Myujth

I have this error when i try to insert an object into a set of a stl vector, Node is a class that i have created. ¿Could you explain to me how to solve this error?

Code:

void car::expandnode(Node& current_node,std::set<vector<Node> >& closed_list,grid& map){

 int c_a = current_node.get_x();
 int c_b= current_node.get_y();

 if((map.get(c_a,++c_b))!=1)

 point p(c_a,++c_b);
 Node ns(p,costtan);

 costtan= 1+ heuristic1(ns); // cost to arrive node

 if(std::find((*closed_list.end()).begin(),(*closed_list.end()).end(),ns)==((*closed_list.end()).end()))
 closed_list.end()->push_back(ns); //error

 


float car::heuristic1(Nodo& successor)
 int c1= successor.get_x();
 int c2= successor.get_y();
 float result = sqrt(pow((c1-destination_point_.get_x()),2) + pow((c2-destination_point_.get_y()),2));

 return resultado;

 

Error:

 error: passing ‘const std::vector<Node>’ as ‘this’ argument discards qualifiers [-fpermissive]
 closed_list.end()->push_back(ns);

Thanks

EDIT1:

I am implementing the A star algorithm, so in the function expandnode if a successor is not an obstacle (!=1), i insert it in the set of vector, this set contains the successors nodes of each node, i added more code to the question to clarify my doubt

Because i am calling expandnode() from other function (main A-star function), i need to insert the succesors of each node on the last vector of the set, i use .end() for that purpose, because initially each vector have one node, once made the call to expandnode() this vector have the node and its successors

closed_list is a std::set. The objects stored in a set are const objects, since modifying them can potentially change how the modified object sorts in relation to the other objects in the set.

When you dereference an iterator of a set, the reference you get is a const &. When you then try calling push_back on that object, the compiler generates an error because push_back cannot be called on a const object.

Another problem with the code is that the end iterator of any standard container is not dereferencable, and doing so as you do results in Undefined Behavior. Perhaps you meant to use back() instead, which returns a reference to the last item in the container?

This still won't address the problem of modifying an object in a set. To do that, you need to erase the object from the set, modify it, then reinsert the modified object.

Another problem is that all elements in a set are ordered by operator < by default. You may want to override it.