c++運算符重載+實例

【項目2拓展2（思考）】這個思考題吊一下大家的胃口：設定義了兩個分數類的對象，如CFraction c1, c2。如果定義了int i，我們能用cin>>i>>j;在鍵盤上輸入i和j的值，是否期望用cin>>c1>>c2;輸入分數呢？同理，用cout<<c1<<c2;進行輸出，可以嗎？進一步，用c1+c2得到新的一個分數，用c1/c2實現兩個分數的除法，以及其他加、減、比較、求倒數等也是理所當然的。實際上，要自定義分數類，這些直觀的基本運算應該要實現，這叫運算符的重載。本任務中用amplify()給出了“放大”運算的一種實現方案，更多內容值得期待地。

首先要說明：有的C++編譯系統（如VC++6.0）沒有完全實現C++標准，它所提供的後綴.h的頭文件不支持把成員函數重載為友元函數，因此在VC++6.0，應把程序的頭兩行：

#include <iosteam>

using namespace std;

改為一行：#include <iosteam.h>   //C語言的風格

這是我自己編寫的有關運算符重載的程序：

[cpp]
#include <iostream.h>  
 
enum style_enum{zero, one, two, three }; 
 
class CFraction 
{private: 
    int nume;  // 分子  
    int deno;  // 分母  
 public: 
     CFraction(int nu=0,int de=1):nume(nu),deno(de){}   //構造函數，初始化用  
 
    void simplify();                //化簡（使分子分母沒有公因子）  
 
    //輸入輸出重載  
    friend ostream& operator<<(ostream &out,const CFraction &cf); 
    friend istream& operator>>(istream &in,CFraction &cf); 
     
    //加減乘除，結果需要化簡  
    friend CFraction operator+(const CFraction &lcf,const CFraction &rcf); 
    friend CFraction operator-(const CFraction &lcf,const CFraction &rcf); 
    friend CFraction operator*(const CFraction &lcf,const CFraction &rcf); 
    friend CFraction operator/(const CFraction &lcf,const CFraction &rcf); 
     
    //關系運算符  
    friend bool operator>(const CFraction &lcf,const CFraction &rcf); 
    friend bool operator<(const CFraction &lcf,const CFraction &rcf); 
    friend bool operator>=(const CFraction &lcf,const CFraction &rcf); 
    friend bool operator<=(const CFraction &lcf,const CFraction &rcf); 
    friend bool operator==(const CFraction &lcf,const CFraction &rcf); 
    friend bool operator!=(const CFraction &lcf,const CFraction &rcf); 
 
 
    //取+、-一目運算符  
    CFraction operator+(); 
    CFraction operator-(); 
}; 
 
 
 
void CFraction::simplify() 
{ 
    int v1 = nume; 
    int v2 = deno; 
    while(v2) 
    { 
        int temp = v2; 
        v2 = v1 % v2; 
        v1 = temp; 
    } 
    nume /= v1; 
    deno /= v1; 
    if(deno < 0) 
    { 
        deno = -deno; 
        nume = -nume; 
    } 
} 
 
//輸出重載  
ostream& operator<<(ostream &out,const CFraction &cf) 
{ 
    out << cf.nume << '/' << cf.deno; 
    return out; 
} 
 
//輸入重載  
istream& operator>>(istream &in,CFraction &cf) 
{ 
    char ch; 
    while(1) 
    { 
        in >> cf.nume >> ch >> cf.deno; 
        if(cf.deno == 0) 
            cerr << "分母為0請重新輸入\n"; 
        else if(ch != '/') 
            cerr << "格式錯誤（形如m/n）請重新輸入\n"; 
        else break; 
    } 
    return in; 
} 
//加法重載  
CFraction operator+(const CFraction &lcf,const CFraction &rcf) 
{ 
    CFraction cf; 
    cf.nume = lcf.nume*rcf.deno + lcf.deno*rcf.nume; 
    cf.deno = lcf.deno*rcf.deno; 
    cf.simplify(); 
    return cf; 
} 
//減法重載  
CFraction operator-(const CFraction &lcf,const CFraction &rcf) 
{ 
    CFraction cf; 
    cf.nume = lcf.nume*rcf.deno - rcf.nume*lcf.deno; 
    cf.deno = lcf.deno*rcf.deno; 
    cf.simplify(); 
    return cf; 
} 
//乘法重載  
CFraction operator*(const CFraction &lcf,const CFraction &rcf) 
{ 
    CFraction cf; 
    cf.nume = lcf.nume*rcf.nume; 
    cf.deno = lcf.deno*rcf.deno; 
    cf.simplify(); 
    return cf; 
} 
//除法重載  
CFraction operator/(const CFraction &lcf,const CFraction &rcf) 
{ 
    CFraction cf; 
    cf.nume = lcf.nume*rcf.deno; 
    cf.deno = lcf.deno*rcf.nume; 
    cf.simplify(); 
    return cf; 
} 
//取正重載  
CFraction CFraction::operator+() 
{ 
    simplify(); 
    if(nume < 0) 
        nume = -nume; 
    return *this; 
} 
//取負重載  
CFraction CFraction::operator-() 
{ 
    simplify(); 
    nume = -nume; 
    return *this; 
} 
 
