SP_get_list()     #include <sicstus/sicstus.h>
     
     int
     SP_get_list(SP_term_ref term,
                 SP_term_ref head,
                 SP_term_ref tail);
   Assigns to head and tail the head and tail of
a Prolog list.
Zero if the conversion fails (as far as failure can be detected), and a nonzero value otherwise.