iostream

Clearly, streams can't be copied. It should be possible to move streams. According to 27.9.1.11 [ofstream.cons] paragraph 4 it is possible to move construct an std::ofstream (the same is true for std::ifstream , std::fstream , and the std::*stringstream variants). For example: #include <iostream> #include <fstream> #include <string> std::ofstream makeStream(std::string const& name) { return std::ofstream(name); } int main() { std::ofstream out{ makeStream("example.log") }; } Trying to move an std::ostream , e.g., to have a factory function creating an std::ofstream , an std::ostringstream , or

How do you print a double to a stream so that when it is read in you don't lose precision? I tried: std::stringstream ss; double v = 0.1 * 0.1; ss << std::setprecision(std::numeric_limits<T>::digits10) << v << " "; double u; ss >> u; std::cout << "precision " << ((u == v) ? "retained" : "lost") << std::endl; This did not work as I expected. But I can increase precision (which surprised me as I thought that digits10 was the maximum required). ss << std::setprecision(std::numeric_limits<T>::digits10 + 2) << v << " "; // ^^^^^^ +2 It has to do with the number of significant digits and the first

Common std::cin usage int X; cin >> X; The main disadvantage of this is that X cannot be const . It can easily introduce bugs; and I am looking for some trick to be able to create a const value, and write to it just once. The naive solution // Naive int X_temp; cin >> X_temp; const int X = X_temp; You could obviously improve it by changing X to const& ; still, the original variable can be modified. I'm looking for a short and clever solution of how to do this. I am sure I am not the only one who will benefit from a good answer to this question. // EDIT: I'd like the solution to be easily

how do I bind a std::ostream to either std::cout or to an std::ofstream object, depending on a certain program condition? Although this invalid for many reasons, I would like to achieve something that is semantically equivalent to the following: std::ostream out = condition ? &std::cout : std::ofstream(filename); I've seen some examples that are not exception-safe, such as one from http://www2.roguewave.com/support/docs/sourcepro/edition9/html/stdlibug/34-2.html : int main(int argc, char *argv[]) { std::ostream* fp; //1 if (argc > 1) fp = new std::ofstream(argv[1]); //2 else fp = &std::cout /

I'm trying to learn a bit more about how I/O streams work in C++, and I'm really confused at when to use what. What exactly is a streambuf ? When do I use a streambuf , as compared to a string , an istream , or a vector ? (I already know the last three, but not how streambuf compares to them, if it does at all.) bames53 Stream buffers represent input or output devices and provide a low level interface for unformatted I/O to that device. Streams, on the other hand, provide a higher level wrapper around the buffer by way of basic unformatted I/O functions and especially via formatted I/O