lst-0077-book.cpp
// https://godbolt.org/z/8eGvWY45o
set source{1,2,3,4,5};
set<int> target{};
set<int> target2{};
cout <<= source; // Output: 1 2 3 4 5
cout <<= target; // Output:
cout <<= target2; // Output:
target = source; // copy afterward
cout <<= source; // Output: 1 2 3 4 5
cout <<= target; // Output: 1 2 3 4 5
target2 = std::move(source); // move
cout <<= source; // Output:
cout <<= target2; // Output: 1 2 3 4 5