18. References themselves can't be changed

• Given:

  
      int i = 4;
      int x = 8;
      int& r = i;
  
  

• Silly attempts to get r to refer to x instead of i:

  
      r = x;      // NO: now i == 8
      int& r = x; // NO: variable redefinitions are illegal
      r = &x;     // NO: type mismatch, r not a pointer-type
      r& = x;     // NO: plain syntax error
      &r = &x;    // NO: left operand must be l-value
  
  

  Conclusion: r refers to i for r's entire life.