Initializing One vector with the Contents of Another

The C++ Standard Library class template vector allows you to create a new vector object that’s initialized with the contents of an existing vector. Line 46 creates a vector object integers3 and initializes it with a copy of integers1. This invokes vector’s so-called copy constructor to perform the copy operation. You’ll learn about copy constructors in detail in Chapter 10. Lines 48–50 output the size and contents of integers3 to demonstrate that it was initialized correctly.