lst-0076-book.cpp
// https://godbolt.org/z/1dTPEd3nP
set source{1,2,3,4,5};
cout <<= source; // Output: 1 2 3 4 5
set target( std::move(source) ); // move instead of copy
cout <<= source; // Output:
cout <<= target; // Output: 1 2 3 4 5