(x) (2nd attempt)

[David Warren]

Roberto Bagnara writes:
 > Bart Demoen wrote:
 > > should be easy to fix: seems like is_var does not deref
 > 
 > I have checked: none of the is_*() functions seems to dereference.
 > However, other interface functions do dereference.
 > 
 > Notice also that, while cinterf.h contains the declaration of
 > p2p_deref() along with the rather obscure comment
 > 
 > **              p2p_deref:      prolog_term -> prolog_term   !! uncommon
 > 
 > p2p_deref() is never mentioned in the XSB manuals.
 > 
 > So the questions are: how is one supposed to use the foreign
 > language interface?  Calling p2p_deref() before any invocation
 > of is_*()?  Are there other interface functions that require
 > the client code to call p2p_deref() for proper operation?

This certainly looks to me like a bug.  I think we should put deref's
into all those interface functions.  I can only imagine that Jiyang,
when he wrote these routines, expected to use the p2p_deref, but
somehow that "convention" got lost down through the ages (in the later
documentation in particular).  Does anyone have any reason we
shouldn't add the derefs?

-David