//
// simple test of ADL (Koenig lookup)
//
#include <iostream>
using namespace std;

namespace A {

    struct S { // class, all public
        int data;
        S(int d = 0): data(d) {} // implicit ctr
        // copy ctr created by default
        // operator = created by default
        // dtr created by default
        void m(); // undefined - no problem if not used
    };

    void f(int i, const S &a) {
        cout << "A::f(i,S)\n";
    }

    void f() {
        cout << "A::f()\n";
    }

    S operator + (S s1, S s2) {
        cout << "A::operator+(S,S)\n";
        return s1.data+s2.data;
    }

} // namespace A

// macro for testing
#define TEST(command) cout << ">>>>> " << #command << ":\n  "; command

int main() {
    A::S  s1(1), s2(2), s3;

    TEST(s3 = s1 + s2);         // output:  A::operator+(S,S)
    // operator+ found in the namespace where type of s1,s2 is defined
    TEST(f(5, s1));             // output:  A::f(i,S)
    // f(int i, S&a) found in the namespace where type of s1 is defined
    TEST(A::f());               // output:  A::f()
    // f() should be qualified because of no arguments
}