Why does “most important const” have to be const?

Question

In http://herbsutter.com/2008/01/01/gotw-88-a-candidate-for-the-most-important-const/ it mentions \"most important const\" where by C++ deliberately specifies that binding a

Answer 1

Here's an example:

void square(int &x)
{
  x = x * x;
}

int main()
{
  float f = 3.0f;

  square(f);

  std::cout << f << '\n';
}

If temporaries could bind to non-const lvalue references, the above would happily compile, but produce rather surprising results (an output of 3 instead of 9).