---

String s1;
    assert(s1.Size() == 0);
    String const s2("Hello, world!");
    assert(s2.Size() == 13);
    String s3(s2);
    s3 = s1 + s2;
    std::cout << s3 << '\n'; // prints "Hello, world!"
    s1 += s2;
    std::cout << s1 << '\n'; // prints "Hello, world!"
    s1[7] = s2[7] - 32;  // s2[7] is 'w', and in ASCII 'W' = 'w' - 32
    std::cout << s1 << '\n'; // prints "Hello, World!"
}