Reference

Notes for reading C++ Primer 4/e.

Reference

nonconst reference can only reference to the same nonconst object.

int incr(int val) {
  return ++val;
}

int incrRef(int &val) {
  return ++val;
}

int incrRefConst(const int &val) {
  cout << val << endl;

  return val;
}

int main() {
  short v1 = 0;
  const int v2 = 42;
  double v4 = 3.4;

  int v3 = incr(v1);
  v3 = incrRef(v1);  // X: no matching function for call to 'incrRef'
  v3 = incrRefConst(v1);  // 0

  int v5 = incr(v4);
  v5 = incrRef(v4);  // X: no matching function for call to 'incrRef'
  v5 = incrRefConst(v4);  // 3
  cout << v4 << " " << v5 << endl;  // 3.4 3

  return 0;
}

[note]:

• nonconst refernce parameter 的彈性較低，不能以 const object 初始化，也不能以字面常數 (ex. 42, 'a', "Hello", 3.14...) 或 rvalue 做為 argument.