10_2.cpp

c++书籍的源代码

#include<iostream.h>
#include<iomanip.h>
 class Zero
{
 public:
   void print(void);
};
 void Zero::print(void)
{
  cout<<"分数对象的分母不能为零!"<<endl; 
}
 class fraction
{
 public:
	fraction(int x=1,int y=1);
	~fraction();
	friend ostream& operator <<(ostream& out,const fraction& s);
    fraction& operator +(fraction& c);
 private:
	int a;
	int b;
};
 fraction::fraction(int x,int y)
{
	if(y==0)
	{
		cout<<"分母是零，抛出异常"<<endl;
		throw Zero();
	}
	a=x;
	b=y;
}
 fraction::~fraction()
{
	cout<<"分数对象消失"<<endl;
}
 fraction& fraction::operator +(fraction& c)
{
	fraction temp;
	temp.b=b*c.b;
	temp.a=a*c.b+b*c.a;
	return (temp);
}
 ostream& operator <<(ostream& out,const fraction& s)
{
	out<<s.a<<"/"<<s.b;
    return(out); 
}
 int main()
{
 try
 {
  fraction x(3,4),y(1,2),z;
  z=x+y;
  cout<<z<<endl;
 }
 catch(Zero z)
 {
  z.print(); 
 }
 cout<<"程序结束"<<endl; 
 return(0);
}