iostream

Possible Duplicate: C++: “std::endl” vs “\n” I'm wondering if there is any significant difference between these two ways to print newline : cout << endl; //approach1 cout << "\n"; //approach2 Is there any practical difference? Yes, they're different. "\n" is just a string of length 1 that gets appended to stdout. std::endl , instead, is an object that will cause to append the newline character ( "\n" ) AND to flush stdout buffer. For this reason it will take more processing. 来源： https://stackoverflow.com/questions/4512631/difference-between-endl-and-n

In thinking about C++ iterator question , I wrote this sample program: #include <vector> #include <iostream> #include <iterator> #include <algorithm> template <class T> std::ostream& operator<<(std::ostream&os, const std::vector<T>& v) { os<<"("; std::copy(v.begin(), v.end(), std::ostream_iterator<T>(os, ", ")); return os<<")"; } int main() { std::vector<int> v(3); std::vector<std::vector<int> > vv(3, v); std::cout << v << "\n"; // this line works std::cout << vv << "\n"; // this line produces error } I compile this program with gcc and get the typical 100 lines of errors. The relevant part, I

I just learned of the existence of the ios_base::sync_with_stdio function, which basically allows you to turn off (or on if you already turned it off) the synchronization between iostream streams that are used in C++ and the cstdio streams that are part of Standard C. Now, I always thought that stdout , stderr and stdin in C were essentially wrapped in a set of objects in C++ in the iostreams classes. But if they have to be synchronized with each other, this would indicate that C++'s iostream classes are not a wrapper around C's stdin etc. I'm quite confused by this? Can someone clarify how C+

Possible Duplicate: C++ Filehandling: Difference between ios:app and ios:ate? What is the difference between these two file opening modes ? ios:ate sets the get/put pointer position to the end of the file => reading/writing will begin from end, but how is it different from ios::app, which again opens a file in append mode...but when I have created a ofstream and opened it in ios:app mode, the put stream pointer still points to the beginning, how does the appending work then ? Also I understand that ifstream, ofstream and fstream are high level classes to manage the underlying stream buffer. So

Online references have rather brief and vague descriptions on the purpose of std::iostream::sentry . When should I concern myself with this little critter? If it's only intended to be used internally, why make it public? Most people will never write any code that needs to deal with creating sentry objects. A sentry object is needed when/if you extract data from (or insert it into) the stream buffer that underlies the stream object itself. As long as your insertion/extraction operator uses other iostream members/operators to do its work, it does not have to deal with creating a sentry object

I have this code and I searched for hours why it fails to print my income int const income = 0; std::cout << "I'm sorry, your income is: " < income; Until I found I missed to write << but wrote < . Why doesn't the compiler detect this and error out? I'm not sure why comparing cout makes sense? integral constant 0 is also a null pointer constant - it can be compared to the result of ostream 's operator void * . Note that it'll fail if the constant has any value but 0. The prototypes of the < operator are like : ​bool T::operator <(const T& b) const; So I guess the compiler transtype the