Why allocators?
Allocators tend to scare people, including some experts, but you will not be scared as you are already in possession of significant memory management knowledge and skills (and you are probably curious to know more about the topic given the fact that you are reading this book). Knowing this, the first question we need to address, before even expressing what an allocator is, is “Why do allocators exist?”. Why would we concern ourselves with an additional layer of complexity in our memory management code?
Well, this is C++, and C++ is all about giving users control, so that’s where our explanation begins. To make an analogy, think about iterators: why they are useful, and how they make your life as a programmer better. They decouple iterating over elements of a sequence from how the elements are organized in that sequence, such that you can write code that computes something such as the sum of the values in std::list<int> or std::vector<...
