iostream

The output of the following code: #include <limits> #include <iostream> #include <iomanip> #include <limits> #include <string> #include <sstream> using namespace std; inline string lexical_cast(const float arg) { stringstream ss; ss << fixed << setprecision(numeric_limits<float>::digits10) << arg; if (!ss) throw "Conversion failed"; return ss.str(); } int main() { cout << numeric_limits<float>::digits10 << '\n'; cout << lexical_cast(32.123456789) << '\n'; } is: 6 32.123455 I expected, and wanted: 6 32.1234 because, to the best of my knowledge, that's the extent of what a float can reliably

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)

I am trying to set $stdout to write to a file temporarily and then back to a file. test.rb : old_stdout = $stdout $stdout.reopen("mytestfile.out",'w+') puts "this goes in mytestfile" $stdout= old_stdout puts "this should be on the console" $stdout.reopen("mytestfile1.out",'w+') puts "this goes in mytestfile1:" $stdout = old_stdout puts "this should be back on the console" Here is the output. ruby test.rb => no output on the console cat mytestfile.out this goes in mytestfile this should be on the console cat mytestfile1.out this goes in mytestfile1: this should be back on the console I am not

I'd like to read some text from a file that uses UTF-8 encoding and convert it to UTF-16, using std::wifstream , something like this: // // Read UTF-8 text and convert to UTF-16 // std::wifstream src; src.imbue(std::locale("???")); // UTF-8 ??? src.open("some_text_file_using_utf8"); std::wstring line; // UTF-16 string while (std::getline(src, line)) { ... do something processing the UTF-16 string ... } Is there a standard locale name for the UTF-8 conversion? Is it possible to achieve that goal using std::locale ? I'm using Visual Studio 2013. NOTE: I know that I/O streams tend to be slow, and

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