c++中重载输入运算符的问题

我最近开始学习C++，遇到了使用重载输入运算符的问题>gt；。

我正在写一个描述复数的类。我的问题是：如果我把main((放在Complex.cpp中，我的程序就会正常运行。但如果我创建了一个新的文件main.cpp并将main((放在那里，我就会出错。

错误：二进制表达式("st:：istream"(又名"basic_stream"(和"Complex"(的操作数无效

候选函数不可行：第一个参数没有从"std:：istream"(又名"basic_stream"(到"std:"istream*(又名"asic_istream*"(的已知转换；用&

(下面还有很多错误，但它们指向istream，所以我认为这不是问题所在(

这是我的头文件：

#include <iostream>
using namespace std;
#ifndef HEADER_H
#define HEADER_H
#endif // HEADER_H
class Complex
{
public:
double _real;
double _imag;
public:
Complex(double, double);
double getReal() const;
double getImag() const;
void setReal(double);
public:
Complex operator=(const Complex&);
Complex * operator+(const Complex&);
Complex * operator+(const double&);
friend Complex * operator+(const double&, const Complex&);
Complex * operator++();
Complex * operator++(int);
Complex * operator--();
Complex * operator--(int);
operator double() const;
friend ostream &operator<<(ostream*, const Complex&);
friend istream &operator>>(istream*, Complex&);
};

我创建了Complex.cpp来识别函数：

#include "Complex.h"
using namespace std;
Complex::Complex(double a, double b)
{
this->_real = a;
this->_imag = b;
}
double Complex::getReal() const{...}
void Complex::setReal(double x){...}
double Complex::getImag() const{...}
Complex Complex::operator=(const Complex& other){...}
Complex * Complex::operator+(const Complex& other){...}
Complex * Complex::operator+(const double &other){...}
Complex * operator+(const double &first, const Complex &second){...}
Complex * Complex::operator++(){...}
Complex * Complex::operator++(int){...}
Complex * Complex::operator--(){...}
Complex * Complex::operator--(int){...}
Complex::operator double() const{...}
ostream &operator<<(ostream &output, const Complex &comp)
{
output << comp._real << " + " << comp._imag << "i";
return output;
}
istream &operator>>(istream &input, Complex &comp)
{
input >> comp._real >> comp._imag;
return input;
}

这是我的主要：

#include "Complex.h"
int main()
{
Complex com4(0,0);
cout << "Input Complex: ";
cin >> com4;
cout << com4 <<endl;
}