operator& 返回一个 int 并对 2 个向量进行操作？

Question

I would like to define an & operator between two std::vector<int> . This operator should bit-wise and each element of both vectors together and return the number of non-zero components of the resulting vector.

However, if I define int operator&(const std::vector<int> &lhs, const std::vector<int> &rhs) , it the compiler doesn't like it and requires operator& to return a boolean. Is this actually a restriction with operator& ?

Answer 1

I would like to define an & operator between two std::vector<int> .

You may not (at least not globally; it can in theory be done in a custom namespace but I recommend against it). Operator overloads for standard templates with no user defined type arguments are reserved to the standard library.

I recommend writing a regular function instead.

Any idea why there's that restriction?

Because this restriction allows the standard library to change and add any operator overload that the committee wishes without breaking previously well defined programs that have their own conflicting overloads (by virtue of not allowing such overloads to be defined).

---

operator& to return a boolean. Is this actually a restriction with operator&?

No. This is actually not a restriction of binary operator&. It may return int .