// examples/ns3.cc #include <iostream> namespace cxx_course { unsigned int participant_count { 0 }; auto greet() -> void { std::cout << "Study and practice. Years of it!\n"; } } namespace gardening_course { unsigned int participant_count { 0 }; auto greet() -> void { std::cout << "You reap what you sow.\n"; } } namespace hpc_course { using namespace cxx_course; unsigned long corehours{0}; } auto main(int argc, char *argv[]) -> int { if (argc > 1) { using namespace cxx_course; std::cout << "We are using the hpc_course namespace\n"; greet(); std::cout << "The number of participants is " << participant_count << "\n"; } else { using namespace hpc_course; std::cout << "We are using the hpc_course namespace\n"; greet(); } }