Member pointer to array element

Question

It\'s possible to define a pointer to a member and using this later on:

struct foo
{
  int a;
  int b[2];
};


int main()
{

  foo bar;
  int foo::*          


        

Answer 1

However, the compiler just complains about an "invalid use of non-static data member 'foo::b'"

This is because foo::a and foo::b have different types. More specifically, foo::b is an array of size 2 of ints. Your pointer declaration has to be compatible i.e:

int (foo::*aptr)[2]=&foo::b;

Is it possible to do this at all (or at least without unions)?

Yes, see below:

struct foo
{
  int a;
  int b[2];
};

int main()
{

  foo bar;

  int (foo::*aptr)[2]=&foo::b;
  /* this is a plain int pointer */
  int *bptr=&((bar.*aptr)[1]);

  bar.a=1; 
  bar.b[0] = 2;
  bar.b[1] = 11;

  std::cout << (bar.*aptr)[1] << std::endl;
  std::cout << *bptr << std::endl;
}

Updated post with OP's requirements.