Availability:C-language interface function
int PL_get_name_arity(term_t 
+t, atom_t *name, size_t *arity)If t is compound or an atom, the functor name will be 
assigned over name and the arity over arity. See 
also
PL_get_functor() 
and PL_is_functor(). 
See section 
11.3.2.1.