A Deeper Look at Iterators

In this chapter, you will learn about the C++ iterator concept and how versatile it can be, even though its syntax mimics a plain old C-pointer. By looking at some examples, you will also learn how to create a custom iterator that iterates a linear range.

The iterator concept

Before going further into STL algorithms, we are going to take a deeper look at iterators in C++, as they form the basis of STL algorithms. Note that the iterator concept is not at all a C++ exclusive concept, rather it exists in most programming languages. What differentiates the C++ implementation of the iterator concept from other programming languages is that C++ mimics the syntax of raw memory pointers.

A simplified basic iterator is an object which represent a position in a sequence and therefore basically incorporate the following functionality:

• Are we out of the sequence? (denoted as is_end() -> bool)
• Retrieve the value at the current position (denoted read() -> T)
• Step to the next position (denoted step_fwd() -> void)

Note that the named functions is_end(), read() and so on, does not exist in C++, they are only here for readability. In...

Summary

In this chapter, you learned how to create a custom iterator and how to use iterator_traits to inform the STL library of how your custom iterator can be used.

In the next chapter, we will look into the algorithm library of STL, and also learn how to use the new ranges library for a more expressive C++ syntax.