C++ 覆盖全局运算符逗号给出错误

Question

第二个函数给出错误 C2803 http://msdn.microsoft.com/en-us/library/zy7kx46x%28VS.80%29.aspx :“operator”必须至少有一个类类型的形式参数。有什么线索吗？

template<class T,class A = std::allocator<T>> 
class Sequence : public std::vector<T,A> {
 public:
    Sequence<T,A>& operator,(const T& a) {
        this->push_back(a);
        return *this;
    }
    Sequence<T,A>& operator,(const Sequence<T,A>& a) {
        for(Sequence<T,A>::size_type i=0 ; i<a.size() ; i++) {
            this->push_back(a.at(i));
        }
        return *this;
    }
};

//this works!
template<typename T> 
Sequence<T> operator,(const T& a, const T&b) {
    Sequence<T> seq;
    seq.push_back(a);
    seq.push_back(b);
    return seq;
}

//this gives error C2803!
Sequence<double> operator,(const double& a, const double& b) {
    Sequence<double> seq;
    seq.push_back(a);
    seq.push_back(b);
    return seq;
}

Answer 1

在 C++ 中，如果运算符的至少一个参数不是自定义类或非像枚举这样的原始类型，则不能重载运算符。您不能为 int 类型重载 +，同样，您也不能为 double 类型重载 ,。