文章目录
8.1
8-1and8-2.cpp
#include <iostream>
using namespace std;
istream &test(istream &is)
{
string st;
A: while(is.good())
{
is>>st;
cout<<st<<'\n';
}
if(is.bad())
cout<<"fatal error!"<<endl;
else if(is.eof())
cout<<"End of file."<<endl;
else if(is.fail())
goto A;
is.clear();
return is;
}
int main()
{
test(cin);
return 0;
}8.2
8.3
情况很多，比如cin流崩溃，IO操作失败或者遇到文件结束符等。
8.4
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
using namespace std;
void rf(const string &str)
{
vector<string> vs;
string stemp;
ifstream ifst(str);
if(ifst)
{
while(getline(ifst,stemp))
vs.push_back(stemp);
for(auto p:vs)
cout<<p<<"#";
cout<<endl;
}
else
cout<<"open file failed."<<'\n';
}
int main(void)
{
rf("text");
return 0;
}8.5
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
using namespace std;
void rf(const string &str)
{
vector<string> vs;
string stemp;
ifstream ifst(str);
if(ifst)
{
while(ifst>>stemp)
vs.push_back(stemp);
for(auto p:vs)
cout<<p<<"#";
cout<<endl;
}
else
cout<<"open file failed."<<'\n';
}
int main(void)
{
rf("text");
return 0;
}8.6
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
struct Sales_data
{
string bookNo;
unsigned units_sold{0};
double revenue{0.0};
};
int main(int argc,char *argv[])
{
struct Sales_data total,trans;
double price;
ifstream ifst(argv[1]);
if(ifst>>total.bookNo)
{
ifst>>total.units_sold>>price;
total.revenue=total.units_sold*price;
while(ifst>>trans.bookNo)
{
ifst>>trans.units_sold>>price;
trans.revenue=trans.units_sold*price;
if(total.bookNo==trans.bookNo)
{
total.units_sold+=trans.units_sold;
total.revenue+=trans.revenue;
}
else
{
cout<<total.bookNo<<" "<<total.units_sold<<" "<<total.revenue<<" "<<total.revenue/total.units_sold<<endl;
total.bookNo=trans.bookNo;
total.units_sold=trans.units_sold;
total.revenue=trans.revenue;
}
}
cout<<total.bookNo<<" "<<total.units_sold<<" "<<total.revenue<<" "<<total.revenue/total.units_sold<<endl;
}
else
{
cerr<<"No data?"<<endl;
return -1;
}
return 0;
}8.7
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
struct Sales_data
{
string bookNo;
unsigned units_sold{0};
double revenue{0.0};
};
int main(int argc,char *argv[])
{
struct Sales_data total,trans;
double price;
ifstream ifst(argv[1]);
ofstream ofst(argv[2]);
if(ifst>>total.bookNo)
{
ifst>>total.units_sold>>price;
total.revenue=total.units_sold*price;
while(ifst>>trans.bookNo)
{
ifst>>trans.units_sold>>price;
trans.revenue=trans.units_sold*price;
if(total.bookNo==trans.bookNo)
{
total.units_sold+=trans.units_sold;
total.revenue+=trans.revenue;
}
else
{
ofst<<total.bookNo<<" "<<total.units_sold<<" "<<total.revenue<<" "<<total.revenue/total.units_sold<<endl;
total.bookNo=trans.bookNo;
total.units_sold=trans.units_sold;
total.revenue=trans.revenue;
}
}
ofst<<total.bookNo<<" "<<total.units_sold<<" "<<total.revenue<<" "<<total.revenue/total.units_sold<<endl;
}
else
{
cerr<<"No data?"<<endl;
return -1;
}
return 0;
}8.8
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
struct Sales_data
{
string bookNo;
unsigned units_sold{0};
double revenue{0.0};
};
int main(int argc,char *argv[])
{
struct Sales_data total,trans;
double price;
ifstream ifst(argv[1]);
ofstream ofst(argv[2],ofstream::app|ofstream::out);
if(ifst>>total.bookNo)
{
ifst>>total.units_sold>>price;
total.revenue=total.units_sold*price;
while(ifst>>trans.bookNo)
{
ifst>>trans.units_sold>>price;
trans.revenue=trans.units_sold*price;
if(total.bookNo==trans.bookNo)
{
total.units_sold+=trans.units_sold;
total.revenue+=trans.revenue;
}
else
{
ofst<<total.bookNo<<" "<<total.units_sold<<" "<<total.revenue<<" "<<total.revenue/total.units_sold<<endl;
total.bookNo=trans.bookNo;
total.units_sold=trans.units_sold;
total.revenue=trans.revenue;
}
}
ofst<<total.bookNo<<" "<<total.units_sold<<" "<<total.revenue<<" "<<total.revenue/total.units_sold<<endl;
}
else
{
cerr<<"No data?"<<endl;
return -1;
}
return 0;
}8.9
#include <sstream>
#include <iostream>
using namespace std;
istream &test(istream &is)
{
string st;
A: while(is.good())
{
is>>st;
cout<<st<<'\n';
}
if(is.bad())
cout<<"fatal error!"<<endl;
else if(is.eof())
cout<<"End of file."<<endl;
else if(is.fail())
goto A;
is.clear();
return is;
}
int main(void)
{
istringstream istm("wo shi shei");
test(istm);
return 0;
}8.10
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <string>
using namespace std;
int main(int argc,char *argv[])
{
string tmp;
vector<string> svec;
ifstream ifst(argv[1]);
while(getline(ifst,tmp))
svec.push_back(tmp);
for(auto element:svec)
{
istringstream isstm(element);
while(isstm>>tmp)
cout<<tmp<<endl;
}
return 0;
}8.11
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
struct PersonInfo
{
string name;
vector<string> phones;
};
int main(void)
{
string line,word;
vector<PersonInfo> people;
istringstream record;
while(getline(cin,line))
{
PersonInfo info;
record.clear(record.rdstate()&~record.failbit&~record.eofbit);
record.str(line);
record>>info.name;
while(record>>word)
info.phones.push_back(word);
people.push_back(info);
}
for(auto pi:people)
{
cout<<pi.name<<endl;
for(auto ph:pi.phones)
cout<<ph<<" ";
cout<<endl;
}
return 0;
}8.12
因为每个人的电话条目数量不同，所以应该缺省初始化后在程序中设置人名，并逐个添加电话。
8.13
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
bool valid(const string &str);
string format(const string &str);
struct PersonInfo
{
string name;
vector<string> phones;
};
int main(int argc,char *argv[])
{
string line,word;
vector<PersonInfo> people;
istringstream record;
ifstream ifst(argv[1]);
ofstream ofst(argv[2]);
while(getline(ifst,line))
{
PersonInfo info;
record.clear(record.rdstate()&~record.failbit&~record.eofbit);
record.str(line);
record>>info.name;
while(record>>word)
info.phones.push_back(word);
people.push_back(info);
}
for(const auto &pi:people)
{
ostringstream formatted,badnums;
for(const auto &ph:pi.phones)
{
if(!valid(ph))
badnums<<" "<<ph;
else
formatted<<" "<<format(ph);
}
if(badnums.str().empty())
ofst<<pi.name<<" "<<formatted.str()<<endl;
else
cerr<<"input error: "<<pi.name<<" invalid numbers "<<badnums.str()<<endl;
}
return 0;
}
bool valid(const string &str)
{
if(str.size()==11)
return true;
else
return false;
}
string format(const string &str)
{
return str;
}8.14
const表明循环中不会改变这些项的值，auto利用编译器推断entry和nums的类型，简化代码，&表示引用可以避免拷贝。