io流.txt

钱能主编 C++程序设计教程（第一版） 该书习题的答案代码

//**************************
//**      ch19_1.cpp      **
//**************************
#include <iostream.h>

void fn(int a,int b)
{
	if(b==0)
		cerr<<"zero encountered."
			<<"The message cannot be redirected."<<endl;
	else
		cout<<a/b<<endl;
}

void main()
{
	fn(20,2);
	fn(20,0);
}

//**************************
//**      ch19_2.cpp      **
//**************************
#include <fstream.h>

void fn()
{
	ofstream myf("e:\\c++\\myname.txt");
	myf<<"In each of the following questions, a related pair"<<endl
		<<"of words or phrases is followed by five lettered pairs"<<endl
		<<"of words or phrases."<<endl;
}

void main()
{
	fn();
}

//**************************
//**      ch19_3.cpp      **
//**************************
#include <iostream.h>
#include <strstrea.h>

char* parseString(char* pString)
{
	istrstream inp(pString,0);
	int aNumber;
	float balance;
	inp>>aNumber>>balance;
	char* pBuffer = new char[128];
	ostrstream outp(pBuffer,128);
	outp<<"a Number = "<<aNumber
		<<", balance = "<<balance;
	return pBuffer;
}
void main()
{
	char* str="1234 100.35";
	char* pBuf=parseString(str);
	cout<<pBuf<<endl;
	delete []pBuf;
}

//**************************
//**      ch19_4.cpp      **
//**************************
#include <iostream.h>

void fn(float interest,float amount)
{
	cout<<"RMB amount = ";
	cout.precision(2);
	cout<<amount;
	cout<<endl<<"the interest = ";
	cout.precision(4);
	cout<<interest<<endl;
}

void main()
{
	float f1=29.45167894;
	float f2=12.5645678;
	fn(f1,f2);
}

//**************************
//**      ch19_5.cpp      **
//**************************
#include <iostream.h>
#include <iomanip.h>

void fn(float interest,float amount)
{
	cout<<"RMB amount = ";
	cout<<setprecision(2)<<amount;
	cout<<endl<<"the interest = "
		<<setprecision(4)<<interest<<endl;
}

void main()
{
	float f1=29.45167894;
	float f2=12.5645678;
	fn(f1,f2);
}

//**************************
//**      ch19_6.cpp      **
//**************************
#include <iostream.h>
#include <iomanip.h>

void main()
{
	cout.width(8);
	cout<<10
		<<20<<endl;
}

//**************************
//**      ch19_9.cpp      **
//**************************
#include <iostream.h>
#include <iomanip.h>

void main()
{
	float value = 2.345678;
	int prePrecision;
	prePrecision=cout.precision(4);
	cout<<value<<endl;
	cout.precision(prePrecision);
	cout<<value<<endl;
	cout<<prePrecision<<endl;

}

//***************************
//**      ch19_10.cpp      **
//***************************
#include <iostream.h>

void main()
{
	char str[128];

	cout<<"Type in a line of text and press Enter"<<endl;
	cin.getline(str,sizeof(str),'X');
	cout<<"First line: "<<str<<endl;
	cin.getline(str,sizeof(str));
	cout<<"Second line: "<<str<<endl;
}

//***************************
//**      ch19_11.cpp      **
//***************************
#include <iostream.h>
#include <ctype.h>

void main()
{
	char letter;
	while(!cin.eof())
	{
		letter=cin.get();
		letter=toupper(letter);

		if(letter=='Y')
		{
			cout<<"'Y' be met."<<endl;
			break;
		}
		cout<<letter;
	}
}

//***************************
//**      ch19_13.cpp      **
//***************************
//打开文件的操作
#include <fstream.h>
#include <iostream.h>

void main(int argc, char** argv)
{
	ifstream in(argv[1]);

	if(in.fail())
	{
		cerr<<"Error opening the file: "<<argv[1]<<endl;
		return;
	}
	while(!in.eof())
		cout<<(char)(in.get());

	in.close();
}

//***************************
//**      ch19_14.cpp      **
//***************************
#include <iostream.h>
//#include <fstream.h>
#include <iomanip.h>

class RMB
{
public:
	RMB(double v=0.0)
	{
		yuan=v;
		jf=(v-yuan)*100.0+0.5;
	}
	operator double()
	{
		return yuan+jf/100.0;
	}

	void display(ostream& out)
	{
		out<<yuan<<"."
			<<setfill('0')<<setw(2)<<jf
			<<setfill(' ');
	}
protected:
	unsigned int yuan;
	unsigned int jf;
};

ostream& operator << (ostream& oo, RMB& d)
{
	d.display(oo);
	return oo;
}

void main()
{
	RMB rmb(1.5);
	cout<<"Initially rmb = "<<rmb<<endl;
	rmb=2.1 * rmb;
	cout<<"then rmb = "<<rmb<<endl;

	ofstream out("ab.txt");
	out<<rmb;