 
//大於號重載  
bool operator>(const CFraction &lcf,const CFraction &rcf) 
{ 
    int l_nume = lcf.nume * rcf.deno; 
    int r_nume = rcf.nume * lcf.deno; 
    int common_deno = lcf.deno * rcf.deno; 
    if((l_nume-r_nume) * common_deno > 0) return true; 
    return false; 
} 
 
//小於號重載  
bool operator<(const CFraction &lcf,const CFraction &rcf) 
{ 
    return !(lcf > rcf); 
} 
 
//等於重載  
bool operator==(const CFraction &lcf,const CFraction &rcf) 
{ 
    return lcf.nume==rcf.nume && lcf.deno == rcf.deno; 
} 
 
//不等於重載  
bool operator!=(const CFraction &lcf,const CFraction &rcf) 
{ 
    return !(lcf==rcf); 
} 
 
//  
bool operator>=(const CFraction &lcf,const CFraction &rcf) 
{ 
    if(lcf < rcf) return false; 
    return true; 
} 
 
//  
bool operator<=(const CFraction &lcf,const CFraction &rcf) 
{ 
    if(lcf > rcf) return false; 
    return true; 
} 
 
int main() 
{ 
    CFraction cf1; 
    CFraction cf2; 
    cin >> cf1 >> cf2; 
    cout << "cf1: "<< cf1 << '\t' << "cf2: "<< cf2 << endl 
         << "cf1 + cf2 : " << cf1+cf2 << endl 
         << "cf1 - cf2 : " << cf1-cf2 << endl 
         << "cf1 * cf2 : " << cf1*cf2 << endl 
         << "cf1 / cf2 : " << cf1/cf2 << endl 
         << " +cf1 :     " << +cf1    << endl 
         << " -cf1 :     " << -cf1    << endl 
         << " +cf2 : 　　" << +cf2    << endl 
         << " -cf2 :     " << -cf2    << endl 
         << " cf1 > cf2? 1/YES 0/NO " << (cf1 > cf2) << endl 
         << " cf1 < cf2? 1/YES 0/NO " << (cf1 < cf2) << endl 
         << " cf1 == cf2? 1/YES 0/NO " << (cf1 == cf2) << endl 
         << " cf1 != cf2? 1/YES 0/NO " << (cf1 != cf2) << endl 
         << " cf1 >= cf2? 1/YES 0/NO " << (cf1 >= cf2) << endl 
         << " cf1 <= cf2? 1/YES  
 
    
    return 0; 
} 

#include <iostream.h>

enum style_enum{zero, one, two, three };

class CFraction
{private:
 int nume;  // 分子
 int deno;  // 分母
 public:
  CFraction(int nu=0,int de=1):nume(nu),deno(de){}   //構造函數，初始化用

 void simplify();    //化簡（使分子分母沒有公因子）

 //輸入輸出重載
 friend ostream& operator<<(ostream &out,const CFraction &cf);
    friend istream& operator>>(istream &in,CFraction &cf);
   
    //加減乘除，結果需要化簡
 friend CFraction operator+(const CFraction &lcf,const CFraction &rcf);
 friend CFraction operator-(const CFraction &lcf,const CFraction &rcf);
 friend CFraction operator*(const CFraction &lcf,const CFraction &rcf);
 friend CFraction operator/(const CFraction &lcf,const CFraction &rcf);
   
 //關系運算符
 friend bool operator>(const CFraction &lcf,const CFraction &rcf);
 friend bool operator<(const CFraction &lcf,const CFraction &rcf);
 friend bool operator>=(const CFraction &lcf,const CFraction &rcf);
 friend bool operator<=(const CFraction &lcf,const CFraction &rcf);
 friend bool operator==(const CFraction &lcf,const CFraction &rcf);
 friend bool operator!=(const CFraction &lcf,const CFraction &rcf);

