异常处理.txt

钱能主编 C++程序设计教程（第一版） 该书习题的答案代码

//**************************
//**      ch21_1.cpp      **
//**************************
#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>

void main(int argc,char** argv)
{
	ifstream source(argv[1]);
	char line[128];
	
	try
	{
		if(source.fail())
			throw argv[1];
	}

	catch(char* s)
	{
		cout<<"error opening the file "<<s<<endl;  //实际运行中，不会打印出这行错误信息，而是新建一个空的与argv[1]同名的新文件。
		exit(1);
	}

	while(!source.eof())
	{
		source.getline(line,sizeof(line));
		cout<<line<<endl;
	}
	source.close();
}

//**************************
//**      ch21_2.cpp      **
//**************************
#include <iostream.h>

double Div(double,double);

void main()
{
	try
	{
		cout<<"7.3/2.0="<<Div(7.3,2.0)<<endl;
		cout<<"7.3/0.0="<<Div(7.3,0.0)<<endl;
		cout<<"7.3/1.0="<<Div(7.3,1.0)<<endl;
	}
	catch(double)
	{
		cout<<"except of deviding zero."<<endl;
	}
	cout<<"That is OK!"<<endl;
}

double Div(double a,double b)
{
	if(b==0)
		throw b;
	return a/b;
}

//**************************
//**      ch21_3.cpp      **
//**************************
#include <iostream.h>
#include <string.h>

class String
{
public:
	String(char*,int);

	class Range
	{
	public:
		Range(int j):index(j) {}
		int index;
	};

	class Size{};

	char& operator [] (int k)
	{
		if(0<=k && k<len)
			return p[k];
		throw Range(k);
	}
	private:
		char* p;
		int len;
		static int max;
};
int String::max=20;

String::String(char* str,int si)
{
	if(si<0||max<si)
		throw Size();

	p=new char[si];
	strncpy(p,str,si);
	len=si;
}
void g(String& str)
{
	int num=10;
	for(int n=0;n<num;n++)
		cout<<str[n];
	cout<<endl;
}
void f()
{
	//code segment 1
	try
	{
		//code segment 2
		String s("abcdefghijklmnopqrstuvwxyz",10);
		g(s);
	}
	catch(String::Range r)
	{
		cerr<<"->out of range:"<<r.index<<endl;
		//code segment 3
	}
	catch(String::Size)
	{
		cerr<<"size illegal!"<<endl;
	}
	cout<<"The program will be continued here."<<endl;
	//code segment 4
}

void main()
{
	//code segment 5
	f();
	cout<<"These code is not effected by probably exception in f()."<<endl;
}