	//ofstream out("e:\\c++\\test.txt"); //注意路径的写法
	//out<<rmb;
}
//****************************
//**      ch19_140.cpp      **
//****************************、
//文件及流操作练习
#include <fstream.h>
#include <iostream.h>
//#include <ostream.h>
#include <iomanip.h>

class Currency
{
public:
	Currency(double v=0.0)
	{
		yuan=v;
		jf=(v-yuan)*100.0+0.5;
	}
	virtual void display(ostream& out)=0;
protected:
	unsigned int yuan;
	unsigned int jf;
};

class RMB:public Currency
{
public:
	RMB(double v=0.0):Currency(v){}
	virtual void display(ostream& out)
	{
		out<<yuan<<"."
			<<setfill('0')<<setw(2)<<jf<<setfill(' ')
			<<" RMB";
	}
};

class Dmark: public Currency
{
public:
	Dmark(double v=0.0):Currency(v){};
	virtual void display(ostream& out)
	{
		out<<yuan<<"."
			<<setfill('0')<<setw(2)<<jf<<setfill(' ')
			<<" DM";
	}
};

class WHQ: public RMB
{
public:
	WHQ(double v=0.0): RMB(v) {}
	virtual void display(ostream& out)
	{
		RMB::display(out);
		out<<" WHQ";
	}
};


ostream& operator << (ostream& oo,Currency &c)
{
	c.display(oo);
	oo<<endl;
	return oo;
}

void fn(Currency &c)
{
	cout<<"Deposit is "<<c<<endl;
}

void main()
{
	RMB rmb(5.5);
	fn(rmb);
	WHQ whq(5.6);
	fn(whq);
	Dmark mark(10.6);
	fn(mark);

	ofstream out("test.txt");
	out<<rmb<<whq<<mark;
}

//--------ch19_15.prj--------//
//---------------------------//
//************************
//**      main.cpp      **
//************************
#include <fstream.h>
#include "student.h"
#include "master.h"

void main()
{
	ofstream out("e:\\c++\\ch19\\master.txt");

	Student s1("Dill Arnson",12567,3.5);
	Master s2("Welchi Shammas",12667,4.1,'A');
	Master s3("Portel Braumbel",12579,3.8,'B');

	out<<s1;
	out<<s2;
	out<<s3;
}
//*************************
//**      student.h      **
//*************************
#include <iostream.h>
#include <string.h>

#ifndef STUDENT
#define STUDENT

class Student
{
public:
	Student(char* pS,unsigned num,float g)
	{
		strcpy(pName,pS);
		uID=num;
		grade=g;
	}
	virtual void display(ostream& out);
protected:
	char pName[20];
	unsigned int uID;
	float grade;
};
ostream& operator << (ostream& out,Student& st);
#endif
//***************************
//**      student.cpp      **
//***************************
#include "student.h"
#include <iomanip.h>
#include <iostream.h>

void Student::display(ostream& out)
{
	out<<setiosflags(ios::left)<<setw(20)<<pName
		<<uID<<","
		<<setiosflags(ios::right)<<setw(4)<<grade;
}
ostream& operator << (ostream& out,Student& st)
{
	st.display(out);
	out<<endl;
	return out;
}
//************************
//**      master.h      **
//************************
#include "student.h"
#include <iostream.h>

class Master:public Student
{
public:
	Master(char* pS,unsigned num,float g,char t):
	  Student(pS,num,g),type(t) {}
	void display(ostream& out);
protected:
	char type;
};
//**************************
//**      master.cpp      **
//**************************
#include <iostream.h>
#include "master.h"

void Master::display(ostream& out)
{
	Student::display(out);
	out<<","<<type;
}