Mastering the C++17 STL

Classically polymorphic functions

We can increase the abstraction level of our algorithms via the techniques of classical object-oriented (OO) programming, as seen in languages such as Java and C#. The OO approach is to decide exactly which behaviors we'd like to be customizable, and then declare them as the public virtual member functions of an abstract base class:

    class container_of_ints {      public:      virtual int size() const = 0;      virtual int& at(int) = 0;    };    class array_of_ints : public container_of_ints {      int data[10] = {};      public:        int size() const override { return 10; }        int& at(int i) override { return data[i]; }    };    class list_of_ints : public container_of_ints {      struct node {        int data;        node *next;      };      node *head_ = nullptr; int size_ = ...