有人可以向我解释这段代码用于在 C++ 中重载运算符吗？ [复制]

Question

谁能帮我理解这段代码。我迷失了，因为教授刚刚在课堂上飞过它

class OpClass
  {
   private:
     int x;
   public:
     OpClassoperator+(OpClass right);
  };
OpClass OpClass::operator+(OpClass r)
{  OpClass sum;
sum.x = this->x + r.x; 
// or  sum.x = x + r.x;
return sum;
}

Answer 1

class OpClass
{
private:
  int x;
public:
 // declare operator+ - i.e. OpClass + OpClass
 // this function will be returning a copy since the expression
 // z = x + y does not modify x or y
 OpClass operator+(OpClass right); // should really be const!
};

OpClass OpClass::operator+(OpClass r)
{  
  // this part is actually garbage.
  OpClass sum;
  sum.x = this->x + r.x; 
  // or  sum.x = x + r.x;
  return sum;
}

这是正确完成的方法：

class OpClass
{
private:
  int x;
public:
 // always perform binary operations in terms of +=, -=, *= etc
 OpClass& operator+=(const OpClass& r) {
   x += r.x;
   return *this;
 }

};

// define binary operators in terms of unary

OpClass operator+(OpClass l, const OpClass& r)
{
  // note that the l argument is implicitly a copy
  l.x += r.x;
  return l;
}