fixed small bug in SCMPC where single slacks were not substituted in …

…constraints

src/csnlp/multistart/multistart_nlp.py

@@ -34,11 +34,13 @@ def _chained_subevalf(
 ) -> Union[SymType, cs.DM, np.ndarray]:
     """Internal utility to perform :func:`subevalf` on variables, dual variables and
     parameters in chain."""
-    expr = subsevalf(expr, old_vars, new_vars, eval=False)
-    if old_dual_vars is None:
-        return subsevalf(expr, old_pars, new_pars, eval=eval)
-    expr = subsevalf(expr, old_pars, new_pars, eval=False)
-    return subsevalf(expr, old_dual_vars, new_dual_vars, eval=eval)
+    if old_dual_vars is not None and old_dual_vars:
+        expr = subsevalf(expr, old_dual_vars, new_dual_vars, False)
+    if old_vars:
+        expr = subsevalf(expr, old_vars, new_vars, False)
+    if old_pars:
+        return subsevalf(expr, old_pars, new_pars, eval)
+    return cs.evalf(expr) if eval else expr
 
 
 def _cmp_key(sol: dict[str, Any]) -> tuple[bool, bool, float]:

src/csnlp/wrappers/mpc/scenario_based_mpc.py

@@ -280,6 +280,8 @@ def constraint_from_single(
                 self.states_i(i),
                 self.single_disturbances,
                 self.disturbances_i(i),
+                self.single_slacks,
+                self.slacks_i(i),
                 eval=False,
             )