重载'operator ++'必须是一元或二元运算符(有3个参数)

Question

我有一个头文件和一个.cpp文件.我试图实现前缀和后缀运算符重载,但我在设置重载时不断收到此错误.

fraction.h

#ifndef FRACTION_H
#define FRACTION_H

#include <iostream>

using namespace std;

class Fraction 
{
   public:
      Fraction();
      Fraction(int, int);
      int getTop() {return m_top;}
      int getBottom() {return m_bottom;}
      void set(int t, int b) {m_top=t; m_bottom=b; reduce();
      }

   protected:
   private:
      void reduce();
      int gcf(int, int);

      int m_top;
      int m_bottom;
};

Fraction& operator ++ (Fraction);
Fraction operator++(Fraction, int);

#endif

Main.cpp的

#include <iostream>

using namespace std;
#include "fraction.h"

int main {
   cout << "The fraction is" << f;
   cout << "The output of ++f is " << (++f) << endl;
   cout << "The fraction is" << f;
   cout << "The output of f++ is " << (f++) << endl;
   cout << "The fraction is" << f;

   return 0;
}

Fraction& Fraction::operator ++ (Fraction){
   // Increment prefix
   m_top += m_bottom;
   return *this;
}

Fraction Fraction::operator ++ (Fraction, int){
   //Increment postfix
}

这是我得到的两个错误:

 prefix error: "Parameter of overloaded post-increment operator must have type 'int' (not 'Fraction')"

postfix error: "Overloaded 'Operator++' must be a unary or binary operator (has 3 parameters)"

前缀错误实际上是我的ide错误吗？我知道后增量必须是'int',但我试图做一个预增量.我用xcode.

Answer 1

您将类外部的运算符声明为非类函数

Fraction& operator ++ (Fraction);
Fraction operator++(Fraction, int);

但是，然后您尝试像类成员函数一样定义它们

Fraction& Fraction::operator ++ (Fraction){
   // Increment prefix
   m_top += m_bottom;
   return *this;
}

Fraction Fraction::operator ++ (Fraction, int){
   //Increment postfix
}

通过以下方式将它们声明为类成员函数

class Fraction
{
public:
    Fraction & operator ++();
    Fraction operator ++( int );
    //...

在这种情况下，预自增运算符的定义可以如下所示

Fraction & Fraction::operator ++(){
   // Increment prefix
   m_top += m_bottom;
   return *this;
}

或者将它们声明为非类函数，它们是类的友元，因为它们需要访问类的私有数据成员

class Fraction
{
public:
    friend Fraction & operator ++( Fraction & );
    friend Fraction operator ++( Fraction &, int );
    //...

在这种情况下，预自增运算符的定义可以如下所示

Fraction & operator ++( Fraction &f ){
   // Increment prefix
   f.m_top += f.m_bottom;
   return f;
}