ostream

This question follows a discussion in the comments here . In Eric Niebler's ranges-v3 library (which is sort-of becoming part of the standard for C++20), ranges::ostream_iterator is default-constructible - without an ostream. How come? I thought that "dummy" construction with effective construction later is an anti-pattern in C++, a wart we are gradually getting rid of. std::ostream iterator can only be constructed with a stream (for now - before C++20). And it's not as though we can do anything with the default-constructed range::ostream_iterator ... So, what's the deal? This follows the

I decided to try Visual Studio 2012 Express today. First thing to do was to write "Hello world!" application, however, I couldn't make it work. I created a Windows console application project, wrote standard code and it resulted in a run-time error. Here's my code: #include <iostream> using namespace std; int main() { cout << "Hello world!" << endl; system("pause"); return 0; } Looks like something is broken (maybe I missed something?). It gets a runtime error at line 7: http://img443.imageshack.us/img443/7497/coutbroken.png Any help please? :) Your CPU is in urgent need of being junked. Your

I want to write a simple program that depending on the options passed it the executable will print the output to the screen or to a file. The program is simple. #include<iostream> int main(int argc, char* argv[]){ ... process options... std::ostream& out = ... // maybe std::cout, maybe a *new* std::ofstream; out << "content\n"; } Is there a good idiom to make out refer alternatively to std::cout or a file stream at runtime? I tried with pointers, but it is horrible. I couldn't avoid using pointers (Not to mention that more ugly code is needed to delete the pointer later). #include<iostream>

My program compiles fines but upon inputting a file I get a "Segmentation fault (core dumped)" error. Am I not handling the ostream correctly? #include <std_lib_facilities.h> struct Reading { int hour; double temperature; Reading(int h, double t): hour(h), temperature(t) { } bool operator<(const Reading &r) const; }; bool Reading::operator<(const Reading &r) const { // stub version if (temperature < r.temperature){ return true; } else if (r.temperature < temperature) { return false; } } /* * function declarations */ ostream& operator<<(ostream& ost, const Reading &r); vector<Reading> get_temps

This question arose from a discussion I was having about the correct way to output a numeric value using the usual ostream & operator << (ostream &, some_type) for a numeric type in C++. The way I'm familiar with the behavior of std::showbase and std::showpos in each base, they are basically mutually exclusive. That is: in decimal no base is shown, and the '+' is added on positive numbers; whereas in hexadecimal or octal, the base is shown, but a '+' is not shown (nor is a minus), as the value of the type is printed as if it's cast to an unsigned type. For example, this simple (verbose)

class foo { public: friend ostream& operator << (ostream &os, const foo &f); foo(int n) : a(n) {} private: vector <int> a; }; ostream& operator << (ostream &os, const foo &f) { for (int i = 0; i < f.a.size(); ++i) os << f.a[i] << " "; os << endl; // why is this line a must? } int main(void) { foo f(2); cout << f << endl; return 0; } In the above code, if the marked line is removed, there will be a segment fault error, can someone explain why? ostream& operator << (ostream &os, const foo &f) { for (int i = 0; i < f.a.size(); ++i) os << f.a[i] << " "; os << endl; // why is this line a must? } is

I have been doing research on creating my own ostream and along with that a streambuf to handle the buffer for my ostream. I actually have most of it working, I can insert (<<) into my stream and get strings no problem. I do this by implimenting the virtual function xsputn. However if I input (<<) a float or an int to the stream instead of a string xsputn never gets called. I have walked through the code and I see that the stream is calling do_put, then f_put which eventually tries to put the float 1 character at a time into the buffer. I can get it to call my implementation of the virtual

We have created and filled some std::vector<uchar> with openCV imencode for example. Now we want to stream it for example into some http_lib which can take some sort of ostream (ostringstream) for example, or we just want to save in while we debug our programm with ofstream. So I wonder how to put std::vector<uchar> into std::ostream ? Use write : void send_data(std::ostream & o, const std::vector<uchar> & v) { o.write(reinterpret_cast<const char*>(v.data()), v.size()); } The ostream expects naked char s, but it's fine to treat uchars as those by casting that pointer. On older compilers you