C++ Surprise 1 – const reference

“There are just two kinds of languages: the ones everybody complains about and the ones nobody uses.” — Bjarne

This doesn’t compile:

int main(){
  int x = 10;
  double &y = x; // error: invalid initialization of reference of 
                 // type 'double&' from expression of type 'int'
}

int main(){

int x = 10;

double &y = x; // error: invalid initialization of reference of

// type 'double&' from expression of type 'int'

}

This does:

int main(){
  int x = 10;
  const double &y = x;
}

int main(){

int x = 10;

const double &y = x;

}

In the second case, y is initialized by a temporary double initialized from x. Not sure what the rationale is but read up TCPPPL 5.5.

Here is where the inconsistency becomes very difficult to ignore:

#include <iostream>
using std::cout;
using std::endl;

int main(){
  int x = 10;
  const int &iy = x;
  const double &dy = x;
  x = 20;
  cout << x << endl;
  cout << iy << endl;
  cout << dy << endl;

  return 0;
}

#include

using std::cout;

using std::endl;

int main(){

int x = 10;

const int &iy = x;

const double &dy = x;

x = 20;

cout << x << endl;

cout << iy << endl;

cout << dy << endl;

return 0;

}

If anyone knows the reasoning behind this, let me know.