exch.cpp

#include <stdexcept>
#include <iostream>
using namespace std;

class base//:public exception
{
private:
	double x;
	double y;
public:
	explicit base(double a,double b):x(a),y(b){};
	virtual void show()const
	{
		cout<<x<<" and  "<<y<<"  ";	
	}
};


class bad_hmean:public base
{;
public:
	explicit bad_hmean(double a,double b):base(a,b)
	{};
	virtual void show()const
	{
		base::show();
		cout<<"should not be x=-y "<<endl;
	}
};
class bad_gmean:public base
{
public:
	explicit bad_gmean(double a,double b):base(a,b){};
	virtual void  show()const
	{
		base::show();
		cout<<"should be >=0"<<endl;
	}
};

main153.cpp

#include <iostream>
#include "exch.cpp"
using namespace std;

double hmean(double x,double y)
{
	//if(x=-y)别写成了我这样哈
	if(x==-y)
		throw bad_hmean(x,y);
	else
		return 2.0*x*y/(x+y);
};
double gmean(double x,double y)
{
	if(x<0||y<0)
		throw bad_gmean(x,y);
	else
		return sqrt(x*y);
};
void main153()
{
	double x,y,z;
	cout<<"Enter two numbers:";
	while(cin>>x>>y)
	{
		try{
			z=hmean(x,y);
			cout<<"Harmonic mean of "<<x<<"  and  "<<y
				<<"  is  "<<z<<endl;
			cout<<"Geometric mean of "<<x<<"  and  "<<y
				<<" is "<<gmean(x,y)<<endl;
			cout<<"Enter the next set of numbers <q to quit>:";
		}
		catch(base &b)
		{
			b.show();
			//h.what();
			//cout<<h.what()<<endl;
		}
		/*
		catch(bad_hmean &h)//会在这里捕获
		{
			h.show();
		}*/
		catch(bad_gmean &g)
		{
			g.show();
			//cout<<g.what()<<endl;
		}
		cin.get();

	}

	cout<<"Bye"<<endl;
		cin.get();

}