8_2.cpp

来自「c++书籍的源代码」· C++ 代码 · 共 61 行

#include<iostream.h>
 class fraction
{
 public:
	fraction(int x=1,int y=1);
    friend fraction& operator +(fraction& c1,fraction& c2);//运算符+重载为友元函数
    friend fraction& operator ++(fraction& s);//前缀运算符++重载为友元函数
    friend fraction& operator ++(fraction& s,int);//后缀运算符++重载为友元函数
	friend ostream& operator <<(ostream& out,const fraction& s);//<<重载为友元函数
 private:
	int a;
	int b;
};
 fraction::fraction(int x,int y)
{
	if(y==0)
	 b=1;
	else
	 b=y;
	a=x;
    cout<<"构造函数被调用"<<endl;
}
 fraction& operator +(fraction& c1,fraction& c2)
{
	int m,n;
	n=c1.b*c2.b;
	m=c1.a*c2.b+c1.b*c2.a;
    return(fraction(m,n));
}
 fraction& operator ++(fraction& s)
{
	s.a=s.a+s.b;
	cout<<"前缀运算符++"<<endl;
	return(s);
}
 fraction& operator ++(fraction& s,int)
{
	fraction temp;
	temp=s;
	s.a=s.a+s.b;
	cout<<"后缀运算符++"<<endl;
	return(fraction(temp.a,temp.b));
}
 ostream& operator <<(ostream& out,const fraction& s)
{
	cout<<s.a<<"/"<<s.b;
	return(out);
}
 int main()
{
    fraction x(3,4),y(1,2),z;
	z=x+y;
	cout<<"z="<<z<<endl;
	z=++x;
	cout<<"x="<<x<<" z="<<z<<endl; 
	z=y++;
    cout<<"y="<<y<<" z="<<z<<endl;
	return(0);
}