“error:passing 'const std::vector<int>' as 'this' argument discards qualifiers [-fpermissive]”

[neuronphysics]

I am trying to apply DESPOT POMDP solver with using given examples to build my own decision making problem and I followed the documentation in the repository to build different relevant classes and functions in the header file

class SimpleState: public State {
public:
int position;
int context;
int time;

        SimpleState();
        SimpleState(int \_position, int \_context, int \_time) :
        rat\_position(\_position),
        context(\_context),
        time(\_time) {
        }
        SimpleState(int \_state\_id);
        ~SimpleState();

        std::string text() const;
};
    SimpleState::SimpleState() {
    }

class StarMazeProblem : public DSPOMDP,
     public MDP {
protected:
        std::vector > > transition\_probabilities\_; //state, action, \[state, weight\]

        mutable MemoryPool memory\_pool\_;

        std::vector states\_;

        mutable std::vector mdp\_policy\_;

public:
        enum {CENTER = 0, RIGHT = 1, LEFT = 2};
        
public:
      StarMazeProblem();
      int NumStates() const;
      void ComputeDefaultActions(std::string type)  const;
      ParticleUpperBound\* CreateParticleUpperBound(std::string name = "DEFAULT") const;//?
      ScenarioUpperBound\* CreateScenarioUpperBound(std::string name = "DEFAULT",
              std::string particle\_bound\_name = "DEFAULT") const;

      ScenarioLowerBound\* CreateScenarioLowerBound(std::string name = "DEFAULT",
              std::string particle\_bound\_name = "DEFAULT") const;
     }

and in the `starmaze.cpp` file the relevant lines are

int StarMazeProblem::NumStates() const {
return CONTEXT * POSITIONS * TIME;
}
void StarMazeProblem::ComputeDefaultActions(string type) const {
cerr << "Default action = " << type << endl;
if (type == "MDP") {
const_cast(this)->ComputeOptimalPolicyUsingVI();
int num_states = NumStates();
default_action_.resize(num_states);

		double value = 0;
		for (int s = 0; s < num\_states; s++) {
			default\_action\_\[s\] = policy\_\[s\].action;
			value += policy\_\[s\].value;
		}
	} else {
		cerr << "Unsupported default action type " << type << endl;
		exi