Question

I would like to implement, in c++, a class b where it would be possible to do some kind of iteration through a member set encapsulating the type of that iterator. Like:

b_object.for_each_x_do(function_f);

so function_f would get everyone of the x members and do anything. Let’s say:

void function_f(x_member_type x){ cout << x << endl; }

Ok. So I’m trying to achieve that through a code like:

class b{
    int *x;
public:
    void foreach_x_do(void (*f)(int)){
            while(*x++)  // or any kind of iteration through x
                    f(*x);
    }
};

class a{
    b b_inst;
public:
    void f(int x) {  }     
    a(){
            b_inst.foreach_x_do(f); // by mistake it was b_inst.foreach_x_do(f)(), however this wasn't the point at all. 
    }
    ~a(){}
};

int main(){} 

However, I’m getting this error, compile-time:

fp.cpp: In constructor ‘a::a()’:
fp.cpp:17: error: no matching function for call to ‘b::foreach_x_do(<unresolved overloaded function type>)’
fp.cpp:6: note: candidates are: void b::foreach_x_do(void (*)(int))

Anybody can help getting it to compile?

Answer 1

It should just be:

b_inst.foreach_x_do(f);

You also need to make f static, not a non-static member method since the original signature for your foreach_x_do function is for a stand-alone function pointer, not a pointer-to-member-function. So i.e.,

static void f(int x) {  }