模板化运算符重载技巧

Question

Is there a way to by using some metaprogramming trick make situation like this works:

int* get();//this fnc returns pointer to int OR nullptr
int k = 1;
//this is the operator which is supposed to compare value and pointer
template<class T>
bool operator!=(const T& left, const T* right)
{
    if (right)
    {
        return left != *right;
    }
    else
    {
        return false;
    }
}


//And this is the code fragment which interests me most  
if (k != get())
{
    ///

}

The crux is that I would like NOT TO change this line k != get() and yet for some reason my operator!= seems not to work. What's the problem?

Answer 1

You can only overload operators with at least one user-defined type as an argument. Neither int nor int* are user-defined types.

Answer 2

您不能为内置类型重载运算符。

Answer 3

As already mentioned in other answers that you cannot have operator != for non userdefined types like int , char and so on.

One option is to wrap int inside your user defined struct and achieve the goal.

struct Int
{
  int i;
  // define all the necessary operators/constructor who deal with 'int'
  Int(int x) : i(x) {}
  bool operator != (const int* right)
  {
    return (right)? (i != *right) : false;
  }
};

Now declare

Int k = 1;