c++ - Vector sorting with different objects in it -

i trying come out sort function, previously, help, manage sort sorts base on variable stored object vector.

pointtwod object.

bool compare(const pointtwod& a, const pointtwod& b) {      return a.getcivindex() > b.getcivindex();     //sort high low  }  //to sort, have call in function void sort(vector<pointtwod>& vector) {     sort(vector.begin(), vector.end(), compare); } 

base on this, tried recreate it.

shapetwod object now, parent class. have 3 sub classes polymorphism store sub class objects vector.

bool compareascend(shapetwod& a, shapetwod& b) {      return b.getarea() > a.getarea();        }  bool comparedescend(shapetwod& a, shapetwod& b) {      return a.getarea() > b.getarea();        } //if compile this, compiler fine  void sort(vector<shapetwod*>& vector) {     string choice;      cout << "\n\na)\tsort area (ascending)" << endl;     cout << "b)\tsort area (descending)" << endl;     cout << "c)\tsort special type , area" << endl;      cout << "\tplease select sort option (‘q’ go main menu): ";     cin >> choice;     transform(choice.begin(), choice.end(), choice.begin(), ::tolower);      if (choice == "a")     {         sort(vector.begin(), vector.end(), compareascend);         //these lines giving error     }     else if (choice == "b")     {         sort(vector.begin(), vector.end(), comparedescend);         //these lines giving error     } } 

but when try compile, compiler give me load of errors, don't understand.

when trying sort vector containing shapetwod*s, compare function must work shapetwod* too, not shapetwod& or shapetwod const&.

change

bool compareascend(shapetwod& a, shapetwod& b) {      return b.getarea() > a.getarea();        } 

to

bool compareascend(shapetwod* a, shapetwod* b) {      return b->getarea() > a->getarea();        } 

change comparedescend similarly.