如何修复分数类的重载+运算符的输出？

我对我的fractionType类有疑问。我正在为赋值进行编码，并且赋值要求我将基本算术运算符（+，-，/，*），逻辑运算符（==，<，>，= <，=>）和系统运算符（<< ，>>）到目前为止，我有系统运算符以及乘法和除法运算符。当我测试+和-运算符时出现了我的问题。我的输入被硬编码为2/4和1/8，但是我的输出是3/8。这个不对。

我的来自fractionType.cpp的代码

#include <iostream>
#include "fractionType.h"

fractionType::fractionType(){
}
fractionType::fractionType(int a, int b) {
  numerator = a;
  denominator = b;
}
fractionType fractionType::operator+(fractionType fraction) {
  fractionType anotherFraction;
  if (denominator = fraction.denominator) {

      anotherFraction.numerator = numerator + fraction.numerator;

      anotherFraction.denominator = denominator;
  }
if (denominator != fraction.denominator) {
    anotherFraction.numerator = ((numerator) * (fraction.denominator)) +         ((fraction.numerator) * (denominator));

    anotherFraction.denominator = denominator * fraction.denominator;
}
return anotherFraction;
}
fractionType fractionType::operator-(fractionType fraction) {

fractionType anotherFraction;

if (denominator = fraction.denominator) {

    anotherFraction.numerator = numerator - fraction.numerator;

    anotherFraction.denominator = denominator;
}
else {
    anotherFraction.numerator = (numerator * fraction.denominator) - (fraction.numerator * fraction.denominator);

    anotherFraction.denominator = denominator * fraction.denominator;
}

return anotherFraction;


}

我的来自fractionType.h的代码

#include <iostream>

class fractionType {
public: 
  fractionType(int a, int b);
  fractionType();
  fractionType operator*(fractionType fraction);
  fractionType operator/(fractionType fraction);
  fractionType operator+(fractionType fraction);
  fractionType operator-(fractionType fraction);
  friend std::ostream& operator<<(std::ostream& out, const fractionType &fraction) {
    out << fraction.numerator << '/' << fraction.denominator;
    return out;
}
friend std::istream& operator>> (std::istream& in, fractionType &fraction) {
    char c;
    in >> fraction.numerator >> c >> fraction.denominator;
    return in;
}
private:
int numerator, denominator;
};
#endif FRACTIONTYPE_H

和我的source.cpp

#include <iostream>
#include "fractionType.h"

int main() {
  fractionType aFraction(2, 4);
  fractionType bFraction(1, 8);
  fractionType cFraction;
  cFraction = aFraction + bFraction;
  std::cout << cFraction << std::endl;
  system("PAUSE");
}

我删除了操作员*和操作员/，因为它们可以正常工作。我不知道我做错了什么，在我发布这个问题之前，我已经一遍又一遍地研究了数学。是因为我没有使用指针吗？一个const？还是有所不同？在此先感谢您的帮助！