C++ Primer, Fifth Edition

The alloc_n_copy Member

The alloc_n_copy member is called when we copy or assign a StrVec. Our StrVec class, like vector, will have valuelike behavior (§ 13.2.1, p. 511); when we copy or assign a StrVec, we have to allocate independent memory and copy the elements from the original to the new StrVec.

The alloc_n_copy member will allocate enough storage to hold its given range of elements, and will copy those elements into the newly allocated space. This function returns a pair (§ 11.2.3, p. 426) of pointers, pointing to the beginning of the new space and just past the last element it copied:

pair<string*, string*> StrVec::alloc_n_copy(const string *b, const string *e) {     // allocate space to hold as many elements as are in the range     auto ...