Allow the user to not expand the dynamics

bioptim/dynamics/configure_problem.py

@@ -340,7 +340,7 @@ def muscle_driven(
         ConfigureProblem.configure_soft_contact_function(ocp, nlp)
 
     @staticmethod
-    def configure_dynamics_function(ocp, nlp, dyn_func, **extra_params):
+    def configure_dynamics_function(ocp, nlp, dyn_func, expand: bool = True, **extra_params):
         """
         Configure the dynamics of the system
 
@@ -352,6 +352,8 @@ def configure_dynamics_function(ocp, nlp, dyn_func, **extra_params):
             A reference to the phase
         dyn_func: Callable[states, controls, param]
             The function to get the derivative of the states
+        expand: bool
+            If the dynamics should be expanded with casadi
         """
 
         nlp.parameters = ocp.v.parameters_in_list
@@ -365,7 +367,9 @@ def configure_dynamics_function(ocp, nlp, dyn_func, **extra_params):
             [dynamics],
             ["x", "u", "p"],
             ["xdot"],
-        ).expand()
+        )
+        if expand:
+            nlp.dynamics_func = nlp.dynamics_func.expand()
 
     @staticmethod
     def configure_contact_function(ocp, nlp, dyn_func: Callable, **extra_params):