 //取+、-一目運算符
 CFraction operator+();
 CFraction operator-();
};

void CFraction::simplify()
{
 int v1 = nume;
 int v2 = deno;
 while(v2)
 {
  int temp = v2;
  v2 = v1 % v2;
  v1 = temp;
 }
 nume /= v1;
 deno /= v1;
 if(deno < 0)
 {
  deno = -deno;
  nume = -nume;
 }
}

//輸出重載
ostream& operator<<(ostream &out,const CFraction &cf)
{
 out << cf.nume << '/' << cf.deno;
 return out;
}

//輸入重載
istream& operator>>(istream &in,CFraction &cf)
{
 char ch;
 while(1)
 {
  in >> cf.nume >> ch >> cf.deno;
  if(cf.deno == 0)
   cerr << "分母為0請重新輸入\n";
  else if(ch != '/')
   cerr << "格式錯誤（形如m/n）請重新輸入\n";
  else break;
 }
 return in;
}
//加法重載
CFraction operator+(const CFraction &lcf,const CFraction &rcf)
{
 CFraction cf;
 cf.nume = lcf.nume*rcf.deno + lcf.deno*rcf.nume;
 cf.deno = lcf.deno*rcf.deno;
 cf.simplify();
 return cf;
}
//減法重載
CFraction operator-(const CFraction &lcf,const CFraction &rcf)
{
 CFraction cf;
 cf.nume = lcf.nume*rcf.deno - rcf.nume*lcf.deno;
 cf.deno = lcf.deno*rcf.deno;
 cf.simplify();
 return cf;
}
//乘法重載
CFraction operator*(const CFraction &lcf,const CFraction &rcf)
{
 CFraction cf;
 cf.nume = lcf.nume*rcf.nume;
 cf.deno = lcf.deno*rcf.deno;
 cf.simplify();
 return cf;
}
//除法重載
CFraction operator/(const CFraction &lcf,const CFraction &rcf)
{
 CFraction cf;
 cf.nume = lcf.nume*rcf.deno;
 cf.deno = lcf.deno*rcf.nume;
 cf.simplify();
 return cf;
}
//取正重載
CFraction CFraction::operator+()
{
 simplify();
 if(nume < 0)
  nume = -nume;
 return *this;
}
//取負重載
CFraction CFraction::operator-()
{
 simplify();
 nume = -nume;
 return *this;
}

//大於號重載
bool operator>(const CFraction &lcf,const CFraction &rcf)
{
 int l_nume = lcf.nume * rcf.deno;
 int r_nume = rcf.nume * lcf.deno;
 int common_deno = lcf.deno * rcf.deno;
 if((l_nume-r_nume) * common_deno > 0) return true;
 return false;
}

//小於號重載
bool operator<(const CFraction &lcf,const CFraction &rcf)
{
 return !(lcf > rcf);
}

//等於重載
bool operator==(const CFraction &lcf,const CFraction &rcf)
{
 return lcf.nume==rcf.nume && lcf.deno == rcf.deno;
}

//不等於重載
bool operator!=(const CFraction &lcf,const CFraction &rcf)
{
 return !(lcf==rcf);
}

//
bool operator>=(const CFraction &lcf,const CFraction &rcf)
{
 if(lcf < rcf) return false;
 return true;
}

//
bool operator<=(const CFraction &lcf,const CFraction &rcf)
{
 if(lcf > rcf) return false;
 return true;
}

int main()
{
 CFraction cf1;
 CFraction cf2;
 cin >> cf1 >> cf2;
 cout << "cf1: "<< cf1 << '\t' << "cf2: "<< cf2 << endl
   << "cf1 + cf2 : " << cf1+cf2 << endl
   << "cf1 - cf2 : " << cf1-cf2 << endl
   << "cf1 * cf2 : " << cf1*cf2 << endl
   << "cf1 / cf2 : " << cf1/cf2 << endl
   << " +cf1 :     " << +cf1    << endl
   << " -cf1 :     " << -cf1    << endl
   << " +cf2 : 　　" << +cf2    << endl
   << " -cf2 :     " << -cf2    << endl
   << " cf1 > cf2? 1/YES 0/NO " << (cf1 > cf2) << endl
   << " cf1 < cf2? 1/YES 0/NO " << (cf1 < cf2) << endl
   << " cf1 == cf2? 1/YES 0/NO " << (cf1 == cf2) << endl
   << " cf1 != cf2? 1/YES 0/NO " << (cf1 != cf2) << endl
   << " cf1 >= cf2? 1/YES 0/NO " << (cf1 >= cf2) << endl
   << " cf1 <= cf2? 1/YES

  
 return 0;
}