声明与 "void Complex::add(Complex &right)" 不兼容

// Lab 4: Complex.h
#ifndef COMPLEX_H
#define COMPLEX_H

/* Write class definition for Complex */
class Complex {
public:
    Complex(double, double);
    Complex();
    void add(Complex &right);
    void subtract(Complex &right);
    void setComplexNumber(double,double);
    void printComplex();

private:
    double imaginaryPart;
    double realPart;
};

#endif

.h文件是这样

// Lab 4: Complex.cpp
// Member-function definitions for class Complex.
#include <iostream> 
using namespace std; 

#include "Complex.h"

Complex::Complex( double real, double imaginary )
{ 
   setComplexNumber( real, imaginary ); 
} // end Complex constructor
Complex Complex::add(  Complex &right )
{
    Complex num;
    num.imaginaryPart = imaginaryPart + right.imaginaryPart;
    num.realPart = realPart + right .realPart;
    return num;
   /* Write a statement to return a Complex object. Add
      the realPart of right to the realPart of this Complex
      object and add the imaginaryPart of right to the
      imaginaryPart of this Complex object */
} // end function add

Complex Complex ::subtract(Complex& right)//然后这个地方报错   
//声明与 "void Complex::add(Complex &right)" (已声明 所在行数:10，所属文件:"C:\USERS\86182\DESKTOP\Complex.h") 不兼容    Project19    C:\Users\86182\Desktop\Complex.cpp    12    

{
    Complex num;
    num.imaginaryPart = imaginaryPart - right.imaginaryPart;
    num.realPart = realPart - right.realPart;
    return num;
   /* Write a statement to return a Complex object. Subtract
      the realPart of right from the realPart of this Complex
      object and subtract the imaginaryPart of right from
      the imaginaryPart of this Complex object */
} // end function subtract

void Complex::printComplex()
{
   cout << '(' << realPart << ", " << imaginaryPart << ')';
} // end function printComplex

void Complex::setComplexNumber( double rp, double ip ) 
{
   realPart = rp;
   imaginaryPart = ip;
} // end function setComplexNumber 

你的声明是void 实现却有返回值。

返回值不对一个是void,一个是complex