C++ Primer 读书笔记 - 第八章
添加时间:2013-5-28 点击量:
1. IO library types do not allow copy or assignment.
Only element types that support copy can be stored in vectors or other container types.
We cannot have a parameter or return type that is one of the stream types. If we need to pass or return an IO object， it must be passed or returned as a pointer or reference.
2. Condition States
＃include <iostream>
＃include <fstream>
＃include <sstream>
＃include <stdexcept>
using namespace std;
int main（）
{
int val1 = 512， val2 = 1024;
ostringstream format_message;
format_message << val1: << val1 << \n
<< val2: << val2 << \n;
istringstream input_string（format_message.str（））;
string dump;
input_string >> dump >> val1 >> dump >> val2;
cout << val1 << << val2 << endl;
int ival;
while （cin >> ival， !cin.eof（）） {
if （cin.bad（）） {
throw runtime_error（IO stream corrupted）;
} else if （cin.fail（）） {
cerr << bad data， try again << endl;
cin.clear（istream::goodbit）;
cin.ignore（）;
continue;
} else {
cout << Input is << ival << endl;
}
}
return 0;
}
3. Five ways to cause the buffer to be flushed.
- The program completes normally.
- The buffer becomes full.
- Using a maipulator， such as endl， flush...
- Use the unitbuf manipulator to set the streams internal state to empty the buffer after each output operation.
- Tie the output stream to an input stream， in which case the output buffer is flushed whenever the associated input stream is read.
cout << Hello << flush; //flushes the buffer， adds no data
cout << Hello << ends; //s a null， then flushes the buffer
cout << Hello << endl; // a newline， then flushes the buffer
cout << unitbuf << first << second << nounitbuf;
same as
cout << fisrt << flush << second << flush;
4. Supplying a file name as an initializer to an ifstream or ofstream object has the effect of opening the specified file.
To associate the fstream with a different file， we must first close the existing file and then open a different file.
Closing a stream does not change the internal state of the stream object.
If we reuse a file stream to read or write more thant one file， we must clear the stream before using it to read another file.
ifstream input;
vector<string>::const_iterator it = files.begin（）;
while （it != files.end（）） {
input.open（it->c_str（））; //open the file
if （!input）
break;
while （input >> s）
process（s）;
input.close（）; //close file when were done with it
input.clear（）; //reset state to OK
++it;
}
5. The only way to preserve the existing data in a file opened by an ofstream by an ofstream is to specify app mode explicitly.
in
out
app
ate
trunc
binary
彼此相爱，却不要让爱成了束缚：不如让它成为涌动的大海，两岸乃是你们的灵魂。互斟满杯，却不要同饮一杯。相赠面包，却不要共食一个。一起歌舞欢喜，却依然各自独立，相互交心，却不是让对方收藏。因为唯有生命之手，方能收容你们的心。站在一起却不要过于靠近。—— 纪伯伦《先知》
1. IO library types do not allow copy or assignment.
Only element types that support copy can be stored in vectors or other container types.
We cannot have a parameter or return type that is one of the stream types. If we need to pass or return an IO object， it must be passed or returned as a pointer or reference.
2. Condition States
＃include <iostream>
＃include <fstream>
＃include <sstream>
＃include <stdexcept>
using namespace std;
int main（）
{
int val1 = 512， val2 = 1024;
ostringstream format_message;
format_message << val1: << val1 << \n
<< val2: << val2 << \n;
istringstream input_string（format_message.str（））;
string dump;
input_string >> dump >> val1 >> dump >> val2;
cout << val1 << << val2 << endl;
int ival;
while （cin >> ival， !cin.eof（）） {
if （cin.bad（）） {
throw runtime_error（IO stream corrupted）;
} else if （cin.fail（）） {
cerr << bad data， try again << endl;
cin.clear（istream::goodbit）;
cin.ignore（）;
continue;
} else {
cout << Input is << ival << endl;
}
}
return 0;
}
3. Five ways to cause the buffer to be flushed.
- The program completes normally.
- The buffer becomes full.
- Using a maipulator， such as endl， flush...
- Use the unitbuf manipulator to set the streams internal state to empty the buffer after each output operation.
- Tie the output stream to an input stream， in which case the output buffer is flushed whenever the associated input stream is read.
cout << Hello << flush; //flushes the buffer， adds no data
cout << Hello << ends; //s a null， then flushes the buffer
cout << Hello << endl; // a newline， then flushes the buffer
cout << unitbuf << first << second << nounitbuf;
same as
cout << fisrt << flush << second << flush;
4. Supplying a file name as an initializer to an ifstream or ofstream object has the effect of opening the specified file.
To associate the fstream with a different file， we must first close the existing file and then open a different file.
Closing a stream does not change the internal state of the stream object.
If we reuse a file stream to read or write more thant one file， we must clear the stream before using it to read another file.
ifstream input;
vector<string>::const_iterator it = files.begin（）;
while （it != files.end（）） {
input.open（it->c_str（））; //open the file
if （!input）
break;
while （input >> s）
process（s）;
input.close（）; //close file when were done with it
input.clear（）; //reset state to OK
++it;
}
5. The only way to preserve the existing data in a file opened by an ofstream by an ofstream is to specify app mode explicitly.
in
out
app
ate
trunc
binary
彼此相爱，却不要让爱成了束缚：不如让它成为涌动的大海，两岸乃是你们的灵魂。互斟满杯，却不要同饮一杯。相赠面包，却不要共食一个。一起歌舞欢喜，却依然各自独立，相互交心，却不是让对方收藏。因为唯有生命之手，方能收容你们的心。站在一起却不要过于靠近。—— 纪伯伦《先知》
