In C++20 you can use std::format for safe printf-like formatting: std::cout << std::format(“The answer is {}.\n”, 42); In addition to that the {fmt} library, std::format is based on, provides the print function that combines formatting and output: fmt::print(“The answer is {}.\n”, 42); Disclaimer: I’m the author of {fmt} and C++20 std::format.
If you have boost, then there’s a null ostream & istream implementation available in boost/iostreams/device/null.hpp . The gist of it: #include “boost/iostreams/stream.hpp” #include “boost/iostreams/device/null.hpp” … boost::iostreams::stream< boost::iostreams::null_sink > nullOstream( ( boost::iostreams::null_sink() ) ); …
I was spinning my head around how to do the same thing and i found out it’s actually not that hard. Basically just subclass the ostream and the streambuf objects, and construct the ostream with itself as the buffer. the virtual overflow() from std::streambuf will be called for every character sent to the stream. To … Read more
There are two different issues in your code, the first is that the friend declaration (as the warning clearly says, maybe not so clear to understand) declares a single non-templated function as a friend. That is, when you instantiate the template NVector<int,5> it declares a non-templated function std::ostream& operator<<(std::ostream&,NVector<int,5>) as a friend. Note that this … Read more
The compiler can evaluate the function printcbase() as this: void printcbase(cbase* b ){ int a = b->FooA(); // line 1 int b = b->FooB(); // line 2 std::cout << a; // line 3 std::cout << b; // line 4 stc::cout << std::endl; } or some of many permutatins of lines marked as 1 – 4. … Read more
The standard defines the following operator<< overload in the basic_ostream class template: basic_ostream<charT,traits>& operator<<( basic_ostream<charT,traits>& (*pf) (basic_ostream<charT,traits>&) ); Effects: None. Does not behave as a formatted output function (as described in 27.6.2.5.1). Returns: pf(*this). The parameter is a pointer to a function taking and returning a reference to a std::ostream. This means that you can … Read more
The canonical approach consists in defining your own streambuf. You should have a look at: Angelika LAnger’s articles on IOStreams derivation James Kanze’s articles on filtering streambufs boost.iostream for examples of application
Use std::fixed stream manipulator: cout<<fixed<<“Bas ana: “<<x<<“\tSon faiz: “<<t<<“\tSon ana: “<<x+t<<endl;
std::cout << std::fixed << std::setw(11) << std::setprecision(6) << my_double; You need to add #include <iomanip> You need stream manipulators You may “fill” the empty places with whatever char you want. Like this: std::cout << std::fixed << std::setw(11) << std::setprecision(6) << std::setfill(‘0’) << my_double;
Use: cout << “a is ” << hex << (int) a <<“; b is ” << hex << (int) b << endl; And if you want padding with leading zeros then: #include <iomanip> … cout << “a is ” << setw(2) << setfill(‘0’) << hex << (int) a ; As we are using C-style casts, … Read more