算术运算符 (+) 运算符是否会同时检查 return 类型和传递的参数？

Question

#include<iostream>
using namespace std;
class B;
class A {
private:
    int a,b;
public:
    A() {
        a=b=10;
    }
    void show() {
        cout<<"Hello of A: \n a:"<<a<<"  b:"<<b;
    }
friend  A operator+( A AA ,B BB) ;
friend  B operator+ ( B BB,A AA);
friend  B operator+( A AAA ,B BB) ; 
};
class B {
private:
    int c,d;
public:
    B() {
        c=d=20;
    }
    void show() {
        cout<<"\nHello of B: \n c:"<<c<<" d:"<<d;
    }
friend  A operator+ ( A AA,B BB);
friend  B operator+ ( B BB, A AA);
friend  B operator+( A AA ,B BB) ;
};
A operator+(A AA ,B BB) {
         A temp ;
         temp.a = AA.a + BB.c;
         temp.b = AA.b + BB.d; 
         return temp;
}
B operator+( B BB, A AA) {
        B temp;
        temp.c = AA.a+BB.c;
        temp.d = AA.b+BB.d;
        return temp;
} 

int main() {
class A aa;class B bb;
class A aa1 = aa + bb;
aa1.show();
class B bb1 = bb + aa;
bb1.show() ;
}

你好，我刚试过这个程序，作为朋友 A operator+ ( A AA,B BB) 出现了编译错误；再次被重新定义为 friend B operator+ ( A AA,B BB)；据我了解，重载将同时检查 return 类型和传递的参数。但是在这里我不确定为什么我会收到编译时错误标记，函数重新定义已完成！！有人可以帮帮我！！

以下是我在 unix 终端中尝试运行时遇到的错误，

CC overloading.cpp

"overloading.cpp"，第 17 行：错误：operator+(A, B), returning B, was previously declared returning A. "overloading.cpp"，第 29 行：错误：operator+(A, B), returning A, was previously declared returning B. "overloading.cpp"，第 31 行：错误：operator+(A, B), returning B, was previously declared returning A. "overloading.cpp"，第 33 行：错误：operator+(A, B), returning A, was previously declared returning B. "overloading.cpp"，第 45 行：错误："operator+(A, B)" 和 "operator+(A, B)" 之间的重载歧义。检测到 5 个错误。 #

以及如何使用 class B b2 = aa + bb;在上面的代码中 ?

Answer 1

return 类型的函数不参与重载决策。只有函数名和参数列表（以及成员函数的 cv 限定符）才重要。但是我在您的代码中看不到多个 definition 。错误是您用不同的 return 类型重新声明了相同的函数：

friend  A operator+( A AA ,B BB) ;
friend  B operator+( A AAA ,B BB) ; // same function, different return type!

算术运算符 (+) 运算符是否会同时检查 return 类型和传递的参数？

Arithmentic operator(+) operator will check both return type and passing arguments or not?

c++

visual-c++

c++11

CC overloading.cpp