#include <iostream>

namespace standards
{
    struct datastructure
    {
    };

    void algorithm(const datastructure& ds)
    {
        std::cout << "standards::algorithm" << std::endl;
    }

    void foo()
    {
        std::cout << "standards::foo" << std::endl;
    }
}

int main(int argc, char** argv)
{
    // does not compile, can't find a function foo
    // foo();

    standards::datastructure ds;

    // the function standards::algorithm will be found based on koenig lookup
    algorithm(ds);

    return 0;
}