c++ - 容器前后行为

Question

引用自《Effective STL》:

When you get an object from a container (via. e.g., front or back), what you set is a copy of what was contained. Copy in, copy out. That's the STL way.

我很难理解这部分。据我所知，front 返回第一个元素的引用(至少对于 std::vector 而言)。你能解释一下上面的句子吗？

Answer 1

这实际上是本书早期版本中的一个错误。来自errata :

! 6/29/01 jk     20  The first para of Item 3 is incorrect:  front      7/25/04
                     and back do NOT return copies of elements, they 
                     return references to elements.  I 
                     removed all mention of front and back.

所以这句话的解释是:哎呀，是时候得到一个新版本了!