++ Primer 4/e在Sequence Container Operations这个地方有一个关键观念：‘When we add an element to a container, we do so by copying the element value into the container. Similarly, when we initialize a container by providing a range of elements, the new container contains copies of the original range of elements. There is no relationship between the element in the container and the value from which it was copied. Subsequent changes to the element in the container have no effect on the value that was copied, and vice versa.’
中文版的这样写：‘当我们为容器添加元素时，是“把元素复制到容器”。同样地，当我们提供某一区间元素来初始化容器时，新建容器所含的是原始区间元素的复件（副本）。容器内的元素和被复制的原始值之间没有关联。容器元素如果被改动，并不影响原始值；反之亦然。’
这个观念我还觉很一般，所以就继续保持这样的观念。