Question

In C++, how do you declare a static member function of a class to be const with respect to the static member variables of that class?

Consider the following simple example.

myclass.h:

class myclass
{
    myclass()
    {
        myint = 0;
    }

    ~myclass() { }

    int myint;
    static int my_static_int;

    void foo(const int yourint) const;
    static void bar(const int newint );
};

myclass.cpp:

myclass::my_static_int = 0;

void myclass::foo(const int yourint) const
{
  if (yourint <= myint + my_static_int)
     std::cerr << "yourint  <= myint + my_static_int";
  else
      std::cerr << "yourint  >  myint + my_static_int";

  bar( yourint );
}

void myclass:bar(const int newint)
{
  my_static_int = newint;
}

main.cpp

...
myclass A;
A.foo(4);
A.foo(4);
..

The output would be:

yourint  >  myint + my_static_int
yourint  <= myint + my_static_int

Clearly, bar can be used within const member functions to change the static member variables of the class and thus change the result of const member function foo.

Can you declare bar to be const with respect to my_static_int ?

Answer 1

Original code (I only tidied up the formatting):

class myclass
{
    myclass()
    {
        myint = 0;
    } 
    ~myclass()
    {}

    int myint;
    static int my_static_int;

    void foo(const int yourint) const;
    static void bar(const int newint );
};

In this class everything is private, inaccessible, by default: it is unusable.

That is one example why it is so important to post real code.

You then ask:

“Can you declare bar to be const with respect to my_static_int?”

Yes, but there is no direct syntax for that.

You will have to use the existing language features.

They are adequate to the task.

class something
{
private:
    int my_int;
public:
    void bar( int const newint ) const;
    something();
};

class myclass
{
private:
    int myint;
    static something;
public:
    void foo( int const yourint ) const;
    ~myclass() {}
    myclass(): myint( 0 ) {}
};