Monday, May 21, 2012

probably no shallow copy by STL containers

As hinted in Item 3 of [[effSTL]] and [[c++primer]], element copy is performed during insert, sort, container clone... On each element, copy-ctor and op= are used.

Q: Excluding container of pointers, is there any "shallow copy"?
%%A: I don't think so. Container doesn't remember the original (incoming) object's address. Once an element is in the container, container does know its address, and often returns its address. For example, vector has many member functions returning by reference.

Q: does vector subscript accessor return address rather than a copy?
AA: yes, pbref. &vecA[0] gives the address of 1st element. See [[effSTL]] item on getting a C-style array from a given vector.

Q: does deferenced iterator return an address or a copy?
%%A: not sure. remember iterators are smart pointers, so by definition they redefine operator*()

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