implement less defaulty interface in cont.pl

src/prolog/lib/cont.pl

@@ -1,16 +1,19 @@
 
 :- module(cont, [reset/3, shift/1]).
 
-reset(Goal, Cont, Term) :-
+reset(Goal, Ball, Cont) :-
     call(Goal),
     '$reset_cont_marker',
     '$bind_from_register'(Cont, 3),
-    '$bind_from_register'(Term, 4).
+    '$bind_from_register'(Ball, 4).
 
 shift(Term) :-
     '$nextEP'(first, E, P),
     get_chunks(E, P, L),
-    Cont = cont(call_continuation(L)),
+    (  L == [] ->
+       Cont = none
+    ;  Cont = cont(call_continuation(L))
+    ),
     '$write_cont_and_term'(_, _, Cont, Term),
     '$unwind_environments'.
 

src/prolog/machine/system_calls.rs

@@ -2197,8 +2197,12 @@ impl MachineState {
                 self.reset_block(addr);
             }
             &SystemClauseType::ResetContinuationMarker => {
-                self[temp_v!(3)] = Addr::Con(Constant::Integer(Integer::from(0)));
-                self[temp_v!(4)] = Addr::Con(Constant::Integer(Integer::from(0)));
+                self[temp_v!(3)] = Addr::Con(Constant::Atom(clause_name!("none"), None));
+
+                let h = self.heap.h;
+                self.heap.push(HeapCellValue::Addr(Addr::HeapCell(h)));
+
+                self[temp_v!(4)] = Addr::HeapCell(h);
             }
             &SystemClauseType::SetBall =>
                 self.set_ball(),