Mastering the C++17 STL

Solving the sticky-manipulator problem

Our "sticky std::hex" problem can be solved by saving and restoring the state of the ostream around each complicated output operation, or by creating a brand-new ostream each time we want to output something. An example of the former is as follows:

    void test() {      std::ios old_state(nullptr);      old_state.copyfmt(std::cout);        std::cout << std::hex << 225; // "e1"      std::cout.copyfmt(old_state);      std::cout << 42; // "42"    }

An example of the latter is as follows:

    void test() {      std::ostream os(std::cout.rdbuf());      os << std::hex << 225; // "e1"      std::cout << 42; // "42"    }

Notice how convenient it is that the iostreams library separates the idea of a "streambuf" from the idea of a "stream"; in the preceding example, ...