Using Declarations

A using declaration brings one selected name from a namespace into the current scope.

using_declarations.cpp

#include <iostream>
#include <string>

namespace greetings {
std::string hello(const std::string& name) {
    return "Hello, " + name;
}
}

int main() {
    using greetings::hello;

    std::string name = ;

    std::string message = hello(name);

    std::cout << "name=" << name << std::endl;
    std::cout << "message=" << message << std::endl;
    return 0;
}

#include <iostream>
#include <string>

namespace greetings {
std::string hello(const std::string& name) {
    return "Hello, " + name;
}
}

int main() {
    using greetings::hello;

    std::string name = ;

    std::string message = hello(name);

    std::cout << "name=" << name << std::endl;
    std::cout << "message=" << message << std::endl;
    return 0;
}

#include <iostream>
#include <string>

namespace greetings {
std::string hello(const std::string& name) {
    return "Hello, " + name;
}
}

int main() {
    using greetings::hello;

    std::string name = ;

    std::string message = hello(name);

    std::cout << "name=" << name << std::endl;
    std::cout << "message=" << message << std::endl;
    return 0;
}

using declaration A using declaration names exactly what should be brought into the current scope.