Error "no match operator []" when entering data in a map inside an object

class Calculator{
private:
    map <string,int>* var;
//                  ^
};

Look at that asterisk ... thanks to him, var is a pointer. If the access to the map is done through a pointer you should write something such that:

void Calculator::addVal(string name, int val){
    (*var)[name]=val;
}

Although you could also do the following:

void Calculator::addVal(string name, int val){
    var->operator[](name)=val;
}

Even so, everything indicates that the error in your case is the use of the asterisk. Delete it and then you can access the map methods without problems.

As a final note, try not to use using namespace in the header files. In bigger programs it can give you problems.

Your corrected code would look like this:

class Calculator{
public: 
    void addVal(string name, int val);
    int getVal(string name);
private:
    int memory;
    map <string,int> var;
};

Calculator::Calculator()
  : memory(0)
{ }
void Calculator::addVal(string name, int val){
  var[name]=val;
}

int Calculator::getVal(string name){
  return var[name];
}

If you compile it, it gives you the errors:

• The member functions addVal and getVal do not have the return in the declaration but if they have it in the definition, so the compiler can not identify them.
• getVal is declared with the parameters (string, name) and defined with the parameter (string name) .
• You define the constructor of Calculator but you do not declare it.
• var is a pointer not an object, to use it you should first de-reference and then use: (*var)[name] = val and return (*var)[name] .

By the way, you do not delete var in the destructor.

Have you tried to compile or understand the errors? They seem pretty self-explanatory.