the article does not mention rvalues and move semantics (i think it's one of the bigest features).

here is an explanation http://stackoverflow.com/questions/6815685/move-semantics-wh...

it is supposed to save extra copies like here

string a("a"); string b("b");

string c = a + b; // creates temporary object that is copied into C by value - the temporary is just a 'full copy'; so that for the temporary it needs an extra allocation and strcpy and free.

the fix is to add the following to the string class

string(string &&r) { ... }

string &operator=(string &&r) { ... }

so the operator with the && receives and 'rvalue' reference - which is a special reference to just this temprorary and the implementation of this is supposed to swap the data of the temporary with that of the this object; the temporary is then discarded.