Question

Is it only my compiler or is it forbidden to use cons references in std::vector elements. Consider following structure:

struct Y
{
  const int & x;

  Y(const int & p_x):
        x(p_x)
  {
  }
};

Now, when I try to push such object onto vector:

std::vector<Y> yv;
int x = 5;
Y y(x);
yv.push_back(y);

I get compiler error: “error: non-static reference member `const int&Y::x’, can’t use default assignment operator”. Shouldn’t copy ctor be enough?

Answer 1

The vector elements must be assignable. From section 23.2.4 Class template vector of the C++ standard:

…the stored object shall meet the requirements of Assignable.