运算符重载----有理数类

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/*
定义一个有理数类Rational，重载算术运算符。写一个完整的程序，测试各种运算符的使用，要求输出化简后的计算结果，注意分母不能为零！
测试代码样例：
Rational A(2,6),B(1,-2),C;
C = -A;  
C.print( );//输出1/3   
C = A + B ;  
C.print( );  //输出-1/6
C = C*A/B;  
C.print( );   
C =  ++A ;   
A.print( ); 
C.print( ); 
C =  B-- ;    
B.print( );
C.print(  );
*/
#include<iostream.h>
class Rational
{
public:
Rational(int nn=1,int mm=1);
void print();
void simple();  
Rational  operator+(Rational & a);	//加法
friend  Rational  operator-(Rational & a,Rational & b);//减法
friend  Rational  operator*(Rational & a,Rational & b);//乘法
friend  Rational  operator/(Rational & a,Rational & b);//除法
Rational  operator-();//取反
Rational &  operator ++ ();//r=++r1
Rational  operator ++ (int);//r = r1++
Rational &  operator -- ();//r=--r1
Rational  operator -- (int);//r = r1--
operator double();
friend ostream& operator<<(ostream& output, Rational& a);
bool operator<(Rational &);
friend bool operator==(Rational& ,Rational& );
private:
int m;   // 分母 
int n;   // 分子
};
Rational:: Rational(int nn,int mm )
{
m= (mm!=0) ? mm:1;
n=nn; 
}
// r = r1 + r2 ; 
Rational Rational::operator+(Rational & A)
{
Rational C;
C.n = n*A.m+m*A.n;
C.m = m*A.m;
C.simple();
return C;
}
Rational Rational::operator-()
{  
Rational C(-n,m); 
C.simple();
return C;
}
// r = r1 - r2 ; 
Rational operator-(Rational & A,Rational & B)
{
Rational C;
C.n = A.n*B.m-A.m*B.n;
C.m = A.m*B.m;
C.simple();
return C;
}
// r = r1 * r2 ; 
Rational operator*(Rational & A,Rational & B)
{
Rational C;
C.n = A.n*B.n;
C.m = A.m*B.m;
C.simple();
return C;
}
// r = r1 / r2 ; 
Rational operator/(Rational & A,Rational & B)
{
Rational C;
C.n = A.n*B.m;
C.m = A.m*B.n;
C.simple();
return C;
}
//r = ++r1;
Rational&  Rational::operator++()
{ 
n = n+m;
return *this;
}
//r = r1++;
Rational Rational::operator++(int)
{ 
Rational C(n,m);
n+=m;
return C; 
}
//r = --r1;
Rational&  Rational::operator--()
{ 
n = n-m;
return *this;
}
//r = r1--;
Rational Rational::operator--(int)
{ 
Rational C(n,m);
n-=m;
return C; 
}
Rational::operator double()
{
return (double)n/m;  
}
// r1>r2
bool Rational::operator<(Rational& a)
{
return double(n)/m >(double)a.n/a.m ? true : false;
}
//r1==r2
bool operator==(Rational& a,Rational&b )
{
return double(a.n)/a.m == (double)b.n/b.m ? true : false;
}
//cout<<r;
ostream& operator<<(ostream& output, Rational& a)
{
//output<<(double)a.n/a.m<<endl;
if(a.m<0)  
output<<"The value is "<< -a.n <<'/'<<-a.m<<endl;
else
output<<"The value is "<< a.n <<'/'<<a.m<<endl;
return output;
}
void Rational::print()
{
simple();
if(m<0)
cout<<"The value is "<< -n <<'/'<<-m<<endl;
else
cout<<"The value is "<< n <<'/'<<m<<endl;
}
void  Rational::simple()
{
int a = m ,b = n, r = 0;
if(m<n)
{
a = n;
b = m;
}
r = a % b ;			
while ( r != 0 )
{
a = b ;
b = r ; 
r = a % b ;	
}	
n /= b;
m /= b;
}
void main()
{
Rational A(2,6),B(1,-2),C;
C = -A;
C.print();// -1/3   
C = A + B;
C.print();// -1/6
C = C*A/B;  
C.print();// 1/9
C =  ++A ;
A.print();// 4/3
C.print();// 4/3
C =  B-- ;
B.print();// -3/2
C.print();// -1/2
}